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 plants with fleshy fruits was examined in a xeric habitat on the island of Tenerife, Canary Islands. An analysis of 441 droppings collected in May 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 droppings: Rubia fruticosa, Neochamaelea pulverulenta, Withania aristata, Lycium intricatum, Atriplex semibaccata, Opuntia dillenii and Scilla cf. haemorrhoidalis. The number of fruit species consumed at each area by 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 control seeds. The gut passage of seeds significantly reduced the germination of R. fruticosa and N. pulverulenta, increased that of W aristata while no differences were found for the rest. Gallotia galloti preferred 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 fleshy fruits. Omnivorous lizards on islands can act as important seed dispersers over short distances for plant species with fleshy fruits, actively influencing both their relative abundance and vegetation structure in xeric habitats.