Ithaca College

Environmental Science and Biology students Sydney O'Shaughnessy and Adam Zelehowsky win the best undergraduate poster award at the annual plant biology meeting held at Yale University, New Haven, CT April 22-23rd, for the plnat biology research that they did in Puerto Rico with Professor Melcher (Biol).

The research focused on the impacts of an introduced species on coastal plant habitats on the beaches of the Puerto Rican islands.   The work presented at this meeting was a culmination of research, some of which was collected by alum Erika Bucior (ENVS '16) and is part of a larger collaborative project with Professors Melcher and Susan Witherup (Biol).  The findings of the study show that the introduced species has a high potential to outcompete the native species.  The published abstract is given below:

A Physiological Approach to Understand Invasiveness of Scaevola taccada in Coastal Habitats on the Islands of Puerto Rico

Sydney O'Shaughnessy*, Adam Zelehowsky*, Susan Witherup and Peter Melcher

 Physiological and morphological measurements were made on an introduced species, Scaevola taccada, and compared to an endemic species, S. plumieri growing at multiple coastal sites on the islands of Culebra and Vieques, Puerto Rico.  The goal of this project was to determine if one species had any physiological or morphological advantages that would enable it to out- compete the other species.  To accomplish this, differences in each of the species ability to photosynthesize, conserve water, allocate carbon (C) and nitrogen (N), and alter sub-canopy light environments were measured.  Differences in leaf construction costs and variation in leaf area and leaf mass were also measured in both species.  Photosynthetic light response curves and diurnal measurements of leaf-level photosynthesis and transpiration revealed that these species behave similarly with regard to sugar production and consumption with the endemic species showing slightly higher rates of photosynthesis than the introduced species. Carbon isotope analysis showed no significant differences in water use efficiency (WUE) between the species. However, differences in leaf sap osmolarity were observed in the morning and in the afternoon, such that the endemic species tended to be slightly more water stressed than the introduced species.  We also found that the leaves of the introduced species were higher in carbon and lower in nitrogen, and therefore had a higher C:N ratio compared to the endemic species.  It seems that differences in leaf and stem biomass allocation provide the introduced species with a mechanism to grow taller and produce larger and thinner leaves that increase its capacity to shade-out other species growing near it, including the endemic species.  These data suggest that the introduced species has both morphological and physiological adaptations that allow it to grow faster and shade out competitors. Therefore, we predict that this will result in S. taccada displacing S. plumieri over time.