Abstract
Madagascar has a rich fauna of dung beetles (Scarabaeinae and Aphodiinae) with almost 300 species described to date. Like most other taxa in Madagascar, dung beetles exhibit an exceptionally high level of endemism (96% of the species). Here, we review the current knowledge of the origin and diversification of Malagasy dung beetles. Based on molecular phylogenies, the extant dung beetles originate from eight colonizations, of which four have given rise to extensive radiations. These radiations have occurred in wet forests, while the few extant species in the less successful radiations occur in open and semi-open habitats. We discuss the likely mechanisms of speciation and the ecological characteristics of the extant communities, emphasizing the role of adaptation along environmental gradients and allopatric speciation in generating the exceptionally high beta diversity in Malagasy dung beetles. Phylogeographic analyses of selected species reveal complex patterns with evidence for genetic introgression between old taxa. The introduction of cattle to Madagascar 1500 years ago created a new abundant resource, onto which a few species have shifted and thereby been able to greatly expand their geographical ranges.
Highlights
Madagascar has an exceptional biota characterized by a remarkably high level of endemism at all taxonomic levels [1]
Dung beetles are a great example of Madagascar‟s biological uniqueness: of the almost 300 species described to date, 285 (96%) are endemic, with several endemic genera and 1 endemic subtribe (Helictopleurina in the tribe Oniticellini) (Figure A1)
Why have some of the lineages experienced extensive radiations while others have failed to radiate at all? As we describe below, this is most likely related to the ecology and evolutionary biology of the lineages, but the order of colonizations may have played an important role
Summary
Madagascar has an exceptional biota characterized by a remarkably high level of endemism at all taxonomic levels [1]. Many endemic lineages in Madagascar must be part of more recent radiations due to overseas dispersal (e.g., [13,14,15]). Several different mechanisms of species diversification have been proposed for Madagascar [1,15], all of them intimately associated with the topographic and climatic particularities of the island. The large area and great physiographic complexity of Madagascar have provided a multitude of different climates and habitats that have allowed many lineages to diversify, following successful overseas colonization, through extensive adaptive and non-adaptive radiations. Dung beetles are a great example of Madagascar‟s biological uniqueness: of the almost 300 species described to date, 285 (96%) are endemic, with several endemic genera and 1 endemic subtribe (Helictopleurina in the tribe Oniticellini) (Figure A1). Vs. unsuccessful radiations, and we conclude by discussing the likely ecological and evolutionary mechanisms that are responsible for the distributional patterns we observe today
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