Are humans responsible for diversity loss in coral reef fish?

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Colorful reef fish school in large numbers at Rapture Reef in Hawaii.

Research published in Current Biology on January 20th by Stephanie D’agata and her colleagues at Institut de Recherche pour le Développement focused on the impacts that humans have on coral reef fishes.  Coral reefs are under severe threats due to human activities.  Fish species richness, which is the number of species present in a particular ecosystem, is decreasing slowly and linearly with increasing human density.  Beyond species richness, human activities also deplete phylogenetic diversity, which looks at evolutionary differences among species.

Human activities shape the structure of ecological communities.  The research team sampled 1553 communities through underwater surveys in 17 Pacific countries.  The results showed a large decrease in functional and phylogenetic diversity levels as the density of humans on the reef increase to 20 people per sq. km, while species richness was hardly impacted along the gradient. Functional diversity can be defined as the range and value that species influence ecosystem functioning.  Functional diversity is of ecological importance because it is the component of diversity that influences ecosystem dynamics, stability, productivity, and nutrient balance.  When the density of human population on the reef reached 1600 per sq. km, the impact on species richness (-12%) was less than the impact on functional and phylogenetic diversity levels (-46% and -36%).

The results of this research show that looking solely at the number of species in an ecosystem will not indicate how strong the anthropogenic pressures are.  The diversity of phylogenic lineages and the diversity of biological traits are essential for the proper functioning of coral reed ecosystems.  The research demonstrated the importance in conserving all components of biodiversity.  The research also indicated that trait and lineage diversity were a reliable display of the damage that is caused to species communities.

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Journal Article

  1. Stéphanie D’agata, David Mouillot, Michel Kulbicki, Serge Andréfouët, David R. Bellwood, Joshua E. Cinner, Peter F. Cowman, Mecki Kronen, Silvia Pinca, Laurent Vigliola. Human-Mediated Loss of Phylogenetic and Functional Diversity in Coral Reef FishesCurrent Biology, 2014; DOI: 10.1016/j.cub.2014.01.049

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