Current work in the lab revolves around three major foci: 1) The contribution of polyploidy to functional and genomic biodiversity; 2) Ecological and evolutionary studies of separate sexes and sex chromosomes; and 3) The factors that shape plant-pollinator interactions, and the consequences for phenotypic evolution, microbial-plant interactions and community structure of flowering plants.
How does polyploidy contribute to biodiversity?
Most, if not all, flowering plants are polyploids, and as such polyploidy is identified as an important mode of speciation in plants and a main driver of biological adaptation and range expansion. As a consequence, it may be key to plant evolutionary/ecological potential to respond to environmental change. However, exactly how polyploidy contributes to biodiversity and which genomic mechanisms or functional traits underlie the success of polyploids remain unanswered questions. We are using Fragaria as a model system to address these long standing questions and test fundamental hypotheses on how polyploidy contributes to biodiversity. With an international group of collaborators (China and USA) we are conducting an integrated study of genetic, functional (phenotypic and transcriptomic) and phylogenomic biodiversity. We aim to produce an authoritative understanding of whether similarities in functional diversity and ecological amplitude of polyploid species are the result of the same patterns (‘rules’) of genetic diversity, chromosome structure or gene expression in a polyploid genome or whether multiple genetic and genomic pathways could lead to successful responses to environmental change.
How can plants provide key insight into the nature of the evolving sex chromosome?
Our extensive ecological and genetic work on the evolution of separate sexes (dioecy) in strawberry (Fragaria) places us in a unique position to evaluate the dynamics of sex chromosome evolution--not only the crucial first steps but also whether other processes, usually ascribed to later stages, take place in younger sex chromosomes as well. Despite numerous studies in a wide range of organisms, the very earliest step in sex chromosome evolution -- from two linked but recombining loci to suppression of recombination between them (and thus the transition from subdioecy to dioecy) --remains unexplored. We are merging genetic, genomic and bioinformatic approaches with ecology and phylogeny to test hypotheses regarding recombination suppression, sequence divergence and selection for sexually antagonistic genes linked to sex. We are utilizing several species within the sexually variable clade of Fragaria to gain transformative insight into early sex chromosome evolution, as well as the unique roles of hybridization and polyploidy in the transition from hermaphroditism to separate sexes.
How do pollinators mediate plant-plant and plant-microbe(viral) interactions and in turn how do these affect pollination sufficiency?
Understanding the nature of plant-plant-pollinator interactions (i.e., whether plants compete for pollinators or facilitate each other’s pollination) and how they translate into pollination sufficiency and ultimately plant population persistence is central to our understanding of the generation and maintenance diversity in plant communities. Shared pollinators also mediate interactions between flowers and microbes (and viruses) that can affect plant fitness both positively and negatively.
Work in both of these areas is even more relevant in the Anthropocene as native pollinator-plant interactions are at risk from land-use and climate change, and as species invasions reshape interaction networks. One current emphasis of the lab is to understand how pre- and post-pollination interactions contribute to plant community assembly and coexistence, and how pollinator networks that include intentional and spontaneous plants lead to novel plant-pathogen interactions and/or disrupt microbial mutualisms. We are addressing these questions in flowering communities in native habitats of California, Hawaii and Mexico and urban contexts of Pittsburgh and Germany.
What drives floral trait evolution and plant speciation?
We seek to understand both the context-dependency of pollinator-mediated selection and the direct effects of non-pollinator agents of selection on floral traits. Members of my lab and I do so by considering the ways that biotic (antagonists or soil mutualisms) or abiotic (soil conditions) modify plant-pollinator interactions as well as taking a holistic approach to floral evolution and exposing novel agents of selection.We approach these issues using mechanistic ecological experiments, geographic surveys and phylogenetically-controlled large scale comparisons. We are keenly interested in addressing the multivariate functional floral phenotype and all sensory modalities of pollinators have addressed evolution of less well-studied characters, such as floral fragrance, longevity, reward chemistry, and ultra-violet color patterns. Each of these has been implicated in mediating interactions with pollinators but also may be under selection via a variety of other agents (herbivores, pathogens, mycorrhizal fungi, rhizobia, foliar endophytes, soil chemistry, UV radiation) either directly or indirectly, and understanding how these interactions lead to evolution of floral phenotype, mating system and reproductive isolation is a main agenda in the lab.