Understanding the factors influencing species distribution is key to predicting the potential for range shifts under changing climate and land use conditions. Nowhere is this research more crucial than in rare, highly specialized, narrowly endemic species, which are likely to be particularly susceptible to such changes.
At ~3270 species, Astragalus (Fabaceae) is the largest genus of flowering plants in the world. Its morphologically discrete, highly endemic species grow globally as herbaceous perennials in arid to semi-arid regions, with hotspots of biodiversity in temperate mountain ranges. Though they have many commercial, pharmacological, and agricultural uses, they are a leading cause of livestock death in the United States through a potent combination of phytotoxins and selenium hyper-accumulation. Similarly, while some members of the genus are endangered, others are considered noxious weeds. Nonetheless, the life history, physiology, and ecology of more than 99% of the species have yet to be studied in any detail.
The southern Rocky Mountain region is host to several recently divergent Astragalus clades. Their high rate of speciation may be due to a combination of extremely low reported dispersal capabilities and high adaptive capacity, resulting in a proliferation of narrow endemic species. Indeed, while some Rocky Mountain Astragalus seem to be substrate generalists, many appear to be largely confined to loose soils of Cretaceous sedimentary origin. There, they tolerate or accumulate high levels of selenium, a trait unknown in their published old-world counterparts. In Colorado alone, 24 species of Astragalus are considered “critically imperiled” by the Colorado Natural Heritage Program, some of which are endemic to a single geological stratum, including Colorado’s two federally endangered species and its one candidate species.
I will use a multidisciplinary approach to study the distribution of rare and understudied members of this incredibly successful genus.
In the past, I have studied white oak speciation and gene flow in the Chicagoland area, brown-headed cowbird breeding in Illinois prairies, Costa Rican tropical rainforest reforestation plantations and seedling recruitment, airborne nitrogen deposition and chaparral in the Los Angeles Basin, sediment toxicity in the New York/New Jersey harbor complex, and protein expression in human growth restricted placentas.
