Reinforcement of male mate preferences in sympatric killifish species Lucania goodei and Lucania parva

Reinforcement occurs when reduced hybrid fitness leads to the evolution of a stronger prezygotic isolation. Populations sympatric with closely related species, where hybridization occurs, are predicted to have stronger mate preferences than allopatric populations. The reinforcement of male mate preference is thought to be rarer than the reinforcement of female preference, but this inference may be biased by the lack of studies on male preference. We tested male mate preferences from sympatric and allopatric populations of two closely related species of killifish: Lucania goodei and Lucania parva. We found that sympatric males had greater preferences for conspecific females than allopatric males. Furthermore, conspecific preferences in allopatric populations were weakest when these populations were geographically distant (> 50 km) from those of heterospecifics. Our data suggest that reinforcement has contributed to male conspecific preference and speciation in Lucania.