Contrasting Phylogenetic and Diversity Patterns in Octodontoid Rodents and a New Definition of the Family Abrocomidae

Abstract

Octodontoidea is the most species-rich clade among hystricomorph rodents. Based on a combined parsimony analysis of morphological and molecular data of extinct and extant species, we analyze the history of South American octodontoids and propose ages of divergence older than interpreted so far. Early Abrocomidae are recognized for the first time, and a new definition of the family is provided. Traditionally accepted fossil-based times of origin for the southern clades are reinterpreted as later stages of differentiation markedly uncoupled from the origin, differentiation implying specializations for open environments as shown in a morphospace of skull variation. Origin of crown groups is also strongly uncoupled from origin of clades as a consequence of extinction of deep lineages. In the resulting diversity pattern of modern southern clades of octodontoids, the combination of greater disparity, less content of evolutionary history, and lower taxonomic diversity, compared to their northern counterparts, appears at first counterintuitive. We propose that primary components of diversity derived from evolutionary transformation or anagenesis, on the one hand, and from cladogenesis and extinction, on the other, should not be considered associated, or at least not necessarily. Certain patterns of relationships between these distinct components could be driven by environmental dynamics. Like environments, octodontoid diversity would have been more stable in northern South America, whereas in the south, both strong adaptive change and extinction would have been triggered by emerging derived environments.

Historical and ecological influence in the evolutionary diversification of external morphology of neotropical spiny rats (Echimyidae, Rodentia)

“…Differently from the pattern found in muroid lineages (Verde Arregoitia et al., ), ecological pressures along echimyid evolution did not overshadow phylogenetic components of external morphology because ecological specializations, although more concentrated during early diversification, emerged gradually during the phyletic diversification of this family. This was consistent with a relatively small disparification of echimyid skulls respective to other closely related caviomorph families (Octodontidae and Abrocomidae) that were exposed to more stringent environmental pressures during diversification (Verzi et al., ). The restriction of echimyids to the relatively stable Miocene and Pliocene hydric and mesic environments probably prevented them to evolve under the strong ecological pressures operating along the diversification of other caviomorph rodents (Verzi et al., ).…”

“…This was consistent with a relatively small disparification of echimyid skulls respective to other closely related caviomorph families (Octodontidae and Abrocomidae) that were exposed to more stringent environmental pressures during diversification (Verzi et al., ). The restriction of echimyids to the relatively stable Miocene and Pliocene hydric and mesic environments probably prevented them to evolve under the strong ecological pressures operating along the diversification of other caviomorph rodents (Verzi et al., ). A further, more comprehensive study including all caviomorphs will probably reveal more complex relationships between historical, ecological, and structural factors shaping external morphology evolution.…”

“…This phylogenetic scenario allowed for the understanding of the relative effects of historical (= phylogenetic) and ecological factors on the phyletic and morphological diversification of spiny rats (Monteiro, Bonato, & dos Reis, ; Monteiro & dos Reis, ; Nicola et al., ). It is well known that the morphological evolution of echimyid skulls was partially shaped by historical and ecological factors associated with locomotory habits (Álvarez, Perez, & Verzi, ; Perez, Diniz‐Filho, Rohlf, & dos Reis, ) and with restriction to hydric and mesic environments (Verzi, Olivares, Morgan, & Álvarez, ). Both ecological and historical factors were also operative in shaping the appendicular skeleton (Morgan & Álvarez, ; Morgan & Verzi, ).…”

Morphology of the limbs in the semi-fossorial desert rodent species of Tympanoctomys (Octodontidae, Rodentia)

“…It was estimated that Tympanoctomys diverged about six million years ago (Gallardo and Kirsch 2001) in coincidence with the origin of deserts at Late Miocene (Gallardo et al 2006); but other authors mentioned different times of divergence from 2.5 to 6.5 million years (see Upham and Patterson 2012; Gallardo et al 2013; Upham and Patterson 2015; Verzi et al 2016; Suarez-Villota et al 2016; Alvarez et al 2017). This genus is one of the few mammals (all rodents) most highly adapted to desert environments (Mares 1975, 1993; Bozinovic and Contreras 1990; Ojeda et al 1996; Mares et al 2000; Honeycutt et al 2003).…”

Spatial and temporal divergence of the torquatus species group of the subterranean rodent Ctenomys

“…Each entry begins with the referred clade and its code (matching labeled nodes shown in Supplementary Figure S1), and followed by the lognormal prior's upper 95% range in Millons years (Myr) and the distribution's shape parameters (mean, SD) as implemented in BEAST. Each prior was offset to the minimum age of the oldest crown fossil assigned to that clade that has consensus in recent cladistic studies involving both living and fossil Octodontoid taxa (Vucetich et al 2015, Verzi et al 2016 and references therein), and a soft maximum age set at the lower 5% of the prior, using dates from the youngest fossil assemblage that did not include fossils belonging to the calibrated group. SALMAs stand for South American Land Mammal Age.…”