Female preferences all treatments

Female preference scores for each wing patch size

Interspecific interactions and learning variability jointly drive geographic differences in mate preferences

Co-occurrence of closely related species can cause behavioral interference in mating and increase hybridization risk. Theoretically, this could lead to the evolution of more species-specific mate preferences and sexual signaling traits. Alternatively, females can learn to reject heterospecific males, to avoid male sexual interference from closely related species. Such learned mate discrimination could also affect conspecific mate preferences if females generalize from between species differences to prefer more species-specific mating signals. Female damselflies of the banded demoiselle (Calopteryx splendens) learn to reject heterospecific males of the beautiful demoiselle (C. virgo) through direct premating interactions. These two species co-occur in a geographic mosaic of sympatric and microallopatric populations. Whereas C. virgo males have fully melanized wings, male C. splendens wings are partly melanized. We show that C. splendens females in sympatry with C. virgo prefer smaller male wing patches in conspecific males after learning to reject heterospecific males. In contrast, allopatric C. splendens females with experimentally induced experience with C. virgo males did not discriminate against larger male wing patches. Wing patch size might indicate conspecific male quality in allopatry. Co-occurrence with C. virgo therefore causes females to prefer conspecific male traits that are more species specific, contributing to population divergence and geographic variation in female mate preferences

Data from: Interspecific interactions and learning variability jointly drive geographic differences in mate preferences

Co-occurrence of closely related species can cause behavioral interference in mating and increase hybridization risk. Theoretically, this could lead to the evolution of more species-specific mate preferences and sexual signaling traits. Alternatively, females can learn to reject heterospecific males, to avoid male sexual interference from closely related species. Such learned mate discrimination could also affect conspecific mate preferences if females generalize from between species differences to prefer more species-specific mating signals. Female damselflies of the banded demoiselle (Calopteryx splendens) learn to reject heterospecific males of the beautiful demoiselle (C. virgo) through direct premating interactions. These two species co-occur in a geographic mosaic of sympatric and microallopatric populations. Whereas C. virgo males have fully melanized wings, male C. splendens wings are partly melanized. We show that C. splendens females in sympatry with C. virgo prefer smaller male wing patches in conspecific males after learning to reject heterospecific males. In contrast, allopatric C. splendens females with experimentally induced experience with C. virgo males did not discriminate against larger male wing patches. Wing patch size might indicate conspecific male quality in allopatry. Co-occurrence with C. virgo therefore causes females to prefer conspecific male traits that are more species specific, contributing to population divergence and geographic variation in female mate preferences

Early learning influences species assortative mating preferences in Lake Victoria cichlid fish

The Lake Victoria ‘species flock’ of cichlids is puzzling because reproductive isolation often occurs in the absence of substantial ecological differences among species. Theory predicts that this cannot evolve with most genetic mechanisms for mate choice. We provide the first evidence that learning, in the form of sexual imprinting, helps maintain reproductive isolation among closely related cichlid species. Using a cross-fostering experiment, we show that young females develop a sexual preference for males of their foster mothers' species, even reversing species assortative mating preferences. We suggest that learning creates favourable conditions for reproductive isolation to evolve

Behaviour during experimental exposures

The behaviour of both females and males during the exposure treatment

Data from: Sex differences in developmental plasticity and canalization shape population divergence in mate preferences

Sexual selection of high-quality mates can conflict with species recognition if traits that govern intraspecific mate preferences also influence interspecific recognition. This conflict might be resolved by developmental plasticity and learned mate preferences, which could drive preference divergence in populations that differ in local species composition. We integrate field and laboratory experiments on two calopterygid damselfly species with population genetic data to investigate how sex differences in developmental plasticity affect population divergence in the face of gene flow. Whereas male species recognition is fixed at emergence, females instead learn to recognize heterospecifics. Females are therefore more plastic in their mate preferences than males. We suggest that this results from sex differences in the balance between sexual selection for high-quality mates and selection for species recognition. As a result of these sex differences, females develop more pronounced population divergence in their mate preferences compared with males. Local ecological community context and presence of heterospecifics in combination with sex differences in plasticity and canalization therefore shape population divergence in mate preferences. As ongoing environmental change and habitat fragmentation bring formerly allopatric species into secondary contact, developmental plasticity of mate preferences in either or both sexes might facilitate coexistence and prevent local species extinction

Data from: Sex differences in developmental plasticity and canalization shape population divergence in mate preferences

Sexual selection of high-quality mates can conflict with species recognition if traits that govern intraspecific mate preferences also influence interspecific recognition. This conflict might be resolved by developmental plasticity and learned mate preferences, which could drive preference divergence in populations that differ in local species composition. We integrate field and laboratory experiments on two calopterygid damselfly species with population genetic data to investigate how sex differences in developmental plasticity affect population divergence in the face of gene flow. Whereas male species recognition is fixed at emergence, females instead learn to recognize heterospecifics. Females are therefore more plastic in their mate preferences than males. We suggest that this results from sex differences in the balance between sexual selection for high-quality mates and selection for species recognition. As a result of these sex differences, females develop more pronounced population divergence in their mate preferences compared with males. Local ecological community context and presence of heterospecifics in combination with sex differences in plasticity and canalization therefore shape population divergence in mate preferences. As ongoing environmental change and habitat fragmentation bring formerly allopatric species into secondary contact, developmental plasticity of mate preferences in either or both sexes might facilitate coexistence and prevent local species extinction

Male Drosophila melanogaster learn to prefer an arbitrary trait associated with female mating status

Although males are generally less discriminating than females when it comes to choosing a mate, they still benefit from distinguishing between mates that are receptive to courtship and those that are not, in order to avoid wasting time and energy. It is known that males of Drosophila melanogaster are able to learn to associate olfactory and gustatory cues with female receptivity, but the role of more arbitrary, visual cues in mate choice learning has been overlooked to date in this species. We therefore carried out a series of experiments to determine: 1) whether males had a baseline preference for female eye color (red versus brown), 2) if males could learn to associate an eye color cue with female receptivity, and 3) whether this association disappeared when the males were unable to use this visual cue in the dark. We found that naive males had no baseline preference for females of either eye color, but that males which were trained with sexually receptive females of a given eye color showed a preference for that color during a standard binary choice experiment. The learned cue was indeed likely to be truly visual, since the preference disappeared when the binary choice phase of the experiment was carried out in darkness. This is, to our knowledge 1) the first evidence that male D. melanogaster can use more arbitrary cues and 2) the first evidence that males use visual cues during mate choice learning. Our findings suggest that that D. melanogaster has untapped potential as a model system for mate choice learning

Divergent hormonal responses to social competition in closely related species of haplochromine cichlid fish

The diverse cichlid species flocks of the East African lakes provide a classical example of adaptive radiation. Territorial aggression is thought to influence the evolution of phenotypic diversity in this system. Most vertebrates mount hormonal (androgen, glucocorticoid) responses to a territorial challenge. These hormones, in turn, influence behavior and multiple aspects of physiology and morphology. Examining variation in competition-induced hormone secretion patterns is thus fundamental to an understanding of the mechanisms of phenotypic diversification. We test here the hypothesis that diversification in male aggression has been accompanied by differentiation in steroid hormone levels. We studied two pairs of sibling species from Lake Victoria belonging to the genera Pundamilia and Mbipia. The two genera are ecologically differentiated, while sibling species pairs differ mainly in male color patterns. We found that aggression directed toward conspecific males varied between species and across genera: Pundamilia nyererei males were more aggressive than Pundamilia pundamilia males, and Mbipia mbipi males were more aggressive than Mbipia lutea males. Males of both genera exhibited comparable attack rates during acute exposure to a novel conspecific intruder, while Mbipia males were more aggressive than Pundamilia males during continuous exposure to a conspecific rival, consistent with the genus difference in feeding ecology. Variation in aggressiveness between genera, but not between sibling species, was reflected in androgen levels. We further found that M. mbipi displayed lower levels of cortisol than M. lutea. Our results suggest that concerted divergence in hormones and behavior might play an important role in the rapid speciation of cichlid fishes.