Research
Muroidea

            We are investigating the diversification of the muroid rodents, one of the largest and most successful groups of mammals that includes mice, rats, hamster, gerbils, and others. We have been using DNA sequence data from multiple nuclear and mitochondrial genes to estimate the phylogeny of this group, currently including over 900 species. These phylogenies are being used to explore the history of diversification in this group, both taxonomic and morphological, using muroids as a model of diversification. Much of this work has been in collaboration with Ronald Adkins at Univ. Tenn., Memphis (now NIH) and Kevin Rowe, Museum Victoria, Australia. Of particular interest are two of the most diverse lineages, the sigmodontine mice of South America and the murines of Australian and New Guinea. In addition, two genera of muroids have been the subject of detailed studies on phylogeography and speciation, the leaf-eared mice Phyllotis of the Andes and the Philippine forest mice Apomys (see below for more detail).


BiTS: Bivalves in Time and Space

            We are developing bivalves as a model system for macroevolutionary studies in conjunction with Dave Jablonski (Univ. Chicago), Rüdiger Bieler (Field Museum), John Huelsenbeck (UC Berkeley), Paula Mikkelsen (Paleontological Research Institution), and Jan Johan ter Poorten (Zoological Museum, Univ. Amsterdam). Collectively, we are producing a combined molecular and morphological phylogeny of extant and many extinct species to test methods of ancestral state reconstruction, molecular clock dating, and biogeographic reconstruction, and models of spatial diversification. Our lab’s contribution is overall coordination and the molecular data. See the BiTS website for more information. 

Phyllotis

            We continue exploring the systematics and evolution of the leaf-eared mice of the Andes. Topics include alpha taxonomy, phylogeography using multiple loci, speciation, biogeography, and as models to study comparative quantitative genetics (see below). Some of this research is in collaboration with Oswaldo Ramirez (Univ. Peruna Cayetano Heredia), and Angel Spotorno and Laura Walker (Univ. de Chile).

Apomys

            The forest mice Apomys are a radiation endemic to the Philippines with eight described and an impressive number of unnamed species. We have been working Lawrence Heaney of The Field Museum in reconstructing the phylogeny and historical biogeography of this group. Together we have discovered between 11 and 14 new species just in this one genus (4 identified in Steppan et al. (2003), 7 described in Heaney et al. (2011), and several more are in the process of being described.

Comparative Quantitative Genetics (G-Matrix evolution)

            The genetic variance-covariance matrix (G-matrix) describes the heritable patterns of correlations among phenotypic traits. At least in the short term, the G-matrix has a powerful effect on the evolutionary change of a population, even directing evolution in directions opposite those favored by natural selection. A major question is what role does the G-matrix play in macroevolution and whether it evolves as wellin a predictable fashion. We are expanding upon older P-matrix studies by estimating  G-matrices in four species of Phyllotis in collaboration with Ramirez, Walker, and Spotorno.


Eurycea

            The dwarf salamanders Eurycea form a complex radiation in the south-eastern US. Grad student Ken Wray is using multiple markers to explore the phylogeography of this group and test patterns of speciation. 

Crocodylian bite force

            We are working with Greg Erickson (FSU) and Paul Gignac (Stonybrook) in conducting comparative analyses of the evolution of bite force among crocodilians.

Vertebral evolution in rodents

            Using the growing rodent phylogenies, we are testing patterns of evolution and possible constraint in the vertebral column.




Evolution of invasiveness

            Invasive species have a major economic impact but the properties that make a species invasive are poorly understood. Jean Burns-Moriuchi (Case Western Reserve University) has been estimating the phylogeny of and using comparative data from the plant family Commelinaceae to identify traits associated with invasiveness.


Chipmunk mitochondrial introgression

            In collaboration with Jack Sullivan (Univ. Idaho), Jeff Good (Univ. Montana), and John Demboski (Denver Museum of Nature & Science), we sequenced several nuclear loci to understand the extent of mitochondrial introgression and hybridization between two species of Tamias chipmunks.





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