Do natural differences in acoustic signals really interfere in conspecific recognition in the pan-Amazonian frog Allobates femoralis ?

Abstract

The call of the pan-Amazonian frog Allobates femoralis shows wide geographical variation, and males show a stereotyped and conspicuous phonotactic response to playback of conspecific calls. We evaluated the capacity of males of A. femoralis and a closely related species A. hodli to respond aggressively to natural conspecific and heterospecific calls varying in number of notes, by means of field playback experiments performed at two sites in the Brazilian Amazon. The first site, Cachoeira do Jirau (Porto Velho, Rondonia), is a parapatric contact zone between A. femoralis that use 4-note calls, and A. hodli with 2-note calls, where we performed cross-playbacks in both focal populations. The second site, the Reserva Florestal Adolpho Ducke (Manaus, Amazonas), contained only A. femoralis with 4-note calls. There, we broadcast natural stimuli of 2-note A. hodli, 3-note and 4-note A. femoralis, and 6-note A. myersi. We found that the phonotactic behaviour of A. femoralis and A. hodli males did not differ toward conspecific and heterospecific stimuli, even in parapatry. Our results indicated that the evolutionary rates of call design and call perception are different, because the geographical variation in calls was not accompanied by variation in the males' aggressive behaviour.