Asymmetrical competition between Neotropical dung beetles and its consequences for assemblage structure |
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Authors: | Finbarr G Horgan René C Fuentes |
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Institution: | Population Ecology Group, Department of Biology, University of New Brunswick, Fredericton, New Brunswick, Canada and;Escuela de Biología, Universidad de El Salvador, San Salvador, El Salvador |
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Abstract: | Abstract. 1. This study combines the results of laboratory experiments using representative assemblage components and pitfall trapping over a large geographical area to examine the hypothesis that ongoing interspecific competition structures Neotropical dung beetle assemblages. 2. From Guatemala to Panama assemblages of large to medium-sized, fast-tunnelling dung beetles include a single large, nocturnal dichotomiine species, Dichotomius annae (Kohlmann & Solís, 1997). In competition experiments, this species out-competed the medium-sized coprine species, Copris lugubris Boheman and Phanaeus demon Laporte-Castelnau, for dung and nesting space, in spite of earlier colonisation by the diurnal species, P. demon . 3. Differences in the abundance of D. annae at Central American sites did not affect total fast-tunnelling dung beetle assemblage richness over the rainy season. However, D. annae rank order was directly related to the probability of interspecific encounters (Hurlbert's Δ 1) among species. These trends were also observed when species lists from published and unpublished studies of other large allopatric dichotomiine species, with a more northerly distribution, were included in the analyses. 4. The results obtained suggest that where large dichotomiine species are abundant, their efficient pre-emption of a considerable proportion of available resources drives all, or most, other fast-tunnelling species to a lower population density, thereby decreasing assemblage diversity. |
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Keywords: | Central America Dichotomius dung beetle assemblages rank order Scarabaeinae |
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