2.7 Species Distribution Modeling
MAXENT 3.3.3e(Phillips, Anderson, & Schapire, 2006) was used to predict
the distribution of Notholirion in China during 4 time periods:
Last Interglacial (LIG), Last Glacial Maximum (LGM), and the present and
future. The samples collected in this study covered the distribution of
all 30 populations of the genus Notholirion throughout China for
which specimens were recorded. Nineteen bioclimatic environment
variables(Alemu & Wimberly, 2020) from four time periods above were
downloaded from the WorldClim database(Fick & Hijmans, 2017) and
employed in modeling analyses. In MAXENT, due to the small sample size
of our data (15–79 localities), only the linear + quadratic + hinge
functional forms were used. Here, models were built using linear +
quadratic + hinge features, random training data was set to 25%, repeat
run type was set to Subsample, maximum iterations were set to 1000, and
other parameters were set by default. We also calculated the area under
the Receiver Operating Characteristic (ROC)(Fawcett, 2005) and Operating
Characteric Curve (AUC)(Ellis, Yahr, Belinchón, & Coppins, 2014) to
observe the accuracy of each model prediction. Usually, good model
performance was assessed by AUC values above 0.7(Elith & Leathwick,
2009; Fielding, 1997; Peterson, Pape, & Soberón., 2008). The spatial
distribution range map of the final modeling results was plotted by the
software DIVA-GIS v 7.5(Hijmans, Cameron, Parra, Jones, & Jarvis,
2010).