Geographic distribution of the genera of the Tribe Oryzomyini (Rodentia: Cricetidae: Sigmodontinae) in South America: patterns of distribution and diversity

Abstract

The Oryzomyini is the most diverse tribe of the sigmodontine (Cricetidae: Sigmodontinae) radiation, including 28 genera and about 130 species, with this diversity reflected in the ecological and morphological variation observed among members. There are many hypotheses to explain the emergence and diversification of the Sigmodontinae in South America, includ- ing areas of original differentiation (AOD). In this paper we provide information on the geographic distribution of all extant genera in the tribe Oryzomyini, organizing these data in a gazetteer that includes provenance (collection locality, state or province, country), eleva- tion, and geographical coordenates. Distribution maps generated for all genera and species then serve as the starting point for testing patterns of geographic distribution and diversity, and especially the AOD hypothesis advocating origination in the northern Andes. Our re- sults reveal considerable generic and specific richness and show that there are three general patterns of distribution, the Trans-Andean, Andean, and Cis-Andean. Moreover, different genera encompass distributions that are endemic, disjunct, or widely distributed, as well as those restricted by habitats in both forest and open areas. Recent phylogenetic hypotheses in- dicate that the distribution patterns of oryzomyines do not correlate with the major lineages of the inclusive clades; rather, each main lineage displays most of the biogeographic patterns described for the tribe as a whole. The northern Andes cannot be considered as AOD, since the most records for Oryzomyini are located in the Cis-Andes area. The northern Andes is the second region in number of species, while the Trans-Andean represents the third richest region in South America. Patterns of richness of the tribe are strongly concordant with several of the centers or regions of endemism described in the literature. Areas of high richness are located mainly in the Andes, followed in lesser degree by areas in the Guyanan Shield, Brazilian Atlantic and Amazon Forests, and Paraguayan Chaco.