Flightlessness in psammophilous beetles inhabiting a Mediterranean coastal area: ecological and biogeographical implications

Abstract

Biogeographia vol. XXI/I - 2002 (Pubblicato il 1” ottobre 2002) Biogeografia degli ambienti costieri Flightlessness in psarnmophilous beetles inhabiting a Mediterranean coastal area: ecological and biogeographical implications GIUSEPPE M. CARPANETO*, SIMONE FATTORINI** *Dz;z2artimem‘0 a'z' Biologia, Uniz/errita alegli Stadi “Roma Tre’: Vials Marconi 446 — 1300146 Roma (Italy) **Dz']1artz'mmta ali Biologia Animale e dell’Uom0 (Z00[ogia), Universita di Roma qLa Sapienza ”, Vials cle[[’Uaz'ver5z'tz‘z 32 — I—00]85 Roma (Italy) Key words: Coleoptera, aptery, beetle community, sand dunes, Central Italy SUMMARY Many psammophilous beeles are known to be wingless ground dwellers, and flightlessness has been frequently regarded as an adaptation to arid environments. Also, as Hightlessness reduces dispersal ability, flightless species should have reduced ranges compared with those of winged species. The aim of this W0l‘l( was to study (1) the incidence of flightlessness in the psammophilous beetles living in a Mediterranean beach-dune system, and (2) possible relationships between distribution patterns and wing conditions. The study was based on the beetle fauna living on the beach—dune system of the Circeo National Park (Central Italy, Tyrrhenian coast). To obtain a complete faunal inventory of the true psarnmophilic beetles, monthly samplings were performed by sieving a fixed volume of sand and detritus. A total of 26 strictly psammophilous species, belonging to 10 beetle families were recorded. As a whole, 10 species were apterous, 5 brachypterous and 1 1 macropterous. If apterous and brachypterous species are computed together as flightless species, we found a total of 15 flightless species 67.69%) versus 11 macropterous species (42.31%). In accordance with the geographical location of the study area and the thermophilic preferences of many species, most of the species have distribution patterns restricted to Mediterranean or South European areas, only two being more widely distributed. As to the size of their ranges, 12 (-46.15%) species showed restricted distributions (i.e. types of distribution restricted to the western or the eastern sector of the Mediterranean basin), while 14 63.35%) were widely distributed. As a whole, a relationship can be observed between flightlessness and species ranges. Most (83.33%) of the species with reduced ranges are flightless. By contrast, flightless species represent 35.71% of the widely distributed species. A number of factors and circumstances can be evoked to explain the occurrence of flightlessness in the study community. Dune habitats are distributed so that a ground dwelling insect can move from one patch to another by walking and burrowing, a condition that can favour flightlessness. As coastal dunes have scarce trophic sources, loss of flight could allow to conserve energy that can be allocated to other functions. Due to their high winds, coastal dunes require a great amount of energy for flight. Shoreline strands are clearly isolated habitats, with unfriendly and isolating habitats on each side, favouring non—dispersing individuals. Finally, a high incidence of flightlessness in some beetles can be due to their burrowing lifestyle and detritivorous habits. As a whole, flightless species show more restricted ranges compared with winged species. Thus, even if many littoral beetles are known to be capable of swift movement on the ground, Hightlessness probably plays an important role in determining a reduced dispersal ability, which, in turn, affects species distributions.