Comparison of Dietary Overlap between Allopatric and Sympatric Geckos

Two gecko species, Hemidactylus turcicus and Cyrtopodion scabrum, have been introduced into the Port of Galveston, Texas. While H. turcicus has been established for a longer period of time, the relatively recent introduction of C. scabrum near the entrance of the Port has apparently led to the displacement of H. turcicus in that area. This has resulted in a distribution in which the two populations’ are largely allopatric except for a narrow band of sympatry at the periphery of each of their ranges. We examined stomach contents of both species in allopatry and sympatry in order to determine if dietary overlap in sympatry is less than that in allopatry. We calculated Pianka\u27s (1973) symmetric overlap for geckos occupying sympatric areas (0.55) and allopatric areas (0.81). We found significant differences between the resource utilization distributions of the two species in sympatry but not in allopatry. In addition, we compared overlap between allopatric and sympatric populations within each species and found that the differences in resource utilization between the two species in sympatry was due to a dietary shift exhibited in H. turcicus but not C. scabrum. Observed differences in resource utilization may be a response to competition between these two species in sympatry which may have led to the exclusion of H. turcicus on areas of the docks occupied by this species prior to the introduction of C. scabrum

Coqui frog populations are negatively affected by canopy opening but not detritus deposition following an experimental hurricane in a tropical rainforest

Hurricanes, cyclones, and typhoons are common disturbances in many island and coastal forests. There is a lack of understanding of the importance to forest biota of the two major physical aspects that occur simultaneously during a hurricane: canopy disturbance and detritus (debris) deposition onto the ground. Using a replicated factorial design, our study involved experimentally determining the independent and interactive effects of canopy opening and debris additions to the forest floor on densities of coqui frogs (Eleutherodactylus coqui). Coquies are the dominant amphibian, and second most common vertebrate species, in the Luquillo Experimental Forest (LEF), a montane, tropical rainforest in northeastern Puerto Rico that frequently experiences hurricanes. Frogs were sampled in all twelve 30 x 30 m plots at three periods prior to installing treatments (July 2003, January 2004, July 2004), and at months 1, 3, 6, and 12 post-treatment. The degree of canopy opening and amount of debris deposited onto the forest floor by our experimental treatments closely mimicked conditions resulting from Hurricane Hugo, a severe hurricane that passed over the LEF in 1989. Based on findings from past studies involving natural hurricanes in the LEF, we predicted that coqui densities would increase in response to debris additions, and decrease or remain unchanged in response to canopy disturbance. However, we found that debris deposition had no significant effect on coqui density and that the opening of the canopy was the dominant aspect affecting coqui by significantly reducing their densities. We identified several possible explanations for the decreased coqui densities in open-canopy plots, including decreased litter moisture and insect prey, and temporal and spatial scales associated with disturbance that may have influenced coqui behavior. Following natural hurricanes, and in light of our findings from experimental hurricane impacts, we expect that coquies benefit from patches of intact canopy while suffering reduced densities in opencanopy settings. Furthermore, based on our study and other experimental forest studies involving frogs, future forest practices that remove significant canopy should probably be viewed as having an initially (up to 1 year) negative effect on the frog community

Geographic and Ecological Setting of the Luquillo Mountains

This chapter describes the geologic, geographic, and ecological context of the location of Luquillo Mountains, particularly the factors affecting the response mechanisms of terrestrial and aquatic ecosystems to disturbance. It describes the existing conditions of the physical environment, chemical environment, and the biota of the Luquillo Mountains as they respond to disturbances. It then merges the decade-long research about the Mountains with the other tropical ecosystems around the globe

Geographic and Ecological Setting of the Luquillo Mountains

This chapter describes the geologic, geographic, and ecological context of the location of Luquillo Mountains, particularly the factors affecting the response mechanisms of terrestrial and aquatic ecosystems to disturbance. It describes the existing conditions of the physical environment, chemical environment, and the biota of the Luquillo Mountains as they respond to disturbances. It then merges the decade-long research about the Mountains with the other tropical ecosystems around the globe

Geographic and ecological setting of the Luquillo Mountains

This chapter describes the geologic, geographic, and ecological context of the location of Luquillo Mountains, particularly the factors affecting the response mechanisms of terrestrial and aquatic ecosystems to disturbance. It describes the existing conditions of the physical environment, chemical environment, and the biota of the Luquillo Mountains as they respond to disturbances. It then merges the decade-long research about the Mountains with the other tropical ecosystems around the globe