My research interests lie broadly in understanding the evolution of novel floral traits. For my dissertation, I am working to understand the ecological function and genetic basis of personate flowers in Penstemon wildflowers. Personate flowers are characterized by an upward bulge in the lower lip of the corolla tube that ultimately seals off the floral passageway (see P. hirsutus). This floral trait has evolved at least two times in the genus Penstemon, but no previous research has focused on understanding why or how this trait evolved.
Several of my experiments use the personate Penstemon hirsutus (left) and open-tubed Penstemon smallii (right) as my focal species because they represent contrasting extremes of floral morphology.
Below, you will find information regarding each of the projects I am currently working on!
What is the morphological basis of personate flowers?
Understanding morphological characteristics that differentiate personate flowers from open-tubed flowers is a necessary component for my research. I have used several different methods including size-standardized photos, microCT scanning, and geometric morphometrics. To date, the best method for quantifying a flower’s degree of personate-ness is by taking photographs of cross-sections sliced through the flower (see right). With these photos, I measure the height of the “pleat” that pushes into the flower and compare this measure to total flower height.
Right: Cross-section cuts through flowers that clearly show the difference in personate-ness between open-tubed (top), intermediate (mid), and personate (bottom)
Above: Three dimensional rendering of P. hirsutus from MicroCT scans.
How many times have personate flowers evolved in the Eastern North American Penstemons?
The presence of three personate species in Penstemon’s Eastern section (sect. Penstemon) provides an excellent opportunity to ask how many times this novel floral trait has evolved. Are all three personate Penstemons each others closest relative? Or is there a deviation from what we would expect based on the species’ shared phenotype? I am using whole-genome level sequencing data and a phylogenomics approach to answer my questions.
What is the ecological function of personate flowers?
I am using a combination of pollinator observations and a mating system study to answer this question!
The pollinator observations provide me with the opportunity to determine if personate flowers are filtering pollinators in any way. My initial hypothesis was that personate flowers were filtering bees based on size. However, results from my 2022 field season indicates that this hypothesis is incorrect as both large (i.e., Bombus) and small (i.e., Osmia and Ceratina) bees visit both floral types.
The mating system study is driven by my observation that the upward bulge in the lower lip of personate flowers causes the anthers and stigma to be closer to each other (compared to their positions in the open-tubed flowers). My hypothesis is that the decreased distance between reproductive structures makes personate flowers better adapted to selfing. To test this hypothesis, I assign both open-tubed and personate flowers to different treatment groups and then quantify seed set to determine the fitness of each group.
What is the genetic basis of personate flowers?
To determine how personate flowers evolved I am conducting a Quantitative Trait Locus (or QTL) mapping analysis. Broadly, this analysis looks for correlations between phenotypes and genotypes within an F2 mapping population. I completed my initial parental cross for this study during my first year of grad school and three years later an initial batch of F2 plants are about to flower! The floral phenotypes of the F2 individuals will provide the ability to make predictions regarding the number of loci that are responsible for personate flowers. I am super excited to see these flowers… stay tuned on my twitter for updates!
