Maximum plant-community endemism at intermediate intensities of anthropogenic disturbance in Bolivian montane forests

I compared the endemism of four plant groups (Araceae, Bromeliaceae, Palmae , Pteridophyta) along gradients of increasing anthropogenic forest disturba nce, from undisturbed mature forest to disturbed forest (logged, grazed or burned), secondary forest, secondary scrub, ,and finally pasture, at 16 sit es in the Bolivian Andes. I measured endemism as the mean inverse range siz e (number of 1 degrees cells) of all species per sturdy group encountered i n each habitat and site. Overall, endemism was significantly higher in dist urbed forest than in mature forest, but it declined in more strongly distur bed habitats To explain the relationship of range size to habitat disturban ce, I propose that endemic species are somewhat competitively inferior to o ther co-occurring taxa, limited in their ability to establish and maintain new populations following dispersal and thus to expand their ranges. within their established ranges endemic species depend on natural habitat disturb ances to prevent their competitive exclusion by other species, so they prof it from a certain level of anthropogenic disturbance. This pattern and the explanatory hypotheses should be subjected to critical evaluation. Although the pattern does not apply to every endemic tropical plant species, it ind icates that conservation of part of the endemic tropical forest flora may b e achieved in forest areas subject to sustainable forest use without the ne ed to completely exclude human activities.