DIFFERENTIAL SPECIES RECOGNITION ABILITIES OF MALES AND FEMALES IN A FLYCATCHER HYBRID ZONE

When mating between members of differentiated populations results in t he production of unfit hybrids, selection may favour mechanisms that r educe the probability of interbreeding. One such mechanism is a mate p reference for own type. Hybridisation between sympatric Pied Flycatche rs Ficedula hypoleuca and Collared Flycatchers Ficedula albicollis, oc curs less frequently than expected from random mating and hybrids have very low fertility. In two aviary experiments we tested the hypothesi s that males and females prefer to mate conspecifically. First, female s had a simultaneous choice between one male of each species. The fema le showed the strongest sexual response to the conspecific male. Secon d, males had a simultaneous choice between a conspecific and a heteros pecific female. The males showed no preference for conspecific or hete rospecific female flycatchers. We discuss possible factors behind this sexual difference in species recognition.