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Hoeveel kan jy prestasie verbeter deur selektiewe teling?

Hoeveel kan jy prestasie verbeter deur selektiewe teling?


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Hoeveel kan jy prestasie verbeter deur selektiewe teling? Ek is nuuskierig oor alle soorte prestasie, fisies sowel as kognitief, maar ek dink laasgenoemde is moeiliker om te beantwoord om die vraag baie konkreet en meetbaar te maak: hoeveel het resiesperde en honde se prestasie die afgelope 100 jaar toegeneem of so? Hulle behoort goeie voorbeelde te wees van wat oor baie generasies se selektiewe teling gebeur wat daarop gemik is om een ​​spesifieke eienskap te verbeter (hardloop vinnig), nie waar nie? En dit behoort maklik te wees om die vordering te meet: wat was die wêreldrekord op 1000 m (of so iets) vir perde/honde 1920 en wat is dit vandag?

Kan hierdie getalle na mense vertaal word?

Vertraag of neem die vordering onder perd-/hondprestasie af?

Enige argumente vir hoekom/waarom nie kognitiewe vermoë sou vorder op 'n soortgelyke wyse as selektiewe teling gebruik word en daarop gemik is in plaas van fisiese vermoë?


Kartering van gene wat drafprestasie reguleer deur selektiewe sweep-kartering in 'n unieke Nordiese perdmodel

Die hibriede oorsprong van die Koelbloedige draf bied 'n unieke geleentheid om gene te identifiseer wat liggaamsamestelling en voortreflike atletiese prestasie beïnvloed. Ons veronderstel dat ons 'n geenvloei sal kan opspoor wat tussen Standardbreds en Coldblooded-drawers plaasgevind het as gevolg van beperkte kruisteling en 'n daaropvolgende (baie) sterk seleksie vir wedrenprestasie in die Coldblooded-drawers.

Die Koelbloedige draf kom van die Noord-Sweedse trekperd wat 'n trekperd is wat in boerdery en bosbou gebruik word. Eers in 1960 is die Koelbloedige draf gedefinieer as 'n aparte ras van die Noord-Sweedse trekperd. Dit is goed vasgestel dat 'n mate van kruisteling tussen Standardbreds en Koelbloedige drawers voorgekom het voordat verpligte vaderskaptoetsing in Swede ingestel is.

'n Merkwaardige verbetering in wedrenprestasie van die Koelbloedige draf het gedurende die afgelope sestig jaar plaasgevind. Ons neem aan dat hierdie verbetering deels verklaar word deur 'n merkbare toename van sommige gunstige genetiese variante wat van Standardbreds afkomstig is en deur kruisteling aan die Koelbloedige draf bekendgestel is. Hierdie proses behoort “genetiese voetspore” in die genoom van Koelbloedige drafvoëls te laat in die vorm van chromosoomsegmente wat van Standardbreds afkomstig is. Ons vergelyk tans die genetiese samestelling van Noord-Sweedse drawers (30 top-presterende individue), Noord-Sweedse trekperde (30 ewekansig geselekteerde individue) en Standardbreds (30 top-presterende individue) deur ontleding van heelgenoom-hervolgordedata. Om chromosoomstreke onder seleksie te identifiseer, sal ons die genetiese variasie tussen rasse kwantifiseer deur eenvoudige Fst-statistieke te gebruik. Vir die meeste chromosoomsegmente verwag ons dat die twee voormalige rasse die meeste ooreenstem, wat hul noue verwantskap weerspieël. Vir daardie chromosoomsegmente wat gunstige genetiese variante huisves wat van Standardbreds afkomstig is, verwag ons egter dat die Koelbloeddrawers 'n groter ooreenkoms met die Standardbreds behoort te deel. Chromosoomstreke onder sterk seleksie sal waarskynlik gene bevat wat morfologiese en fisiologiese eienskappe beïnvloed wat belangrik is vir prestasie in hierdie modelstelsel. Gene wat energiemetabolisme reguleer en ander biologiese prosesse wat wedrenprestasie beïnvloed, kan ook lig werp op metaboliese defekte en siektes in ander spesies.


Abstrak

Ons gebruik regressiediskontinuïteitsontwerp om die effek van 'n stelsel van openbare eksamenhoërskole, wat studente slegs deur voorafbestaande prestasies toelaat, op studentekollege-toelatingseksamentellings in Beijing, China, te ondersoek. Meer selektiewe eksamenskole het dalk hoër portuurgehalte en is soms toegerus met meer ervare onderwysers en beter fasiliteite. Ons vind egter dat elite-eksamen hoërskole, wat die selektiefste is, geen uitwerking op studentetoetsuitslae het nie. Ons vind dat die stelsel van eksamenskole gemiddeld studenteprestasie op die eksamen verbeter, wat daarop dui dat studente baat by die bywoning van meer selektiewe nie-elite skole. Die resultate oor die kwalifikasie vir kollege-toelating stem ooreen met ons bevindinge oor toetstellings. Verskille tussen skole in portuurprestasie, student/onderwyser-verhouding en die persentasie gesertifiseerde en ervare onderwysers verklaar gedeeltelik ons ​​bevindinge selfkeuses van baan- en eksamendeelname verduidelik nie toetstellings of kollege-toelating nie.


3 RESULTATE

3.1 Ouderdomsverwante patrone in teelprestasie

Uit ons ontleding, insluitend voëls tussen die ouderdomme van 3–26 jaar, het drempelmodelle broeisukses en broeiproduktiwiteit vir beide manlike en vroulike witstertarende die beste verteenwoordig (Sien ondersteunende inligtingstabelle S1 en S2). Alhoewel daar 'n beperkte ondersteuning was vir 'n kwadratiese term om relevant te wees in die voorspelling van vroulike telingsukses (ΔAICc 0.34) en teelproduktiwiteit (ΔAICc 1.56), is die drempelmodel gekies om verdere vergelyking tussen geslagte moontlik te maak (Tabel S1).

Daar was duidelike bewyse dat namate arende ouer geword het, broeisukses toegeneem het tot ongeveer 16 jaar oud by vroulike arende en tot 19 jaar by mannetjies en daarna afgeneem het (Figuur 1, Ondersteunende Inligting Tabel S3). Die variansie van die ewekansige term "vroulike individuele identiteit" ( = 1,04, 95% CI: 0,96–1,13) verduidelik meer onder individuele variansie as die variansie van die ewekansige term "manlike individuele identiteit" ( = 0.34, 95% CI: 0.29–0.38), maar in beide gevalle het die insluiting van die individuele identiteit as 'n ewekansige term nie die algehele tendense verander nie. Vir alle mannetjies gelyk aan en ouer as 23 jaar wat in ons ontleding gebruik is (teelrekords n = 10, individue n = 3), is geen jong geproduseer nie. Dieselfde patrone was duidelik vir teelproduktiwiteit, wat toegeneem het tot 14 jaar oud by wyfies en 19 jaar oud by mans en ook in die latere lewe afgeplat of afgeneem het (Figuur 1, Ondersteunende Inligting Tabel S3). Weereens, individuele identiteit het nie die algehele neigings verander nie en die ewekansige term was verantwoordelik vir beperkte variansie in beide vroulike ( = 0,45, 95% CI: 0,0002–0,85) en manlik ( = 0.23, 95% CI: 0.0002–0.92) teelproduktiwiteit. Hierdie neigings is nie verander wanneer slegs op arende getoets is wat nie van maat verander het nie (Figuur S1).

3.2 Verbetering in teelprestasie gedurende die vroeë lewe

Arende het ouderdomverwante verbetering in beide telingsukses getoon (skatting = 0.19, Z = 7.32, 95% CI = 0.14–0.25) en teelproduktiwiteit (Posterior gemiddelde = 0.15, 95% CI = 0.11–0.19) gedurende die vroeë lewe (dws tussen die ouderdom van 3 en 16 jaar vir vrouens en tussen 3 en 19 jaar vir mans). Mannetjies en wyfies toon baie soortgelyke vlakke van verbetering in teelprestasie met ouderdom, met min ondersteuning vir 'n interaksie tussen ouderdom en geslag vir óf telingsukses óf produktiwiteit (Tabel 1 en Ondersteunende Inligting Tabel S4). Op dieselfde wyse is geen effekte van oorsprong op teelprestasie in die vroeë lewe opgespoor nie (Tabel 1).

Modelstruktuur df logLike AICc/DIC ΔAICc/ΔDIC ω i
(i) Teelsukses
Vroeë lewe (n = 949) ouderdom 5 −559.71 1,129.47 0.00 0.47
ouderdom + geslag 6 −559.65 1,131.38 1.91 0.18
ouderdom+oorsprong 7 −558.81 1,131.73 2.26 0.15
ouderdom*geslag 7 −559.58 1,133.27 3.80 0.07
ouderdom+geslag+oorsprong 8 −558.64 1,133.44 3.97 0.07
ouderdom*geslag+oorsprong 9 −558.60 1,135.39 5.92 0.02
ouderdom*oorsprong 9 −558.73 1,135.64 6.17 0.02
ouderdom*oorsprong+geslag 10 −558.57 1,137.37 7.90 0.01
ouderdom*geslag+ouderdom*oorsprong 11 −558.52 1,139.33 9.86 0.00
nul 4 −586.21 1,180.47 51.00 0.00
seks 5 −586.21 1,182.49 53.02 0.00
oorsprong 6 −585.71 1,183.51 54.04 0.00
seks+oorsprong 7 −585.70 1,185.52 56.05 0.00
Laat lewe (n = 160) ouderdom*geslag 7 −81.38 177.50 0.00 0.92
ouderdom 5 −86.42 183.24 5.74 0.05
ouderdom + geslag 6 −85.96 184.48 6.98 0.03
seks 5 −89.78 189.95 12.45 0.00
nul 4 −91.13 190.51 13.01 0.00
Laat-lewe subset (n = 142) ouderdom*geslag 6 −77.16 166.94 0.00 0.41
ouderdom*geslag+ouderdom*oorsprong 8 −75.01 167.10 0.16 0.38
ouderdom*geslag+oorsprong 7 −77.08 168.99 2.05 0.15
ouderdom 4 −82.12 172.53 5.59 0.03
ouderdom + geslag 5 −82.05 174.54 7.60 0.01
ouderdom+oorsprong 5 −82.08 174.59 7.65 0.01
ouderdom*oorsprong 6 −81.31 175.23 8.29 0.01
ouderdom+geslag+oorsprong 6 −81.99 176.59 9.65 0.00
nul 3 −85.35 176.87 9.93 0.00
ouderdom*oorsprong+geslag 7 −81.11 177.06 10.12 0.00
seks 4 −85.04 178.36 11.42 0.00
oorsprong 4 −85.17 178.63 11.69 0.00
seks+oorsprong 5 −84.79 180.01 13.07 0.00
(ii) Teelproduktiwiteit
Vroeë lewe (n = 898) ouderdom 6 −569.32 1,472.28 0.00 0.97
ouderdom+geslag+oorsprong 9 −569.35 1,482.53 10.25 0.01
ouderdom*geslag+oorsprong 10 −569.14 1,482.76 10.48 0.01
ouderdom*geslag 8 −569.39 1,482.92 10.64 0.01
ouderdom + geslag 7 −569.21 1,483.86 11.58 0.00
ouderdom+oorsprong 8 −569.67 1,484.02 11.74 0.00
ouderdom*geslag+ouderdom*oorsprong 12 −568.36 1,484.66 12.38 0.00
ouderdom*oorsprong 10 −568.90 1,485.13 12.85 0.00
ouderdom*oorsprong+geslag 11 −568.66 1,485.25 12.97 0.00
nul 5 −586.88 1,528.60 56.32 0.00
oorsprong 7 −586.83 1,530.12 57.84 0.00
seks 6 −587.07 1,531.02 58.74 0.00
seks+oorsprong 8 −586.98 1,532.20 59.92 0.00
Laat lewe (n = 211) ouderdom*geslag 8 −140.27 369.33 0.00 1.00
ouderdom + geslag 7 −146.05 382.94 13.61 0.00
seks 6 −147.89 383.68 14.35 0.00
ouderdom 6 −146.11 383.85 14.52 0.00
nul 5 −147.62 388.08 18.75 0.00
Laat-lewe subset (n = 181) ouderdom*geslag 7 −120.02 311.63 0.00 0.77
ouderdom*geslag+oorsprong 8 −119.94 314.36 2.73 0.20
ouderdom*geslag+ouderdom*oorsprong 9 −119.95 317.53 5.90 0.04
ouderdom*oorsprong+geslag 8 −125.81 329.01 17.38 0.00
ouderdom 5 −126.04 330.09 18.46 0.00
ouderdom+oorsprong+geslag 7 −125.55 330.45 18.82 0.00
ouderdom + geslag 6 −125.88 330.59 18.96 0.00
ouderdom+oorsprong 6 −125.81 330.70 19.07 0.00
ouderdom*oorsprong 7 −125.81 331.67 20.04 0.00
nul 4 −127.73 332.11 20.48 0.00
oorsprong 5 −127.23 334.17 22.54 0.00
oorsprong+seks 6 −127.22 334.24 22.61 0.00
seks 5 −127.61 334.91 23.28 0.00

Notas

  • AICc: Akaike se inligtingskriterium met 'n regstelling vir klein steekproefgrootte DIC: afwykingsinligtingkriterium ωi: model gewig.
  • Veranderlikes sluit in ouderdom (gestandaardiseer), geslag (manlik/vroulik) en oorsprong (vrystellingsfase 1, vrylatingsfase 2, wildgeteelde) in vroeë- en laatleweperiodes van witstertarende. Oorsprong in die laat-lewe subset bevat vrylatingsfase 1 en slegs wildgeteelde arende. Alle modelle sluit arend-ID, jaar- en gebied-ID as ewekansige terme in, behalwe in die laat-lewe-subversamelings waar gebied-ID as 'n ewekansige term weggelaat word as gevolg van volledige konvergensie tussen individuele ID en gebied-ID. “*” dui op 'n interaksie wat ook die individuele terme insluit. Topmodelle binne <2 ΔAICc/DIC word in vetdruk getoon.

3.3 Binne-individuele effekte en selektiewe voorkoms

Die verbetering in teelprestasie by vroulike en manlike witstertarende kan toegeskryf word aan beide binne- en tussen-individuele effekte (Tabel 2). By vroue, vir beide maatreëls, het jare sedert die eerste teelpoging (dws binne-individuele neigings) 'n hoër veranderlike belangrikheid gehad (gestandaardiseerde regressiekoeffisiente sukses: 0.47, 95% KI: 0.20–0.74 produktiwiteit: 0.41, 95% KI: 0.20– 0.64) as tussen-individuele veranderinge wat veroorsaak word deur selektiewe voorkoms (gestandaardiseerde regressiekoëffisiënte sukses: 0.39, 95% CI: 0.08–0.70 produktiwiteit: 0.29, 95% BI: 0.03–0.54). Die verbetering in teelprestasie by witstert-arende manlike is ook hoofsaaklik bepaal deur binne-individuele effekte (gestandaardiseerde regressiekoëffisiënte sukses: 0,83, 95% KI: 0,55–1,14 produktiwiteit: 0,57, 95% KI: 0,39–0,77) in vergelyking met tussen -individuele effekte (gestandaardiseerde regressiekoëffisiënte sukses: 0.07, 95% CI: -0.30 tot 0.45 produktiwiteit: -0.02, 95% CI: -0.32 tot 0.25). Daar was geen aanduiding dat ouderdomspesifieke teelprestasie beïnvloed is deur of dit 'n individu se eerste teelpoging vir albei die geslagte was of nie (Tabel 2).

Skat Z Vertrouensintervalle
Laer Boonste
(i) Teelsukses
Vroulik (n = 466) Onderskep −1.73 −2.70 −2.98 −0.47
Jare sedert eerste poging 0.14 3.40 0.06 0.23
Ouderdom by eerste teling 0.28 2.45 0.06 0.51
Eerste poging −0.45 −1.27 −1.15 0.25
Manlik (n = 503) Onderskep −1.14 −1.58 −2.56 0.27
Jare sedert eerste poging 0.20 5.60 0.13 0.27
Ouderdom by eerste teling 0.06 0.40 −0.22 0.34
Eerste poging −0.08 −0.21 −0.79 0.64
Posterior gemiddelde Effektiewe monstergrootte Vertrouensintervalle
Laer Boonste
(ii) Teelproduktiwiteit
Vroulik (n = 395) Onderskep −1.51 4,000 −2.59 −0.39
Jare sedert eerste poging 0.15 4,000 0.07 0.23
Ouderdom by eerste teling 0.22 4,000 0.02 0.42
Eerste poging −0.31 4,000 −0.91 0.26
Manlik (n = 503) Onderskep −0.57 4,000 −1.73 0.53
Jare sedert eerste poging 0.14 4,000 0.09 0.19
Ouderdom by eerste teling −0.02 4,000 −0.24 0.20
Eerste poging −0.16 3,685 −0.70 0.40

Let wel

3.4 Veroudering in teelprestasie

Die tempo van afname in broeisukses en produktiwiteit in die laat lewe (veroudering) het verskil tussen mans en wyfies, aangedui deur die insluiting van die interaksie tussen ouderdom en geslag in die top laatlewe modelle (Tabel 1 en Ondersteunende Inligting Tabel S4). In die laatlewe het manlike telingsukses (koëffisiëntskatting = -1.38, 95% KI's = -2.49 tot -0.27) en produktiwiteit (Posterior gemiddelde = -0.99, 95% KI's = -1.55 tot -0.48) aansienlik afgeneem. Daarteenoor het vroulike telingsukses (koëffisiëntskatting = -0.13, 95% KI's = -0.33 tot 0.06) en teelproduktiwiteit (Posterior gemiddelde = -0.06, 95% KI's = -0.16 tot 0.03) geen bewyse van 'n afname in die laat lewe getoon nie. gedurende die ouderdomspan wat ons getoets het. Vir broeisukses, maar nie produktiwiteit nie, was daar bewyse dat oorsprong (R1 of W) 'n effek op die verouderingspatrone gehad het (Tabel 1 en Ondersteunende Inligting Tabel S4), waar arende afkomstig van die eerste vrystelling 'n neiging toon tot 'n steiler afname in broeisukses (koëffisiëntskatting = -0.34, 95% KI's = -0.68 tot -0.09) as wildgeteelde arende (koëffisiëntskatting = -0.09, 95% CI's = -0.42 tot 0.22). Alhoewel die 95% vertrouensintervalle van hierdie skattings nul oorvleuel, wat daarop dui dat oorsprong 'n beperkte rol gespeel het in die bepaling van die tempo van afname in telingsukses gedurende die laatlewe, toe dit in meer besonderhede ondersoek is, was geslagspesifieke neigings duidelik. Vroulike R1-teelsukses het afgeneem (−0.21, 95% KI: −0.23 tot −0.21), maar vroulike W-teelsukses het nie (0.10, 95% KI: −0.26 tot 0.48). Hierdie verskille was nie duidelik by manlike arende van verskillende oorsprong nie.

3.5 Binne-individuele effekte en selektiewe verdwyning

Daar was geen bewyse om te ondersteun dat die afname in sukses of produktiwiteit in die laat lewe gedryf is deur die selektiewe verdwyning by mans of vrouens nie. Die afname in manlike broeisukses tussen die ouderdomme van 19 en 22 jaar vir 'n subset van individue wat nie gedurende hierdie ouderdomsgroep "verdwyn" het nie (regressiekoëffisiënt: -1.67, 95% KI: -4.57 tot -0.38) stem ooreen met dit vir almal individue in dieselfde ouderdomsgroep (regressiekoëffisiënt: -1.67, 95% CI: -2.91 tot -0.34). Op dieselfde manier was tendense vir ouderdomspesifieke vroulike broeisukses tussen die ouderdomme van 16 en 23 jaar (-0,11, 95% CI: -0,06 tot 5,86) vergelykbaar met 'n subset van "nie-verdwynende" individue wat deurgaans teenwoordig was. ouderdomsreeks (−0.09, 95% CI: −0.30 tot 0.10). Dieselfde was waar vir teelproduktiwiteit, waar vir mans (19–22 jaar oud) produktiwiteit afgeneem het (Posterior gemiddelde: -0.91, 95% CI: -1.51 tot -0.32) op dieselfde wyse as die data-subset met slegs individue wat nie verdwyn (Posterior gemiddelde: -1.23, 95% CI: -2.10 tot -0.42). Vroulike (ouderdom 14–23 jaar) teelproduktiwiteit was ook soortgelyk tussen alle individue (Posterior gemiddeld: -0.10, 95% CI: -0.22 tot 0.01) en dié wat nie verdwyn het nie (-0.08, 95% BI: -0.23 tot 0.07 ). Die ooreenkomste in hierdie neigings (Figuur S3) ondersteun die idee dat afnames in teelprestasie waarskynlik nie deur selektiewe verdwyning gedryf sal word nie.


Bespreking

Baie van die bronne van seleksie wat moontlik kan optree om 'n hoë kapasiteit vir langdurige swem in mariene drierugsteelrug te handhaaf, is verslap toe stokrug varswaterstrome gekoloniseer het. In hierdie studie het ons die evolusionêre uitkoms van ontspanne seleksie op hierdie hele-dier prestasie-eienskap ondersoek deur pare stroom-inwonende en anadrome-mariene stokrug vanaf twee plekke in 'n gemeenskaplike laboratoriumomgewing groot te maak. Ons het gevind dat stokbewoners van beide plekke 'n verlaagde kapasiteit vir langdurige swem ontwikkel het (gemeet met 'n Ukrit toets), en dat drie bykomende wild-gevang stroom-inwonende bevolkings ook laag het Ukrities. Vergelykings van die prestasie van F1-basters met dié van hul suiwer ouerkruisings het verskille in die Ukrities van simpriese stroom-inwonende en seevisse kom hoofsaaklik voor deur nie-additiewe genetiese effekte, maar via verskillende genetiese meganismes in hierdie twee populasies.

Ons het ook die funksionele basis vir verlagings in langdurige swemprestasie ondersoek deur die rigting van evolusie te meet in geselekteerde kandidaat-eienskappe wat voorspel word om swemkapasiteit te beïnvloed. Ons het gevind dat 'n aantal morfologiese (borsvingrootte en -vorm en liggaamsvorm) en fisiologiese eienskappe (MMR) ontwikkel het soos voorspel na varswaterkolonisasie en kan bydra tot evolusionêre variasie in swemprestasie tussen ekotipes. Slegs MMR het egter ook 'n genetiese basis gehad soortgelyk aan langdurige swemkapasiteit in beide Bonsall en West Creeks. Hierdie data dui daarop dat MMR die mees waarskynlike van ons kandidaat-eienskappe is om evolusionêre variasies in langdurige swemprestasie te veroorsaak.

EVOLUSIONÊRE KRAGTE WAT LANGDURIGE SWEMPRESTASIE BEÏNVLOED: BEWYSE VIR KEURING?

Neutrale faktore, soos mutasie-akkumulasie, beïnvloed dikwels eienskap-evolusie nadat 'n bron van seleksie verslap is, maar die invloede van direkte en indirekte fiksheidseffekte kan ook belangrik wees (Maughan et al. 2007 Hall en Colgrave 2008 Lahti et al. 2009). Die waarneming van herhaalde onafhanklike evolusie van verminderde swemprestasie in ons populasies van stokrug dui op 'n moontlike rol vir selektiewe eienskapvermindering na verslapping van seleksie. Hierdie hipotese word ondersteun deur onafhanklike waarnemings van ander dele van die spesiereeks. Byvoorbeeld, Tudorache et al. (2007) het bevind dat wilde stroom-inwonende drieswerwelstokkies van België 'n laer langdurige swemkapasiteit (~6.5 BL·s -1 ) het as simpriese anadrome-mariene visse (~8.25 BL·s -1 ). Daarteenoor het Schaarschmidt en Jürss (2003) bevind dat slegs een van twee stroombewoners van die Oossee 'n laer Ukrit as seevisse van hierdie streek, maar hul visse is getoets na voortplanting en het 'n baie lae langdurige swemvermoë gehad (Ukrities van ~3,5–4,5 BL·s −1 , in vergelyking met ons waardes van ~6–10 BL·s −1 ). Ons data dui daarop dat hierdie na reproduktiewe visse waarskynlik verouderend was (sien Fig. S3). Varswaterkolonisasies van stokrug in Oos-Europa en die Wes-Stille Oseaan het onafhanklik plaasgevind (Orti et al. 1994), en ons bevindinge dat daar 'n ander genetiese basis vir Ukrit in West en Bonsall Creeks stel ook voor dat hierdie kolonisasies onafhanklik kan wees. 'n Soortgelyke verlies van die kapasiteit vir langdurige swem is ook waargeneem in nie-migrerende populasies van sokkie-salm (Oncorhynchus nerka), wat na die laaste gletsering uit anadrome visse ontwikkel het (Taylor en Foote 1991). Hierdie vinnige (<12 000 jaar gelede), en onafhanklike, verlagings in langdurige swemprestasie in stroom-inwonende visse, dikwels in die lig van geenvloei van mariene bevolkings (bv. Hagen 1967 Jones et al. 2006), stem ooreen met 'n rol vir natuurlike seleksie in die evolusie van verminderde swemprestasie.

Selektiewe eienskapvermindering na 'n verslapping van seleksie sal na verwagting deur twee tipes faktore beïnvloed word: direkte en indirekte fiksheidseffekte (Fong et al. 1995 Lahti et al. 2009). Direkte fiksheidseffekte sluit die koste van eienskapinstandhouding in, terwyl indirekte fiksheidseffekte moontlike funksionele en genetiese afwykings insluit met ander prestasie-eienskappe wat steeds onder seleksie is (Lahti et al. 2009). Sulke afwykings onder prestasie-eienskappe is onderskei van klassieke lewensgeskiedenis-afwegings (Roff en Fairbairn 2007), omdat dit nie verlig kan word deur toenemende hulpbronverkryging nie (hersien deur Ghalambor et al. 2003 Walker 2007). In ooreenstemming met 'n rol vir indirekte koste wat die evolusie van langdurige swem beïnvloed, word twee prestasie-eienskappe veronderstel om sterk positiewe rigtingseleksie in varswater stokrug, jeugdige groeikoers (Barrett et al. 2008 Marchinko 2009) en bars swemprestasie te ervaar (Walker 1997 Bergstrom 2002). , is negatief gekorreleer met die kapasiteit vir langdurige swemprestasie. Afwegings tussen groeitempo en langdurige swemkapasiteit is in baie visse opgespoor (bv. Kolok en Oris 1995 Farrell et al. 1997 Billerbeck et al. 2001), insluitend driespiere stokrug (Alvarez en Metcalfe 2005 Lee et al. 2010), en afwegings tussen bars en langdurige swem word ook by visse gevind (Langerhans 2009 Oufiero et al. 2011). By stokrug is bars-swemprestasie oorerflik (Garenc et al. 1998), en wilde stroom-inwonende visse is superieure bars-swemmers, maar slegter langdurige swemmers as seevisse (Taylor en McPhail 1986), in ooreenstemming met die hipotese van 'n funksionele handels- af.

Daar word voorspel dat hierdie afwegings tussen uitbarsting en langdurige swem by visse sal plaasvind omdat die liggaamsvorme wat langdurige swem maksimeer antagonisties optree op barsswem (hersien deur Webb 1982 Weihs en Webb 1983 Blake 2004 Langerhans en Reznick 2009). Inderdaad, afwegings in swemprestasie word geassosieer met verskille in liggaamsvorm in Westerse muskietvis (Langerhans 2009). Die meganistiese basis vir funksionele afwykings tussen groeitempo en langdurige swem word nie so goed verstaan ​​nie, maar kan deur metaboliese energieverdeling bemiddel word. Byvoorbeeld, in Atlantiese silwerkante het vinniger groeiende noordelike bevolkings 'n hoër SMR, en dus 'n kleiner ruimte vir aërobiese aktiwiteit, as suidelike bevolkings wat hoër kan bereik Ukrities (Arnott et al. 2006). In hierdie studie het ons bewyse gevind vir geneties gebaseerde verskille in liggaamsvorm-eienskappe wat voorspel word om afwykings tussen bars en langdurige swem te bemiddel (bv. stertarea, stertsteeldiepte, kopgrootte), in ooreenstemming met 'n rol vir afwegings die evolusie van langdurige swem te beïnvloed. Ons vind egter geen verskille in SMR tussen stroom-inwonende en mariene stekelrug nie, ten spyte van die waargenome hoër groeitempo's in lae-geplateerde stekelrug (Martinko en Schluter 2007 Barrett et al. 2009). Omdat SMR die som van alle metaboliese prosesse in rus verteenwoordig, en baie energie-eisende eienskappe wissel tussen stroom-inwonende en mariene stokrug, is die onttrekking van die effekte van enige een proses (bv. groei) op ​​SMR uitdagend. Daarbenewens word beide bars-swem en groei geassosieer met laterale plaatmorfologie in stokrug (Bergstrom 2002 Marchinko en Schluter 2007 Barrett et al. 2009 Hendry et al. 2011), dus om te bepaal watter eienskappe prestasie-afwegings bemiddel sal studies vereis wat beheer vir variasie in plaatmorfologie en ander gekorreleerde eienskappe, terwyl al drie prestasie-eienskappe gemeet word.

MORFOLOGIESE EN FISIOLOGIESE EIENSKAPPE WAT BYDRA TOT VERLAGINGS IN LANGDURIGE SWEMPRESTASIE

Die kapasiteit vir langdurige swem is 'n heel-organisme-prestasie-eienskap wat deur 'n aantal onderliggende morfologiese, fisiologiese en gedragseienskappe beïnvloed word (Walker 2010). Daarom vertoon hierdie eienskap die verskynsel van veel-tot-een kartering, aangesien baie verskillende kombinasies van eienskapwaardes ekwivalente prestasie kan lewer (Wainwright et al. 2005). Daarbenewens dra baie van die eienskappe wat langdurige swemprestasie beïnvloed ook by tot ander prestasie-eienskappe, en vertoon dus "multi-tasking" (bv. borsvinne word ook vir maneuvering gebruik) (Walker 2010). Die bepaling van die meganismes waardeur 'n komplekse eienskap ontwikkel, gegewe die baie beskikbare weë, kan insig gee in die selektiewe kragte wat op organismes in die natuur inwerk, en die afwegings of fasiliteringe wat eienskap-evolusie beïnvloed (Walker 2007).

Ons het gevind dat 'n aantal morfologiese en fisiologiese eienskappe wat voorspel is om langdurige swem te beïnvloed, ontwikkel het in stroom-inwonende visse, en het ontwikkel in die rigting wat voorspel is deur vermindering in Ukrit. Die evolusie van 'n kleiner, en meer geronde borsvin, en 'n minder vaartbelynde liggaamsvorm stem ooreen met data van wilde stroombewoners en mariene visse (Taylor en McPhail 1986 Schaarschmidt en Jürss 2003), en hierdie verskille word ook in ander varswater-driehoeke gevind. stickleback-ekotipes wat in langdurige swemprestasie verskil (dws benties vs. limneties [Blake et al. 2005], inlaat vs. meer [Hendry et al. 2011] onder mere [Walker 1997]), wat daarop dui dat dit 'n algemene reaksie is op 'n verslapping van seleksie op langdurige swem. Daarbenewens het ons gevind dat stroom-inwonende visse van British Columbia 'n verlaagde MMR ontwikkel het, wat ooreenstem met die bevindinge van Tudorache et al. (2007) in wilde stekelrug uit België. Die SMR van ons stroom-inwonende visse het egter nie ontwikkel nie, in teenstelling met die bevindinge van Kitano et al. (2010) en Tudorache et al. (2007) het albei hierdie studies bevind dat seevisse aansienlik hoër SMR'e het as vis wat in die stroom woon. Hierdie verskil tussen studies is waarskynlik te wyte aan metodologiese verskille. Byvoorbeeld, Tudorache et al. (2007) en Kitano et al. (2010) het SMR gedurende die dag gemeet, en Kitano et al. (2010) het visse bestudeer wat aan 'n ander fotoperiode geakklimatiseer is. Daarbenewens kan enige verskille in die hoeveelheid tyd wat visse toegelaat is om aan te pas by die stres van bevalling in 'n metaboliese kamer SMR beïnvloed het, aangesien daar variasie in die respiratoriese reaksie op bevallingstres onder stokrugbevolkings is (Bell et al. 2010). Soos verwag, gebaseer op sirkadiese ritmes in metabolisme, was ons nagmaatstawwe van SMR laer as dié van Kitano et al. (2010) en Tudorache et al. (2007). Dus, terwyl ons eksperimente vind dat die SMR's van stroom-inwonende en mariene driespier-stokrug nie in varswater verskil nie, het die werk van Kitano et al. (2010) en Tudorache et al. (2007) dui aan dat die roetine of aktiewe metaboliese tempo gedurende die dag wel verskil.

Ons het ook geneties gebaseerde verskille in liggaamsvorm en MMR tussen mariene bevolkings van Bonsall en West Creeks gevind, so dat West Creek seevisse 'n aansienlik meer vaartbelynde liggaamsvorm en hoër MMR gehad het. Hierdie verskil kan geassosieer word met ekologiese verskille tussen hierdie twee populasies, aangesien West Creek seevisse ten minste 35 km langs die Fraserrivier af reis om die see te bereik, terwyl Bonsall Creek stokrug net 'n paar kilometer van die monding van die riviermond broei (Hagen 1967, TH Vines en AC Dalziel, ongepubliseerde data). Hierdie data dui daarop dat seevisse die vermoë kan hê om aan te pas by plaaslike trektoestande, soortgelyk aan populasies van sokkie-salm (Elason et al. 2011). Boonop dui hierdie data daarop dat daar moontlik genetiese verskille in voorvaderlike seebevolkings was ten tyde van varswaterkolonisasie. As dit die geval is, verskille in die genetiese basis vir Ukrit tussen West Creek en Bonsall Creek F1 basters kan te wyte wees aan verskille in die genetiese argitektuur van mariene bevolkings.

Om verder te toets vir assosiasies tussen kandidaat-eienskappe en prestasie, het ons die patrone van oorerwing van Ukrit en kandidaat-eienskappe. Nie een van die eienskappe wat ons gemeet het, het bewyse van moederlike effekte getoon nie, maar daar was beduidende variasie in dominansie tussen eienskappe en tussen liggings. Hierdie data het ons in staat gestel om 'n sterk, eenvoudige, funksionele verband tussen liggaamsvorm, borsvin-area, borsvinvorm en Ukrit in West Creek vis, en borsvin area en Ukrit in Bonsall Creek vis. Hendry et al. (2011) het ook gemengde ondersteuning gevind vir die impak van borsvingrootte op Ukrit, wat verder aandui dat die assosiasies tussen vinmorfologie en swemprestasie populasiespesifiek kan wees, of afhanklik kan wees van ander ongemeet eienskappe, soos die grootte van die borsspiere wat swem aandryf. In ons Bonsall Creek-kruisings het ons gevind dat liggaamsvorm en vinvorm geassosieer word met Ukrit in suiwer en F1 baster kruisings, wat aandui dat hierdie eienskappe 'n soortgelyke genetiese argitektuur het, en belangrike bemiddelaars van Ukrit optrede. Hierdie twee vormeienskappe het egter nie 'n soortgelyke genetiese argitektuur as Ukrit in West Creek kruise, wat aandui dat die funksionele argitektuur onderliggend is Ukrit kapasiteit kan tussen liggings verskil. Die enigste eienskap wat dieselfde genetiese basis gehad het, as het Ukrit in beide populasies was MMR. Hierdie sterk assosiasie in beide plekke dui daarop dat MMR die evolusionêre variasie in Ukrit gevind onder migrerende en nie-migrerende driespiere stokkies.

MMR is self 'n komplekse eienskap, wat afhanklik is van 'n reeks onderliggende eienskappe wat suurstofopname by die kieu beïnvloed, vervoer na die swemspiere en benutting in die mitochondriale elektronvervoerketting. Daarom kan veranderinge in enige stap van die suurstofvervoerkaskade, en enige van die vele gene wat bydra tot elk van hierdie onderliggende eienskappe MMR teoreties verminder (hersien deur Turner et al. 2006 Montgomery en Safari 2007). Deur die onderliggende eienskappe wat bydra tot MMR te ondersoek, kan ons verdere insig verkry in die meganistiese basis vir verlagings op swemprestasie, moontlike afwykings met ander prestasie-eienskappe ondersoek, en bepaal of dieselfde onderliggende eienskappe bydra tot evolusionêre verlagings in prestasie in veelvuldige prestasies. bevolkings van nie-migrerende stokrug.

Mederedakteur: C. Peichel


BESPREKING

Die resultate wat in hierdie studie aangebied word, toon dat slegs ongeveer die helfte van die sade wat deur die vrugte van Bauhinia ungulata in staat is om te ontkiem, en dat saadontkieming beïnvloed word deur die posisie waarin die saad geproduseer word. Daarbenewens het die huidige data aan die lig gebring dat die verskille in groeikragtigheid onder nageslag van B. ungulata is nie lukraak met betrekking tot die posisie van ovules in die peul nie: die algehele prestasie van die sade word, inteendeel, geassosieer met die waarskynlikheid van saadrypwording. Algehele, saadposisies geleë by die basale helfte van die behandelingsvrugte het laer groeikragtigheid getoon as sade geleë op die stilêre helfte van die vrugte. Die effek van posisie op groeikrag word hoofsaaklik waargeneem in ovules van die twee basale afdelings, 3 en 4 in die algemeen, saadgrootte en boomidentiteit is die belangrikste veranderlikes wat groeikragtigheid beïnvloed, veral in vroeë stadiums.

Daar is baie faktore wat saadontkieming beïnvloed, sommige van hulle is genetiese verskille tussen sade. Saadontkieming hang egter ook af van eksterne veranderlikes soos temperatuur en waterbeskikbaarheid. Een faktor wat ontkiemingsukses kan beïnvloed, is die afwesigheid van verkortingsbehandelings, wat wateropname en wortelopkoms moeiliker maak vir die sade om te voltooi.

Wanneer saadontkieming onder behandelings ontleed is, is gevind dat behandelings 1 en 2 'n laer persentasie ontkieming as die kontrole gehad het, terwyl behandelings 3 en 4 waardes van persentasie ontkieming soortgelyk aan die kontrole vrugte getoon het. In behandelings 1 en 2 is sade met 'n lae waarskynlikheid van aborsie selektief vernietig, hierdie vermindering in kompetisie het waarskynlik minder fikse nageslag toegelaat om hul ontwikkeling te voltooi en volwassenheid te bereik. Dit kan die laer waarskynlikheid van ontkieming wat waargeneem word verklaar. Daarenteen, vir behandelings 3 en 4, is sade met 'n hoë waarskynlikheid van aborsie verwyder, daarom is verwag dat die vermindering van kompetisie 'n mindere effek op die prestasie van die oorblywende sade sou hê. In ooreenstemming met hierdie verwagting was die persentasie ontkieming op hierdie behandelings nie betekenisvol verskillend van die kontrole vrugte nie (Tabel 1). Gutierrez et al. (1996) het soortgelyke patrone gevind in Ulex gallii (Fabaceae) die waarskynlikheid van saadrypwording het afgehang van die posisie wat dit in die vrugte beklee het. Verder het posisies met 'n hoë waarskynlikheid van aborsie ligter sade geproduseer as posisies met 'n lae waarskynlikheid van aborsie, hierdie eienskap het met ontkieming gekorreleer.

Hierdie afhanklikheid van die prestasie van die nageslag van die posisie van die saad in Bauhinia is verder ondersteun toe elke afdeling afsonderlik ontleed is. Sade wat in die stilêre helfte van behandelde vrugte ontwikkel is, het patrone van nageslagprestasie soortgelyk aan die kontrolevrugte gegee (Tabelle 2 en 3A en B). Daarenteen is die prestasie van die saailinge wat in die basale helfte (afdelings 3 en 4) geproduseer is, deur hierdie vermindering in kompetisie beïnvloed. Hierdie verskil in antwoorde dui daarop dat die vermindering in fiksheid veroorsaak kan word deur 'n toename in die frekwensie van rypwording van minder geskikte saad wanneer die kompetisie verslap is, eerder as deur die deursteektegniek wat gebruik word om die eksperimentele toestande van verminderde kompetisie te verkry.

In Phaseolus coccineus, Rocha en Stephenson (1990, 1991) het bevind dat, wanneer kompetisie verslap was wat rypwording van sade met 'n hoë waarskynlikheid van aborsie moontlik gemaak het, dit 'n laer groeikragtigheid getoon het as sade wat in posisies geproduseer is met 'n lae waarskynlikheid van aborsie. Ander studies het soortgelyke resultate gevind. Selektiewe saad aborsie in Cynoglossum officinale (Boraginaceae) het tot fikser nageslag gelei met verhoogde persentasies oorlewing (Melser en Klinkhamer, 2001). In Mirabilis jalapa (Nyctaginaceae), pollen performance correlated with the vigour of the offspring furthermore, selective abortion produced more vigorous progeny ( Niesenbaum, 1999). In Acacia caven (Fabaceae), the performance of seedlings was associated with the probability of maturation of fruits ( Torres et al., 2002).

In B. ungulata, it was found that the only consistent effects of treatment were on early fitness variables: days to germination and days to first leaf ( Tables 2 and 3). This is by contrast with findings in other studies. In P. coccineus, the position of the seed had a significant effect on all estimates of fitness, from seed weight and germination to flower production ( Rocha and Stephenson, 1991).

One reason why it was not possible to detect differences at later stages of seedling growth might be that the parameters of late fitness measured in B. ungulata dealt with general seedling growth. These variables might be under strong selective canalization, therefore showing less observable variation than early estimates of vigour. This also suggests that early establishment is the critical stage for the survival of the seeds. Once the seedlings become established, their growth might follow a strongly canalized allometric pattern therefore the variables we measured would not reflect any differences in vigour among offspring at later stages.

Another reason why it was not possible to detect differences at later stages of growth might be that other variables, like protection against herbivores or responses to drought, were not examined. Variation in the vigour of the offspring might affect the differential allocation of resources to these factors at post-establishment stages. These factors might be especially important, since each individual has to grow for several years before reaching a reproductive status. These factors might exert a strong selection on young plants in nature ( Gerhardt, 1993), but it might be hard to detect any differences under greenhouse conditions. Studies of seed production and survival have shown that, in the Santa Rosa National Park, the initial seed output of many tree species is highly reduced by rodent predation ( Janzen, 1967 Janzen et al., 1990 O. J. Rocha, Universidad de Costa Rica, unpubl. res.). Therefore, faster rates of germination might be constantly selected and faster-germinating seeds might have a higher probability of survival. Studies of survival and establishment under natural conditions are needed, along with long-term follow-up studies to determine to what extent the performance of the offspring is affected by the patterns of seed abortion in perennial species.

Present address: Department of Biological Sciences, Kent State University, Kent, OH 44242, USA


LS4.B: Natural Selection and LS4.C: Adaptation (MS-LS4 Biological Evolution: Unity and Diversity)

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Disciplinary Core Ideas
LS4.B: Natural Selection
&bull Natural selection leads to the predominance of certain traits in a population, and the suppression of others. (MS-LS4-4)
&bull In artificial selection, humans have the capacity to influence certain characteristics of organisms by selective breeding. One can choose desired parental traits determined by genes, which are then passed on to offspring. (MS-LS4-5)

LS4.C: Adaptation
&bull Adaptation by natural selection acting over generations is one important process by which species change over time in response to changes in environmental conditions. Traits that support successful survival and reproduction in the new environment become more common those that do not become less common. Thus, the distribution of traits in a population changes. (MS-LS4-6)

Use the Template and Resource Links to Fulfill NGSS

  1. Understand that n atural selection leads to the predominance of certain traits in a population, and the suppression of others .
  2. Understand that i n artificial selection, humans can influence certain characteristics of organisms by selective breeding. One can choose desired parental traits determined by genes, which are then passed on to offspring.
  3. Understand that adaptation by natural selection acting over generations is one important process by which species change over time in response to changes in environmental conditions.
  4. Understand that traits that support successful survival and reproduction in the new environment become more common those that do not become less common. Thus, the distribution of traits in a population changes.
  5. Understand that collection of fossils and their placement in chronological order is the fossil record and documents the existence, diversity, extinction, and change of many life forms throughout the history of life on Earth.

Noodsaaklike vrae:

  1. What leads to the predominance of certain traits in a population, and the suppression of others?
  2. How can humans influence certain characteristics of organisms?
  3. How do species change over time in response to changes in environmental conditions?
  4. How do the distribution of traits in a population change?

NGSS Note: Think, question, entertain ideas.

ll. Introductory Activities to Assess Prior Knowledge

A. Brainstorming Sessions
Vraag: What are some examples of natural selection in animal coloring?
1. Break students down into groups of 3-4.
2. Ask students to generate a list of the different animals they know that have adaptive coloring.
3 . Discuss

Brainstorming Sessions
Vraag: What are some examples of artificial selection in animal selective breeding?
1. Break students down into groups of 3-4.
2. Ask students to generate a list of the the animals they know of that have been affected by artificial selection.
3 . Discuss

lll. New Knowledge - Text

A. Lees about:
Aanpassing en natuurlike seleksie

B. Examples of Models (depicts the concept expressed in the reading):

Ask students to look at the models and explain how each illustrates the concepts they've read about.

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lV. Experiments, Activities, Model-making (Critical Thinking)

A. Critical Thinking Activities related to adaptation and natural selection:
Adaptation and Natural Selection Activities

B. Authentic Performance - Understanding by Design (UbD) assessment tool.
Use critical thinking to complete thse Authentic Performance Activities and deepen your understanding about the above topics.

V. Summarize Knowledge - Enduring Understandings

  1. A natomical similarities and differences between organisms living today and in the fossil record, enable the reconstruction of evolutionary history and the inference of lines of evolutionary descent .
  2. A c omparison of the embryological development of different species also reveals similarities that show relationships not evident in the fully-formed anatomy .
  3. Na tural selection leads to the predominance of certain traits in a population, and the suppression of others .
  4. A rtificial selection, humans can influence certain characteristics of organisms by selective breeding. One can choose desired parental traits determined by genes, which are then passed on to offspring.
  5. A daptation by natural selection acting over generations is one important process by which species change over time in response to changes in environmental conditions.
  6. Traits that support successful survival and reproduction in the new environment become more common those that do not become less common. Thus, the distribution of traits in a population changes.
  7. A collection of fossils and their placement in chronological order is the fossil record and documents the existence, diversity, extinction, and change of many life forms throughout the history of life on Earth.

Vl. New Generation of Science Standards (NGSS) - Middle School Life Science

Disciplinary Core Ideas

LS4.A: Evidence of Common Ancestry and Diversity
&bull The collection of fossils and their placement in chronological order (e.g., through the location of the sedimentary layers in which they are found or through radioactive dating) is known as the fossil record. It documents the existence, diversity, extinction, and change of many life forms throughout the history of life on Earth. (MS-LS4-1)
&bull Anatomical similarities and differences between various organisms living today and between them and organisms in the fossil record, enable the reconstruction of evolutionary history and the inference of lines of evolutionary descent. (MS-LS4-2)
&bull Comparison of the embryological development of different species also reveals similarities that show relationships not evident in the fully-formed anatomy. (MS-LS4-3)

LS4.B: Natural Selection
&bull Natural selection leads to the predominance of certain traits in a population, and the suppression of others. (MS-LS4-4)
&bull In artificial selection, humans have the capacity to influence certain characteristics of organisms by selective breeding. One can choose desired parental traits determined by genes, which are then passed on to offspring. (MS-LS4-5)

LS4.C: Adaptation
&bull Adaptation by natural selection acting over generations is one important process by which species change over time in response to changes in environmental conditions. Traits that support successful survival and reproduction in the new environment become more common those that do not become less common. Thus, the distribution of traits in a population changes. (MS-LS4-6)

Science and Engineering Practices

Ontleding en interpretasie van data
Analyzing data in 6&ndash8 builds on K&ndash5 experiences and progresses to extending quantitative analysis to investigations, distinguishing between correlation and causation, and basic statistical techniques of data and error analysis.
&bull Analyze displays of data to identify linear and nonlinear relationships. (MS-LS4-3)
&bull Analyze and interpret data to determine similarities and differences in findings. (MS-LS4-1)

Using Mathematics and Computational Thinking
Mathematical and computational thinking in 6&ndash8 builds on K&ndash5 experiences and progresses to identifying patterns in large data sets and using mathematical concepts to support explanations and arguments.
&bull Use mathematical representations to support scientific conclusions and design solutions. (MS-LS4-6)

Constructing Explanations and Designing Solutions
Constructing explanations and designing solutions in 6&ndash8 builds on K&ndash5 experiences and progresses to include constructing explanations and designing solutions supported by multiple sources of evidence consistent with scientific ideas, principles, and theories.
&bull Apply scientific ideas to construct an explanation for real-world phenomena, examples, or events. (MS-LS4-2)
&bull Construct an explanation that includes qualitative or quantitative relationships between variables that describe phenomena. (MS-LS4-4)

Obtaining, Evaluating, and Communicating Information

Obtaining, evaluating, and communicating information in 6&ndash8 builds on K&ndash5 experiences and progresses to evaluating the merit and validity of ideas and methods.
&bull Gather, read, and synthesize information from multiple appropriate sources and assess the credibility, accuracy, and possible bias of each publication and methods used, and describe how they are supported or not supported by evidence. (MS-LS4-5)


Pollen quantity and quality affect fruit abortion in small populations of a rare fleshy-fruited shrub

Little is known about changed rates of fruit abortion due to pollen limitation or inbreeding in small and isolated populations of flowering plants. We report on a pollination experiment with the fleshy-fruited tall-shrub Prunus mahaleb at the margin of its distributional range, where reproduction might be especially limiting. Two small and isolated populations in northern Switzerland were studied for effects of pollen quantity and pollen quality on the timing of fruit abortion. There was evidence that spontaneous self-pollination led to particularly high abortion. Fruit abortion was delayed after hand pollination, which indicates limitation of pollen quantity. Self-pollination led to earlier abortion compared with experimental pollination within or between populations. There was no significant evidence for outbreeding depression in fruit abortion. We conclude that reproduction and dispersal of P. mahaleb in central Europe might be negatively affected by pollen limitation and inbreeding effects, i.e. by both pollen quantity and quality.

Die Auswirkungen von Pollenlimitierung und Inzucht auf die Fruchtabortion in kleinen und isolierten Populationen von Blütenpflanzen sind wenig untersucht. Wir berichten über ein Bestäubungsexperiment mit dem endozoochoren Strauch Prunus mahaleb an der Verbreitungsgrenze der Art, wo sexuelle Fortpflanzung vermutlich in besonderem Maße begrenzend wirkt. Die Fruchtabortion in zwei kleinen Populationen in der Nordschweiz wurden untersucht nach experimentell variierter Pollenquantität und -qualität. Spontane Selbstbestäubung führte zu besonders hoher Abortion. Handbestäubung verzögerte die Fruchtabortion und läßt damit auf Pollenlimitierung des Fruchtansatz schließen. Selbstbestäubung verursachte frühere Abortion als Handbestäubung innerhalb oder zwischen den Populationen, während eine mögliche Auszuchtdepression in bezug auf die Fruchtabortion nicht signifikant war. Reproduktion und Ausbreitung in kleinen Populationen von P. mahaleb in Mitteleuropa werden vermutlich negativ beeinflusst von Pollenlimitierung und Inzuchteffekten, das heißt sowohl von Pollenquantität als auch von Pollenqualität.


Materiale en Metodes

FISH COLLECTION, FERTILIZATION, AND REARING

Common-garden reared crosses: Bonsall and West Creek stickleback

We collected fish from Bonsall and West Creeks (British Columbia, Canada Fig. 1) from May to June in 2006 and 2007. Stream and marine ecotypes hybridize in these streams ( Hagen 1967 T. H. Vines and A. C. Dalziel, unpubl. data), so we collected our fish from sites >500 m from the hybrid zone, where <1% of fish from the opposite population are found. Parents for F1 crosses were identified as either marine or stream-resident based upon morphology (see Hagen 1967 McPhail 1994 ), and their genotype at markers for two loci under differential selection: Eda, a gene that controls lateral plate morphology ( Colosimo et al. 2005 ) and sodium potassium ATPase, an ion transporter that plays a major role in ion transport ( Jones et al. 2006 Shimada et al. 2010 ), following the methods of Barrett et al. (2008). These fish were used to produce F1 crosses by artificial fertilization following the methods of Marchinko and Schluter (2007) . In total, 23 crosses were made from Bonsall Creek parents (seven pure stream [SS], five pure marine [MM], six stream mother x marine father [SM], and five marine mother x stream father [MS] crosses) and 16 crosses were made from West Creek parents (five SS, five MM, three SM, three MS).

Locations of the threespine stickleback populations used in this study. (A) Western North America with the sampling area outlined with a gray hatched square. (B) Region within the gray hatched square, with stickleback collection sites marked with gray stars and labeled in italics.

Fish were raised in dechlorinated Vancouver tap water brought to 2 ± 0.5 ppt with Instant Ocean® sea salt. Fish ate live brine shrimp twice per day for their first month, Daphnia and bloodworms (Chironomid larvae) daily for the next 3 months, and Mysis shrimp and bloodworms from 4 months on. All individuals were fed to satiation at every feeding. Families were raised in separate tanks and split to 20 fish per tank at 2 months of age. Fish were reared at a natural photoperiod and temperatures ranging from 11–17°C until March (∼9–11 months of age). At this date fish were 3.5–4.5 cm standard length, a size generally considered to be adult (e.g., Garenc et al. 1998 ), and were individually marked with elastomer tags (Northwest Marine Technology, Shaw Island, WA). Fish were then transferred to a 15°C environmental chamber with controlled 12L:12D photoperiod to prevent them from entering a reproductive state, and acclimated to these constant conditions for at least a month. We studied swimming performance in young adults that were not yet sexually mature to reduce the effects of reproduction (e.g., Ghalambor et al. 2004 ). Marine fish migrate prior to reproduction so swimming performance is ecologically relevant at this life stage. The University of British Columbia animal care committee approved all experimental procedures (A07–0288).

Wild-caught fish: Kanaka Creek, Salmon River, and Little Campbell River stickleback

We collected adult stream-resident fish from Salmon River (as in Taylor and McPhail 1986 ), Little Campbell River, and Kanaka Creek in June 2008 (Fig. 1). Wild-caught fish were held at the same conditions as laboratory-bred adults for 1 month and remained healthy.

MEASUREMENT OF MAXIMUM PROLONGED SWIMMING SPEED: CRITICAL SWIMMING SPEED (Ukrit)

We used a critical swimming speed (Ukrit) test to measure prolonged swimming performance ( Brett 1964 ). In this test water speed is increased in a stepwise manner until a fish can no longer maintain its position in the current. Ukrit is predicted to be an ecologically relevant measure of prolonged swimming for fish that migrate, live in the open ocean, or live in high-flow streams ( Kolok 1999 Plaut 2001 ), and performance correlates with migratory difficulty among populations of salmonids (e.g., Lee et al. 2003 ).

We swam six individually labeled siblings in a Brett style 10-L swim tunnel (SWIM-10 Loligo Systems, Hobro, Denmark), at a water temperature of 15 ± 1°C and salinity of 2 ppt. Water speed was calibrated with a vane wheel flow sensor (Höntzch ZSR25, GmbH, Waiblingen, Germany). Fish swam spread throughout the flume, and were constantly observed to be sure that they did not draft. All fish were <0.25% of the cross-sectional area of the tunnel so correction for solid blocking effects was not required. Die Ukrit trial followed Fangue et al. (2008) , with minor modifications. We placed fish in the tunnel and let them acclimate for 30 min at 0.5 body lengths/second (BL·s −1 ). We then performed a training test by increasing the speed at 0.5 BL·s −1 increments every 2 min until failure. Fish then recovered for 3 h. To measure Ukrit, we increased speed at 0.5 BL increments every 2 min until water velocity reached 50% of the training failure speed. Thereafter, we increased speed every 10 min until the fish could not maintain its position in the current and fell back against the end of the tunnel three times. Critical swimming speed was determined using the following formula: Ukrit=Ui+ (ti/tii·Uii), waar Ui is the highest speed the fish was able to swim for a full 10 min interval (BL·s −1 ), Uii is the incremental speed increase (BL·s −1 ), ti is the time the fish swam at the final speed (min), and tii is the prescribed period of swimming per speed (10 min). We also recorded the gait transition speed (Fig. S1), and found that Ukrit was significantly repeatable over 1 month (Fig. S2).

To test for an effect of sex on Ukrit, we dissected fish and sexed them anatomically after our experiments were completed, but only 100 of the original 234 fish swum could be classified unequivocally. Of these 100 fish, 81 fish from 21 of the 39 families has at least one known male and female per family and could be used to test for the effect of sex. We did not detect any effect of sex on Ukrit (data not shown nested analysis of variance [ANOVA], F1,20= 0.067, P= 0.799), which is in agreement with Whoriskey and Wooton's (1987) previous work. Thus, we combined the sexes in all later analyses. Note that Hendry et al. (2011) did find significant effects of sex in older, sexually mature stickleback kept at a summer photoperiod.

MEASUREMENT OF MORPHOLOGICAL TRAITS PREDICTED TO INFLUENCE PROLONGED SWIMMING SPEED

Photographs of laboratory-bred stickleback (n= 234 fish six fish per family) were taken within a month of Ucrits. Fish were anesthetized with 0.2 g tricaine methanesulfonate buffered with 0.4 g sodium bicarbonate in 1 L of water. The right side of the fish was photographed with a ruler in the field of view. A second photograph was taken of the right pectoral fin maximally spread over a laminated sheet of paper. Pectoral fin area was measured by tracing an outline of the fin using Image J (Fig. 3A). We used TPSdig 2.1 ( Rohlf 2010 ) to digitize 12 landmarks onto the stickleback's body (Fig. 4A, B) and six landmarks onto the stickleback's pectoral fin (Fig. 3C). We aligned and corrected pectoral fin landmarks for differences in geometric size using tpsRelw ( Rohlf 2010 ), following Albert et al. (2008). To analyze pectoral fin shape, we performed a linear discriminant (ld) function analysis (DFA) on the aligned x en y pectoral fin coordinates, grouping our fish into six cross-types (reciprocal hybrid crosses were pooled), with the MASS package in R ( Venables and Ripley 2002 ). We chose to use DFA so that we could determine how F1 hybrid fin shape compared the fin shape of pure stream and marine fish along the axis of variation that best distinguishes pure parental types. We also used the landmarks depicted in Figure 4A, B to measure six body shape traits predicted to mediate evolutionary variation in prolonged swimming capacity in fish (e.g., Hawkins and Quinn 1996 Walker 1997 McGuigan et al. 2003 Seiler and Keeley 2007 Langerhans 2009 Rouleau et al. 2010 ). These traits were: (1) fineness ratio (maximum body depth [landmarks 5–11] divided by standard length [landmarks 2–8]), (2) shoulder point (distance from landmark 8 to intersection with line from 5 to 11 [point of maximum depth]), (3) head depth (landmarks 6–10), (4) posterior depth at third spine (landmarks 4–12), (5) caudal peduncle depth (landmarks 1–3), and (6) caudal area (sum of area of the two triangles formed by connecting landmarks 1, 3, 12 and 3, 4, 12). Interlandmark distances were calculated by TMorphGen6c (IMP suite 2006, Zeldith et al. 2004 ). We corrected measurements for overall body size by performing a least-squared regression against mass and using residuals in all subsequent analyses. Residuals were made positive by the addition of a constant, log10 transformed, and divided by 2 for linear measures and by 3 for caudal area. We performed a DFA on the six body shape measures following our methods for pectoral fin landmarks.

(A) Representative anadromous stickleback with a pectoral fin (shaded gray) spread maximally. (B) Pectoral fin area residuals (corrected for body mass) of laboratory-bred F1 families from Bonsall and West Creek parents. Data are presented as in Figure 2A, and reciprocal hybrids from each location are pooled. Different letters indicate significant differences among cross-types (P < 0,001). (C) Landmarks used to measure pectoral fin shape are labeled 1–6 and are located at the center of the nearest arrow. Arrows multiply by 4 the changes in landmark position that occur among cross-types for pectoral fin shape linear discriminant 1 (ld1), and generally summarize changes in fin shape from a stream-resident to marine fish. (D) Plot of pectoral fin shape ld1 and ld2 scores of laboratory-bred F1 families from Bonsall (Bon) and West Creek (West) parents. Abbreviations for cross-types are presented as in Figure 2A, and reciprocal hybrids from each location are pooled (West-H and Bon-H). Different letters indicate significant differences among cross-types for pectoral fin ld1 (P < 0,00001). Different symbols indicate significant differences among cross-types for pectoral fin ld2 (P < 0,0001). Albei P-values were calculated from a null distribution of randomized F-values (Fig. S5–S6).

Representative stream-resident (A) and anadromous (B) sticklebacks showing landmarks (numbered circles) used to measure the six body shape variables (from black lines connecting landmarks, see materials and methods). (C) Plot of body shape ld1 and ld2 scores for laboratory-bred F1 families from Bonsall (Bon) and West Creek (West) parents. Abbreviations and data presentation follow Figure 3D. Different letters indicate significant differences among cross-types for body shape ld1 (P < 0,00001). Different symbols indicate significant differences among cross-types for body shape ld2 (P < 0,00001). Albei P-values were calculated from a null distribution of randomized F-values (Fig. S7–S8).

Reproductively mature stickleback show sexual dimorphism in body and pectoral fin shape, but there is little differentiation in these characteristics in nonbreeding fish ( Hoffmann and Borg 2006 Kitano et al. 2007 ). Our fish did not enter breeding condition, and sex did not affect Ukrit (see results), so we did not include sex as a variable in our morphological analysis.

MEASUREMENT OF STANDARD AND MAXIMUM METABOLIC RATES

We measured metabolic rate indirectly via oxygen consumption. Both standard (SMR) and maximum oxygen consumption rates (MMR) were measured on individual fish in Beamish-style swim tunnels by intermittent flow respirometry (233 mL SWIM-MINI Loligo Systems) modified for use with FOXY fiber-optic oxygen probes (Ocean Optics, Dunedin, FL). Swim tunnels were housed in an external tank to maintain temperature, and a connecting water pump could be turned on to flush the inner tunnel with fully oxygenated water from the outer tank. During measurement of oxygen consumption, the pump was turned off and the tunnel was sealed. Fish were fasted for 24–36 h pretrial, temperature was maintained at 15 ± 1°C, salinity at 2 ± 0.3 ppt, and oxygen never dropped below 75% saturation. Oxygen probes were calibrated in air and N2 gas at the start and end of every trial. If calibrations drifted by >5% the data were discarded. Background bacterial respiration was measured daily and subtracted from all measures, and tunnels were cleaned with bleach biweekly. SMR was measured overnight in the dark for 90-min intervals (with a 10 min flush with oxygenated water), at a tunnel speed of <10% of critical velocity: this speed mixed the water but allowed fish to rest at the bottom of the tunnel. The mass-specific oxygen consumption rate (μmol·g −1 wet weight·h −1 ) was calculated from the slope of the oxygen trace (recorded as partial pressure of oxygen in torr), over a 50-min period within each 90-min interval. Water oxygen content was corrected for barometric pressure, solubility of oxygen in water at 15°C and 2 ppt, and calculated based upon fish weight and respirometer volume. SMR was calculated as the average of all 50-min intervals for which no activity or stress (noted as higher oxygen consumption rates) occurred.

MMR was measured during a ramp-speed trial similar to our Ukrit protocol. Fish were acclimated in the tunnel for 30 min at a speed of <10%Ukrit while the oxygen probes stabilized. The speed was then immediately increased to 50% of Ukrit, and oxygen consumption was measured continuously for at least three 30-min intervals in which the velocity was increased continuously such that the fish was constantly increasing its swimming speed. Over a 30-min interval velocity increased on average by 15% of fish's Ukrit in 2.5–5% increments. Between intervals there was a 5-min flush to replenish oxygenated water. Oxygen consumption was measured during at least three 30-min intervals approaching, and reaching, MMR. We used a continuous increase in speed to accurately capture MMR. MMR data were not collected for one Bonsall SS family, and SMR data were not collected for four Bonsall SM and three MS crosses.

STATISTIESE ANALISE

All statistical analyses were conducted using R version 2.11.1 ( R Development Core Team, 2010 ). Multivariate analyses of morphology are described in the section “Measurement of morphological traits.” To test the influence of cross-type on Ukrit, pectoral fin surface area, and MMR, we used a mixed-effects model with individual nested within family (random effects), and family nested within cross-type (fixed effect) with the nlme package in R ( Pinheiro et al. 2009 ). All data met the assumptions of homogeneity of variance and normality. Tukey HSD post-hoc tests were used to detect pairwise differences using the multcomp package in R ( Hothorn et al. 2008 ). Because there was an elevated type I error rate when testing the influence of cross-type on the lds obtained from DFA, P-values for these measures were obtained from a null distribution of F-statistics. We generated this distribution by randomly assigning family groupings to pectoral fin (aligned x, y coordinates) and body shape (six traits) values 10,000 times, performing DFAs on these new data, and then comparing ld1 and ld2 values with ANOVA. The resulting F-values generated a null distribution, to which we compared our F-values to calculate a P-value (Fig. S5–S8). Because there are no major differences between the results of our nested ANOVA and ANOVA on collapsed family means (data not shown), we conducted the randomizations on the family means of our 39 cross-types, and tested the influence of cross-type on pectoral fin ld1 and ld2 and body shape ld1 and ld2 using a one-way ANOVA on family means, and not a mixed-effects model. Values for reciprocal hybrid crosses were not significantly different for any of our measures, so we collapsed these crosses in all analyses, with the exception of Ukrit (Fig. 1A).

To compare the Ukrit of our laboratory-bred stream-resident crosses (Fig. 2A) to our wild-caught stream-resident fish (Fig. 2B), we conducted a one-way ANOVA, using family means as replicates for laboratory crosses, and individual fish as replicates for wild-caught fish. We compared patterns of variation in Ukrit and candidate morphological and physiological traits to examine associations between underlying traits and performance, and did not use correlation analysis, because of the statistical problems that arise when using nonindependent F1 hybrids. We also explicitly tested for differences in dominance between West and Bonsall Creeks for Ukrit, pectoral fin surface area, pectoral fin shape ld1, body shape ld1, and MMR by modifying our original model into a genetic model with terms for additivity, dominance, location, and interactions between degree of dominance and location (y∼ location + additive + dominance + location × dominance), with the nlme package in R ( Pinheiro et al. 2009 ). Differences in dominance were tested by examining the interaction between location and dominance.

(A) Critical swimming speed (Ukrit) of laboratory-bred F1 families from Bonsall and West Creek parents. The ecotypes of the crosses’ parents (stream x stream [SS, white circles], marine x marine [MM, solid black circles], stream mother x marine father [SM, gray circles], and marine mother x stream father [MS, gray circles]) are presented on the x-axis. Data are presented as the grand means ±SEM (SEM = standard error of the mean) of all family means, but statistical tests included all individuals in a nested ANOVA model (see results text). Different letters indicate significant differences among the eight cross-types (P < 0,0001). (B) Ukrit of wild-caught stream-resident fish from three additional populations (see Fig. 1), with collection location (Sal = Salmon River, Kan = Kanaka Creek, LC = Little Campbell River) noted on the x-axis. Data are presented as means ±SEM.