How do organisms evolve in the face of selection from competing directions? Most traits experience evolution from multiple selective agents simultaneously, and the evolution of phenotype is thus a function of those competing selective agents. My research studies plant evolution in the face of diverse selective agents from different scales of biology, ranging from the molecular to the macro-scale. I primarily use fruit coloration and seed dispersal to address these questions, with forays into other systems from time to time.
The evolution of trait syndromes. One of the organizing principles of plant evolution is that traits often evolve in a syndrome-like fashion, namely that multiple traits repeatedly evolve to converge on the same set of states across the plant tree of life. Although some syndromes (such as succulence) are adapted to particular environmental conditions, many syndromes evolve in the context of interactions with animals. One major theme of my research is to 1) evaluate the evidence for (or against) syndromes in a variety of contexts, and 2) assess cross-scale drivers of trait syndromes, such as animal interactors (pollinators, seed dispersers, herbivores) along with the cost of production of the traits (e.g., the cost of producing nutrients to provide reward to animal seed dispersers). Previously, I have focused on seed dispersal syndromes, but I am currently working on defense syndromes in thistles. Relevant papers: Sinnott-Armstrong et al 2020, 2021, 2022, 2023.
Coevolution and constraint between flowers and fruits. Flowers and fruits are developmentally continuous organs, with fruits developing from the ovary after fertilization. In spite of this developmental continuity, flowers and fruits are usually studied as separate (modular) entities. A second major theme of my research is to cross organ boundaries to understand why and how flowers and fruits impose evolutionary, ecological, and developmental contraints upon one another. Relevant papers: Sinnott-Armstrong et al (submitted), Dellinger et al (submitted), Sinnott-Armstrong 2024.
Origins of structural colors in fruits. Most plants use pigments, such as anthocyanins and carotenoids, to color their flowers and fruits. Some plants, however, use structural colors, where nanostructures interfere with light to reflect only some wavelengths, creating colors (most commonly, blue). In fruits, only a handful of structurally colored species are known, but we are discovering more species regularly. A third major theme of my research is 1) to identify and describe new structurally colored plant species, 2) to characterize the evolutionary origins of those newly identified structural colors, and 3) to assess the ecological consequences of evolving structural colors. The most common type of structural color in fruits involves layers of lipids that reflect blue wavelengths, but which simultaneously may contribute to the nutritional reward of the fruit. Relevant papers: Middleton, Sinnott-Armstrong et al 2020, Sinnott-Armstrong et al 2022, 2023, Middleton and Sinnott-Armstrong 2024.
