Abstract:
Although vascular epiphytes contribute substantially to the biodiversity of tropical montane forests, it is
unclear how their diversity and community composition is affected by forest alteration. We studied the
response of vascular epiphyte assemblages to different intensities of land-use in a montane wet forest of
northeastern Ecuador: (1) unmanaged mature forest; (2) mature forest with mid- and understorey opened
for cattle grazing; and (3) isolated remnant trees in cattle pastures. The numbers of individuals and species
of epiphytes per host tree did not differ significantly between land-use types, neither did total epiphyte
species richness (n = 30 trees). However, total species richness of pteridophytes was significantly lower on
isolated remnant trees compared to unmanaged forest, whereas several taxa rich in xerotolerant species
(Bromeliaceae, Orchidaceae, Piperaceae) exhibited the opposite trend. An analysis of floristic composition
using ordination (NMS) and randomisation techniques (MRPP) showed that epiphyte assemblages on
isolated remnant trees were significantly distinct from unmanaged forest while managed forest was
intermediate between those two vegetation types. Ordination analysis further indicated reduced floristic
heterogeneity in disturbed habitats. These results suggest considerable, rapid species turnover since
land-use change 6 years prior to study, with pteridophytes being replaced by more xerotolerant taxa.
We attribute this floristic turnover primarily to changes in microclimate towards higher levels of light
and desiccation stress associated with forest disturbance. Our results support the notion that community
composition offers a more sensitive indicator of human disturbance than species richness.
