干旱区生态环境知识资源中心

In the past few years several studies have been conducted on the eco-ethology of different populations of Eurynebria complanata (Linnaeus, 1767) living along the Atlantic shores of France and on the Tyrrhenian sandy beaches of Italy. It was demonstrated that Mediterranean populations differed from Atlantic ones in their life cycles as they presented summer aestivation and shorter pre-imaginal phases. Moreover, differences in morphology were found between the two populations and these were related to differences in life cycles and to different adaptations due to climatic conditions. The aim of present study was to analyse the surface activity of E. complanata in relation to the most important environmental factors in order to understand which ecological constraints influence the behavioural adaptations of Atlantic and Mediterranean populations. Being a strictly nocturnal species, both in France and in Italy, night surveys were carried out on the field. Standard trapping methods (directional pitfall traps) were used. Simultaneously, environmental factors (air temperature, relative humidity, pressure, wind speed and direction, sand temperature and moisture, tidal level, light intensity) and prey presence (Talitrus saltator) were registered each hour. Zonation patterns and migrations perpendicular to the shoreline to and from the trophic zone were analysed both in daily and tidal hours. Movements parallel to the shoreline were also recorded. Mean hour of activity, hourly mean zonations and orientation indexes were calculated. To study the correlations between surface activity, hourly mean zonations and the different environmental factors multiple regression analysis was employed. The results indicate that both populations present daily variations in their activity patterns related to changes in the microclimatic conditions and to other environmental factors such as prey activity and tidal level. For the Italian population variations in the mean zonation of the beetle's activity showed a more seaward zonation at the beginning of the period of activity and a more landward one at the end of such period. For the French population different results were obtained according to the synodic phases and seasons of the year. Furthermore in this species diet rhythms were predominant over tidal ones. The results indicate that E. complanata is a highly specialized beetle and presents a great plasticity in its behavioural adaptations.