Behavioural adaptations to zonal maintenance of five species of tenebrionids living along a Tyrrhenian sandy shore

Abstract

The spatial distribution of the following five nocturnal tenebrionid species was studied along a beach dune system: Phaleria provincialis Fauvel, Phaleria bimaculata Linnaeus, Halammobia pellucida Herbst, Xanthomus pallidus Curtis and Xanthomus pellucidus Mulsant. An integrated system of traps was used to sample the beetles during their active and resting phases. Environmental parameters were recorded locally during the experiments. Preference experiments were performed under controlled laboratory conditions. The aim of the study was to understand the environmental constraints influencing the species' spatial distribution and the mechanisms involved in zonal maintenance. The results indicate that beetles exploit chemical and physical gradients of the beach dune system; and the mechanisms used for zonal recovery and/or maintenance are based on behavioural responses to visual and environmental stimuli. Controlled laboratory experiments showed that sand salinity was a limiting factor for all five species. For the two Phaleria species, which had a relatively seaward distribution, sand moistures were also important. In contrast, for the two Xanthomus species, which were distributed more landwards, grain size was a regulating factor. In the present study gradients in beetle responses to different environmental factors were observed.