Sexual isolation between two newt species, Triturus vulgaris and T-montandoni (Amphibia, Urodela, Salamandridae)

In the present study we investigated sexual isolation between Triturus vulg aris and T. montandoni in mating experiments run under semi-natural conditi ons. The two newt species offer a suitable model for studying evolution of reproductive isolation and mating preferences because they are genetically the most similar species within the genus and readily hybridize in nature. Separate experiments were conducted in which groups of virgin females were placed together (in artificial pools) with groups of homospecific, heterosp ecific or both types of males. The estimates of reproductive isolation and mating propensity were based on the numbers of females producing hybrids an d/or non-hybrid progeny. The levels of reproductive isolation, isolation as ymmetry (IA) and propensity asymmetry (Ph) were significant only for experi ments in which females were given a choice between conspecific and heterosp ecific males. This implies that mating experiments with no interspecific ch oice may reduce discrimination and affect patterns of IA and PA. Asymmetry reproductive isolation was also significant when the analysis Tvas confined to just inseminated females. Differences in habitat preferences and condit ion of females possibly contributed to the relatively high values of PA. (C ) 1999 The Linnean Society of London.