Department of Biological Science, Florida State University, Tallahassee, FL 32306-1100, USA.
Mol Ecol. 2011 Oct;20(19):4140-51. doi: 10.1111/j.1365-294X.2011.05264.x. Epub 2011 Sep 14.
Matrotrophy, the provisioning of embryos between fertilization and birth, creates the potential for conflict between mothers and embryos over the level of maternal investment. This conflict is predicted to drive the evolution of reproductive isolation between populations with different mating systems. In this study, we examine whether density-driven mating system differences explain the patterns of asymmetric reproductive isolation observed in previous studies involving four populations of the matrotrophic least killifish, Heterandria formosa. Minimum sire number reconstructions suggested that two populations characterized by low densities had lower levels of concurrent multiple paternity than two populations characterized by high densities. However, low levels of genetic variation in the low-density populations greatly reduced our probability of detecting multiple mating in them. Once we took the lower level of genetic variation into account in our estimations, high levels of multiple paternity appeared the rule in all four populations. In the population where we had the greatest power of detecting multiple mating, we found that multiple paternity in H. formosa typically involves multiple sires contributing to offspring within the same brood instead of different fathers contributing to distinct, simultaneously provisioned broods. Paternity was often skewed towards one sire. Our results suggest that differences between H. formosa populations in the levels of multiple paternity are not sufficient to explain the reproductive isolation seen in previous studies. We suggest that other influences on maternal-foetal conflict may contribute to the pattern of reproductive isolation observed previously. Alternatively, the asymmetric reproductive isolation seen in previous studies might reflect the disruption of maternal-foetal coadaptation.
胎生，即在胚胎受精和出生之间为其提供营养，这使得母体和胚胎之间在母体投资水平上存在潜在的冲突。这种冲突预计会推动具有不同交配系统的种群之间生殖隔离的进化。在这项研究中，我们研究了密度驱动的交配系统差异是否可以解释先前涉及四种胎生最小的丽鱼，Heterandria formosa 的种群不对称生殖隔离模式。最小亲代数量重建表明，两个密度较低的种群的同时多父本比例低于两个密度较高的种群。然而，低密度种群中遗传变异水平较低极大地降低了我们在其中检测到多次交配的可能性。一旦我们在估计中考虑到遗传变异水平较低的因素，所有四个种群中多父本的水平都很高。在我们有最大能力检测多次交配的种群中，我们发现 H. formosa 中的多父本通常涉及同一窝内的多个亲代为后代做出贡献，而不是不同的父亲为不同的同时提供营养的窝做出贡献。亲代往往偏向于一个亲代。我们的研究结果表明，H. formosa 种群在多父本水平上的差异不足以解释先前研究中观察到的生殖隔离。我们认为，其他影响母体-胎儿冲突的因素可能会导致先前观察到的生殖隔离模式。或者，先前研究中观察到的不对称生殖隔离可能反映了母体-胎儿共适应的破坏。
