Incongruence between genetic and morphological diversity in Microcebus griseorufus of Beza Mahafaly

Abstract

Background: The past decade has seen a remarkable increase in the number of recognized mouse lemur species (genus Microcebus). As recently as 1994, only two species of mouse lemur were recognized according to the rules of zoological nomenclature. That number has now climbed to as many as fifteen proposed species. Indeed, increases in recognized species diversity have also characterized other nocturnal primates--galagos, sportive lemurs, and tarsiers. Presumably, the movement relates more to a previous lack of information than it does to any recent proclivity for taxonomic splitting. Due to their nocturnal habits, one can hypothesize that mouse lemurs will show only minimal variation in pelage coloration as such variation should be inconsequential for the purposes of mate and/or species recognition. Even so, current species descriptions for nocturnal strepsirrhines place a good deal of emphasis on relatively fine distinctions in pelage coloration.

Results: Here, we report results from a multi-year study of mouse lemur populations from Beza Mahafaly in southern Madagascar. On the basis of morphological and pelage variation, we initially hypothesized the presence of up to three species of mouse lemurs occurring sympatrically at this locality, one of which appeared to be undescribed. Genetic analysis reveals definitively, however, that all three color morphs belong to a single recognized species, Microcebus griseorufus. Indeed, in some cases, the three color morphs can be characterized by identical mitochondrial haplotypes.

Conclusion: Given these results, we conclude that investigators should always proceed with caution when using a single data source to identify novel species. A synthetic approach that combines morphological, genetic, geographic, and ecological data is most likely to reveal the true nature of species diversity.

Figure 1

Map of the Beza Mahafaly region and sampling locations. P1 and P2 indicate the locations of the two parcels that belong to the reserve. The Ihazoara River is a tributary to the Sakamena River, which in turn flows into the Onilahy River to the north. The Ihazoara dry forest surrounds the village of Ihazoara. Locations of additional villages within a radius of 7 km from the reserve are also shown. For scale, the distance across P1 (east to west) is 1.25 km.

Figure 2

Two morphotypes collected at Beza Mahafaly. On the left is 0659-D2FC (the "all-red" variant), and on the right is 0659-CE82 (with "typical" M. griseorufus coloration). Both of these individuals were found in the gallery forest. Photo by L.R. Godfrey.

Figure 3

Phylogenetic tree of Microcebus derived from cytochrome b sequences. Asterisks along branches indicate posterior probabilities greaters than 95%. Microcebus sequences generated during the course of this study are in red. Gray arrows are indicative of haplotypes from individuals with the all-red variant. Black arrows are indicative of haplotypes from individuals with the murinus-type variant.

Figure 4

This is the network of Beza Mahafaly and Berenty cytochrome b haplotypes. In this figure each color represents a separate habitat type and each circle represents a single haplotype. The number of individuals that share each haplotype is drawn in proportion to the size of each circle.