Community assembly of coral reef fishes along the Melanesian biodiversity gradient

Background/Question/Methods

The Indo-West Pacific is home to Earth’s most biodiverse coral reefs. Diversity on these reefs varies biogeographically, steeply decreasing from the Coral Triangle to the reefs of peripheral islands in Melanesia. Understanding patterns of community structure across this gradient may help determine conservation efforts in the region. Our goal in this study was to evaluate the structure of coral reef fish communities across the Melanesian biodiversity gradient. We obtained distributional records for 402 reef fish species in the families Balistidae, Chaetodontidae, Labridae including Scarines, Monacanthidae, and Pomacentridae across seven reef sites.  We used hierarchical clustering methods, ordination, and nestedness analyses to evaluate the community structure of these reef fish families.

Results/Conclusions

Our data support observations that coral reef fish diversity declines along the Melanesian biodiversity gradient, from a high of 337 species on Papua New Guinea to a low of 210 species on Samoa. Species richness is significantly related to longitude but not habitat area. We found that these communities are significantly nested, indicating that species-poor communities are largely composed of subsets of the species found on species rich reefs.  These trends are robust across taxonomic groups, and allow us to conclude that distance from the Coral Triangle dominates community structure in this faunal group.