Abstract
BackgroundGibbons (Hylobatidae) are the most diverse group of living apes. They exist as geographically-contiguous species which diverged more rapidly than did their close relatives, the great apes (Hominidae). Of the four extant gibbon genera, the evolutionary histories of two polyspecific genera, Hylobates and Nomascus, have been the particular focus of research but the DNA sequence data used was largely derived from the maternally inherited mitochondrial DNA (mtDNA) locus.ResultsTo investigate the evolutionary relationships and divergence processes of gibbon species, particularly those of the Hylobates genus, we produced and analyzed a total of 11.5 kb DNA of sequence at 14 biparentally inherited autosomal loci. We find that on average gibbon genera have a high average sequence diversity but a lower degree of genetic differentiation as compared to great ape genera. Our multilocus species tree features H. pileatus in a basal position and a grouping of the four Sundaic island species (H. agilis, H. klossii, H. moloch and H. muelleri). We conducted pairwise comparisons based on an isolation-with-migration (IM) model and detect signals of asymmetric gene flow between H. lar and H. moloch, between H. agilis and H. muelleri, and between N. leucogenys and N. siki.ConclusionsOur multilocus analyses provide inferences of gibbon evolutionary histories complementary to those based on single gene data. The results of IM analyses suggest that the divergence processes of gibbons may be accompanied by gene flow. Future studies using analyses of multi-population model with samples of known provenance for Hylobates and Nomascus species would expand the understanding of histories of gene flow during divergences for these two gibbon genera.
Highlights
Gibbons (Hylobatidae) are the most diverse group of living apes
Different phylogenetic trees have been proposed, and a basal position of Nomascus was indicated based on sequences of mitochondrial DNA (mtDNA) control region and cytochrome b gene [10,20,23] but this result conflicts with the basal placement of the genus Hoolock in studies based on sequences of mtDNA ND3-ND4 genes [24], the concatenated sequences of mtDNA, Y-linked and X-linked loci [17], sequences of autosomal and X chromosomal regions [22] and chromosomal analysis [3], as well as with the basal position of the Symphalangus genus in an Alu-based phylogeny of gibbons [27]
For Hylobates species, we found that the divergence time estimates were fairly consistent with the branching patterns of the species tree: (((H. agilis, H. muelleri, H. moloch, H. klossii), H. lar), H. pileatus) (Figures 2A and 3A)
Summary
Gibbons (Hylobatidae) are the most diverse group of living apes. They exist as geographicallycontiguous species which diverged more rapidly than did their close relatives, the great apes (Hominidae). Gibbons are a family (Hylobatidae) of ape species endemic to the rainforests of the mainland and islands of Southeast Asia, including the Malay Peninsula, Sumatra, Borneo, Java and Mentawai Islands (Figure 1). They are the closest relatives of the great ape family (Hominidae) to which humans belong, and offer an interesting opportunity for comparisons. Like present-day great apes, the extant gibbons comprise four genera, which feature strikingly occurred within less than two million years [10,17] Due to their close relationship to great apes, high taxonomic diversity and rapid diversification, gibbons have increasingly been the subject of molecular genetic analyses The phylogenetic tree inferences from several datasets of mtDNA sequences (Figure 2B; [24,25]) and the concatenated sequences of the mtDNA, Y-linked and X-linked loci [17] suggest that the two northernmost mainland species (H. lar and H. pileatus) may have branched off earlier than other Hylobates gibbons, the tree inferences from other sequence datasets of mtDNA cytochrome b gene and Y chromosome placed H. klossii [10], H. moloch [20] or H. muelleri (Figure 2C [19]) as basal species in Hylobates phylogeny Figure 2
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