The bromeliad microcosm and the assessment of faunal diversity in a Neotropical forest

The faunas of tank bromeliads were sampled over two years in three forest t ypes at different elevations in the Luquillo Experimental Forest, Puerto Ri co, and the diversity of their animal communities compared. Bromeliad plant s behaved as islands in that, within forests, the species richness and abun dance of their animal communities were significantly and positively correla ted with increase in plans size. The amount of canopy debris they accumulat ed was similarly correlated with increase in plant size. Overall diversity was lowest in the dwarf forest, where plants were uniformly small. Animal c ommunities were stable from year so year, and could be characterised for ea ch forest type and for compartments within the plane. They showed a pattern of high dominance, which increased with elevation (McNaughton index 37, 54 , and 73, respectively, for the tabonuco, palo colorado, and dwarf forest). Alpha-diversity for sites sampled in each year reflected net primary produ ctivity (NPP) of the forest, declining with increasing elevation when anima abundance measures were used (jackknife estimates of Simpson's diversity i ndex 6.54 & 11.04 [tabonuco], 3.53 & 6.22 [pao colorado], and 2.75 & 2.17 [ dwarf forest]). Species richness over the two years, however, was highest i n the intermediate pale colorado forest (187 species), compared to 146 and 88 in the tabonuco and dwarf forests, respectively. These figures were clos e to jackknife estimates of maximum species richness. The difference in spe cies richness between tabonuco and pale colorado forests was significant in one year only. In addition to NPP, other factors, such as litter quality a nd the structural complexity of the habitat in the pale colorado forest, ma y have: influenced species richness. The most abundant species in individua l plants were also the most widely occurring, confirming known patterns of abundance and distribution in other functional groups. Diversity within bro meliad microcosms at different elevations supported known relationships bet ween diversity productivity, and habitat complexity along gradients and was not related to differences in the total bromeliad habitat available for co lonization.