Summary: Abstract The northern karst of Puerto Rico is a
unique formation that contains one of the island's
largest remaining forested tracts. The region is
under ever-increasing human pressure, but large
portions of it are being considered for conserva-
tion. Forest classification of the region is at a coarse
scale, such that it is considered one vegetation type.
We asked whether there were distinct tree
assemblages which would necessitate targeted
conservation strategies to ensure their protection.
We examined tree species and communities across
the region at three different major topographic
positions along mogotes, or haystack-shaped hills.
We found distinct tree communities on hilltops and
valleys, with significantly more non-native species
in valleys and significantly more endemic species
on hilltops and hillsides. At a landscape level, we
identified at least four different communities
within each topographic position. Two mogote top
communities were separated geographically (west