Major Radiations in the Evolution of Caviid Rodents: Reconciling Fossils, Ghost Lineages, and Relaxed Molecular Clocks

Abstract

BackgroundCaviidae is a diverse group of caviomorph rodents that is broadly distributed in South America and is divided into three highly divergent extant lineages: Caviinae (cavies), Dolichotinae (maras), and Hydrochoerinae (capybaras). The fossil record of Caviidae is only abundant and diverse since the late Miocene. Caviids belongs to Cavioidea sensu stricto (Cavioidea s.s.) that also includes a diverse assemblage of extinct taxa recorded from the late Oligocene to the middle Miocene of South America (“eocardiids”).ResultsA phylogenetic analysis combining morphological and molecular data is presented here, evaluating the time of diversification of selected nodes based on the calibration of phylogenetic trees with fossil taxa and the use of relaxed molecular clocks. This analysis reveals three major phases of diversification in the evolutionary history of Cavioidea s.s. The first two phases involve two successive radiations of extinct lineages that occurred during the late Oligocene and the early Miocene. The third phase consists of the diversification of Caviidae. The initial split of caviids is dated as middle Miocene by the fossil record. This date falls within the 95% higher probability distribution estimated by the relaxed Bayesian molecular clock, although the mean age estimate ages are 3.5 to 7 Myr older. The initial split of caviids is followed by an obscure period of poor fossil record (refered here as the Mayoan gap) and then by the appearance of highly differentiated modern lineages of caviids, which evidentially occurred at the late Miocene as indicated by both the fossil record and molecular clock estimates.ConclusionsThe integrated approach used here allowed us identifying the agreements and discrepancies of the fossil record and molecular clock estimates on the timing of the major events in cavioid evolution, revealing evolutionary patterns that would not have been possible to gather using only molecular or paleontological data alone.

The evolution of mammal body sizes: responses to Cenozoic climate change in North American mammals

“…The oldest known Neotropical rodents were comparatively small and ranged in size from 30 to 120 g (Antoine et al, 2012). Although the ecological correlates of the body size radiation in the caviomorphs is obscure (Perez & Pol, 2012), weak competition from other co-existing mammals, such as marsupials, armadillos and small notoungulates (Antoine et al, 2012), is worthy of investigation.…”

Circulating white blood cell counts in captive and wild rodents are influenced by body mass rather than testes mass, a correlate of mating promiscuity

“…; List et al . ; Geffen, Rowe & Yom‐Tov ; Pérez & Pol ; Voss, Hubbard & Jansa ). We then compared different models of character evolution and identified the one that best accounts for the potential phylogenetic inertia in our analyses.…”

“…To account for the non-independence between species that results from the phylogeny, we initially established the phylogenetic tree of our rodent species (Fig. 1) by building a consensus tree based on eight partial phylogenies (Herron, Castoe & Parkinson 2004;Jansa & Weksler 2004;Steppan, Adkins & Anderson 2004;Blanga-Kanfi et al 2009;List et al 2010;Geffen, Rowe & Yom-Tov 2011;P erez & Pol 2012;Voss, Hubbard & Jansa 2013). We then compared different models of character evolution and identified the one that best accounts for the potential phylogenetic inertia in our analyses.…”

Hindlimb musculature of the largest living rodent Hydrochoerus hydrochaeris (Caviomorpha): Adaptations to semiaquatic and terrestrial styles of life

“…In taxonomy, H. hydrochaeris and H. isthmius (the other species of the genus) have been assigned to its own family, Hydrochoeridae (e.g., Woods, 1984). More recent phylogenetic analyses based on molecular (Rowe and Honeycutt, 2002;Rowe et al, 2010;Fabre et al, 2012;Upham and Patterson, 2012) and morphological characters (P erez and Pol, 2012) included Hydrochoerus within Caviidae, related to the rock cavy (Kerodon). This clade also comprises the cavies (Cavia, Galea, Microcavia) and the maras (Dolichotis and Pediolagus).…”