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Research

Some of our primary projects

Peromyscus maniculatus (Deer Mouse), Photo Credit: Glenn and Martha Vargas (California Academy of Sciences)

Muroidea

We are investigating the diversification of the muroid rodents, one of the largest and most successful groups of mammals.

Phyllotis darwini (Darwin's leaf-eared mouse), Photo Credit: P. L. Meserve (tolweb.org/Phyllotis/16683)

Phyllotis

We continue to explore the DNA-based phylogenetics, phylogeography, and morphological systematics of Phyllotis, the leaf-eared mice of the Andes.

Apomys brownorum (Mount Tapulao forest mouse), Illustration Credit: V. Simeonovski (The Field Museum, https://www.fieldmuseum.org/apomys-brownorum)

Apomys

We are working to reveal the complex systematics and biogeography of Apomys, a large genus of forest mice in the Philippines.

BiTS Project

BiTS: Bivalves in Time and Space

We are developing bivalves (clams and their relatives) as a model system for macrovolutionary studies.

Periophthalmus kalolo (Common Mudskipper), Photo Credit: Bernard Dupont (https://www.flickr.com/photos/berniedup/10292242043/)

Mudskippers

Mudskippers are a living clade of amphibious fish that we are using as a model system to explore the morphological and bio-mechanical adaptations to the changing stresses of living above water. This system will be used as a proxy to understand the selective stresses that occured during the tetrapod transition from water to land over 400 million years ago.

The Genetic constraints due to the G-matrix on adaptation, Figure Credit: Steppan, Scott J., Patrick C. Phillips, and David Houle. "Comparative quantitative genetics: evolution of the G matrix." Trends in Ecology & Evolution 17.7 (2002): 320-327.

Comparative Quantitative Genetics

The heritable component of covarying organismal traits may direct the evolutionary trajectories of lineages, making some morphologies easier to evolve, and others difficult. To what extent is this true? And, to what extent are the genetic covariances themselves able to evolve?

Vertebral Evolution

Evolution of the Vertebral Column

The vertebral column is, literally, central to the body plan of vertebrates and yet few comparative studies of its evolution have been conducted. We are exploring this through detailed surveys including hundreds of rodent species, modern phylogenetic comparative methods, and quantitative genetics.

Student Projects

Student-led projects

Other projects on systematics, phylogenetics, and morphometrics taken on by students in the lab have covered a diversity of species including: dwarf salamanders, echinoderms, carnivores, marsupials, and plants.

Muroidea

We have been using DNA sequence data from multiple nuclear and mitochondrial genes to estimate the phylogeny of this group, culminating in over 900 species (Steppan & Schenk, 2017 PLoSOne). 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.

Of particular interest are two of the most diverse lineages, the sigmodontine mice of South America and the murines of Australian and New Guinea. Our current NSF grant is to explore the adaptive radiation of the Sigmodontinae using phylogenomics, post-cranial morphology, and comparative quantitative genetics. 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.

Much of the past work was in collaboration with Ronald Adkins at Univ. Tenn., Memphis (now NIH), Kevin Rowe, Museum Victoria, Australia, and John Schenk, Georgia Southern University. 

Phyllotis

We continue exploring the systematics and evolution of the leaf-eared mice of the Andes.

The leaf-eared mice Phyllotis live throughout the Andes and nearby xeric regions and are often the most abundant mammals within their range.

We are expanding our systematic studies of the DNA-based phylogenetics, phylogeography, and morphological systematics.

Apomys

As part of a long-running collaboration with Lawrence Heaney of the Field Museum and the Univ. of Chicago, we are working to reveal the complex systematics and biogeography of this large genus of forest mice in the Philippines.

Our past work on the morphology and DNA of Apomys resulted in the discovery of at least 16 new species, while also revealing that the Philippine Islands have the highest density of mammal species in the world.

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 working with the molecular data.

Mudskippers

Tetrapods first evolved to conquer the land over 400 million years ago, but there are few fossils from that transition and no living organisms to see how they functioned.

In collaboration with Greg Erickson (FSU) and Paul Gignac (Oklahoma State Univ.) we are using the diverse living clade of mudskippers as a model system to explore the morphology and biomechanical adaptations to changing stresses of living above water.

Comparative Quantitative Genetics

The heritable component of how traits in an organism covary are predicted to help direct the long-term evolutionary trajectories of lineages, making some morphologies easy to evolve, others difficult.

To what extent is this true? And, to what extent do the genetic covariances themselves evolve?

A core aspect of my research program is to unify, in part, the disparate fields of quantitative genetics and macroevolution, via phylogenetic comparative analysis of these quantitative genetic components.

Evolution of the Vertebral Column

The vertebral column is, literally, central to the body plan of vertebrates and yet few comparative studies of its evolution have been conducted.

We are exploring this through detailed surveys including hundreds of rodent species, modern phylogenetic comparative methods, and quantitative genetics.

Student-led projects

I have also participated on a variety of other projects through my students, including: systematics of dwarf salamanders Eurycea (Kenny Wray), phylogeography in echinoderms with Kathleen Torrence, new Bayesian Species distribution Modeling methods with John Humphreys, carnivore phylogenetics and morphological specialization with Jill Holliday, constraints on marsupial evolution with Jim Cooper, and plant phylogentics (Commelinaceae) with Jean Burns.

Address

Florida State University
Department of Biological Science
King Life Science, Room 4066
Tallahassee, FL 32306-4295

Contact

Office: (850) 644-6536
Lab: (850) 644-6045
Fax: (850) 645-8447
Email: steppan @ bio.fsu.edu