Variable selection
The variables that were below the 0.5 correlation threshold in the
cluster analysis but most strongly correlated to the occurrence ofCochemiea halei in the biserial correlation analysis were annual
temperature range, mean temperature of the warmest quarter,
precipitation of the warmest quarter and precipitation of the coldest
quarter. These variables, along with soil type, were used in the species
distribution models. Annual temperature range differs on the islands
versus the peninsula, with island temperature ranges of approximately
20○ C and the peninsular range 10○wider at 30○ C. Mean temperature of the warmest
quarter ranges from 24○ C in the northwestern region
of Isla Magdalena to approximately 30○ C at the lowest
elevation in the center of Isla Margarita and on the peninsula.
Precipitation of the warmest quarter ranges from 20–40 mm on the
islands, except for the highest elevations on Isla Margarita at 70 mm.
The majority of peninsular precipitation is also at 70 mm. Precipitation
of the coldest quarter is from 20–30 mm on the islands, to slightly
over 40 mm on the peninsula. (Fig. 2)