Consideration of biotype to improve invasive species management



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ABSTRACT As globalization continues, the movement of species increases and provides more opportunities for introduction and establishment of nonindigenous invasive species. Species distribution models (SDM) represent widely used prevention tools to assess species’ potential ranges. Model predictions identify regions at-risk to invasions so that managers can target prevention efforts to areas where they would be most cost-effective. SDMs may be influenced by atmospheric and environmental variables; however, it is unknown if species organization under the biological species level, such as subspecies or biotype, influence SDM predictions. This thesis uses modelling methods, Maxent and Maxlike to generate global forecasts for invasive aquatic plant hydrilla (Hydrilla verticillata). To observe if hydrilla biotype influence SDMs, forecasts were produced and compared using data partitioned by biotype and all known hydrilla data. Further, differences in desiccation response between biotypes were observed to see if either had a competitive advantage at surviving and resisting desiccation. SDMs and desiccation experiments in this thesis support hydrilla as high-risk invasive species and suggest that biotype-specific traits influence its invasion potential. Predicted ranges and viability of hydrilla varied by biotype. Monoecious hydrilla exhibited greater viability but lost more mass during desiccation than dioecious hydrilla; suggesting one biotype may have a competitive advantage for successful invasions. Management of other nonindigenous invasive species may also benefit from incorporation of biotype, or other subspecies biological traits into predictions.



Invasive, Maxent