Ecomorphological structure of an Amozonian phyllostomid bat assemblage

Date
2008-05
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Abstract

Morphologically similar species likely consume similar resources and thus engage in competitive interactions. Competitive exclusion arises if a superior species causes on the inferior species to become locally extinct. Alternatively, the populations may diverge in morphology and resource use, thus reducing competition and allowing coexistence. If competition is not intense enough to produce such patterns, it may nonetheless, have an effect on the population sizes of competitors by a mechanism known as density compensation. This deterministic mechanism should be expressed as a positive association between abundance and ecomorphological dissimilarity.
Bats are ideal organisms with which to test hypotheses related to coexistence, especially in the Neotropics, where they reach their highest levels of taxonomic and functional diversity. In terms of species richness and abundance, the ensemble of frugivorous species is most dominant in those Neotropical assemblages. Herein, I use simulation models to evaluate the presence of interspecific competition, expressed as density compensation, in structuring the frugivore ensemble of the Iquitos bat assemblage in three habitats that differ in degree of modification. In each habitat, analyses were conducted with respect to four different scenarios based on proximity of morphological neighbors. In each scenario, parametric and non-parametric analyses were conducted, using multivariate and univariate metrics. Evidence of density compensation was weak in primary and mixed forest, and nonexistent in secondary forest. As such, interspecific competition may not be the main factor structuring the ensemble of frugivorous bats in Iquitos. A state of non-equilibrium produced by deforestation, a combination of mechanisms that operate at local and regional scales such as source-sink dynamics, or particular characteristics of the natural history of the bat species are possible factors that might account for the absence of evidence for strong deterministic mechanisms.

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Keywords
Bats, Assemblage, Density compensation, Competition
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