Systematics and biogeography of Madagascan mycalesine butterflies (Lepidoptera: Satyrinae)

Abstract

Studies on the systematics, theoretical and applied biogeography of the largest radiation of Madagascan butterflies (Lepidoptera: Satyrinae: Mycalesina) are presented in six papers. First, their alpha-taxonomy is revised and synonymic problems encountered are described. Morphological character systems, mostly derived from males, are next described and illustrated. Based on these characters, cladograms encompassing 67 recognised species, all endemic to the Malagasy Region, are presented, and broader biogeographic implications discussed. The analyses suggest that most generic groupings currently applied to these butterflies are paraphyletic, as appears to be the case for the entire Malagasy Region mycalesine fauna in relation to African and Indian taxa. The phylogenetic results are then used to investigate biogeography within Madagascar. Vicariant patterns, mainly within distributions of individual elevationally restricted species, contrasts with little allopatry for sister species pairs, but markedly different distributions of latitudinal species richness occur within different clades. Species richness gradients of the entire Madagascan mycalesine fauna along both latitudinal and elevational gradients are then analysed by range size class, compared with other animal taxa, and an appropriate null model developed. Trends in latitudinal species richness approximate to the model, especially for widespread species, tending to be symmetrically parabolic, suggesting the predominance of geometric constraints. Finally, the performance of mycalesines is compared with other animal groups as potential target taxa for estimating regional patterns of biodiversity in Madagascar, and relevance to conservation planning is assessed. Taxa rate differently depending upon the measure examined. Mycalesines and other adaptive radiations exhibited the same species richness ratio locally as regionally, as did a high-performing randomly drawn polyphyletic taxon. This suggests that an ideal species richness surrogate should reflect other biodiversity in its frequency distribution of range sizes and range placements. The validity of the target taxon approach to prioritising areas for conservation and in reserve design is discussed.