Reconstructing the evolutionary history of the Lorisidae using morphological, molecular, and geological data

Abstract

Major aspects of lorisid phylogeny and systematics remain unresolved, despite several studies (involving morphology, histology, karyology, immunology, and DNA sequencing) aimed at elucidating them. Our study is the first to investigate the evolution of this enigmatic group using molecular and morphological data for all four well-established genera: Arctocebus, Loris, Nycticebus, and Perodicticus. Data sets consisting of 386 bp of 12S rRNA, 535 bp of 16S rRNA, and 36 craniodental characters were analyzed separately and in combination, using maximum parsimony and maximum likelihood. Outgroups, consisting of two galagid taxa (Otolemur and Galagoides) and a lemuroid (Microcebus), were also varied. The morphological data set yielded a paraphyletic lorisid clade with the robust Nycticebus and Perodicticus grouped as sister taxa, and the galagids allied with Arctocebus. All molecular analyses maximum parsimony (MP) or maximum likelihood (ML) which included Microcebus as an outgroup rendered a paraphyletic lorisid clade, with one exception: the 12S + 16S data set analyzed with ML. The position of the galagids in these paraphyletic topologies was inconsistent, however, and bootstrap values were low. Exclusion of Microcebus generated a monophyletic Lorisidae with Asian and African subclades; bootstrap values for all three clades in the total evidence tree were over 90%. We estimated mean genetic distances for lemuroids vs. lorisoids, lorisids vs. galagids, and Asian vs. African lorisids as a guide to relative divergence times. We present information regarding a temporary land bridge that linked the two now widely separated regions inhabited by lorisids that may explain their distribution. Finally, we make taxonomic recommendations based on our results.

Test of the Optimal Body Size Model for Strepsirhines

“…For example, genetic studies of lemurs result in differing phylogenies depending on phylogenetic method (parsimony, maximum likelihood) and which genes are used (Delpero et al, 2001;Hapke et al, 2005;Pastorini et al, 2002). In addition, there is considerable debate regarding lorisid systematics (Groves, 2001;Masters et al, 2005;Yoder, 2005). Branch length data are becoming available for many lemurs (Pastorini et al, 2001;Yoder and Yang, 2004), and we hope that a complete data set will soon be available for strepsirhines.…”

Geometric Morphometric Investigation of Molar Shape Diversity in Modern Lemurs and Lorises

“…Modern strepsirrhines are incredibly diverse in their body size [between $30 g and 6840 g (0.3-6.84 kg)], ecological habitat, and dietary patterning (Fleagle, 1999). Whereas lemurs and lorises are generally considered the most basal of the extant primates, particular systematic issues continue to be debated in the literature (Crovella et al, 1993;Purvis, 1995;Yoder and Irwin, 1999;Wyner et al, 2000;Yoder et al, 2001;Pastorini et al, 2003;Roos et al, 2004;Karanth et al, 2005;Masters et al, 2005). Discussion also continues regarding the relationships between primates and non-primate outgroup taxa.…”

“…1. Summary of current phylogenetic hypotheses concerning the relationships between lemuriforms, lorisiforms, and outgroup nonprimate taxa (Tupaia) (Crovella et al, 1993;Purvis, 1995;Yoder and Irwin, 1999;Wyner et al, 2000;Yoder et al, 2001;Pastorini et al, 2003;Roos et al, 2004;Karanth et al, 2005;Masters et al, 2005Masters et al, , 2006. Branch lengths are not intended to indicate evolutionary time or distance.…”

The biogeography and ecology of Sri Lankan mammals point to conservation priorities

“…The crown strepsirrhine lineage has African roots dating back to the late Eocene (about 40 Mya), and split into one galagine and two lorisine lineages shortly thereafter (about 38 Mya) (Seiffert et al, 2003;Pozzi et al, 2015). One lorisine lineage remained in tropical Africa with the galagines, the other migrated north out of Africa and into Asia by way of temporary Afro-Arabian land bridges (Masters et al, 2005). Once in Asia, this lineage split into the primorida of genera Nycticebus, now found in Southeast Asia, and Loris, now found in India and Sri Lanka (Yoder, 1997).…”

“…Once in Asia, this lineage split into the primorida of genera Nycticebus, now found in Southeast Asia, and Loris, now found in India and Sri Lanka (Yoder, 1997). This evidence of a past dispersal event involving thousands of kilometers is surprising in the light of the limited vagility of lorises as well as the fact that their much more mobile sister taxon, the Galagidae, does not occur outside sub-Saharan Africa (Masters et al, 2005).…”