Characterization of cave-inhabiting arthropods of Puerto Rico: Potential tools for conservation

Background/Question/Methods                                                                                                                                                                                                                                                                            In Puerto Rico, the smallest island in the Greater Antilles, caves represent a hotspot for tropical biodiversity, especially along the Northern Karst Belt (Peck1974). Sporadic biospeleological taxonomical and paleontological research conducted since 1950’s suggests that these habitats have very rich invertebrate faunas and they are likely to harbor many yet undiscovered cave organisms (Peck 1974; Peck 1981; Lugo et al. 1981).The main purpose of this research is to gather baseline data on arthropod diversity and abundance in four caves with varying human use (moderate to intense based on distance from local populations and population density) and considering inherent variation in environmental characteristics within each of them. Four caves along the North Karst Belt in Puerto Rico were surveyed in October 2009 (rainy season) and April 2010 (dry season) for soil arthropods using pitfall traps. Within each cave, surveys were conducted at three zones distributed along a light gradient from the entrance of the cave inward (entrance, twighlight, dark) that were in turn characterized for visibility, temperature and relative humidity.

Results/Conclusions                                                                                                                                                                                                                                                                                           Zones within caves differed in perceived visibility but these differences did not correlate with differences in temperature or with relative humidity. Overall temperature was negatively correlated with relative humidity but this association was weak. Two caves presented unusually high temperature values and these caves also presented significantly higher arthropod counts. Temperature was only positively correlated with arthropod diversity but the role of temperature on abundance can not be discarded given that diversity and abundance are highly correlated. More species were captured in the April than in the October census but these tendencies were not consistent with temperature or relative humidity differences between censuses Our pooled samples yielded 5,922 soil cave specimens that included 41 morphospecies distributed among 17 orders. Hemiptera (67%), Acari (48%), and Isopoda were the most dominant orders in all caves. The dominance of Hemiptera at these cave systems is a departure from what has been reported in well-studied caves around the world and future studies should focus on their role as potential indicators of change in cave systems of Puerto Rico. Scientific information and local awareness of cave inhabiting species in Puerto Rico is extremely limited. The digital photographs produced by this work can be an important contribution to local biodiversity conservation efforts of these systems.