REGIONAL DISTRIBUTION OF A MEDITERRANEAN LIZARD - INFLUENCE OF HABITAT CUES AND PREY ABUNDANCE

We studied the distribution of a common Mediterranean lacertid lizard, Psammodromus algirus (L.) 1758, on nineteen sites within a regional gradient of homogeneous yet contrasted habitats. This scale was large enough to allow line-transect estimates of lizard abundance, which were related to quantitative (and when possible multivariate) measurements of the structure and floristic composition of vegetation, the abundance of arthropod prey, the relative density of other lizard species, and the climatic data obtained from nearby meteorological stations. Neither the climate not the abundance of other lizards seemed to condition the quantitative distribution of the species. The positive influence of broad-leaved forests on the abundance of P. algirus appeared to be a consequence of structure attributes more directly related to the ecology of lizards than floristic composition per se. Thus, population levels were most highly correlated with the cover of shrubs over 20 cm in height, and once this structural requirement was met, they increased with the abundance of potential prey (itself conditioned by vegetation cover at the ground level and litter cover). We suggest that our results should be interpreted in the context of thermoregulatory, predator avoidance and movement minimization strategies whose influence on survival, and hence abundance, could probably be applied to other insectivorous lizards from temperate zones.