Characterization of climate envelopes
We examined the range of conditions where G. platensis is found
throughout South America (i.e., their “climate envelope”; Hijmans &
Graham, 2006). These ranges were compared to the conditions where the
species is found in Ecuador. This helped us define whether conditions in
Ecuador differ from those in the rest of the continent. Climate
envelopes were constructed using data from the top four environmental
variables with highest contributions (i.e., > 10%) in the
Maxent models and elevation. In order of importance, the variables
included temperature seasonality (bio 4), annual mean temperature (bio
1), precipitation of the coldest quarter (bio 19), and mean temperature
of the coldest month (bio 6). While elevation did not have a high
contribution to the model, we used it here to broadly discuss areas of
predicted suitable habitat of G. platensis . From these data, we
determined the climate and elevation profiles for all localities whereG. platensis was documented by extracting environmental
information across all localities and directly comparing the range of
conditions individually in Ecuador vs. the rest of South America. These
data were not normally distributed; thus, Wilcoxon rank sum tests
followed by a Bonferroni correction for multiple comparisons were used
to examine the differences between conditions in Ecuador vs. the rest of
South America. This framework allowed us to better understand the
variation in environmental niche occupancy in the introduced range ofG. platensis across the continent.