Phylogenetics of Caviomorph Rodents and Genetic Perspectives on the Evolution of Sociality and Mating Systems in the Caviidae

Abstract

The diversity of terrestrial mammals in South America is the result of both isolation and continental interchanges, preceded and followed by extinction and speciation (Simpson 1980; Marshall 1988). Mammalian biodiversity in South America can be partitioned into three major phases, beginning in the Paleocene (65.5–55.8 million years ago – Ma) with xenarthrans, notoungulates, marsupials, and ending with the “Great American Interchange” that occurred with the influx of North American mammals upon formation of the Panamanian land bridge approximately 3 Ma (Simpson 1980; Marshall 1988; Flynn and Wyss 1998). South America’s first rodents, the New World Hystricognathi (Caviomorpha), termed “old native rodents” by Simpson (1980) appear in the fossil record around 37.5–31 Ma in the Eocene/Oligocene transition (Wyss et al. 1993; Vucetich et al. 1999; Flynn et al. 2003). The origin of South American caviomorph rodents is apparently a consequence of over-water dispersal from Africa during the Late Paleocene (c.58 Ma) to Middle Eocene (c.40 Ma; Lavocat 1969, 1980; Huchon and Douzery 2001; Rowe 2002; Rowe et al. 2010). The Late Eocene to Early Oligocene of South America represents a period of transition in terms of climatic and environmental changes (Flynn and Wyss 1998). According to both Mares and Ojeda (1982) and Simpson (1980), caviomorph rodents during this time period experienced an adaptive radiation that resulted in these “hypsodont herbivores” (herbivores with high-crowned cheek teeth) filling niches previously occupied by archaic ungulates from the first phase of mammalian history in South America (Flynn and Wyss 1998). One particular Pliocene/Pleistocene (4–2 Ma) form, Josephoartigasia monesi, was the size of a rhinoceros and adapted for a semiaquatic life style (Rinderknecht and Blanco 2008). By the Late Oligocene (24 Ma), representatives of all four superfamilies and 8 of the 14 recent families of caviomorph rodents were present in the fossil record (Simpson 1980; Vucetich et al. 1999).