Abstract
The diversity of marine communities is in striking contrast with the diversity of terrestrial communities. In all oceans, species richness is low in tropical areas and high at latitudes between 20 and 40°. While species richness is a primary metric used in conservation and management strategies, it is important to take into account the complex phylogenetic patterns of species compositions within communities. We measured the phylogenetic skew and diversity of shark communities throughout the world. We found that shark communities in tropical seas were highly phylogenetically skewed, whereas temperate sea communities had phylogenetically diversified species compositions. Interestingly, although geographically distant from one another, tropical sea communities were all highly skewed toward requiem sharks (Carcharhinidae), hammerhead sharks (Sphyrnidae), and whale sharks (Rhincodon typus). Worldwide, the greatest phylogenetic evenness in terms of clades was found in the North Sea and coastal regions of countries in temperate zones, such as the United Kingdom, Ireland, southern Australia, and Chile. This study is the first to examine patterns of phylogenetic diversity of shark communities on a global scale. Our findings suggest that when establishing conservation activities, it is important to take full account of phylogenetic patterns of species composition and not solely use species richness as a target. Protecting areas of high phylogenetic diversity in sharks, which were identified in this study, could form a broader strategy for protecting other threatened marine species.
Highlights
Global studies of predator diversity reveal predictable patterns, which suggest that there will be ecosystem-wide changes in response to changes in climate and fishing pressure. Worm et al (2005) studied worldwide patterns of predator diversity and revealed distinct subtropical hotspots, which appeared to hold generally for other predators
Ecology and Evolution published by John Wiley & Sons Ltd
We found that the Phylogenetic skew (PS) of sharks was high along tropical coasts and low along temperate ones (Fig. 3A)
Summary
Global studies of predator diversity reveal predictable patterns, which suggest that there will be ecosystem-wide changes in response to changes in climate and fishing pressure. Worm et al (2005) studied worldwide patterns of predator diversity (tuna and billfish) and revealed distinct subtropical hotspots, which appeared to hold generally for other predators. Trebilco et al (2011) examined the interrelationships among species richness distributions of tuna and billfish species, fishing pressure, and increases in sea surface temperatures (SSTs) in tropical to temperate oceans. They found that in the Indian and Pacific Oceans, higher fishing pressure is associated with higher species richness. In the Pacific and Atlantic Oceans, species richness is generally higher in areas that have seen lower levels of change in SST These investigations provided evidence that ambient water temperature tolerances of tuna and billfish can be used to predict broad species richness patterns on a global scale
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