The systematic relationships of cervids with special reference to the South American radiation

Mitochondrial DNA (mtDNA) sequences were used to investigate systematic relationships of 21 species of deer (family Cervidae), with special attention directed towards the poorly understood South American taxa. The nucleotide region examined was a 410 base pair (bp) region of the 12S ribosomal RNA (rRNA) in combination with 401-bp cytochrome b data set. In addition to the cervids, nine other ungulate genera were also sequenced. -- Among the 811-bp of sequence data available, 365 nucleotide positions were variable, of which 296 were phylogenetically informative. The data suggest that cervids consist of two monophyletic clades or subfamilies, corresponding to a previously recognized alternative conditions of the metacarpals of the lateral digits. The plesiometacarpalian state or the loss of the distal portion of the second and fifth metacarpals, is characteristic of the cervines (subfamily Cervinae), whereas the telemetacarpalian state or the loss of the proximal metacarpal portions in the lateral digits, is characteristic of the odocoileines and Hydropotes (subfamily Odocoileinae). Within Cervinae, three taxa were identified: Cervus (including Elaphurus), Axis, and Muntiacus. The Odocoileinae includes three monophyletic tribes: Capreolini (Capreolus and Hydropotes), Alcini (Alces only), and Odocoileini (endemic New World deer and holarctic Rangifer). The Odocoileus species were consistently the sister group to Mazama (M. americana, M. nana, and M bororo) in at least 52% (NJ) of the bootstrap replicates from all three methods of phylogenetic analysis [maximum-parsimony (MP) bootstrap value 77%; maximum-likelihood (ML) bootstrap value 69%; and, neighbor-joining (NJ)]. Hydropotes was identified as a sister species of Capreolus in at least 80% (MP) of the bootstrap replicates and thus is not representative of the plesiomorphic ancestral state for cervids. Relationships among Alces and the remaining odocoileine genera were not well resolved. -- The data challenge conventional assumptions about New World cervid evolution and taxonomy. Odocoileus is distributed throughout North and Central America, and the occurrence of 0. virginianus in South America north of the Amazon basin has been taken to suggest that all South American deer evolved from 0. virginianus. The molecular data instead show that the endemic South American genera (Pudu, Ozotoceros, Blastocerus, and Hippocamelus) as well as one South American species of Mazama (M gouazoupira) form a monophyletic lineage whereas Odocoileus is more closely related to the remaining species of Central and South American Mazama (M americana, M nana, and M bororo ). In all three analyses, H bisulcus, B. dichotomus, P. puda, and 0. Bezoarticus clustered together; with M gouazoupira being the sister group to these other four genera (NJ bootstrap value 76%), with M gouazoupira and H bisulcus being the sister group to the latter three genera (MP bootstrap value 53%), and with P. puda being the sister taxa to these other three genera along with M gouazoupira (ML bootstrap value 88%). All analyses placed the four Mazama species in at least three different clades and the M. americana individuals were often split between two clusters, suggesting a large degree of genetic variability within this genus and species, respectively.