Ecological Interactions of Anolis Cristatellus and Anolis Krugi in Two Secondary Tropical Karst Forests at the Northern Karst Belt of Puerto Rico: Occupancy Estimates and Degree of Omnivory/Frugivory

Abstract

Anolis lizards in the Caribbean islands are a major component of diurnal communities. The natural history of Anolis lizards is well studied, however information about their feeding habits and trophic ecology remains incomplete. Consequently their precise role in ecosystem function and dynamics is poorly understood. In spite of the fact that fruits have been reported on dietary studies, their importance and contribution in the degree of omnivory/frugivory of the lizards is unknown. The purpose of this study was threefold: (1) determine the occurrence and abundance of two sympatric species of the genus Anolis, Anolis cristatellus (Duméril and Bibron) and Anolis krugi (Peters) in mature secondary forests, principal habitat of the region, (2) evaluate their trophic position, and (3) the degree and annual dynamics of omnivory/frugivory of the two species using stable istopes (13C and 15N). The work was carried out at two natural private reserves within the northern karst region of Puerto Rico. Anolis cristatellus and A. krugi occurred sympatrically, however occupancy estimates and abundance differed substantially between species and were influenced primarily by structural features of the habitat. A. cristatellus was the most abundant species at both sites with estimates of occupancy greater than 90%, and positively influence by midstory trees. Occupancy rates for A. krugi were low (55-66%) compared with A. cristatellus, and negatively influenced by richness of saplings at plots but positively influenced by food availability. Isotopic analyses for A. cristatellus and A. krugi revealed that both species have a broad diet with the inclusion of a great diversity of prey and fruits when available. The isotopic composition varies significantly between species. Mean values for trophic position for both species ranged from 2.0 and 3.0, which suggests that they are omnivores. However, fruits seemed to represent an important food xiv resource for A. krugi, which showed the lowest trophic position (2.34). Results from source partition models for both species recognized temporal differences in the contribution of some groups of arthropods. My research contributes to the knowledge of omnivory/frugivory on anoles and lizards in general. It also confirms the importance of microhabitat structure on occurrence of A. cristatellus and A. krugi. These information contributes to the understanding of the functional role of Anolis lizards in the dynamic and structure of food webs and ecosystems of Caribbean forests.