Loss and gain of sexual reproduction in the same stick insect
Mary Morgan-Richards, Shelley S. Langton-Myers, Steven A. Trewick
在发表于《分子生态学》的研究中，研究者发现，在进化过程中，一种新西兰竹节虫能够放弃通过交配繁衍后代，而之后又能再次通过这种途径繁衍后代。
在竹节虫种群中，一些Clitarchus hookeri是有性繁殖，群体中雄性和雌性数量相当；还有一些群体则完全由雌性组成，它们放弃了性行为，进行无性繁殖。
有一群无性繁殖的Clitarchus hookeri生活在距离英国海岸线不远的小岛上。这些昆虫可能在1911年就搭搭乘进口植物的便车来到这里。
新西兰帕默斯顿北部梅西大学的Mary Morgan-Richards和同事追溯了这些英国昆虫的遗传祖先，发现它们来自新西兰的一个有性群体。这表明移居国外的昆虫在100年内或大约100代内转变为无性繁殖。
与此同时，新西兰的两个种群则从无性繁殖转变为有性繁殖。2003年，有一个群体几乎完全由无性繁殖的雌性组成。但仅仅13年后，这个群体就转变出一半的雄性，并显示出有性繁殖的遗传证据。
研究者表示，这种昆虫可以帮助科学家了解有性繁殖和无性繁殖的相对优势。
来源：中国科学报 晋楠
Abstract
The outcome of competition between different reproductive strategies within a single species can be used to infer selective advantage of the winning strategy. Where multiple populations have independently lost or gained sexual reproduction it is possible to investigate whether the advantage is contingent on local conditions. In the New Zealand stick insect Clitarchus hookeri, three populations are distinguished by recent change in reproductive strategy and we determine their likely origins. One parthenogenetic population has established in the United Kingdom and we provide evidence that sexual reproduction has been lost in this population. We identify the sexual population from which the parthenogenetic population was derived, but show that the UK females have a post-mating barrier to fertilisation. We also demonstrate that two sexual populations have recently arisen in New Zealand within the natural range of the mtDNA lineage that otherwise characterizes parthenogenesis in this species. We infer independent origins of males at these two locations using microsatellite genotypes. In one population, a mixture of local and nonlocal alleles suggested males were the result of invasion. Males in another population were most probably the result of loss of an X chromosome that produced a male phenotype in situ. Two successful switches in reproductive strategy suggest local competitive advantage for outcrossing over parthenogenetic reproduction. Clitarchus hookeri provides remarkable evidence of repeated and rapid changes in reproductive strategy, with competitive outcomes dependent on local conditions.
