The caviomorph rodents: distribution and ecological diversification

Abstract

Caviomorph rodents were one of the earliest colonizers of the Neotropics and are now conspicuous inhabitants there. Their body size ranges from about 70 grams to 65,000 grams and their distribution extends throughout South America in habitats which range from sea level to the highest Andean desert (Mares & Ojeda 1982). These organisms are especially good models for various kinds of research, including tests of phylogenetic hypotheses, adaptive radiation, ecological diversification, comparative physiology and behavior. The principal aim of this chapter is to provide a global synthesis of the caviomorph taxa, their phylogeny, and their extraordinary biogeographical and ecological diversification as a framework for following chapters focusing on their social behavior. First, we provided a general introduction of the radiation of major caviomorph clades and phylogenetic relationships (following Upham & Patterson 2012), followed by a characterization of the families, their geographic distributions and then a summary of the genera and ecological attributes. Our literature sources included major reference books on mammals and the Neotropics (Nowak 1991; Redford & Eisenberg 1992; Woods & Kilpatrick 2005; Eisenberg & Redford 1999; Upham & Patterson 2012) as well as databases (Patterson et al. 2007; IUCN Red lists 2012). We provide a table of genera with the ecoregions of their distribution, macroniches (i.e. modes of life and food habits), and general social behavior (See Maher & Burger, this volume). Drawings depicting the ecological diversification of representative genera are presented as well as distributional maps and species richness for all the families. Caviomorph rodents comprise 246 extant species (Upham & Patterson 2012) which represent about 16% of Neotropical mammals. They have radiated and occupied a wide spectrum of topographies, elevations, and habitats of the Neotropics, with 1 species, Erethizon dorsatum, ranging into the Neartic Region. Five families are mainly distributed throughout the tropical region (Erethizontidae, Cuniculidae, Echymidae, Dinomyidae and, Dasyproctidae). The Myocastoridae, Ctenomidae and, Chinchillidae are distributed in temperate regions and Octodontidae and Abrocomidae are mostly distributed along the Andes. The Amazonian and the Atlantic Forest biomes are the 2 major areas with highest species density. Reconstructions of biogeographical areas suggest that the Amazonia and the Atlantic forest are the hypothetical ancestral areas for the Erethizontoidea, whereas Amazonia and the Caatinga-Cerrado-Chaco are the most likely ancestral macrohabitats for the Cavioidea (Ojeda et al. in press). On other hand, the arid - semiarid ecoregions of the Andean-Puna-Chilean scrublands and Patagonia-Monte are the most likely ancestral areas for the evolution of Octodontoidea and Chinchilloidea. The ecological radiation of caviomorphs has filled about 16 macroniche cells. This pattern of extraordinary diversity contrasts with the ecological diversity of their African relatives (Phiomorpha) which number about 35 species filling no more than a few macroniche cells, mainly associated with terrestrial, saxicolous, fossorial and subterranean modes of life and a narrow dietary spectrum of grasses, roots, tubercles, crops and fruits (Nowak 1991). With respect to the hystricognath social systems, the African Phiomorpha display a high degree of sociality (e.g. most species of mole rats and greater cane rats) but also solitary behavior (e.g. rock rats, lesser cane rat, and a few species of mole rats; Nowak 1991; Myers et al. 2014). Similarly the New World hystricognaths or caviomorphs display a broad range of social structure with the family members in the four major lineages (i.e. superfamilies) exhibiting both solitary and highly social behavior.