Asymmetrical competition between Neotropical dung beetles and its consequences for assemblage structure

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 Δ1) 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 These trends were also observed when species lists from published and unpublished studies of other large allopatric dichotomiine species, with a more northerly distribution, were included in the analyses.4.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.

Effects of grazing intensity and the use of veterinary medical products on dung beetle biodiversity in the sub-mountainous landscape of Central Italy

“…Both species may alter the diversity pattern of this treatment by means of a competitive exclusion (Hardin, 1960). The low quantity of the trophic resource available in this site perturbed the dung beetle community, favouring generalist r-strategic species (such as M. consputus ) and highly competitive species such as small tunnellers (e.g., O. medius ) (Horgan & Fuentes, 2005). The low grazed sites studied, in fact, showed more biomass but fewer species than the moderately grazed areas.…”

Use of Food and Space by Tunneler Dung Beetles (Coleoptera; Scarabaeinae) During Reproduction

“…It is also noteworthy that, when several nests of the same species were under a dung pat, these were found at different depths and at varying distances apart, suggesting the avoidance of competition for space. However, in similar tunneler beetle genera but different species that were experimentally subjected to lower resource availability (i.e., 1.5 kg/dung pat) and greater individual densities per pat, Horgan and Fuentes (2005) found that the bigger or more abundant individuals preempted the resource, thus promoting asymmetric interspeciÞc competition. This was not the case in our temperate species assemblage and environments, because densities were not large enough to colonize all dung pats.…”

“…The mode in which fresh dung pats are localized and exploited and whether this is done by one or many species may be explained by resource heterogeneity (Horgan 2005), niche differentiation (Errouissi et al 2004, Chefaoui et al 2005, Feer and Pincebourde 2005, asymmetric competition where bigger individuals consume most of the available resource (Horgan and Fuentes 2005), or a "lottery dynamic" in which the Þrst individual to arrive preempts the resource, decreasing the probability that other individuals from the same or different species will occupy the same dung pat (Hanski andCambefort 1991, Jacobs et al 2008).…”

Dung beetles (Coleoptera: Scarabaeoidea) in three landscapes in Mato Grosso do Sul, Brazil

“…This pattern could be related to the presence of few species adapted to that environment, or could be due to the interspecific competition, or that the species are still under the strong influence of human disturbance to the environment, as pointed out by Horgan and Fuentes (2005).…”