Interpopulational variation in sexual signals may lead to premating reproductive isolation and speciation. Genetic and morphological studies suggest that the Iberian wall lizard, Podarcis hispanica, forms part of a “species complex” with several cryptic species. We explored the role of chemical sexual signals in interpopulational recognition between five distinct populations of Iberian wall lizards in Central Spain. Results showed that these populations differed in morphology and in composition and proportion of chemical compounds in femoral gland secretions of males. Tongue-flick experiments indicated that male and female lizards discriminated and were more interested in scents of lizards from their own area (i.e., Northern versus Southern populations), but did not discriminate between all populations. Moreover, only males from the populations that are geographically located more far away preferred scent of females from their own population. These data suggest that, at least between some populations, there may be reproductive isolation mediated by chemical signals and cryptic speciation. 1. Introduction Interpopulational variation in sexual chemical signals may provide the basis for premating reproductive isolation and speciation in many animals [1, 2]. Phenotypic plasticity in sexual signals could play a key role in initial signal divergence [3], for example, as a way to maximize the efficiency of signals for communication in different environments [4, 5]. These differences can be later amplified by sexual selection leading to differences in mating preferences [6–8], which could preclude mating between populations (e.g., [9–13]), and lead to speciation processes. In many lizards, intraspecific communication and sexual selection are based on chemical signals secreted by specific glands [14–17]. For example, chemical compounds secreted by femoral gland of males can convey information about social status [18–22] and genetic quality of a male [23–26]. Also, differences in chemical signals may preclude interspecific mating between related sympatric species (e.g., [27, 28]). We hypothesized that interpopulational variations in femoral gland secretions within the same species might lead to reproductive isolation and thus promote speciation processes. The Iberian wall lizard, Podarcis hispanica, is a small diurnal lizard, living in rocky habitats of the Iberian Peninsula. Molecular and morphological studies suggest that this lizard is paraphyletic and forms part of a “species complex,” which suggests the existence of cryptic speciation within taxa previously
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