Cruz R, Carballo M, Conde-Padín P, Rolán-Alvarez E
Departamento de Biología Fundamental, Facultad de Biología, Universidad de Santiago de Compostela, Santiago de Compostela, Spain.
J Evol Biol. 2004 Mar;17(2):288-93. doi: 10.1111/j.1420-9101.2003.00689.x.
Two ecotypes of the rough periwinkle Littorina saxatilis occur at different shore levels, showing assortative mating for size and partial reproductive isolation when they meet at the mid-shore. This system represents a putative case of incomplete speciation in sympatry. Two processes contribute to the assortative mating: morph-specific microhabitat aggregation and mate choice. The estimation of mate choice coefficients in nature and a simulation of the aggregation effects on sexual isolation were used to disentangle these processes as well as to test alternative mechanisms of mate choice. Mate choice significantly increased the frequency of within-morph pairs and significantly decreased the frequency of between-morph pairs, whereas those pairs including at least one hybrid morph mated randomly. These results allow us to reject a discriminant mate choice and support a model of evolution of sexual isolation as a side-effect of size-assortative mating in a context of divergent natural selection for size in the population. This mechanism is more compatible with a model of incomplete by-product ecological speciation, as suggested by previous evidence.
粗糙滨螺（Littorina saxatilis）的两种生态型出现在不同的海岸高度，在中海岸相遇时表现出对体型的选型交配和部分生殖隔离。这个系统代表了同域中不完全物种形成的一个假定案例。有两个过程促成了选型交配：形态特异性微生境聚集和配偶选择。通过估计自然环境中的配偶选择系数以及模拟聚集对性隔离的影响，来剖析这些过程，并测试配偶选择的其他机制。配偶选择显著增加了同形态配对的频率，显著降低了不同形态配对的频率，而那些至少包含一个杂交形态的配对则随机交配。这些结果使我们能够否定判别式配偶选择，并支持性隔离进化模型，即在种群中对体型进行趋异自然选择的背景下，性隔离是体型选型交配的一个副作用。如先前证据所示，这种机制与不完全附带生态物种形成模型更为契合。
