生物學(xué)中最古老的問題之一是,，為什么存在不同性別,？通過異體受精繁殖的動物要多于通過自體受精繁殖的動物,，盡管生出雄性后代及尋找交配對象都是有代價(jià)的。人們通常認(rèn)為,，異體受精或異型雜交具有可能超過其代價(jià)的兩個(gè)優(yōu)勢：快速演化的能力和近親繁殖的避免,，但對此很難進(jìn)行實(shí)驗(yàn)驗(yàn)證。
現(xiàn)在,，使線蟲的自體繁殖變種和異體繁殖變種置于選擇壓力之下的一個(gè)實(shí)驗(yàn),，為以上觀點(diǎn)提供了一個(gè)實(shí)用的驗(yàn)證，而且該實(shí)驗(yàn)還證明,，以上兩個(gè)潛在的標(biāo)準(zhǔn)解釋（即兩個(gè)優(yōu)勢）在促進(jìn)異型雜交中似乎都扮演一個(gè)角色,。（生物谷Bioon.com）
生物谷推薦原始出處：
Nature 462, 350-352 (19 November 2009) | doi:10.1038/nature08496
Mutation load and rapid adaptation favour outcrossing over self-fertilization
Levi T. Morran1, Michelle D. Parmenter1 & Patrick C. Phillips1
Center for Ecology & Evolutionary Biology, 5289 University of Oregon, Eugene, Oregon 97403-5289, USA
Correspondence to: Patrick C. Phillips1 Correspondence and requests for materials should be addressed to P.C.P.
The tendency of organisms to reproduce by cross-fertilization despite numerous disadvantages relative to self-fertilization is one of the oldest puzzles in evolutionary biology. For many species, the primary obstacle to the evolution of outcrossing is the cost of production of males1, individuals that do not directly contribute offspring and thus diminish the long-term reproductive output of a lineage. Self-fertilizing ('selfing') organisms do not incur the cost of males and therefore should possess at least a twofold numerical advantage over most outcrossing organisms2. Two competing explanations for the widespread prevalence of outcrossing in nature despite this inherent disadvantage are the avoidance of inbreeding depression generated by selfing3, 4, 5 and the ability of outcrossing populations to adapt more rapidly to environmental change1, 6, 7. Here we show that outcrossing is favoured in populations of Caenorhabditis elegans subject to experimental evolution both under conditions of increased mutation rate and during adaptation to a novel environment. In general, fitness increased with increasing rates of outcrossing. Thus, each of the standard explanations for the maintenance of outcrossing are correct, and it is likely that outcrossing is the predominant mode of reproduction in most species because it is favoured under ecological conditions that are ubiquitous in natural environments.
