Dieta ry patte rns and overlap in an amphibian assemblage at a pond in Mediterranean Central Italy

The trophic niche characteristics of an amphibian assemblage were studied at a pond locality in Canale Monterano, province of Roma, Central Italy. The assemblage consisted of six species, four anurans (Bufo bufo, Hyla intermedia, Rana dalmatina, Pelophylax skl. esculentus), and two salamanders (Triturus carnifex, Triturus vulgaris). Food contents were obtained by stomach flushing. Stomach vacuity index varied substantially among species, and the species spending longer timespan within the reproductive site were also those with lower vacuity index values. Correspondence analysis discriminated two groups of species: one feeding mainly on terrestrial prey and the other on aquatic prey. Pseudo-community analysis revealed that the terrestrial guild of species was non-randomly structured when analysed by RA2 algorithm for volume of prey but neither for number of prey, nor for both number and volume of prey analysed by RA3. The aquatic subset of species appeared to be randomly assembled according to both RA2 and RA3 algorithms, either for number or for volume of prey. These results indicate that for terrestrial species, micro-habitat resource partitioning and body size discrepancy among species could be the factors influencing dietary patterns and facilitating species coexistence, whereas for aquatic species the observed high overlap in diet spectrum is mainly due to both generalist feeding habits of newts and the superabundance of food resources occurring at the study pond.