生物谷報(bào)道：進(jìn)化論認(rèn)為,，物種進(jìn)化永遠(yuǎn)是朝著“最優(yōu)基因”的目標(biāo)前進(jìn),。不過，一項(xiàng)最新的研究表明,，動(dòng)物雌雄兩性在進(jìn)化中可能無法“皆大歡喜”,，對(duì)雄性有利的基因往往會(huì)阻礙雌性同類相關(guān)的適應(yīng)性。相關(guān)論文發(fā)表在6月28日的《自然》雜志上。
英國(guó)愛丁堡大學(xué)（University of Edinburgh）的Katharina Foerster和同事分析了1971年至2005年收集的一種蘇格蘭馬鹿的相關(guān)數(shù)據(jù),，并且利用每只馬鹿對(duì)種群個(gè)體數(shù)量的貢獻(xiàn)來衡量它們的適應(yīng)性,。研究人員通過統(tǒng)計(jì)發(fā)現(xiàn)，如果一只雄性的適應(yīng)性（指生存能力和繁殖數(shù)量）強(qiáng),，那么它的雌性親屬的適應(yīng)性往往低于平均水平,。這一現(xiàn)象表明，兩性在進(jìn)化過程中存在著一種競(jìng)爭(zhēng),，即基因的性別對(duì)抗性選擇（sexually antagonistic selection）,。
Foerster表示，“對(duì)一個(gè)物種的雌雄性個(gè)體而言,，最優(yōu)基因存在著一種平衡。”所謂的最優(yōu)基因是與性別緊密相關(guān)的,。
盡管此前對(duì)黑腹果蠅的實(shí)驗(yàn)室研究得到過類似的結(jié)論,，但這是科學(xué)家第一次真正的“自然”選擇研究。不過,，科學(xué)家并沒有發(fā)現(xiàn)對(duì)應(yīng)的結(jié)論,，即雌性馬鹿的高產(chǎn)會(huì)影響雄性親屬的繁殖能力。研究人員表示,，這可能是由于母親對(duì)雌雄后代的早期影響比較類似,，從而補(bǔ)償了雄性遺傳上的不利條件。
同樣地,，研究人員也沒有發(fā)現(xiàn)雄性馬鹿的適應(yīng)性與其雄性后代有任何關(guān)聯(lián),。她們推測(cè)，雄性無法將自身的適應(yīng)性特征傳達(dá)給雄性后代,，很可能是因?yàn)檫@類性別對(duì)抗基因位于X染色體上,。
加拿大皇后大學(xué)的Adam Chippindale對(duì)該項(xiàng)研究給予了高度的評(píng)價(jià)。他表示,，研究基因選擇中的性別差異并不容易,。“首先，衡量適應(yīng)性就是一項(xiàng)極為困難的工作,，更不用說幾代之間的不同性別差異性的傳遞……即使在實(shí)驗(yàn)室中也很難得到類似的數(shù)據(jù),，研究人員對(duì)馬鹿進(jìn)行了長(zhǎng)達(dá)幾十年的關(guān)注，所得到的結(jié)論也是十分出色的,。”
Chippindale認(rèn)為,，如果能夠收集到更多理想的數(shù)據(jù)，研究人員很可能會(huì)最終發(fā)現(xiàn),，這一與性別相關(guān)的基因選擇是普遍存在的,。“最優(yōu)基因只有在合適的性別環(huán)境中才是最優(yōu)的，”他說,。（引自科學(xué)網(wǎng)）
原始出處:
Nature 447, 1107-1110 (28 June 2007) | doi:10.1038/nature05912; Received 11 December 2006; Accepted 11 May 2007
Sexually antagonistic genetic variation for fitness in red deer
Katharina Foerster1, Tim Coulson2, Ben C. Sheldon3, Josephine M. Pemberton1, Tim H. Clutton-Brock4 & Loeske E. B. Kruuk1
Institute of Evolutionary Biology, University of Edinburgh, Edinburgh EH9 3JT, UK
Division of Biology and Centre for Population Biology, Imperial College, Silwood Park, Ascot, Berkshire SL5 7PY, UK
Edward Grey Institute, Department of Zoology, University of Oxford, Oxford OX1 3PS, UK
Department of Zoology, University of Cambridge, Cambridge CB2 3EJ, UK
Correspondence to: Katharina Foerster1Loeske E. B. Kruuk1 Correspondence and requests for materials should be addressed to K.F. (Email: [email protected]) or L.E.B.K. (Email: [email protected]).
Evolutionary theory predicts the depletion of genetic variation in natural populations as a result of the effects of selection, but genetic variation is nevertheless abundant for many traits that are under directional or stabilizing selection1. Evolutionary geneticists commonly try to explain this paradox with mechanisms that lead to a balance between mutation and selection2. However, theoretical predictions of equilibrium genetic variance under mutation–selection balance are usually lower than the observed values, and the reason for this is unknown3. The potential role of sexually antagonistic selection in maintaining genetic variation has received little attention in this debate, surprisingly given its potential ubiquity in dioecious organisms. At fitness-related loci, a given genotype may be selected in opposite directions in the two sexes. Such sexually antagonistic selection will reduce the otherwise-expected positive genetic correlation between male and female fitness4. Both theory5, 6, 7 and experimental data8, 9, 10, 11, 12 suggest that males and females of the same species may have divergent genetic optima, but supporting data from wild populations are still scarce13, 14, 15. Here we present evidence for sexually antagonistic fitness variation in a natural population, using data from a long-term study of red deer (Cervus elaphus). We show that male red deer with relatively high fitness fathered, on average, daughters with relatively low fitness. This was due to a negative genetic correlation between estimates of fitness in males and females. In particular, we show that selection favours males that carry low breeding values for female fitness. Our results demonstrate that sexually antagonistic selection can lead to a trade-off between the optimal genotypes for males and females; this mechanism will have profound effects on the operation of selection and the maintenance of genetic variation in natural populations.
