Influence of lighting environment on social preferences in sticklebacks from two different photic habitats.I.mate preferences of wild-caught females

Ultraviolet(UV)A signals(320-400 nm)are important in mate choice in numerous species.The sensitivity for UV signals is not only assumed to be costly,but also expected to be a function of the prevailing ecological conditions.Generally,those signals are favored by selection that efficiently reach the receiver.A decisive factor for color signaling is the lighting environment,especially in aquatic habitats,as the visibility of signals,and thus costs and benefits,are instantaneously influenced by it.Although ecological aspects of color signal evolution are relatively well-studied,there is little data on specific effects of environmental UV-light conditions on signaling at these shorter wavelengths.We studied wild-caught gravid female 3-spined sticklebacks Gasterosteus aculeatus of 2 photic habitat types(tea-stained and clear-water lakes),possessing great variation in their UV transmission.In 2 treatments,tea-stained and clear-water,preferences for males viewed under UV-present(UV-1-)and UV-absent(UV-)conditions were tested.A preference for males under UV+conditions was found for females from both habitat types,thus stressing the significance of UV signals in stickleback's mate choice decisions.However,females from both habitat types showed the most pronounced preferences for males under UV-h conditions under clear-water test conditions.Moreover,reflectance measurements revealed that the carotenoid-based orange-red breeding coloration in wild-caught males of both habitat types differed significantly in color intensity(higher in clear-water males)and hue(more red shifted in clear-water males)while no significant differences in UV coloration were found.The differential reflection patterns in longer wavelengths suggest that sticklebacks of both habitat types have adapted to the respective water conditions.Adaptations of UV signals in a sexual context to ambient light conditions in both behavior and coloration seem less evident.

Influence of lighting environment on social preferences in sticklebacks from two different photic habitats.II.Shoaling and mate preferences of lab-bred fishes

Different environmental conditions may lead to diverse morphological,behavioral,and physiological adaptations of different populations of the same species.Lighting conditions,for example,vary vastly especially between aquatic habitats,and have been shown to elicit adaptations.The availability of short-wave ultraviolet(UV)light is especially fluctuating,as UV wavelengths are attenuated strongly depending on water properties.The island of North Uist,Scotland,comprises 2 differential habitat types,tea-stained and clear-water lakes,varying considerably in UV transmission.In previous studies,wild-caught 3-spined stickleback Gasterosteus aculeatus populations(3 populations of each habitat type)were tested with respect to their shoaling and mate preferences for fish viewed under UV-present and UV-absent conditions.The results revealed a habitat-dependent preference of UV cues during shoal choice(tea-stained populations:preference for UV-absent condition in tea-stained water;clear-water populations:no preference in clear-water)but an overall preference for UV-present conditions during mate choice.To assess genetic influences on these behavioral patterns,similar experiments were conducted with lab-bred F1-gen-erations of the same stickleback populations that were raised in a common environment(i.e.standardized clear-water conditions).Offspring of sticklebacks from tea-stained lakes tended to prefer shoals viewed under UV-absent conditions(only in tea-stained water),while sticklebacks from clear-water lakes showed a significant preference for the shoal viewed under UV-present conditions in clear-water but not in tea-stained water.Mate-preference experiments demonstrated that females from the tea-stained lakes significantly preferred and females from the clear-water lakes preferred by trend the male viewed under UV-present conditions in the clear-water treatment.The results for both shoaling-and mate-preference tests were largely similar for wild-caught and lab-bred sticklebacks,thus hinting at a genetic basis for the preference patterns.