FRUGIVORY AND SEED DISPERSAL BY THE LIZARD GALLOTIA-GALLOTI (LACERTIDAE) IN A XERIC HABITAT OF THE CANARY-ISLANDS

The relationship between an endemic lizard (Gallotia galloti) and plan ts with fleshy fruits was examined in a xeric habitat on the island of Tenerife, Canary Islands. An analysis of 441 droppings collected in M ay 1991, showed that fruits are an important item in the diet of this omnivorous lizard; 92% and 56% of droppings contained fruits from two different areas. Fruits of seven plant species were found in the dropp ings: Rubia fruticosa, Neochamaelea pulverulenta, Withania aristata, L ycium intricatum, Atriplex semibaccata, Opuntia dillenii and Scilla cf . haemorrhoidalis. The number of fruit species consumed at each area b y G. galloti was related to their availability. Seed Viability did not differ between control seeds and seeds from the droppings, except for N. pulverulenta and L. intricatum, where viability was higher in cont rol seeds. The gut passage of seeds significantly reduced the germinat ion of R. fruticosa and N. pulverulenta, increased that of W aristata while no differences were found for the rest. Gallotia galloti preferr ed rocky and grassy sites with,less open ground and more shrub cover > 50 cm in height). This should produce a non-random seed shadow in the habitats, potentially affecting the distribution of species with flesh y fruits. Omnivorous lizards on islands can act as important seed disp ersers over short distances for plant species with fleshy fruits, acti vely influencing both their relative abundance and vegetation structur e in xeric habitats.