Human land uses are widely recognized to affect biological communities in both aquatic and terrestrial ecosystems. Stream fish species and community responses to structural changes in adjacent riparian zones are well documented for temperate streams, although comparable studies of tropical streams are relatively rare. Given the current trajectory for land use and climate change in the tropics, we conducted fish community surveys of 21 streams in central Costa Rica to better understand the role of human-mediated changes in riparian structure as a factor that influences stream biodiversity.
Results/Conclusions
Nonmetric multidimensional scaling (NMDS) ordination based on the relative abundance of all fish species occurring at >2 sites revealed that fish communities were generally segregated across a gradient of sites characterized by primary and secondary rainforest to sites with highly modified riparian zones. Several species, including Astyanax aneus, Rhamdia nicaraguensis, and Astatheros alfari occurred at nearly all sites, although their relative abundances were not significantly related to any of the resulting NMDS axes. However, NMDS Axis 1 explained 79% of the variation in Phallichthyes amates relative abundances and NMDS Axis 2 explained 58% of the variation in Priapichthys annectens relative abundances among sites. Our results suggest that while several fish species are apparently tolerant of stream changes associated with riparian degradation, there are detectable patterns of fish species and community response to changes in riparian structure in central Costa Rican streams. These results provide the proof-of-concept to explore the mechanisms underlying these shifts to better understand the consequences of riparian alteration in the tropics and their implications for biodiversity.