Low local but high beta diversity of tropical forest dung beetles in Madagascar


Heidi Viljanen, Metapopulation Research Group, Department of Biological and Environmental Sciences, Viikinkaari 1, 00014 University of Helsinki, Finland.
E-mail: heidi.viljanen@helsinki.fi


Aims  We have compared local (alpha) and regional (beta) species diversities of dung beetles in wet forests in the main tropical regions including Madagascar. Madagascar is exceptional in lacking native large herbivorous mammals which produce the key resource for dung beetles elsewhere.

Location  Central and South America, mainland Africa, Madagascar and Southeast Asia.

Methods  Trapping data on dung beetles and data on mammalian faunas were obtained from published and unpublished studies. We used our original data for Madagascar.

Results  Species richness of dung beetles and that of large-bodied (> 15 mm length) species in particular were highly significantly explained by the regional number of large-bodied (> 10 kg) mammals (R2 from 50 to 80%). For a given pairwise spatial distance between two communities, beta diversity was significantly higher in Madagascar than elsewhere, explaining the very high total species richness in Madagascar in spite of low local diversity.

Main conclusion  The presence and numbers of large herbivorous mammals greatly influence the species richness of dung beetles in tropical wet forests. The lack of native large herbivores rather than a limited species pool explains the low local diversity in Madagascar. Exceptionally high beta diversity in Madagascar suggests a pattern of old radiation involving extensive allopatric speciation.