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 an ecologist. However, my interests span most of the organismal side of biology and delve lightly into physiology and evolution. My research focuses on the morphology, behavior, and ecology of birds, insects, and plants. Past and current projects address 1) paternity in birds and how morphology, population characteristics, habitat, and weather correlates to extra-pair paternity, 2) diversity, ecology, and behavior of ants in relation to environmental factors, 3) demography of long-lived perennial herbs in relation to the environment, and 4) coevolution between long-lived perennial herbs and their pollinators. I have highlighted 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 worked with the Principles of Biology I class at Cameron University to document the biodiversity of ant species in the southwestern region of Oklahoma. I am working with five recent undergraduate researchers and several peers to write and publish these projects, as well as implementing current projects addressing plant demographics and plant-pollinator interactions.
Geographic Variation in Scent and Scent Preference of the Long-lived Perennial Flower and its Nursery Pollinator
Populations of many species exhibit traits that vary across their geographic range. These can be physiological, morphological, behavioral, etc. Trait variation may influence how species interact with each other and how different populations might respond to changing climate and environmental conditions. Along with Drs. Michele Dudash and Charles Fenster, I am interested in how floral traits and scent vary across the broad geographic range of the long-lived perennial flower starry campion (Silene stellata). We have measured floral morphology and sampled scent in the field for populations in Virginia, Alabama, Kansas, South Dakota, and Minnesota. We have also grown from seed individuals from each of those target populations in a common environment in the greenhouse to determine if geographic differences in scent are either maintained (genetic origin) or disappear (environmental origin) in a common garden. We are also interested in how such scent differences might influence interactions with the plant’s obligate nursery pollinator, the campion coronet moth (Hadena ectypa). To test whether moths can distinguish scent and have a preference for plants from a particular region, we are using experimental arrays of greenhouse plants from each region offered to natural populations of moths in the field in each region. We are also conducting this experiment in the greenhouse with lab-reared moths.
Demographic Analysis of a Long-lived Perennial Flower Dataset Collected over 12 Years
While demographics of plants is a well-explored topic, we have little knowledge of demographic patterns in long-lived perennial herbs. To tackle this large topic, Drs. Michele Dudash and Charles Fenster collected demographic data over 12 years at Mountain Lake Biological Station in Virginia. I am using this data to determine how often plants transition between life stages (seedling, non-reproductive, reproductive), how long plants survive, how many times plants reproduce, and how many reproductive units (flowers, seeds) are produced from each reproductive event and across a plant’s lifetime. I am also investigating how ecological and environmental factors influence survival and reproduction.
Thermal Regulation of Red Harvester Ant Foraging
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
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
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
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
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.
Populations of many species exhibit traits that vary across their geographic range. These can be physiological, morphological, behavioral, etc. Trait variation may influence how species interact with each other and how different populations might respond to changing climate and environmental conditions. Along with Drs. Michele Dudash and Charles Fenster, I am interested in how floral traits and scent vary across the broad geographic range of the long-lived perennial flower starry campion (Silene stellata). We have measured floral morphology and sampled scent in the field for populations in Virginia, Alabama, Kansas, South Dakota, and Minnesota. We have also grown from seed individuals from each of those target populations in a common environment in the greenhouse to determine if geographic differences in scent are either maintained (genetic origin) or disappear (environmental origin) in a common garden. We are also interested in how such scent differences might influence interactions with the plant’s obligate nursery pollinator, the campion coronet moth (Hadena ectypa). To test whether moths can distinguish scent and have a preference for plants from a particular region, we are using experimental arrays of greenhouse plants from each region offered to natural populations of moths in the field in each region. We are also conducting this experiment in the greenhouse with lab-reared moths.
While demographics of plants is a well-explored topic, we have little knowledge of demographic patterns in long-lived perennial herbs. To tackle this large topic, Drs. Michele Dudash and Charles Fenster collected demographic data over 12 years at Mountain Lake Biological Station in Virginia. I am using this data to determine how often plants transition between life stages (seedling, non-reproductive, reproductive), how long plants survive, how many times plants reproduce, and how many reproductive units (flowers, seeds) are produced from each reproductive event and across a plant’s lifetime. I am also investigating how ecological and environmental factors influence survival and reproduction.
Diane V. Roeder 