PS 92-175 - Life inside the mat: links between Lepanthes orchids and bryophyte presence in the Luquillo Experiment Forest, Puerto Rico

Friday, August 7, 2009
Exhibit Hall NE & SE, Albuquerque Convention Center
Juan G. García Cancel Jr. , Biology Deparment, University of Puerto Rico at Mayagüez, Mayagüez, PR
Betsabé D. Castro-Escobar , Biology, College of Natural Sciences-Institute for Tropical Ecosystems Studies, San Juan, PR
Paola Olaya , Biology, University of Puerto Rico, Rio Piedras and Center for Applied Tropical Ecology and Conservation (CREST-CATEC), San Juan, PR
Nadia P. Flores , Biology, University of Puerto Rico, Rio Piedras Campus, San Juan, PR
Amelia Merced , University of Puerto Rico, Rio Piedras Campus, San Juan, PR
Raymond L. Tremblay , Biology, University of Puerto Rico at Humacao, Humacao, PR

The distribution of orchids in the epiphytic or lithophytic environment is likely to result from a combination of factors including the interactions with other plant species.  Here we tested for negative associations between bryophyte cover and early demography stages and positive associations of bryophyte cover on adult plants of , a riparian epiphytic and lithophytic tropical orchid. We also tested whether or not there was an association between the density of  plants and the diversity and composition of bryophytes in our study area and whether or not the height of densest orchid aggregate within a phorophyte relative to the water line was related to the height 'moss' line across a rock substrate (indicative of flash flood disturbances).  


Bryophyte cover was not significantly different between phorophytes with neither high nor low orchid density when all plant stages were pooled nor when only the density of adult plants was considered. However, when only the density of early orchid stages was examined, low density phorophytes had a considerably thicker bryophyte cover relative to high density ones. We also found that sites with bryophytes generated higher densities only for adult plants but not for early plant stages. In addition, the number of bryophyte species was significantly higher in phorophytes classified as high density sites for adult plants but this increase was due to a higher number of moss species and not to a higher number of liverworts. Last, the height of the densest Lepanthes patch within a phorophyte was positively related to the recorded height for the moss line forming across a rock substrate. Overall results suggest that the potential interactions between bryophytes and L. rupestris is likely to be dynamic throughout the life cycle of these orchids with negative interactions acting during early stages of the orchid's life history and positive interactions acting at later stages. We discuss the potential mechanisms of these interaction and the role that natural disturbance regimes along stream (i.e. flash floods) play in the population dynamics of this species.


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