Research in the lab is focused on understanding the origin of biological diversity.
To address this long-term goal, we study highly diversified groups of animals ranging from clams to cats and from species to ordinal levels. We reconstruct the phylogenetic relationships of these diverse groups to use as the framework for other analyses of diversification. My primary groups of interest are the muroid rodents, by far the most diverse group of mammals with more than 1,600 species, and various sub-groups among the muroids, especially the South American sigmodontine mice (>360 species), the Andean leaf-eared mice, Phyllotis, and the Philippine forest mice Apomys. These phylogenies are then used to study morphological evolution, patterns of diversification, biogeography, and comparative quantitative genetics. Our techniques include phylogenetic analyses of DNA sequence (primarily large data sets with multiple nuclear genes) and morphological data, comparative analyses of covariation among traits, developing the comparative tools to test these multivariate patterns, analysis of geographic variation, and alpha-level systematics of living and fossil material.
You can explore the lab's research and people in more detail using the navigation bar above, or go to my personal home page for more information.
I welcome prospective students interested in working in any of the general fields described above. Because my research is fundamentally question generated and not taxon based, students need not work on the same groups of animals that form the core of my current research.
The first peer-reviewed reports of the discovery of the highest elevation vertebrate (Phyllotis xanthopygus, the yellow-rumped leaf-eared mouse) has been published in the Proceedings of the National Academy of Science.
The Steppan lab has been collaborating with the original discoverers (Tom Bowen and Matt Farson), microbial biologists (Steve Schmidt and his lab at U. Colorado), and more recently a team of mammalogists (Jay Storz, Guillermo D’Elia, and colleagues), who have collectively established the world records first for mammals and then for all vertebrates, on this mountain.
See links for the paper, including videos from the 2020 discovery at the summit (6739 m, 22,110') and the 2013 discovery at 6,205 m (20,350’).
A National Geographic article by Douglas Main, covers the Steppan Labs work in identifying Phyllotis xanthopygus (the yellow-rumped leaf-eared mouse) as the the world's highest-dwelling mammal.
What began with an observation by mountain climbers of an unidentified rodent surrying about the desolate snow covered terrain near the summit of Llullaillaco, the worlds second highest volcano, would later be associated with environmental sampling and sequencing which confirmed inhabitation of this hostile habitat by P. xanthopygus.
To see the full article, including a video of the sighting on the volcano, click on the link below.
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The Steppan Lab got a new website (this one).