Research

A number of different projects are being conducted in the lab.  My students typically undertake related, but non-overlapping projects with my main projects, but we all work as a team to improve and refine each project. See people pages for all of these projects.

I have three main projects going in the lab currently.

I. Using historical and contemporary approaches to reconstruct the ecological niche.  Using a group of mustards in the genus Streptanthus (sense lato), I am working with colleagues to understand niche evolution in Streptanthus, a diverse group of mustards, many endemic to the California Floristic Province. With my former post-doc N. Ivalu Cacho (now faculty at UNAM in Mexico City) and colleagues from TAMU, Alan Pepper and students, we have generated a phylogenetic hypothesis for the group (Cacho et al. Molecular Evolution and Phylogenetics 2013) and are using this hypothesis to understand various aspects of the niche. Our field sites span  Southern CA to Oregon, from deserts to high mountains, coastal areas and inland. Streptanthus and allies are called ‘jewelflowers’ and I  think these flowers are super cool and beautiful. This helps keep me going when I am struggling in their preferred habitat of hot, south-facing very loose, steep and rocky slopes.

Our most recent work is exploring the evolution of plasticity with respect to drought tolerance in Streptanthus, in collaboration with former post-doc Ian Pearse (now at USGS in Fort Collins, CO). We find that extreme drought-adapted Streptanthus do not capitalize well on later rains, and less drought adapted species are able to greatl expand their flowering period with additional water availability (In press American Naturalist. Pearse, Aguilar and Strauss 2019).

I am also co-PI with my colleagues Jenny Gremer, Annie Schmitt and Julin Maloof in a project to understand the evolution of the germination niche and cues in this clade, and their implications for population trajectories under future climates.

II. Understanding the role of rhizobial mutualists  and soil communities in coexistence of diverse Trifolium species assemblages. At the Bodega Marine Reserve, there are 9 native species of Trifolium, and many introduced ones. In collaboration with Maren Friesen at MSU, and former post-docs Andew Siefert and Sara Grove,  we use field transplants of Trifolium species planted across soil niches, in the presence and absence of the local resident, as well as rhizobial sequencing and rhizobia-species affinity/interactions to understand competitive/mutualistic interactions, N-fixation efficiency and ecological coexistence.

III.   Coexistence in close relatives. With former post-docs Jean Burns (Assoc. Prof Case-Western Reserve University and Brian Anacker (former postdoc, now at Boulder Open Space Commission), we explored niche conservatism and its implications for coexistence at the UC Bodega Marine Reserve (PNAS 2015, Ecology 2017). We use experimental approaches, planting individuals into the full dimensional field niches of more and less closely related species, to understand niche conservatism and coexistence among species. We also measure many traits and environmental attributes across our site to understand the major contributors to coexistence in this diverse community. This project generated the Trifolium study above, as Trifolium are one of a few genera that appear to coexist extremely closely spatially at the reserve.

Recently, this project has led to my greater appreciation of reproductive interference (RIN) as a force that might be structuring coexistence in close relatives. RIN occurs when heterospecifics mate or attempt to mate, and in the process decrease the fitness of one or both species. Close plant relatives often look alike, occupy nearby habitats, share pollinators and flower at the same time. They must, in these cases, be exposed to heterospecific pollen. I am studying this phenomenon with Kyle Christie in Streptanthus, with Marjorie Weber and Magne Friberg in 18 Veronica species on Oland, Sweden, and in Trifolium species in California with Kyle Christie, Susan Harrison and Maren Friesen.