Stevan J. Arnold

Professor

Curator of Amphibians and Reptiles

B.A., U California, Berkeley 1966

Ph.D., U Michigan, Ann Arbor 1972

     E-Mail: arnolds@science.oregonstate.edu, Phone: 541-737-3705, FAX: 541-737-0501 

     Mailing Address: Department of Zoology, Oregon State University, Corvallis, Oregon 97331-2914.

COURSES TAUGHT (List and descriptions).

AREAS OF RESEARCH: phenotypic evolution, quantitative genetics, sexual selection, sexual isolation, protein evolution, molecular systematics.

STATEMENT OF RESEARCH INTERESTS  (full length CV).  The focus of research in my laboratory is on evolutionary processes and pattern in natural populations. I work mainly on snakes and salamanders:

Evolutionary processes in garter snakes.-The over-arching concept in the snake work is to establish a bridge between evolutionary process (inheritance, migration, selection) and pattern (geographic variation and species differences). My recent work with snakes has emphasized the quantitative inheritance of meristic traits (scale and vertebral counts). In collaboration with Patrick C. Phillips (U. Oregon, Eugene), I have been comparing patterns of multivariate inheritance among populations and species of garter snakes. We have been searching - with some success - for regularities in the evolution of inheritance and environmental matrices that describe multivariate inheritance. The significance of those regularities is that they can be used to reconstruct historical patterns of selection and to test neutral models for population differentiation - two important bridges between process and pattern. The snake work is increasingly focused on comparing inheritance matrices on a phylogenetic tree for garter snakes and their relatives, natricine snakes. I have established a molecular lab at OSU to work on the phylogeny of natricines at the population and species levels. This systematic work is being pursued in collaboration with Michael E. Pfrender (Utah State University, Logan), Michael E. Alfaro (Washington State University, Pullman), Robin Lawson (Calif. Acad. Sci., San Francisco), and Frank Burbrink (CUNY).  A primary focus is to deduce the population and species phylogeny of those taxa for which we have estimates of inheritance matrices (Thamnophis couchii complex, T. elegans, T. radix,  sirtalis, and their close relatives) using mitochondrial and nuclear gene sequences. Aside from clarifying the relationships of these taxa, a well-resolved molecular phylogeny will allow us to test models for the evolution of inheritance matrices.

The evolution of the G-matrix.- In a related theoretical project, I am studying the evolution of inheritance matrices (G-matrices) by computer simulation in collaboration with Adam G. Jones (Texas A&M)and Reinhard Burger (Univ. Vienna).  The goal of this project is to establish the conditions of selection, mutation, and population size that are most and least conducive to G-matrix stability.

Aging and stochastic demography in garter snakes.- Anne M. Bronikowski (Iowa State Univ.) and I are continuing a demographic study of T. elegans that has been underway for more than 25 years in the vicinity of Eagle Lake, Lassen County, California. We have discovered two ecotypes with contrasting profiles of age-specific growth, reproduction and mortality.  We are using those ecotypes as a model for studying senescence in natural populations (Amanda's Snake Camp blog)..  In a related set of projects, Mollie K. Manier has completed her doctoral work at OSU on this system.  Manier used microsatellites to study population structure of T. elegans and T. sirtalis and their prey (Bufo boreas) in the Eagle Lake basin.  In the course of that work, she demonstrated strong selection on the scalation and coloration traits that characterize the meadow and lakeshore ecotypes in T. elegans.

The evolution of salamander courtship pheromones.- The salamander work is part of a larger project on the evolution of courtship pheromones in plethodontid salamanders.  The courtship pheromones of these salamanders are cytokines (see diagram below of pheromone - blue -  threaded onto structually-similar human IL-6 , red)  that are either "vaccinated" into the female's circulatory system by the enlarged premaxillary teeth of the courting male or delivered into the female's vomeronasal organ (click here to view video of olfactory delivery in Plethodon shermani).  Lynne Houck and her co-workers have shown that these pheromones speed up the process of insemination.  The process of sperm transfer is shown in this video of Plethodon shermani.  The goal of the project is to understand 

the evolution of courtship pheromones in the genus Plethodon at the level of genes, proteins, physiology and behavior.  The project is headed by Lynne D. Houck (OSU) and consists of a molecular & biochemical team (at OSU and the University of Louisville), a physiological team (at OSU, Univ. Oklahoma and Univ. Bremen) and a behavior team (OSU).  The aim of the molecular work at OSU is to characterize pheromone gene sequences in 30 species of Plethodon and deduce patterns of selection at the codon level.  We are also in the process of localizing and characterizing pheromone receptors.  The primary members of the molecular/biochemical team are Steve Arnold, Frank Moore, Richard Watts (postdoc) and Catherine Palmer (currently or formerly at OSU) and Rick Feldhoff, Pam Wheeler-Feldhoff, Ron Gregg, and Maureen McCall (all at Louisville).  Our team also relies on help from Hilary Godwin's lab (UCLA), Amy Rosenzweig's lab (Northwestern University) and Richard Highton (Univ. Maryland). 

The evolution of sexual isolation.- Louise S. Mead, Paul Hohenlohe, Josef Ueyda and I are collaborating on maximum likelihood and computer simulation studies of the evolution of sexual isolation.  We are using a large data sets on sexual isolation in plethodontid salamanders (Desmognathus), darters (Etheostoma) and Drosophila as test cases. 

CURRENT AND FORMER GRADUATE STUDENTS AND POSTDOCS (Click HERE for a  list).

RESEARCH AND TRAINING SUPPORT (See CV for a list of grants and awards).

HERPETOLOGICAL COLLECTIONS AT OSU (Click HERE for a description).