Geographic variation in male mate choice in a gynogenetic species complex: evaluating long-term data across mating contexts

Aim: To consider how geographic variation in species recognition over time affects the speciation process. Organisms: The gynogenetic livebearing fish Poecilia formosa (Amazon molly) is the hybrid offspring of two bisexual parent species, P. latipinna (sailfin molly) and P. mexicana (Atlantic molly). The Amazon molly is an all-female species that must mate with males of their parent species. But the males of the parent species gain no genetic benefit from these matings, so the Amazon mollies are sexual parasites. Poecilia latipinna males prefer to mate with conspecific females in most sympatric populations but show varying levels of mating mistakes across their broad geographic distribution. Questions: How do reproductive isolation barriers change over time and across populations of the parent species that have been allopatric to, or sympatric with, gynogens for varying amounts of time? Why do some individual populations show consistent species recognition while others do not? Methods: We reviewed the literature and summarized the data from populations for which species recognition had been examined multiple times. We also used our 15-year long data set. We examined variation in species recognition by mollies both temporally (on an evolutionary time scale) and geographically. Conclusions: Species recognition by male sailfin mollies was more consistent in allopatric and early sympatric conditions compared with male sailfin mollies in populations that have existed longer in sympatry with Amazon mollies. However, sailfin molly populations that have co-existed for longer do have more isolation barriers to mating.