A molecular timescale for caviomorph rodents (Mammalia, Hystricognathi)

Abstract

Phylogenetic relationships and divergence times are important pieces of information for evolutionary biologists, given that they provide a framework for understanding the evolution of phenotypes. There are now statistical methods that estimate divergence times without assuming that all lineages evolve at the same rate (Huelsenbeck et al., 2000; Sanderson, 1997; Thorne et al., 1998). Here I apply these methods to the neotropical hystricomorph rodents. The hystricomorph rodents are highly diverse in terms of life history traits, body sizes, and overall reproductive strategies (Begall et al., 1999; ScharV et al., 1999). This diversity in life history strategies and body size is accompanied by considerable heterogeneity in rates of molecular evolution (Honeycutt et al., 2003; Huchon et al., 2000; Huchon and Douzery, 2001; Rowe and Honeycutt, 2002). The faster rate of molecular evolution of rodents compared to other mammals has been attributed to the shorter generation times of rodents (Gu and Li, 1993). However, the rate heterogeneity observed among hystricognath rodents suggests that the causes of rate heterogeneity may be more complex than previously thought (Gu and Li, 1993). Huchon and Douzery (2001) have addressed the problem of divergence times among major clades of hystricomorph rodents. Others have estimated divergence times using more complex taxonomic sampling for speciWc groups such as the caviomorph rodents (neotropical hystricomorph rodents) (Galewski et al., 2005; Honeycutt et al., 2003). Among these rodents, the superfamily Octo-