Food habits of Podarcis filfolensis (Reptilia, Lacertidae) on a small Mediterranean island during the dry season

Food habits of Podarcis filfolensis (Reptilia, Lacertidae) on a small Mediterranean island during the dry season Pierluigi Bombi 1 , Leonardo Vignoli 1 , Riccardo Scalera 2 , Marco A. Bologna 1 Small islands are typically characterised by sim- plified ecosystems with low levels of complex- ity and reduced biodiversity. This condition may determine a scarcity of food resources which in turn can affect several aspects of the ecological features of the species, particularly their trophic niche (e.g., Gorman, 1979; Stephen and Krebs, 1986; Pérez-Mellado and Corti, 1993). Predators are extremely sensitive to the com- plexity and structure of their ecosystems, and lacertids, which are characterised by small size and generalist habits, usually get over the poverty of resources by in some cases adding vegetal material in their diet (Ouboter, 1981; Sorci, 1990; Pérez-Mellado and Corti, 1993; Van Damme, 1999). The Podarcis species in- habiting the Mediterranean islands are a quite well studied group concerning adaptation to is- land conditions (e.g., Ouboter, 1981; Valakos, 1987; Pérez-Mellado and Corti, 1993). The rich background on phylogeny (e.g., Lanza and Cei, 1977; Capula, 1990, 1994; Oliverio et al., 1998, 2000; Harris and Arnold, 1999) and autoecol- ogy (e.g., Valakos, 1987; Rugiero, 1994; Sorci, 1990; Pérez-Mellado and Corti, 1993; Bombi and Bologna, 2002) of these lizards has stimu- lated the use of this genus as a model for eco- ethological studies. Moreover, this group in- cludes a high number of very common species 1 - University of “Roma Tre”, Department of Biology, Viale G. Marconi 446, 00146 Rome, Italy e-mail: [email protected] 2 - Via V. Mazzola 38, 00142 Rome, Italy (17 according to Oliverio et al., 2000), dis- tributed on almost every small island of the Mediterranean basin: six Podarcis species are endemic to volcanic and continental Western and Eastern Mediterranean archipelagos (Oliv- erio et al., 2000); some other species are dis- tributed on mainland areas and on the adjacent islands. One of the less frequently studied species of this genus is Podarcis filfolensis (Bedriaga, 1876), endemic to the Maltese Archipelago and to the Linosa Island and the Lampione Islet (Pelagie Islands) (Lanza, 1973; Turrisi and Vac- caro, 1998; Corti and Lo Cascio, 1999). The only ecological researches carried out on this species concern the trophic habits (Sorci, 1990) and the population structure (Di Palma, 1991; Scalera et al., 2004). The aim of this paper is to describe the food habits of P. filfolensis during the dry season, the hardest period in the Mediterranean Basin. Linosa Island (Agrigento Province) is situated in the Mediterranean Sea, about 150 km SW from Sicily, and 140 km E from Tunisia (between 35 ◦ 51 ′ 07 ′′ N and 35 ◦ 52 ′ 34 ′′ N, and 12 ◦ 50 ′ 43 ′′ E and 12 ◦ 52 ′ 34 ′′ E). From a ge- ological point of view, it is a volcanic island, with a basaltic belt and inner tuffaceous formations (Agnesi and Federico, 1995). The climate is semi-arid (cfr. Agnesi and Federico, 1995 for a review), the vegetation is characterised by xe- rophilic Mediterranean maquis (Brullo and Piccione, 1985) and the main cultivations include vineyards, Indian figs, ce- reals and lentils. Field research was carried out in the second week of June 2000. Captures were made in a sampling area of about half a hectare, in the middle of the island, where specimens were captured by hand, noosed, or by pitfall traps (filled with a small quantity of water to attract them). Ten pitfall traps (cylindrical polyethylene containers, 8.7 cm wide and © Koninklijke Brill NV, Leiden, 2005. Amphibia-Reptilia 26 (2005): 412-417 Also available online - www.brill.nl