Background
I went to college in Massachusetts at Mount Holyoke College. While there, classes and research opportunities helped me figure out that I wanted to study ecological and evolutionary genetics in plants. I followed these interests through a PhD in genetics from Duke University in North Carolina. While there I realized that while research is compelling, I was more interested in pursuing a position that had an emphasis on teaching. I bounced between the Midwest and east coasts with some temporary positions at small colleges. I came to DePauw as part of a “Covid cohort” in 2020. I teach courses in evolution, ecology, and genetics, and I’ve been working with some students doing research on evolution of plant populations in DePauw’s nature park. My research interests center on how plant populations are (or aren’t) able to respond to natural selection, although I’m broadly interested in a number of evolutionary questions.
Lines of Research
- Variation in hemp dogbane populations (Ongoing)
- Chemical defenses in Boechera stricta (Ongoing)
Variation in hemp dogbane populations (Ongoing)
Populations that live in unusual or challenging conditions may require specific traits to thrive there. These different traits may be innate, due to underlying genetic adaptations to the specific environment, or may be plastic, having developed in response to the conditions the individuals have lived in. Understanding whether important, complex traits are genetic or plastic is a key to understanding how fast populations can respond to changing conditions; plastic responses can appear almost instantly, while genetic changes in populations take generations. In our rapidly-changing planet, understanding how and whether populations can respond to disturbed environments and other changes is becoming even more crucial.
My students and I are studying this question in DePauw’s nature park, using the plant hemp dogbane (Apocynum cannabinum). Part of the nature park is a quarry site that has been abandoned for approximately fifty years. It is a highly disturbed and very harsh environment, with little soil, strong sunlight, and inconsistent water availability. Hemp dogbane grows in the quarry and in the less-disturbed surrounding area. We’re using these populations in and out of the quarry to studying how variation may contribute to survival in diverging environments.
Student Collaboration
In my first summer at DePauw, students Marie Spehlman and Michael Aiken worked with me on studying natural populations of hemp dogbane around the Nature Park. We measured a range of traits, including size, timing of flowering and fruiting, pigmentation, and herbivory and defenses against herbivores. We found that populations in the quarry differed from non-quarry populations for many of these traits.
Ongoing field work with students will involve planting dogbane in “common gardens,” in the quarry and less-disturbed meadows, an experimental design that will let us investigate whether the traits that are different between the habitats increase survival and reproduction in the environment where they’re found, and whether these differences have an underlying genetic basis. In the lab, some students are beginning to use genetic techniques to look at the genetic variation within and among dogbane populations.
Work in my lab ranges from spending every day outdoors in the quarry to benchwork in the lab. Students that are interested in participating in research are encouraged to contact me. The majority of my research projects take place over the summer, but there are projects that can be completed during the semester as well.
Chemical defenses in Boechera stricta (Ongoing)
Boechera stricta, a small wildflower found across much of western North America, is a member of the mustard family. Like many other species in the family, it makes chemical compounds known as glucosinolates. These compounds discourage feeding by most insect herbivores, although specialist insects can tolerate or even be attracted by them. There are many different glucosinolate compounds, and B. stricta has genetic variation for which types are made.
My previous work on this question found that evolution of glucosinolates in different parts of the plant is highly constrained; at the site where I conducted my research, different compounds were advantageous in the leaves and fruits, but plants are genetically constrained to make either one type or another in all tissues. Thus, the population is unable to effectively or rapidly respond to natural selection.
Current work on this system includes analyzing past field data to look at patterns of genetic variation within a single population, and the evolutionary forces that may be affecting it.
Student Collaboration
There is no currently ongoing data collecting for this project, but if students are particularly interested in it, I encourage them to contact me. There is substantial opportunity for students who are interested in gaining experience in data analysis to help look at patterns in the large field dataset.
Publications
Carley, L.N., Mojica, J.P., Wang, B., Chen, C.Y., Lin, Y.P., Prasad, K.V., Chan, E., Hsu, C.W., Keith, R., Nuñez, C.L. and Olson-Manning, C.F., 2021. Ecological factors influence balancing selection on leaf chemical profiles of a wildflower. Nature ecology & evolution 5:1-10.
Keith, R. and T. Mitchell-Olds. 2019. Antagonistic selection and pleiotropy constrain the evolution of plant chemical defenses. Evolution 73(5): 947-960.
Keith, R. and T. Mitchell-Olds. 2017. Testing the optimal defense hypothesis in nature: variation for glucosinolate profile within plants. PLOS One 12(7).