Spatially congruent sites of importance for global shark and ray biodiversity

Increasing the cell size from 1˚ to 8˚ led to 13.42% of hotspots being congruent, resulting in a greater than two-fold increase in congruency for all species (5.78% at 1˚ resolution), and the largest percentage of coverage contained within the country boundaries of Australia (44%), South Africa (21%), and southern Brazil and Uruguay (9.5%; Fig 6A; S1 Table). This increase in cell size also shifted the dominant locations of hotspot overlap (Fig 6A–6C). At a 4˚ resolu- tion, areas of congruence disappeared from the coasts of Mexico and Ecuador, shifting to more representation in the USA, Colombia, and Panama (Fig 6B). At an 8˚ resolution, the spa- tial congruence disappeared altogether from the coasts of Brazil (Fig 6C). Similar results were seen in the threatened species subsets; despite overall low spatial overlap between levels of res- olution, overlap increased marginally between 1˚, 4˚, and 8˚ cell size (1.51%, 2.15%, and 2.50% overlap, respectively; S1 Table). Spatially congruent areas between the threatened subsets were predominantly found off the coasts of southern Brazil and Uruguay (66%), which was consis- tent across all levels of spatial resolution examined (Fig 6D–6F). Contrastingly, these congru- ent areas of threatened species were present in Taiwan and Australia at 1˚ resolution, and South Africa at 1˚ and 4˚ (Fig 6D–6F). At 8˚ resolution, congruency locations for threatened species no longer corresponded at all with the areas of congruency identified for all shark and ray species (Fig 6C and 6F).

Fig 3. Biodiversity hotspots derived for three measures of species richness. General richness hotspots of (a) total species, (b) evolutionarily distinct (ED) species, and (c) endemic species. Richness hotspots of the threatened subset for (d) total species, (e) evolutionarily distinct (ED) species, and (f) endemic species. For each species richness measures, hotspots are defined as the richest 5% of grid cells. Geographic coordinate system is in NAD83, projected coordinate system is Lambert equal area, grid cell resolution is 1˚. The data used for this figure under CC BY license is granted permission from the International Union for the Conservation of Nature (IUCN), original copyright 2011. https://doi.org/10.1371/journal.pone.0235559.g003 PLOS ONE Spatially congruent sites of importance for global shark and ray biodiversity PLOS ONE | https://doi.org/10.1371/journal.pone.0235559 July 6, 2020 7 / 19