Different environmental conditions may lead to diverse morphological,behavioral,and physio-logical 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,com-prises 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 popula-tions(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.stand-ardized 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 con-ditions 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.