Research

I am very interested in animal behaviors and how they relate to reproduction and to the biological and environmental context in which they take place.  Because of this, I classify myself as a behavioral ecologist.  However, my interests span most of the organismal side of biology.  My research focuses on the morphology, behavior, and ecology of birds and insects.  Past and current projects address paternity in birds and how morphology, population characteristics, habitat, and weather correlates to extra-pair paternity.  More recently, my work has focused on the diversity, ecology, and behavior of ants.  I have several ongoing projects, most of which involve undergraduate students as field researchers, statistical analysts, and writers.  Three of these projects focus on the red harvester ant (Pogonomyrmex barbatus) and look at how colonies are distributed across space, how individual foragers responds to daily fluctuations in temperature, and how colonies acclimate to changing temperatures across a year.  In addition, I am documenting the biodiversity of ant species in the southwestern region of Oklahoma.  Data collection is now complete on this two-year project involving the Principles of Biology I class at Cameron University as researchers and data collectors.  I am currently working with five recent undergraduate researchers to write and publish these projects and am looking forward to starting new projects in the near future.

Thermal Regulation of Red Harvester Ant Foraging

Pogo with milkweed seed.jpg
All organisms require nutrients for survival and reproduction. These nutrients are acquired in varying quantity when animals forage. The abiotic conditions that animals experience can either constrain or provide windows of opportunity for foraging activity and energy intake. My lab and I are examining how daily fluctuations in abiotic conditions regulate foraging activity and energy intake of the harvester ant, Pogonomyrmex barbatus. We are investigating how travel speed, time spent foraging, and seed size selected vary with daily temperature cycles.  We are also estimating energy expenditure during foraging trips versus energy gained via seed collection to determine how travel speed, body mass, and seed size influence energy balance across a day.

Temporal Variation in Thermal Tolerance

Pogo on poor mans pepper
Thermal tolerance is one physiological trait that dictates the abiotic conditions in which organisms exist.  It can limit an organism’s fundamental niche and dictate when organisms engage in activities such as foraging, reproduction, and defense.  Critical thermal maxima (CT max) and minima (CT min) have been determined for many taxa, however, temporal variability in these measures is not often investigated.   Given that species may experience extreme temperature fluctuations across days, seasons, and years, I am investigating variability in CT max and CT min across a year.  Our goal is to related these physiological tolerances back to variation in average monthly temperature to determine whether or not thermal range of ants acclimates to seasonal warming and cooling.

Diet Breadth Variation across Populations

Pogo with sticker seed 2.jpg
Many species have flexible feeding habits and this variability helps shape their niche.  The niche is defined as the way in which organisms or populations respond to the distribution of resources and competitors, and how it in turn alters those same factors.  This includes how species coexist when competing for limited resources.  While a species’ feeding habits shape its overall niche, the niche breadth of particular populations or individuals within a population may vary due to the resources available to them.  The size of a patch, or area of suitable habitat, is likely to exercise a strong influence on niche breadth by impacting the food resources available to each population or individual.  Small patches have fewer resources than do large patches, which are more likely to have redundant resources such that if one resource becomes unavailable, a species might still be able to persist by shifting to other available resources.  In species such as the red harvester ant (Pogonomyrmex barbatus), an important disperser of seeds in prairie ecosystems, there are often redundant resources available in the form of different grass and forb species, but fewer are available in habitat patches of smaller size.  My lab and I are investigating how diet and niche breadth 1) vary in populations occupying patches of different size, 2) vary across ant colonies within a particular population, 3) vary across individuals in the same colony, and 4) vary across time (i.e. across a year).  Understanding diet and niche breadth and flexibility will allow us to understand how populations persist across time and space and whether they will be resistant to environmental change as resources become more restricted. 

Ants of Oklahoma Project

Ant distribution map of OK
Ants are an incredibly diverse and abundant group of animals that play a vital role in maintaining the health of our biosphere. There are around 15,000 described species of ants on Earth, but we know very little about ant species diversity at small scales. There are few myrmecologists (biologists who study ants) in states such as Oklahoma and, as a result, most of what is known about where ant species occur is around large universities or in state parks. Myself and Karl Roeder are seeking to remedy this. Our goal is three-fold. 1) We aim to catalog ant diversity across under-surveyed regions of Oklahoma. 2) We are surveying for invasive ant species such as red imported fire ants. 3) We are attempting to determine if ant species diversity is related to features of urban environments. We are engaging students from Cameron University as citizen scientists to help survey a broad area in southwest Oklahoma, with a focus on Lawton, Fort Sill, and the surrounding areas. We have been fortunate enough to have the support of the Alongside Wildlife Foundation, Cameron University, and the University of Oklahoma during this adventure.

Correlates of Extra-pair Paternity in Scissor-tailed Flycatchers

stfl 9.jpg
Reproductive success is driven in large part by the mating system of a species, which ultimately determines patterns of gene transmission across generations.  In species with socially monogamous mating systems, an important component of reproductive success is extra-pair paternity (EPP), when males obtain fertilizations outside of their social pairing.  Among birds, >75% of species have appreciable rates of EPP.  Given the prevalence of EPP in birds, it is important that we understand how these factors interact to drive or constrain the opportunity for EPP, and thus sexual selection and the genetic contribution of individuals to the next generation.  I investigated the contribution of individual, ecological, and environment variation to the probability of EPP in nests of a savannah passerine, the Scissor-tailed Flycatcher (Tyrannus forficatus).  In my study population, EPP is prevalent and roughly three-quarters of nests containing extra-pair young and over half of all young result from extra-pair copulations.  Individual characteristics such as body condition, body size (wing and tail length), and ornament quality (tail streamer length and symmetry) might influence EPP if they indicate individual quality as a mate or genetic partner.  Population characteristics, including timing of nesting, breeding density, and breeding synchrony might influence the frequency with which individuals interact, and thus rates of EPP.  Habitat structure on breeding territories might also influence EPP in a similar manner, by providing perches from which individuals can monitor their territory, cover in which to interact with extra-pair individuals, or promoting interactions by bringing individuals together (communal perches and foraging habitat).  Finally, weather conditions, such as temperature, wind velocity, rainfall, and vapor pressure deficit, likely constrain individual movement and thus play a role in shaping EPP.