RESEARCH
Research in the Parkinson Lab focuses on the study of evolutionary processes including speciation, trait evolution, and biogeography by utilizing phylogenetic reconstruction. While our research has spanned many systems including small mammals, marine turtles, lizards, and bacteria, our main interests lie in using venomous snakes, particularly pitvipers, as a model to understand these processes.
You can find a list of our current research projects below.
NATIONAL SCIENCE FOUNDATION
DIMENSIONS OF BIODIVERSITY
Scales of biodiversity - Integrated studies of snake venom evolution and function across multiple levels of diversity
This project is an international collaboration involving researchers in the U.S. and Brazil and is funded by the National Science Foundation and FAPESP. In addition to the Parkinson Lab, the collaborators include Dr. Lisle Gibbs at Ohio State University, Dr. Darin Rokyta at Florida State University, Drs. Inácio de Loiola Meirelles Junqueira de Azevedo, Ana Maria Moura da Silva, and Erika Hingst-Zaher at the Instituto Butantan, and Dr. Hassam Zaher at the University of São Paulo.
This project will determine how key innovations within the venom system have contributed to diversification in the 2,500 species of advanced snakes. Venom is hypothesized to have been the key innovation initiating the evolutionary radiation of snake species by expanding feeding opportunities. This project will seek to determine the factors and traits that promoted that diversification, and will test for biases in the genetic pathways underlying rapid evolution in venoms between closely related species. The study includes the training of two postdoctoral researchers, and multiple high school, undergraduate, and graduate students at three major state universities in Ohio and Florida. The research will produce new data on venom chemistry and function, which may be useful for novel drug discovery and design.
Representative samples of diverse species from three families of venomous snakes will be collected in the United States, Central America, and Brazil to test for relationships between venom function and diversification rates. Venom complexity, composition, and enzymatic-activity profiles will be assayed to test the hypothesis that higher venom evolvability is a prerequisite for rapid evolutionary diversification. Six closely related species pairs with highly divergent venoms will be chosen for molecular assays to evaluate the genetic and protein changes responsible for rapid evolution of venom function. This work will unite diversification studies and the genetics of adaptation to provide an integrated perspective of how adaptations are built and how they affect diversification, leading to an understanding of how biodiversity originates across micro- to macroevolutionary levels.
Rear-Fanged Snake Venom Evolution
Historically, venom studies have focused on front-fanged snakes such as vipers and elapids; however, these account for a small portion of snake diversity. Recent technological advancements have allowed for further exploration into the venom evolution of rear-fanged snakes.
Recently, we have focused on species such as Conophis lineatus, Tantilla nigriceps, the genus Thamnophis, and others to begin shedding light on this understudied group of snakes.
UNITED STATES FISH AND WILDLIFE SERVICE
Evaluating Mole Skink and Salt Marsh Snake
subspecific taxonomy in Florida using genomics
Previous Projects
Mole skinks (Plestiodon (Eumeces) egregius) are semi-fossorial lizards endemic to the North American coastal plain. Mole skinks inhabit dry sandy substrates, including scrub, coastal berm, and coastal hammock in Florida, southern Alabama, and southern Georgia (Mount 1963). Five subspecies of mole skink were described in 1965 based on morphological characters (Mount 1965). There is currently little genetic evidence for or against the current subspecific groups, but according to Branch et al. these subspecies may not be evolutionary significant units (Branch et al. 2003). Currently, the Florida blue-tailed mole skink (P. e. lividus) is listed as federally threatened and there is a proposal to list both the Florida Keys mole skink (P. e. egregius) and Cedar Key mole skink (P. e. insularis). The current subspecies descriptions are based on morphological characters such as tail coloration, scale counts and width of dorsal stripes. Branch et al., (2003) investigated the evolutionary relationships of this species using a very small piece of the mitochondrial cyt-b gene and found that the insular taxa (P. e. egregius, P. e. insularis) have very low genetic diversity. The author also found that the Florida Keys mole skink (P. e. egregius) is more closely related to the federally threatened bluetail mole skink (P. e. lividus) from the Lake Wales Ridge than the northern mole skink (P. e. similis) or peninsular mole skink (P. e. onocrepis), although it most closely resembles the northern subspecies, P. e. similis. Thus, prior to listing these two additional subspecies a taxonomic study of the entire Plestiodon egregius subspecies complex should be undertaken.
The Atlantic Salt Marsh Snake (ASMS, Nerodia clarkii taeniata) inhabits brackish environments in Volusia, Brevard, and Indian River Counties on Florida’s east coast. Due to habitat destruction, and potential genetic introgression this taxon was listed as federally threatened in 1977. Recent population surveys indicate that viable populations might now only exist in Volusia County near Merritt Island National Wildlife refuge. The ASMS is threatened by potential hybridization with the Florida Banded Water Snake, Nerodia fasciata pictiventris. Ergo, the taxonomic validity of the ASMS is also in question. According to the U.S. Fish and Wildlife Service’s 2008 Five-Year Review, there is a major need for demographic and genetic surveys to determine taxonomic validity and current population demographics of the ASMS. A major assumption was made when the UFWS listed this taxon, that being Nerodia clarkii taeniata is taxonomically distinct, either as a subspecies or a distinct population segment of Nerodia clarkii. In 2010 USFWS funded a pilot study to conduct an initial demographic, genetic and taxonomic study of N. c. taeniata. During the next 2 years we spent over 900 man hours in the field searching for Nerodia. During that time we only were able to collect 2 individuals which keyed out to be N. c. taeniata. Since then we have collected an additional 37 N. c. taeniata and over 600 additional individuals in this complex. Initial mtDNA (cyt-b) and nuclear (TATA) gene sequence results indicate that N. c. taeniata is not a unique lineage, that N. c. taeniata and N.c. clarkii form a clade. Our initial morphological results indicate that there are no defining characteristics which would suggest that N. c. taeniata deserves subspecific rank or is a distinct population segment. The taxonomic history of this species is complex and storied and needs to be evaluated in more detail.
MIDDLE AMERICAN BIOGEOGRAPHY
Much of our research has focused on New World pitvipers such as: palm-pitvipers (Bothriechis), rattlesnakes (Crotalus), jumping pitvipers (Atropoides), montane pitvipers (Cerrophidion), and bothropoids (Bothrops-Bothrocophias-Bothriopsis-Bothropoides-Rhinocerophis). We study these lineages to understand the biogeography of the Middle American region that led to the evolution of lineages and to ensure that the current taxonomy matches the lineages we recover in our phylogenetic analyses.
MOJAVE RATTLESNAKE
VENOM EVOLUTION
The focus of Jason Strickland's dissertation research uses Mojave Rattlesnakes, Crotalus scutulatus, as the model to understand the evolution of Type A (neurotoxic) and Type B (hemotoxic) venom. Through the use of comparative transcriptomics and proteomics, he seeks to understand potential selection pressures that are maintaining both venom types within the species in discrete geographic locations. His field work has been conducted in the Chihuahuan, Sonoran, and Mojave Deserts of the U.S. and Mexico collecting rattlesnakes for his dissertation.
PALM PITVIPER PHYLOGENETICS AND VENOM EVOLUTION
The focus of Andrew Mason's dissertation research is to determine the phylogeny of the genus Bothriechis and determine how the environment and phylogenetic- constrained evolution shape the highly-variable venom phenotype seen across the different species. Andrew's field work has been conducted throughout Middle America in Costa Rica, Honduras, and Mexico.
GOPHER TORTOISE
ECOLOGY AND CONSERVATION
The focus of Rhett Rautsaw's thesis research examined the use of roads and railways by Gopher Tortoises (Gopherus polyphemus) at the John F. Kennedy Space Center. The goal was to (1) determine whether roadsides are or could be used as a wildlife corridor to connect distant habitats and (2) evaluate the impacts of railways on tortoise movement and behavior while providing management implications for both roads and railways. Rhett's research also included testing methods of estimating Gopher Tortoise density at a given site based on the presence of their burrows and the occupancy of those burrows.
COLUBRID PHYLOGEOGRAPHY
A variety of projects in the lab utilize phylogenetics to answer questions relating to the biogeography of various groups. This particular project focuses on measuring the effect of the American Cordillera on the genetic structure of two broadly distributed snake species: glossy snakes (Arizona elegans) and long-nosed snakes (Rhinochelius lecontei). Genetic structure as a result of this barrier has been documented in other snake species including black-tail rattlesnakes and western diamondback rattlesnakes. The findings from this project will further elucidate our understanding of vicariance’s effect on evolution and allopatric speciation.