Abstract
Chimpanzees (Pan troglodytes) have region-specific difference in dietary repertoires from East to West across tropical Africa. Such differences may result from different genetic backgrounds in addition to cultural variations. We analyzed the sequences of all bitter taste receptor genes (cTAS2Rs) in a total of 59 chimpanzees, including 4 putative subspecies. We identified genetic variations including single-nucleotide variations (SNVs), insertions and deletions (indels), gene-conversion variations, and copy-number variations (CNVs) in cTAS2Rs. Approximately two-thirds of all cTAS2R haplotypes in the amino acid sequence were unique to each subspecies. We analyzed the evolutionary backgrounds of natural selection behind such diversification. Our previous study concluded that diversification of cTAS2Rs in western chimpanzees (P. t. verus) may have resulted from balancing selection. In contrast, the present study found that purifying selection dominates as the evolutionary form of diversification of the so-called human cluster of cTAS2Rs in eastern chimpanzees (P. t. schweinfurthii) and that the other cTAS2Rs were under no obvious selection as a whole. Such marked diversification of cTAS2Rs with different evolutionary backgrounds among subspecies of chimpanzees probably reflects their subspecies-specific dietary repertoires.
Highlights
One genus of the great apes living in areas spanning from East to West across tropical Africa is Pan, which commonly consists of 2 species, chimpanzees (Pan troglodytes) and bonobos (Pan paniscus)
Most of the 215 nucleotide and 172 protein haplotypes of chimpanzee TAS2Rs (cTAS2Rs) were specific to each subspecies (Figure 2), suggesting the subspecies specificity for the sense of bitter taste, if these haplotype differences are assumed to be associated with functional differences
Numerous protein haplotypes of human TAS2R (hTAS2R) as well as cTAS2Rs were reported, only a few functional differences among these haplotypes, those related to non-synonymous variations, have been documented until date
Summary
One genus of the great apes living in areas spanning from East to West across tropical Africa is Pan, which commonly consists of 2 species, chimpanzees (Pan troglodytes) and bonobos (Pan paniscus). Chimpanzees are divided into 4 subspecies: eastern chimpanzees (Pan troglodytes schweinfurthii), central chimpanzees (Pan troglodytes troglodytes), Nigerian-Cameroonian chimpanzees (Pan troglodytes ellioti or formerly Pan troglodytes vellerosus), and western chimpanzees (Pan troglodytes verus), defined by their geographical ranges [1,2,3]. These 4 subspecies are genetically distinguishable from one another by their mitochondrial DNA (mtDNA) sequences [1,4]. Intergroup differences in chimpanzee behavior have not been sufficiently discussed from the viewpoint of genetic diversification of functional genes
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