Male vocalization and female choice in the hybridogenetic Rana lessonae/Rana esculenta complex

In many species, females can improve their fitness by preferring particular males over others. In Palaearctic water frogs of the Rana lessonae/R. escu lenta complex the consequences of such mate choice are particularly pronoun ced. To produce viable offspring, the hybrid R. esculenta (genotype RL) mus t mate with the parental species R. lessonae (LL); but R. lessonae should a void mating with R. esculenta, because the resulting hybrid offspring will eliminate the L genome from the germline (hybridogenesis). Hence, there exi sts a conflict between the sexual parasite (RL) and its sexual host (LL) ov er the best mating partner. Previous studies have shown a preference for LL males in LL and RL females; but they have also shown that females cannot u sually realize their choice when in close proximity to males, because the m ales forcefully and indiscriminately amplex them. We tested whether females use male vocalizations as a long-distance signal to increase their chances of mating with the preferred LL males. We exposed female R. lessonae and R . esculenta to playbacks of single LL and RL mating calls (experiment 1) an d to choruses with a 3:1 excess of LL and RI, calls, respectively (experime nt 2). In experiment 1, both female types were attracted more by the LL tha n by the RL calls. In experiment 2, no discrimination between LL- and RL-do minated choruses was observed. The results suggest that females do not use distant male vocalization to approach preferentially ponds or arenas within a pond that hold an excess of LL males. But once they have arrived in a ch orus, mating calls from nearby males can direct them to the preferred LL ma tes. We discuss possible reasons for the failure to discriminate between ch oruses and the chances for successful choice between individuals within cho ruses. (C) 2000 The Association for the Study of Animal Behaviour.