Geographical distribution and ecological diversification of South American octodontid rodents

Abstract

Caviomorph rodents represent one of the most distinctive groups of mammals in southern South America drylands; they colonized South America from Africa via trans‐oceanic dispersions in the Eocene (40–50 Ma) and underwent an extraordinary ecological radiation after their arrival, thus making this group of great interest for biogeographic and evolutionary studies. The aim of this article was to provide a working hypothesis regarding the biogeographical history and ecological diversification of one of its conspicuous families, the Octodontidae. We reconstruct the evolutionary theater where their ecological diversification took place, and potential events of dispersal, vicariance and extinctions. We analyzed the historical biogeography of the Octodontidae across the eight ecoregions where they occur, based on species phylogeny and divergence times. Four approaches were used to reconstruct ancestral area: (1) Statistical Dispersal–Vicariance Snalysis (S‐DIVA); (2) Bayesian binary Markov chain Monte Carlo (MCMC) analysis implemented in Reconstruct Ancestral State in Phylogenies (RASP); (3) Fitch optimization method; and (d) weighted ancestral area analysis (WAAA). Parsimony ancestral state reconstructions were implemented in order to explore the evolutionary history of an ecological character, mode of life. We propose the northern portion of the Monte desert ecoregion as the ancestral area in the evolution of the Octodontidae, with subsequent dispersal and enlargement of the family geographic range. The evolution of their ecological specialization (i.e. modes of life) suggests an ambiguous ancestral condition (saxicolous, generalist terrestrial, semifossorial) linked to species adaptation to arid environments, with fossoriality appearing later in octodontid evolution. The evolution of the Octodontidae is associated with contrasting environmental conditions (i.e. climate and vegetation) produced by the Andean Uplift between eastern and western sides.

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

“…Octodontids are terrestrial to fossorial (degus, rock rats, viscacha rats) and subterranean rodents (coruros, tuco-tucos) Electronic supplementary material The online version of this article (doi:10.1007/s10914-015-9301-1) contains supplementary material, which is available to authorized users. endemic to mesic and arid biomes of southern South America (Redford and Eisenberg 1992;Ojeda et al 2013). The living abrocomids make up a less diversified clade, sister to echimyids-octodontids (Upham and Patterson 2012, in press).…”

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

“…Tympanoctomys is member of a clade of the family Octodontidae, restricted to Argentina (Reig 1989; Ojeda et al 2013; Diaz et al 2015). Octodontid rodents are highly diverse in eco-morphological aspects, including six genera with terrestrial, semi-fossorial, fossorial and subterranean forms (Ojeda et al 2013; Verzi et al 2015).…”

“…Octodontid rodents are highly diverse in eco-morphological aspects, including six genera with terrestrial, semi-fossorial, fossorial and subterranean forms (Ojeda et al 2013; Verzi et al 2015). Due to their broad ecological and geographical diversity at both sides of the Andean mountain range, these rodents represent a very interesting group in biogeographical and evolutionary aspects (Lessa et al 2008; Ojeda 2010; Ojeda et al 2013). …”

“…Ecological aspects of the species are poorly known, T. barrerae being the best studied. The colonization success and expanded range of T. barrerae has been suggested to be the result of a set of behavioral, ecomorphological, and physiological features that allows better utilization of salt basin, open xeric habitats, and hypersaline food resources (Mares et al 1997; Ojeda et al 1999; Gallardo et al 2007; Ojeda et al 2013). …”

“…Members of the genus Tympanoctomys have the capability to move on the surface as well as to build complex burrows (Ojeda et al 2013; Teta et al 2014; Diaz et al 2015), a feature that distinguishes the semi-fossorial forms (Eisenberg 1981). According to Lessa et al (2008), this digging ability is not reflected in substantial changes in the locomotor system of subterranean octodontids, strongly suggesting that during the early evolution of these rodents, behavioral events have preceded and probably promoted subsequent morphological changes.…”