Department of Evolution and Ecology, University of California, Davis, CA 95616, USA.
Mol Ecol. 2012 Oct;21(20):5088-97. doi: 10.1111/mec.12009. Epub 2012 Sep 12.
A species' mating system sets limits on the strength of sexual selection. Sexual selection is widespread in dioecious species, but is less well documented in hermaphrodites, and may be less important. We used four highly polymorphic microsatellite markers to assign paternity to broods of the hermaphroditic eastern Pacific volcano barnacle Tetraclita rubescens. These data were used to describe the species' mating system and to examine factors affecting male reproductive success. Tetraclita can sire broods over distances of 11.2 cm, but proximity to the sperm recipient had a highly significant effect on the probability of siring success. There was no effect of body size or the mass of male reproductive tissues on siring success. Broods showed relatively low frequencies of multiple paternity; even at high densities, 75% of broods had only one father. High frequencies of single-paternity broods imply either that this species does not compete via sperm displacement, or that sperm displacement is extremely effective, potentially explaining the lack of a positive relationship between male investment and paternity. In addition, there was low variance in siring success among individuals, suggesting a lack of strong sexual selection on male traits. Low variance among sires and the strong effect of proximity are probably driven by the unusual biology of a sessile copulating species.
物种的交配系统限制了性选择的强度。性选择在雌雄异体物种中广泛存在，但在雌雄同体物种中记录较少，可能也不那么重要。我们使用了四个高度多态的微卫星标记，将亲代身份分配给雌雄同体的东太平洋火山藤壶 Tetraclita rubescens 的繁殖群体。这些数据用于描述该物种的交配系统，并研究影响雄性生殖成功的因素。Tetraclita 可以在 11.2 厘米的距离内使繁殖群体受精，但与精子接受者的距离对授精成功的概率有显著影响。体型大小或雄性生殖组织的质量对授精成功没有影响。繁殖群体的多父系比例相对较低；即使在高密度下，75%的繁殖群体只有一个父亲。高比例的单父系繁殖群体意味着该物种不会通过精子竞争来竞争，或者精子竞争非常有效，这可能解释了雄性投资和父权之间没有正相关关系的原因。此外，个体间的授精成功方差较低，表明对雄性特征的性选择较弱。亲代之间的低方差和接近度的强烈影响可能是由固着交配物种的异常生物学所驱动的。
