Matzner, Steven

• Postdoctoral Associate, Boyce Thompson Institute, Cornell University, Ithaca, N.Y. 

• Ph.D., Ecology, University of California, Davis 

• B.A., Biology, Augustana College

Title: Mechanism of a slow-wilt phenotype in Asclepias speciosa and some A. speciosa X A. syriaca hybrids and its contribution to range limits for the two species and hybrids.

With the threat of climate change resulting in higher temperatures and increasing demands for water resources, understanding how plants respond to both biotic and abiotic stresses is important both for agricultural as well as in natural ecosystems. We are using two species of milkweed (primary food source for Monarch caterpillars) to better understand how hybridization affects their ability to respond to environmental stresses. A. syriaca is native to eastern South Dakota and A. speciosa is native to western South Dakota. South Dakota experiences a strong moisture gradient, with the east receiving >66 cm precipitation/year and the west <43 cm. The transition between the two species occurs over this moisture gradient and within this region of species overlap, we find hybrids. Using reciprocal transplant gardens, we have found that each species has an advantage in its home site and that the hybrids also do worse than the home species. The mechanism of the home species advantage is not entirely clear, but we have explored differences in drought tolerance, soil nutrient composition, and soil bacterial community composition. The two species differ in a number of morphological and physiological traits and appear to utilize distinct stress response metabolites. We hypothesize that the distinct traits of two species allows them to respond to their environment in different ways. We also hypothesize that hybridization disrupts both the traits and their ability to respond effectively to environmental stresses. The ongoing work in this lab involves field trips to our garden sites, greenhouse studies and laboratory work that includes DNA extraction, microscope-based measurements, and metabolite extraction. Our goal is to more fully understand what determines the ranges of these two species and how hybridization affects the ability of these plants to respond to their environment.