Sherman C D H, Wapstra E, Uller T, Olsson M
School of Biological Sciences, The University of Wollongong, Wollongong, NSW 2522, Australia.
Proc Biol Sci. 2008 Apr 22;275(1637):971-8. doi: 10.1098/rspb.2007.1626.
Recent work has confirmed that genetic compatibility among mates can be an important determinant of siring success in sperm competition experiments and in free-ranging populations. Most of this work points towards mate choice of less related mates. However, there may also be the potential for mate choice for intermediate or even genetically similar mates to prevent outbreeding depression or hybridization with closely related taxa. We studied relatedness effects on post-copulatory gametic choice and/or sperm competition in an external fertilizer, Peron's tree frog (Litoria peronii), since external fertilizers offer exceptional control in order to test gametic interaction effects on probability of paternity and zygote viability. Sperm competition experiments were done blindly with respect to genetic relatedness among males and females. Thereafter, paternity of offspring was assigned using eight microsatellite loci. Three hybridization trials between L. peronii and a closely related sympatric species Litoria tyleri were also carried out. In the sperm competition trials, males that are more genetically similar to the female achieved higher siring success compared with less genetically similar males. The hybridization trials confirmed that the two species can interbreed and we suggest that the risk of hybridization may contribute to selection benefits for genetically more similar males at fertilization. To our knowledge, this study is the first to show evidence for post-copulatory selection of sperm from genetically more similar individuals within a natural population.
近期的研究证实，配偶间的基因兼容性可能是精子竞争实验及自由放养种群中父权成功的一个重要决定因素。这项研究大多指向选择亲缘关系较疏的配偶。然而，选择亲缘关系中等甚至基因相似的配偶也有可能预防远交衰退或与近缘类群杂交。我们研究了在体外受精的佩龙氏树蛙（Litoria peronii）中，亲缘关系对交配后配子选择和/或精子竞争的影响，因为体外受精能提供绝佳的控制条件，以便测试配子相互作用对父权概率和受精卵活力的影响。精子竞争实验在对雌雄个体间的基因亲缘关系不知情的情况下进行。此后，利用八个微卫星位点确定后代的父权。我们还进行了佩龙氏树蛙与近缘同域物种泰勒氏树蛙（Litoria tyleri）之间的三次杂交试验。在精子竞争试验中，与基因相似度较低的雄性相比，基因上与雌性更相似的雄性获得了更高的父权成功率。杂交试验证实这两个物种能够杂交，并且我们认为杂交风险可能促使在受精时选择基因上更相似的雄性具有选择优势。据我们所知，本研究首次展示了自然种群中对基因上更相似个体的精子进行交配后选择的证据。
