Spatial and temporal strategies in relation to environmental constraints of four tenebrionids inhabiting a Mediterranean coastal dune system

The activity rhythms and zonation of four tenebrionid beetles were studied along a transect ranging from the high eulittoral to the retrodunal area of the Burano Lagoon (Grosseto, Italy). Environmental parameters were registered in order to understand their correlation with surface activity. For each species, population size estimates were carried out in different months by a mark-recapture method. Under laboratory conditions activity patterns were tested at different temperatures with an aktograph apparatus and preferences for temperature and humidity of the substrate were also analysed. The results indicate that Erodius siculus was the most thermophilic species whereas Scaurus striatus was the least. Activity rhythms varied according to the species and there was a shift from unimodal to bimodal activity as the temperature rose or as the season changed. The study indicates that different behavioural strategies compensate endogenous needs and enable sympatric species to share the same habitat through zonal partitioning and differences in the time of activity. (C) 1997 Academic Press Limited.