Taxonomy of lemurs
The recent rise in species numbers is due to both improved genetic analysis and a push in conservation to encourage the protection of isolated and distinct lemur populations.
Since their arrival on Madagascar, a biogeographically isolated island with a unique mammalian fauna, lemurs have diversified both in behavior and morphology.
Their diversity rivals that of the monkeys and apes found throughout the rest of the world, especially when the recently extinct subfossil lemurs are considered.
[1] Ranging in size from the 30 g (1.1 oz) Madame Berthe's mouse lemur, probably the world's smallest primate,[2] to the extinct 160–200 kg (350–440 lb) Archaeoindris fontoynonti, the largest known prosimian,[3][4][5] lemurs evolved diverse forms of locomotion, varying levels of social complexity, and unique adaptations to the local climate.
The center of the island, the Hauts-Plateaux, was converted by early settlers to rice paddies and grassland through slash-and-burn agriculture, known locally as tavy.
[14] Being familiar with the works of Virgil and Ovid and seeing an analogy that fit with his naming scheme, Linnaeus adapted the term "lemur" for these nocturnal primates.
[14] It has also been speculated that Linnaeus may also have known that some Malagasy people have held legends that lemurs are the souls of their ancestors,[16] but this is unlikely given that the name was selected for slender lorises from India.
[19] Primates, together with their closest relatives, the treeshrews, colugos, and long-extinct plesiadapiforms, form the taxonomically unranked Euarchonta clade within the Euarchontoglires.
Lorisids, some of which were originally placed in the genus Lemur by Carl Linnaeus, have since been moved into either their own infraorder (Lorisiformes) or their own superfamily (Lorisoidea) within Lemuriformes.
[20][21] For the Malagasy primate fauna, taxonomic nomenclature proliferated during the 1800s, with the aid of museum systematists, such as Albert Günther and John Edward Gray, as well as naturalists and explorers, such as Alfred Grandidier.
)[28] This view was upheld by other famous naturalists and zoologists of the time, including Étienne Geoffroy Saint-Hilaire (who first placed lemurs in Strepsirrhini in 1812),[29] Georges Cuvier,[30] and (initially) John Edward Gray.
[31] By 1862, William Henry Flower, a comparative anatomist, was arguing against moving strepsirrhines out of Quadrumana into Insectivora (a now-abandoned biological grouping), claiming that their brain had features transitional between other primates and "inferior" mammals.
In 1873, English comparative anatomist St. George Jackson Mivart countered these arguments and proceeded to define the primates by a list of anatomical features.
He placed all the lemurs together in a "series" Lemuriformes and recognized three families: Daubentoniidae, Indriidae, and Lemuridae (including the current Cheirogaleidae and Lepilemuridae).
[1] Until Owen published a definitive anatomical study in 1866, early naturalists were uncertain whether the aye-aye (genus Daubentonia) was a primate, rodent, or marsupial.
[43][49] In 1996, Ankel-Simons demonstrated that the shape and arrangement of the aye-aye's diminutive deciduous incisors indicate that this genus has a shared ancestry with the toothcombed primates.
[51] Based on its anatomy, researchers have found support for classifying the genus Daubentonia as a specialized indriid, a sister group to all strepsirrhines, and an indeterminate taxon within the primates.
Colin Groves upheld this classification in 2005 because he was not entirely convinced the aye-aye formed a clade with the rest of the Malagasy lemurs,[55] despite molecular tests that had shown Daubentoniidae was basal to all Lemuroidea.
[37][61] However, relevant genetic studies unanimously place cheirogaleids within the lemuroid clade and Groves himself, who had promoted the cheirogaleid-lorisoid relationship in a 1974 paper, by 2001 regarded the idea as refuted.
[62][61] Classifications in the first half of the 20th century divided lemurs into three families: Daubentoniidae, Indriidae, and Lemuridae, with the latter including the current Cheirogaleidae and Lepilemuridae.
[58] Both phylogenies agree that the Malagasy primates are monophyletic and that Daubentoniidae (the aye-aye) is basal to the lemuroid clade, having split off significantly earlier than the other families.
First, the four most closely related living lemur families diverged within a narrow window of approximately 10 million years, making it much harder to distinguish the splits with molecular evidence.
In addition, these families diverged from their last common ancestor approximately 42 mya; such distant splits create a lot of noise for molecular techniques.
[91][92][93] According to Russell Mittermeier, the president of Conservation International (CI), taxonomist Colin Groves, and others, there are currently 101 recognized species or subspecies of extant lemur, divided into five families and 15 genera.
[99] In December 2008, Russell Mittermeier, Colin Groves, and other experts co-wrote an article in the International Journal of Primatology classifying 99 species and subspecies.
Due to the critical condition that most Malagasy primate populations are in, taxonomists and conservationists sometimes favor splitting them into separate species to develop an effective strategy for the conservation of the full range of lemur diversity.
[92][103] Implicitly, this means that full species status will help grant genetically distinct populations added environmental protection.
[120] With molecular research suggesting a more distant split in both genera, these subspecies or undistinguished populations have been promoted to species status.
In the case of the brown lemurs, the diploid number ranges from 2n=44 to 2n=60 while the individual chromosome sizes vary considerably, despite strong similarities in morphology.
