Behaviour 2019
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Negative assortative mating and maintenance of shell colour polymorphism in Littorina (Neritrema) species
Juan Gefaell1, Juan Galindo1, Christian Malvido1, Victor Núñez1, Daniel Estévez2, Sofía Blanco1, Miriam González-Conde1, Irene Novo1, Gonzalo Pérez-Fernández1, Ana Rus1, Inés Mosconi1, Sergio Martínez-Domínguez1, Emilio Rolán-Alvarez1. 1Departamento de Bioquímica, Genética e Inmunología and Centro de Investigación Mariña (CIM-UVIGO), Universidade de Vigo, Vigo, , Spain; 2Greenland Institute of Natural Resources, Nuuk, , Greenland

Shell colour polymorphism is a widespread phenomenon among marine gastropods, especially those of the genus Littorina. Among the possible evolutionary mechanisms that could explain the maintenance of shell colour polymorphism is negative frequency-dependent selection (NFDS). In a previous study, it has been shown that colour polymorphism in L. fabalis could be caused by such mechanism, mediated by a process of mate choice. One of the ways in which mate choice is measured in the wild is through assortative mating, which has been theoretically and empirically related to both NFDS and mate choice. In the present paper, we provide new field evidence regarding the existence of a negative assortative mating pattern for shell colour in two more species from the genus LittorinaL. saxatilisL. obtusata, as well as on new populations of L. fabalis, suggesting the existence of an ancestral behavioural mechanism for mate choice and NFDS. However, alternative explanations cannot be definitely ruled out. We discuss the implications of our finding and suggest future ways of experimentally asses the validity of the NFDS hypothesis.