Patrick Stephens

Research in my lab uses macroecological and phylogenetic approaches to address questions that lie at the interface of ecology and evolutionary biology. Our primary focus is on large-scale infectious disease dynamics and patterns of biodiversity. The tools we use are large datasets, machine learning, and other computational methods.  

Research Interests:

MACROECOLOGY OF INFECTIOUS DISEASES
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A current major focus of research in my lab is large-scale patterns of disease biodiversity, an area in which many basic questions of wide interest remain to be answered. For example, whether parasites follow the same macroecological rules that tend to apply to free living species is largely unknown (see this paper for an overview). One of my recent projects is on the effects of phylogeny, range overlap, and ecological similarity on patterns of parasite sharing among wild ungulate species. This study also considered for the first time the effects of sampling bias on apparent patterns of parasite overlap among hosts (i.e., are pairs of well-studied hosts more likely to have known shared parasites than poorly studied hosts), and the degree to which trophic links promote the spread of parasites among distantly related species (in this case for ungulate parasites to be shared with carnivore hosts). Another recent project investigated methods for extrapolating large scale (e.g., global) patterns of parasite biodiversity from the sparse data on parasite distributions that are currently available, and much of my current work applies a macroecological perspective to more applied questions such as elucidating the ecological and anthropogenic factors that promote the spillover of zoonotic disease from wildlife to humans.

​Much of my work to until recently was associated with a NSF (in collaboration with NIH and USDA) funded research coordination network focused on the macroecology of infectious disease I lead, which you can read about here. I am currently leading a multi-year project (funded by NIH) to study the factors that promote the spillover of Ebolavirus and other filoviruses from wild mammal hosts to humans in Africa, a collaborative project between researchers at OSU and the Center for the Ecology of Infectious Diseases at UGA. We are investigating the role of ecological factors such as climate and host richness, as well as anthropogenic a socioeconomic factors such as human encroachment into wild areas and poverty.

I am also leading a new NSF funded project to look at how socioeconomic factors such as poverty, availability of doctors and vaccine hesitanceny have affected realized case numbers of COVID-19 across Oklahoma counties.  This work is in collaboratioon with many OSU faculty including Merle Eisenberg (History), Tao Hu (Geography), Juwon Hwang (Media and Strategic Communications), Rebecca Kaplan (History), Patrick and Lucas Stolerman (Mathematics). Outside of OSU, Mekala Sundaram, a machine-learning expert and former OSU post-doctoral scholar who recently took a faculty position at the University of Georgia, is also part of the team.  The work began in January 2024 and will be going through 2027.

BIODIVERSITY
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In addition to research on infectious diseases, I have also engaged in collaborative research on global patterns of biodiversity in mammals. Using resources such as published species level mammal supertrees, IUCN data on mammal geographic ranges, and compiled data on mammalian behavioral, morphological, and ecological data in PanTHERIA and other sources it is now possible to address key questions in evolutionary ecology at unprecedented scales. For example, topics that I am currently engaged in include the effects of niche conservatism on the phylogenetic heritability of geographic range distributions in mammals, the factors that affect patterns of parasite community similarity between mammal species, and how trait diversity relates to other dimensions of biodiversity such as species richness and phylogenetic diversity.

In the future, using techniques and theoretical approaches developed in mammals, I will broaden this research to encompass other vertebrate groups, particularly amphibian and reptile groups. Supertrees are available or soon will be available for most major vertebrate groups, and species geographic range data are available for the majority of terrestrial vertebrates. Squamate reptiles are one group that is particularly ripe for this approach.  Squamates consist of more than 10,000 recognized species, constituting more than a quarter of all terrestrial vertebrate biodiversity.  Yet compared to birds, mammals and amphibians we know relatively little about them.  For example, nearly 40% of species have not yet had their risk of extinction evaluated by the IUCN, and the first global biodiversity map to include all squamate species was only published in 2018.  Our knowledge of the factors that drive large scale patterns of squamate biodiversity and variation in the threat status of species remains in its relative infancy compared to other terrestrial vertebrates, and I have several ongoing projects focused on squamate reptile biodiversity and macroecology.

Ongoing work in this area is being funded by a grant from the US-Isreal Binational Science Foundation.  The goal of the project is to explore global dimesions of biodiversity in tetrapods (mammals, birds, reptiles and amphibians).  My collaborators on the project include faculy in Isreal, Canada, Arizona State University and the University of Georgia.   The latest project is to understand how variation in species richness (the number of species in an ecological community) is related to variation in trait diversity across terrestrial assemblages of squamate reptiles (lizards and snakes).  This study includes trait data for more than 10,000 species of squamates, and considers variation among the species found in every 100x100 km grid cell on earth.

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EVOLUTIONARY ECOLOGY OF AMPHIBIANS AND REPTILES
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Much of my research before coming to Oklahoma State University focused on the evolutionary ecology of amphibians and reptiles, particularly turtles in the family Emydidae. Emydidae includes many well known North American Turtle species, such as the Eastern Box Turtle (Terrapene carolina), the Painted Turtle (Chrysemys picta), and the Pond Slider (Trachemys scripta). It has been an ideal study system for me because the family is geographically very widespread and species in it are ecologically incredibly diverse. It is one of the very few families of vertebrates to include aquatic, terrestrial, and semi-terrestrial species as well as herbivorous, carnivorous, and omnivorous species. It is also among the few terrestrial clades to exhibit a "reverse latitudinal diversity gradient," where more species occur in temperate than tropical regions. Some species in the genus Graptemys also exhibit some of the most extreme sexual size dimorphisms known in tetrapods, with adult females that are more than twice as long as adult males and roughly an order of magnitude more massive.

Topics I have addressed in emydids include the origins of large scale patterns of species richness, the evolution of ecological specialization, the origins of large scale patterns of community structure, and the evolution of sexual size dimorphisms. One theme that runs through much of this work is that niche conservatism and dispersal limitation greatly influence emydid biodiversity at large spatial scales. Other projects in herpetology include the origins of large scale patterns of species richness in hylid frogs, the evolution of endosulfin resistance in North American frogs and the evolution of phenotypic plasticity in more than two dozen species of North American ranid, bufonid, and hylid frogs and parallel patterns of adaptive evolution the turtle families Emydidae and Geoemydidae.

More information:

Lab members. 

Opportunties to join my lab.