Evidências de variação interindividual na dieta de Ameivula ocellifera (Squamata: Teiidae) devido a padrões de aninhamento de partição de recursos entre os indivíduos

Abstract

Individual specialization in the diet (ISD) of Ameivula ocellifera (Spix, 1825) was evaluated in three studies in the state of Ceará. In the first, the EID, the patterns of resource use and the topology of the trophic networks of juveniles, males and females were evaluated in a coastal habitat. The degree of variation in the diet of individuals and the degree of nestedness and clustering were assessed using a network-based approach. There was a high level of interindividual variation in the diet of the three groups, which seem to be related to nested patterns of resource use for males and females. The results fits to the Shared Preferences Model, where individuals consume the same optimal prey when food resources are abundant, replacing them by sub-optimal items when those become scarce in the environment. The second study tested MacArthur and Pianka's (1966) prediction that active foragers maintain food habits even when food resources are scarce. The diet of A. ocellifera was evaluated for variations between the dry and rainy periods in two habitats and between the habitats in the two climatic periods. There was seasonal variation in prey abundance in one habitat and in prey volume in the other, in addition to variation in prey abundance consumed between the two areas in the dry period. Ameivula ocellifera acted as a specialist in one habitat and as a generalist in the other, demonstrating that its diet seems to be more related to variation in prey availability. The results support MacArthur and Pianka's (1966) prediction that an exception to their theory could occur in active forager species. In the third study, the diet of A. ocellifera was reanalyzed to test whether previously described resource partition patterns occur in other habitats. ISD, resource use patterns and the topology of trophic networks were assessed using a network-based approach. There was evidence of ISD in both habitats, as well as nested resource use patterns. The level of ISD was higher in the rainy period, while nestedness was higher in the dry period. Most of the results confirm the previous study, in addition to showing that patterns of specialization in the diet and resources use by individuals may vary in different populations of similar habitats, which reinforces the relevance of using networkbased approaches to assess the autoecology of species at the individual level.