Abstract
BackgroundThe lemurs of Madagascar provide an excellent mammalian radiation to explore mechanisms and processes favouring species diversity and evolution. Species diversity, in particular of nocturnal species, increased considerably during the last decade. However, the factors contributing to this high diversity are not well understood. We tested predictions derived from two existing biogeographic models by exploring the genetic and morphological divergence among populations of a widely distributed lemur genus, the sportive lemur (Lepilemur ssp.) along a 560 km long transect from western to northern Madagascar.ResultsBy using the phylogenetic analyses of mtDNA sequence data, molecular diagnostic sites and phenotypic morphometric traits, we uncovered two previously undetected species whose distributions contradict the two existing biogeographic models. Brief species descriptions are provided and a new biogeographic model is proposed (the ”large river model“).ConclusionAccording to the ”large river model“, large rivers in north and northwestern Madagascar acted as geographical barriers for gene flow and facilitated speciation events on a much smaller spatial scale than previously thought. Thereby, this study does not only show that species diversity in nocturnal Malagasy primates is continuously underestimated but aims to emphasize the need for conservation actions if those species with small ranges shall not face extinction in the near future.
Highlights
The lemurs of Madagascar provide an excellent mammalian radiation to explore mechanisms and processes favouring species diversity and evolution
Based on the single-gene-trees, derived for the new and reference sequences, the samples in this study could be classified as follows: The individuals found in IRS 0 clustered with L. aeeclis, the individuals found in IRS I with L. edwardsi, the individuals found in IRS IV with L. sahamalazensis, the individuals found in IRS V and VI with L. dorsalis, the individuals found in IRS VII with L. ankaranensis, the individuals from Kirindy with L. ruficaudatus and the individuals from Mantadia with L. mustelinus
The absolute pairwise distances between all species were in the range of those observed in other lemur genera such as Mirza [31], Microcebus [31,32,33], The revised phylogeny of the genus Lepilemur is based on the combination of molecular differences and morphometric traits
Summary
The lemurs of Madagascar provide an excellent mammalian radiation to explore mechanisms and processes favouring species diversity and evolution. Lemurs show a remarkable species diversity, both numerically and in terms of adaptations making them an excellent mammalian radiation to explore mechanisms and processes underlying speciation and evolution. In relation to the small surface area of Madagascar, diversity of species within this primate radiation is quite high. BMC Evolutionary Biology 2007, 7:83 http://www.biomedcentral.com/1471-2148/7/83 lemur species tend to have small geographic ranges in comparison to other primates. Because of such limited geographic ranges and the high rate of deforestation, the need for conservation action including genetic monitoring and effective management policies is urgent [2,4]. Two major models have been proposed to explain diversity of Malagasy mammals
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