A cytogenetic study of Microcebus myoxinus

Molecular phylogeny and taxonomic revision of the sportive lemurs (Lepilemur, Primates)

BACKGROUND

The number of species within the Malagasy genus Lepilemur and their phylogenetic relationships is disputed and controversial. In order to establish their evolutionary relationships, a comparative cytogenetic and molecular study was performed. We sequenced the complete mitochondrial cytochrome b gene (1140 bp) from 68 individuals representing all eight sportive lemur species and most major populations, and compared the results with those obtained from cytogenetic studies derived from 99 specimens.

RESULTS

Interspecific genetic variation, diagnostic characters and significantly supported phylogenetic relationships were obtained from the mitochondrial sequence data and are in agreement with cytogenetic information. The results confirm the distinctiveness of Lepilemur ankaranensis, L. dorsalis, L. edwardsi, L. leucopus, L. microdon, L. mustelinus, L. ruficaudatus and L. septentrionalis on species level. Additionally, within L. ruficaudatus large genetic differences were observed among different geographic populations. L. dorsalis from Sahamalaza Peninsula and from the Ambanja/Nosy Be region are paraphyletic, with the latter forming a sister group to L. ankaranensis.

CONCLUSION

Our results support the classification of the eight major sportive lemur taxa as independent species. Moreover, our data indicate further cryptic speciation events within L. ruficaudatus and L. dorsalis. Based on molecular data we propose to recognize the sportive lemur populations from north of the Tsiribihina River, south of the Betsiboka River, and from the Sahamalaza Peninsula, as distinct species.

Molecular phylogeny of the lemur family cheirogaleidae (primates) based on mitochondrial DNA sequences

Cheirogaleidae currently comprises five genera whose relationships remain contentious. The taxonomic status and phylogenetic position of both Mirza coquereli and Allocebus trichotis are still unclear. The taxonomic status of the recently discovered Microcebus ravelobensis (a sympatric sibling species of Microcebus murinus) and its phylogenetic position also require further examination. A approximately 2.4-kb mitochondrial DNA sequence including part of the COIII gene, complete ND3, ND4L, and ND4 genes, and 5 tRNAs was used to clarify relationships among cheirogaleids. Mirza and Microcebus form a clade representing the sister group of Allocebus, with a clade containing Cheirogaleus major and Cheirogaleus medius diverging first. M. ravelobensis and Microcebus rufus form a subclade within Microcebus, with M. murinus as its sister group. The molecular data support the generic status of Mirza coquereli and species-level divergence of M. ravelobensis. Furthermore, "M. rufus" may well represent more than one species.

Remarkable species diversity in Malagasy mouse lemurs (primates, Microcebus)

Phylogenetic analysis of mtDNA sequence data confirms the observation that species diversity in the world's smallest living primate (genus Microcebus) has been greatly underestimated. The description of three species new to science, and the resurrection of two others from synonymy, has been justified on morphological grounds and is supported by evidence of reproductive isolation in sympatry. This taxonomic revision doubles the number of recognized mouse lemur species. The molecular data and phylogenetic analyses presented here verify the revision and add a historical framework for understanding mouse lemur species diversity. Phylogenetic analysis revises established hypotheses of ecogeographic constraint for the maintenance of species boundaries in these endemic Malagasy primates. Mouse lemur clades also show conspicuous patterns of regional endemism, thereby emphasizing the threat of local deforestation to Madagascar's unique biodiversity.

A preliminary study of spatial distribution and mating system of pygmy mouse lemurs (Microcebus cf. myoxinus)

According to current hypotheses on the evolution of life history traits and social systems of Malagasy lemurs, nocturnality is associated with a solitary lifestyle and a polygynous or promiscuous mating system. Recent studies, however, have indicated that this may not be true of all lemurs. The goal of this study was to investigate the sociality and the mating system of pygmy mouse lemurs (Microcebus cf myoxinus), which are the smallest known primates, and which retain characteristics of the most primitive primates. I compared my findings with data on the sympatric Microcebus murinus and Cheirogaleus medius. Observational, morphometric and spatial distribution data were obtained by a radiotracking study in 1994, and from a capture-recapture study conducted during 1995/96. Pygmy mouse lemurs usually slept alone in a tangle of vegetation. During the mating season, sleeping sites of males were distributed over a much broader area than were female sites, indicating that male home ranges are larger than those of females. The home ranges of males overlapped during the mating season, and males occasionally roamed over long distances during a single night. Pygmy mouse lemurs forage primarily alone. Analysis of estrus stages indicate that female cycles are unsynchronized during the mating season. There was a lack of sexual dimorphism in body size but not in body mass. Males were heavier than females during the reproductive season but lighter than females the rest of the year. Testes of males varied in size seasonally and enlarged significantly during the mating season. The presence of a vaginal sperm plug in a female indicated the importance of preventing additional matings in this species. Thus pygmy mouse lemurs follow the predictions derived from sexual selection theory for multi-male mating systems with promiscuous matings and male sperm competition.