Which howler monkey (Alouatta, Atelidae, Primates) taxon is living in the Peruvian Madre De Dios River Basin (Southern Peru)? Results from mitochondrial gene analyses and some insights in the phylogeny of Alouatta

We sequenced mitochondrial genes (COI, COII and Cyt-b) from 138 howler monkeys (Alouatta) representing six "a priori" species (A. pigra, A. palliata, A. coibensis trabeata, A. seniculus, A. sara and A. caraya). These data were used to address two main issues: 1- to determine which red howler monkey taxa were distributed in Southern Peru (four of the sequenced were from there) and 2- to provide new insights about the systematics of howler monkeys. Our data support six main findings. 1-There is strong molecular gene heterogeneity between A. seniculus and A. sara. This verifies that A. sara (a taxon currently living in Southern Peru) is a full species; 2- A. seniculus seniculus is present in Colombia as well as across the northern and middle Peruvian Amazon. The alleged full species A. juara and A. puruensis seem to be molecularly un-differentiable from A. s. seniculus. Therefore, until these potential taxa are studied from a karyological point of view, only two red howler species are considered to be living in Peru: A. seniculus and A. sara; 3- The cis and trans-Andean howler monkeys are clearly differentiated agreeing with the results of Cortés-Ortiz et al., (2003). We obtained two temporal split estimates (7.21 Millions of years ago, MYA, and 6.73 MYA) for the separation of the cis and trans-Andean howler monkey species; 4- The evolution of the current mitochondrial haplotypes for the cis-Andean taxa began earlier than the mitochondrial diversification within the trans-Andean howler monkey taxa. This disagrees with the point of view of several authors claiming that A. palliata was the ancestral taxon in the Alouatta genus. Indeed, the haplotypes of A. palliata were derived from those of A. pigra, which agrees with a unique migration of howler monkeys from South America to Central America. The differentiation of both taxa occurred around 3 MYA; 5- No subspecies within A. palliata were detected. Even A. coibensis trabeata seems to be an extension of A. palliata. 6- We analyzed three species for possible population expansions. A. seniculus did not show any evidence of population expansion but there was some evidence of population expansion in A. sara. In contrast, A. palliata had a strikingly positive population expansion that is correlated with its relatively more recent origin.