Altitudinal and Seasonal Variation of Collembola (Hexapoda: Entognatha) in the Luquillo Montains, Puerto Rico

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Understanding biodiversity patterns along environmental gradients is a central theme in ecology. In terms of soil and litter invertebrates, the general observation is that arthropods abundance and richness decreases with elevation. However, other patterns as humped, horizontal and increasing had been commonly reported for invertebrates. These differences may be related to responses of a focus taxonomic gruop to biotic factors such changes in vegetation and leaf litter composition. Collembolans represent a unique group of organism to test apart these changes along gradients because they respond strongly to the physico-chemical and/or biological changes that occur with increasing elevation, even over a relatively small elevation range. The present sudy is taking place in Luquillo Mountains along altitudinal gradient plots (from 330 to over 1000m). We are sampling in the tabonuco, palo colorado and elfin forests. Samples were collected during the dry season (August) and the late wet seson (November). We collected samples in three plots at each forest in four points around the domimant specie on the adjacent areas in soil, leaf litter and epiphyte mats. Samples were freshly weighted and then completely dried in Berlese funnels in order to extract the arthropods. Dry weight of the samples was also recorded. Collembolans were separated, identify to species level and counted. In the 323 evaluated samples 2676 Collembola speciemens were counted. These collembolans belong to 13 families and 46 species. The community composition varied among forest, in terms of number of species, abundance and presence. According to a multidimensional scale analysis, Collembola community in the elfin forest is different from those in the tabonuco and palo colorado forest. The patterns in abundance, diversity and species richness in the altitudinal gradient varies along the microhabitats and sampling seasons. For soil and leaf litter samples, the abundance and diversity were lower during the dry season. There are significant differences in soil and leaf litter Collembola abundance in elfin forest, where was lower than in tabonuco and palo colorado forests (ANOVA; p>0.005). In leaf litter samples the richness was significantly lower in elfin forest, this difference was related with the percentage of litter in samples. These results are part of a bigger survey that includes five sampling dates to look at changes in richness, abundances and diversity of Collembola communities due to seasonal change in the montane forest in Luquillo Experimental Forest.