Mason Kulbaba
Research
Current Research
Capacity for Adaptation
Most studies of adaptation employ a retrospective approach to describe fitness in terms of historical selection. However, prospective approaches to the study of adaptation have the advantage of observing contemporary changes in fitness and even predicting future change. I employed such a prospective approach by estimating the immediate capacity for adaption in pedigreed populations of the annual legume Partridge Pea (Chamaecrista fasciculata). By comparing subsequent generations grown contemporaneously, I determined the extent to which potential adaptation was realized. The rate of adaptation, as described by the Fundamental Theorem of Natural Selection, is related to the additive genetic variation for lifetime fitness: σA2(W). I obtained quantitative predictions of adaptation across consecutive generations through the ratio of σA2(W) to mean population fitness, ̅W. estimating σA2(W) in multiple populations and years found considerable potential for immediate adaptation from standing genetic variation, and a genetically based increase in fitness across generations. A subsequent experiment identified the importance of an interaction between genetically effective population size and density to lifetime fitness and mating system variation. These results directly relate to the potential for evolutionary rescue in vulnerable and declining populations.
Relevant publications
Kulbaba, M. W., Yoko, Z., and J. Hamilton. 2023. Chasing the fitness optimum: temporal variation in the genetic and environmental expression of life-history traits for a perennial plant. Annals of Botany. 132: 1191–1204. PDF
Kulbaba, M. W., Sheth, S. N., Paine, R. E., Eckhart, V. M., Shaw. R. G. 2019. Additive genetic variance for lifetime fitness and the capacity for adaptation in an annual plant. Evolution 73: 1558-5646. PDF.
Sheth, S. N., Kulbaba, M. W., Pain, R. E., and R. G. Shaw 2018. Expression of additive genetic variance for fitness in a population of partridge pea grown in two field sites. Evolution 72: 2537-2545. PDF
Plant Mating Portfolios
Systematic patterns of subindividual trait variation
The interaction between plants and their environments during reproduction is made more complex by the production of similar but not identical flowers within a single floral display. The production of multiple flowers within a single display allows for trait variation among flowers, often in predictable patterns (e.g., decrease in flower size from lower to upper positions). The extent to which these patterns functionally contribute to fitness and differ among individuals is unknown. Through genetic-marker based estimates of quantitative genetic parameters, and function-valued trait analyses, my work provided the first progress in assessing the heritability, evolvability, and selection that maintains systematic patterns of subindividual variation. My findings determined that patterns of within-individual variation have a genetic basis and exhibit substantial estimates of evolvability. Therefore, these patterns may respond rapidly to selection. Finally, both the direction and magnitude of selection changes across flowering times, further highlighting the complexity of the interaction between dynamic plant phenotypes and the environment.
See also ongoing work by Oliver Noseworthy under Current Students
Relevant publications
Harder, L.D., Strelin, M.M, Clocher, I.C, Kulbaba, M.W. and M. A. Aizen. 2019. The dynamic mosaic phenotypes of flowering plants. New Phytologist 224: 1021-1034. Special issue: The ecology, evolution, and genetics of plant reproductive systems. PDF
Kulbaba, M. W., Clocher, I. C., and L. D. Harder. 2017. Inflorescence characteristics as function-valued traits: analysis of heritability and selection on architectural effects. Journal of Systematics and Evolution 55 (6) 559 – 565. Invited for special issue on inflorescence displays. PDF.