| Presentation Detail
Macroevolution Upham, Nathan S [1], Patterson, Bruce D [2]. Diversification of a diverse lineage of Neotropical rodents (Caviomorpha: Octodontoidea): integrating DNA sequences, fossils, and species traits. The Neotropical rodent superfamily Octodontoidea is an informative test case for studying evolutionary patterns and rates because it encompasses both extensive living biodiversity (38 genera, 193 species) and fossil records from numerous time periods over c. 25 million years. Degus, spiny rats, chinchilla rats, tuco-tucos, and hutias are among the ecologically diverse rodents with shared ancestry in Octodontoidea. Collectively they occupy arboreal, fossorial, terrestrial, and semi-aquatic niches and are distributed across South America, Central America, and the Antillean Islands. To reconstruct diversification dynamics and character evolution across this monophyletic lineage, I examined DNA sequence variation in conjunction with fossil ages and species traits. Phylogenetic analysis of five genes (mtDNA: cyt-b, 12S rRNA; nuclear exons: GHR, vWF, and RAG1) from 135 octodontoid species (70% of the extant total) was performed using RAxML-HPC2 v7.4.2 and MrBayes v3.1.2. A robust timetree was also constructed in BEAST 1.7.4, incorporating 13 internal calibrations to facilitate the analysis of divergence times and evolutionary rates. These analyses reveal that the chinchilla rats (Abrocomidae) are consistently recovered as the basal element in the superfamily radiation, sister to a pair of strongly supported clades: degus (Octodontidae) + tuco-tucos (Ctenomyidae), and spiny rats (Echimyidae) + hutias (Capromyidae). The monotypic nutria (Myocastoridae) was also nested firmly inside a terrestrial clade of the Echimyidae. Thirteen genera sequenced here for the first time, including several from dried tissue ancient DNA techniques (e.g., the echimyids Olallamys and Santamartamys, the capromyid Geocapromys) provide useful phylogenetic support for several inter-generic groupings. Maximum-likelihood reconstruction of biogeographic ranges (dispersal-extinction-cladogenesis model in Lagrange) robustly recovers the Patagonia-Southern Andes complex as ancestral for the Octodontoidea. This reconstruction refutes earlier ideas that the diverse, generalized, mainly lowland family Echimyidae, which appears early in the fossil record, gave rise to the Andean lineages of octodontoids—instead, the reverse derivation appears to be true. Within Echimyidae, clades of arboreal rats with Andes-Amazon species distributions are found to show repeated biogeographic transitions between Andean and Amazonian habitats. Amazonian lowland distribution is associated with a significant upward shift in species diversification rates (BiSSE method), which suggests that highland Andean habitats have played a source role in generating lowland species diversity for Echimyidae. Chromosomal speciation also appears to be implicated in the superfamily radiation, with Ctenomyidae and Echimyidae both displaying wide ranges in diploid chromosome number (2N: 10-70 and 22-118, respectively) and 2-3 times higher speciation rates than the three other related families.
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Related Links:
2012 Mol Phy Evol paper with initial results
Upham research page
1 - University of Chicago, Committee on Evolutionary Biology, 1025 E. 57th St., Chicago, IL, 60637, USA
2 - Field Museum of Natural History, Zoology; Mammals, 1400 S. Lake Shore Dr., Chicago, Il, 60605, USA
Keywords:
biogeography
phylogenetics
trait evolution
fossil calibration
phylogeny
South America
diversification
chromosomal rearrangements
life histories
Rodentia
Hystricognathi
Octodontoidea.
Presentation Type: Regular Oral Presentation
Session: 39
Location: Cotton B/Snowbird Center
Date: Saturday, June 22nd, 2013
Time: 4:00 PM
Number: 39003
Abstract ID:406
Candidate for Awards:Ernst Mayr Award,Student Travel Awards from the ASN |
