Cytogenetic Arguments in Favour of a Taxonomic Revision of Lepilemur septentrionalis

Abstract

Cytogenetic investigations performed on 30 specimens of Lepilemur septentrionalis confirmed the existence of 4 karyotypes differing from each other by 1–2 chromosomal rearrangements. These data, pooled with those obtained in earlier studies, showed that out of 60 animals karyotyped only two kinds of hybrids were detected, allowing us to characterise two chromosomally polymorphic populations. No natural hybrids could be found between these two populations, which could thus be considered as two separate species. The possible role of the chromosomal rearrangements in the process of reproductive isolation between these two populations is discussed.

Lemur Diversity in Madagascar

“…Ravaoarimanana et al 1999Ravaoarimanana et al , 2004Rumpler et al 2002). Groves (2005) and Mittermeier et al (2006), therefore, listed 8 species of sportive lemurs, all of them cytogenetically distinct Rumpler and Albignac 1978;Rumpler et al 2001;Thalmann and Ganzhorn 2003;). Since these publications, 3 molecular genetic studies (Andriaholinirina et al 2006a;Louis et al 2006b;Rabarivola et al 2006) have added a further 15 species, making it, with 23 species, the most diverse lemur genus.…”

“…Forms occurring in both dry deciduous and humid forests that extend from Montagne d'Ambre southward to the Mahavavy River near Ambilobe and eastward at least as far as the Manambato River, and probably to the Fanambana River, north of Sambava, have been assigned to this taxon. The diploid chromosome number for the species ranges from 36 to 38 (Ravaoarimanana et al 2004;Rumpler et al 2001). Andriaholinirina et al (2006a) found that Lepilemur ankaranensis was more closely related to L. dorsalis than to L. septentrionalis.…”

“…Morphological and (especially) cytogenetic and molecular genetic studies are resulting in some major changes in our understanding of the diversity, phylogeny, and systematics of the lemurs (Fausser et al 2002;Mayor et al 2004;Ravoarimanana 2001;Rumpler 2000Rumpler , 2004, as well as the identification of numerous new species (Andriaholinirina et al 2006a;Andriantompohavana et al 2006Andriantompohavana et al , 2007Craul et al 2007;Kappeler et al 2005;Lei et al 2008;Louis et al 2006a, b;Olivieri et al 2007;Rabarivola et al 2006;Radespiel et al 2008;Rasoloarison et al 2000;Rylands et al 2002;Geissmann 2000, 2005;Zaramody et al 2006;Zimmermann et al 1998). Groves and Tattersall (1991), Groves (2000Groves ( , 2001Groves ( , 2005Groves ( , 2007, and Groves and Helgen (2007) revised existing museum material intensively.…”

Madagascar's Lemurs: Cryptic diversity or taxonomic inflation?

“…In 2001, Rumpler et al 38 concluded that the most northerly Lepilemur species, L. septentrionalis, already known to be karyotypically polymorphic, consisted of two reproductively incompatible but externally cryptic populations, both karyotypically heteromorphic and each with a distinctive mtDNA (cytochrome b) signature. One of the original subspecies populations, confined to the Sahafary forest to the east of the Montagne d'Ambre, was raised to species level as L. andrafiamenensis.…”

“…All that can be said with certainty is that there is variation within Lepilemur and that much of this variation appears to be organized geographically. On the basis of the karyotypic and hybrid-recognition studies of Rumpler and his colleagues [38][39][40] it seems reasonable that most of the eight ''core'' taxa should provisionally be recognized at the species level. On the other hand, even quite large divergences in the cytochrome b gene seem to constitute rather weak evidence for speciation in the case of the three recently named species embedded within the ranges of L. ruficaudatus and L. dorsalis.…”