MORPHOLOGY, BEHAVIOUR AND MOLECULAR EVOLUTION OF GIANT MOUSE LEMURS (MIRZA SPP.) GRAY, 1870, WITH DESCRIPTION OF A NEW SPECIES.

Abstract

Giant mouse lemurs (genus Mirza) are small nocturnal primates endemic to Madagascar, of which a single species (M. coquereli) is currently recognized. It is distributed along Madagascar’s west coast, with a gap of several hundred kilometres between two presumed subpopulations. Previous studies in the field and in captivity indicated substantial differences in several aspects of the biology of these two subpopulations. We therefore collected morphometric, genetic and behavioural data from populations representing the southern and northern end of their range to examine these differences in more detail. We obtained standard morphometric field measurements and DNA samples from a total of 74 adult males and females at Kirindy (central western Madagascar) and Ambato (northwestern Madagascar) and compared their social organisation. We also studied a total of 9 Mirza specimens housed at the Rijksmuseum van Natuurlijke Historie Leiden (The Netherlands). Our morphometric analyses revealed that the two Mirza populations differed significantly in 12 out of 13 measures, with the northern Mirza sporting smaller values in all traits except testes volume. Northern Mirza spent the day in nests with 2-8 (mean 4.1) individuals, whereas Mirza in the south virtually always slept alone. Moreover, reproduction in the northern population occurred several months earlier than in the south. We also sequenced the complete mitochondrial cytochrome b (cyt b) gene from several specimens and found that (1) the two populations differed by 3.33-3.51 %, which is similar to genetic distances observed among several closely related species of mouse lemurs (Microcebus), (2) DNA extracted from tissue on skulls collected in 1868/1870 yielded partial cyt b sequences that aligned perfectly with the northern and southern population samples, respectively, and (3) Microcebus from Andasibe clearly differed genetically from all other known mouse lemur species, indicating a separate species status for this population. Based on the combination of morphological, behavioural and genetic differences between Mirza from Kirindy and Ambato we conclude that they should be separated at the species level. Because M. coquereli was described based on a specimen from the southern population, we describe the northern Mirza as a species new to science.