Resources exploitation by ants facilitates lizard egg survival

Abstract.  1.  This study investigated the interaction between eggs of the lizard Mabuya longicaudata Hallowell and two species of ant: a lizard egg commensalist ( Paratrechina longicornis Latreille), and an egg predator ( Pheidole taivanensis Forel). The ecological interaction between P. longicornis and lizard eggs was tested, and it was predicted that when the interaction was removed, lizard eggs would be attacked by P. taivanensis .
2. Field observations showed that both ant species actively searched for lizard eggs, and that P. taivanensis typically found new lizard nests earlier than P. longicornis did. Left undisturbed, P. taivanensis predation dramatically reduced lizard egg survival. While P. longicornis usually found nests later, they were able to displace P. taivanensis . As a result, proportional egg survival was higher in nests with P. longicornis (0.95 ± 0.04 eggs) compared to nests without either ant species (0.65 ± 0.09 eggs), or nests occupied by P. taivanensis (0.07 ± 0.02 eggs).
3. When P. longicornis ants were experimentally excluded from lizard nests, the proportion of eggs surviving significantly decreased because of increased P. taivanensis predation. Paratrechina longicornis benefits from water that condenses on the eggs. When this resource disappears P. longicornis abandons the nest, leading to predation of the eggs by P. taivanensis .