Abstract
AbstractAimIdentifying the multifaceted biodiversity hotspots for marine mammals and their spatial overlap with human threats at the global scale.LocationWorld‐wide.MethodsWe compiled a functional trait database for 121 species of marine mammals characterized by 14 functional traits grouped into five categories. We estimated marine mammal species richness (SR) as well as functional (FD) and phylogenetic diversity (PD) per grid cell (1° × 1°) using the FRic index (a measure of trait diversity as the volume of functional space occupied by the species present in an assemblage) and the PD index (the amount of evolutionary history represented by a set of species), respectively. Finally, we assessed the spatial congruence of these three facets of biodiversity hotspots (defined as 2.5% and 5% of the highest values of SR, FD and PD) with human threats at the global scale.ResultsWe showed that the FRic index was weakly correlated with both SR and the PD index. Specifically, SR and FRic displayed a triangular relationship, that is, increasing variability in FRic along the species richness gradient. We also observed a striking lack of spatial congruence (<0.1%) between current human threats and the distribution of the multiple facets of biodiversity hotspots.Main ConclusionsWe highlighted that functional diversity calculated using the FRic index is weakly associated with the species richness of marine mammals world‐wide. This is one of the most endangered vertebrate groups playing a key ecological role in marine ecosystems. This finding calls for caution when using only species richness as a benchmark for defining marine mammal biodiversity hotspots. The very low level of spatial congruence between hotspots of current threats and those of the multiple facets of marine mammal biodiversity suggests that current biodiversity patterns for this group have already been greatly affected by their history of exploitation.
Highlights
Preventing biodiversity loss under growing anthropogenic pressure is one of the greatest challenges in ecology and conservation biology
We estimated marine mammal species richness (SR) as well as functional (FD) and phylogenetic diversity (PD) per grid cell (1° × 1°) using the functional richness index (FRic) index and the PD index, respectively
We showed that the FRic index was weakly correlated with both SR and the PD index
Summary
Preventing biodiversity loss under growing anthropogenic pressure is one of the greatest challenges in ecology and conservation biology. In southwest Alaska, the decline in populations of sea otters and pinnipeds and the resulting diminution of the kelp ecosystem could be attributed to the increasing number of transient killer whales that shift their diet to smaller prey items (Estes 1995; Estes et al, 2009). Their extinction or even their population decay could lead to irreversible consequences for ecosystem functioning (Heithaus et al, 2008; Estes et al, 2011). Effective conservation efforts (e.g., marine spatial planning) require knowledge of the spatial distribution of the main biodiversity facets (Devictor et al, 2010; Mouillot et al, 2011; Stuart-Smith et al, 2013), in the high seas, where monitoring is difficult and where data gaps obstruct conventional management approaches (Ardron et al, 2008)
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