Fraser C I, Brahy O, Mardulyn P, Dohet L, Mayer F, Grégoire J-C
Biological Control and Spatial Ecology Laboratory, CP 160/12 Université Libre de Bruxelles, Brussels, Belgium.
Evolutionary Biology and Ecology, CP 160/12 Université Libre de Bruxelles Université Libre de Bruxelles, Brussels, Belgium.
Heredity (Edinb). 2014 Oct;113(4):327-33. doi: 10.1038/hdy.2014.34. Epub 2014 Apr 16.
There is an evolutionary trade-off between the resources that a species invests in dispersal versus those invested in reproduction. For many insects, reproductive success in patchily-distributed species can be improved by sibling-mating. In many cases, such strategies correspond to sexual dimorphism, with males-whose reproductive activities can take place without dispersal-investing less energy in development of dispersive resources such as large body size and wings. This dimorphism is particularly likely when males have little or no chance of mating outside their place of birth, such as when sperm competition precludes successful fertilisation in females that have already mated. The economically important bark beetle pest species Dendroctonus micans (Coleoptera: Curculionidae, Scolytinae) has been considered to be exclusively sibling-mating, with 90% of females having already mated with their brothers by emergence. The species does not, however, show strong sexual dimorphism; males closely resemble females, and have been observed flying through forests. We hypothesised that this lack of sexual dimorphism indicates that male D. micans are able to mate with unrelated females, and to sire some or all of their offspring, permitting extrafamilial reproduction. Using novel microsatellite markers, we carried out cross-breeding laboratory experiments and conducted paternity analyses of resulting offspring. Our results demonstrate that a second mating with a less-related male can indeed lead to some offspring being sired by the latecomer, but that most are sired by the first, sibling male. We discuss these findings in the context of sperm competition versus possible outbreeding depression.
一个物种在扩散与繁殖上投入的资源之间存在着进化上的权衡。对于许多昆虫来说，在分布零散的物种中，同胞交配可以提高繁殖成功率。在许多情况下，这种策略与两性异形相对应，雄性——其繁殖活动无需扩散——在诸如大体型和翅膀等扩散资源的发育上投入较少的能量。当雄性在出生地之外几乎没有或根本没有交配机会时，比如当精子竞争排除了已交配雌性交配成功的可能性时，这种两性异形就尤其可能出现。具有重要经济意义的树皮甲虫害虫物种米象小蠹（鞘翅目：象甲科，小蠹亚科）一直被认为完全是同胞交配，90%的雌性在羽化时就已经与它们的兄弟交配。然而，该物种并没有表现出强烈的两性异形；雄性与雌性非常相似，并且有人观察到它们在森林中飞行。我们推测，这种缺乏两性异形表明米象小蠹雄性能够与无关的雌性交配，并使部分或全部后代由其孕育，从而实现家族外繁殖。我们使用新的微卫星标记，进行了杂交实验室实验，并对产生的后代进行了父系分析。我们的结果表明，与亲缘关系较远的雄性进行第二次交配确实会导致一些后代由后来者孕育，但大多数后代是由第一个同胞雄性孕育的。我们在精子竞争与可能的远交衰退的背景下讨论了这些发现。
