Using the native climate of Impatiens walleriana to predict its global adventive range Lisa Mandle Fall 2005

Impatiens walleriana Most popular bedding plant in the U.S. Has been widely distributed globally and nationally for over a century Native to tropical East Africa, but has naturalized in N. and S. America, Australia and the Pacific Islands Naturalized: a population is maintained outside of where it was planted; the population may or may not be increasing in size or spreading

Modelling plant invasions Degree of climate match between native and introduced ranges is significant in determining the outcome of plant introductions on a large spatial scale Successful models to predict plant invasion have used parameters such as temperature, precipitation, evapotranspiration and seasonality However, these models favor plants of temperate origins

Can the climate of the native range be used to predict where Impatiens walleriana (a tropical plant) is capable of naturalizing? Provide insight into population and community ecology Inform policies governing the introduction of alien species My question

Methods Obtained latitude/longitude points for native and naturalized populations from herbarium records Obtained/created grids for five climate variables found to be significant in other models: –Actual/potential evapotranspiration (humidity) –Plant productivity index (seasonality) –Growing degree days (base 5) –Minimum temperature of the coldest month –Annual precipitation Compared climate of native and naturalized points

Results Native and naturalized climates by variable

Results Adventive range predicted by native climate Locations matching 5 native range parameters Locations matching 4 native range parameters Native occurrence points Adventive occurrence points

Results Adventive range predicted by naturalized climate Locations matching 5 native range parameters Locations matching 4 native range parameters Native occurrence points Adventive occurrence points

Results No naturalized points match the native climate for all 5 variables Many naturalized populations occur in locations receiving much more precipitation than currently available in the native range of East Africa (e.g. Nicaragua, Columbia, Costa Rica, Panama) Naturalized populations of Impatiens walleriana are prevalent outside areas predicted by native climate

Conclusion Species may naturalize in areas outside the existing climate space of their native range. Naturalization in these places cannot be predicted from the native range alone. The limitations of coarse-scale climate matching to predict naturalization must be considered when creating alien plant introduction policies.