Spatially congruent sites of importance for global shark and ray biodiversity

3]. Species richness, defined as the number of different species in a given area, is generally greatest in the tropical latitudes [4–6]. Although this pattern is dominant in terrestrial systems, hotspots of species richness in the ocean can occur along productive frontal systems and sub- tropical boundary zones [6–8], many of which tend to result from the overlap of wider-ranging species [9]. Global assessments of biodiversity have previously focused on identifying priority areas based on total number of species alone [10], however there are other interpretations of species richness that have not yet been explored, such as evolutionary distinctiveness or endemicity. Evolutionarily distinct (ED) species, defined as species that encompass the greatest share of evolutionary history, usually measured from the branch lengths of a phylogenetic tree [11], are also of conservation value [12]. Areas of high evolutionary distinctiveness are important to conservation because they can capture those species who embody unique forms, functions, and genomes [13]. For example, any one species of echidna embodies a greater fraction of the morphological, physiological, and ecological diversity of class Mammalia than any one species of the 2,000 or so species of rodents [12,14]. In some lineages, especially sharks and rays, extinction risk is greatest in the species that embody the largest share of this evolutionary his- tory because they exhibit traits, such as large body size, that render them intrinsically sensitive

to threats such as hunting or overfishing [13,15–17]. Endemicity is defined as those species that exist only in a defined geographic region [18]. Endemic species tend to merit high conser- vation priority because of their small geographical range sizes and low population numbers [19]. An influential analysis of threatened terrestrial endemics revealed that 44% of all endemic plants and 35% of endemic vertebrates occurred in only 2% of the global land area [18], dem- onstrating how an endemicity-centric approach can be incredibly spatially efficient in identify- ing areas for conservation. Identifying the geographical areas that harbor congregations for different richness metrics, such as total species, evolutionarily distinct species, or endemic spe- cies, have resulted in becoming a significant component of the terrestrial conservation agenda [18]. While there are numerous values that could be used to drive conservation, there is an urgency to conserve those threatened species that are at risk of extinction. The 2020 Aichi biodiversity target to conserve 10% of coastal and marine areas drove a rapid expansion of marine protected areas, with the area covered rising from 0.67% of the world’s oceans in 2000 to 6.4% in 2017 [20]. Within the newly drafted 2030 Kunming biodiver- sity framework, target 2 aims to “protect 30% of sites of particular interest on both land and sea” [21]. Now is the time to shape the rapidly developing 2030 agenda of biodiversity conser- vation by identifying areas that harbour the combination of the greatest richness, endemicity,

and evolutionary distinctiveness [19,22,23], amongst the many other dimensions of biodiver- sity, as well as their threatened counterparts. In addition to shedding light on the distribution of species diversity (and across the different measures with which diversity can be defined), these identified areas can be used to inform regions of focus for subsequent systematic conser- vation planning exercises [24]. One quarter of all sharks, rays, and chimaeras (class Chondrichthyes; hereafter referred to as “sharks and rays”) are categorized as threatened (Vulnerable, Endangered, or Critically Endangered) on the International Union for the Conservation of Nature’s (IUCN) Red List of Threatened Species, or are predicted to be threatened based on their large body size and expo- sure to fisheries [25,26]. Sharks and rays are among the most evolutionarily distinct vertebrate radiation of marine predators [27], and their slow life histories result in low population growth rates [28–30]. These features combine to render them highly sensitive to overfishing [25,31]. The availability of comprehensive Red List Assessments and geographic distribution maps make sharks and rays a good case study to understand how marine species richness measures are spatially distributed and can be conserved most efficiently. There are few analyses that 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 2 / 19 under the repository title: SpatiallyCongruentSites_2020

Funding: This project was funded by the National Science and Engineering Research Council of Canada (NSERC) and the Shark and Ray Conservation Fund. Competing interests: The authors have declared that no competing interests exist.