Slaughter Christin, McCartney Michael A, Yund Philip O
Department of Biological Sciences, Center for Marine Science, University of North Carolina at Wilmington, 5600 Marvin Moss Lane, Wilmington, North Carolina 28409, USA.
Biol Bull. 2008 Feb;214(1):57-66. doi: 10.2307/25066660.
Recent demonstrations of positive selection on genes controlling gamete compatibility have resulted in a proliferation of hypotheses concerning the sources of selection. We tested a prediction of one prominent hypothesis, selection to avoid hybridization (i.e., reinforcement), by comparing heterospecific gamete compatibility in two Mytilus edulis populations: one population in Cobscook Bay, Maine, in which the close congener, M. trossulus, is abundant (a region of sympatry), and one population in Kittery, Maine, in which M. trossulus is absent (a region of allopatry). Three diagnostic nuclear DNA markers were used to identify mussels to species and to estimate the frequency of both species and their hybrids in the two populations. Controlled crosses were then conducted by combining eggs of M. edulis females with a range of M.edulis and M. trossulus sperm concentrations. Results were not consistent with the reinforcement hypothesis. M. edulis females collected from the region of sympatry were no more incompatible with M. trossulus males than were M. edulis females collected from the region of allopatry. A trend in the opposite direction, toward greater compatibility in sympatry, suggests that introgression of M. trossulus genes that control egg compatibility, such as those encoding receptors for sperm, may influence evolution of gametic isolation in hybridizing populations.
最近对控制配子兼容性的基因进行正向选择的研究表明，关于选择来源的假设大量涌现。我们通过比较两个紫贻贝种群的异种配子兼容性，检验了一个突出假设（即选择以避免杂交，也就是强化）的预测：一个种群位于缅因州的科布斯科克湾，那里近缘种横带贻贝数量众多（同域分布区域）；另一个种群位于缅因州的基特里，那里没有横带贻贝（异域分布区域）。使用三个诊断性核DNA标记来鉴定贻贝的物种，并估计两个种群中两个物种及其杂种的频率。然后通过将紫贻贝雌体的卵子与一系列紫贻贝和横带贻贝精子浓度相结合进行控制性杂交。结果与强化假设不一致。从同域分布区域采集的紫贻贝雌体与横带贻贝雄体的不兼容性并不比从异域分布区域采集的紫贻贝雌体更高。相反的趋势，即同域分布中兼容性更高，表明控制卵子兼容性的横带贻贝基因（如编码精子受体的基因）的渐渗可能影响杂交种群中配子隔离的进化。
