Extended Data Fig. 2: Biogeographical regions and sectors of amphibians.
From: A general rule on the organization of biodiversity in Earth’s biogeographical regions
(a) Amphibian’s bioregions. White areas indicate geographical regions where this taxon is absent, or grid cells overlap with ≤ 50% of the Earth’s surface. (b) General biogeographical sectors within amphibian bioregions. Solid black lines represent the boundaries of the biogeographical regions, while colours denote different biogeographical sectors. Warmer colours indicate geographical areas with relatively low overlap of biotas, reflecting distinct biogeographical affinities (i.e. overlap of distinct characteristic species pools). Cooler colours represent areas with higher overlap. Darker and lighter shades within the warm and cold colour ranges, respectively, indicate high and low richness of characteristic species. See Fig. 1 for relationship between the biogeographical sectors and the four-biodiversity metrics. Some biogeographical regions, mostly depicted by blue colours, may represent widely recognized transitional zones. Nonetheless, these biogeographical regions can also correspond to lower biogeographical hierarchical levels, such as subregions or domains58. The identification of these highly transitional biogeographical regions opens possibilities for clustering them into higher biogeographical hierarchical scales, such as the Western subregion of the Neartic or the Chacoan subregion of the Neotropical58. However, to ensure objectivity in delineating bioregions and avoid subjective criteria for thresholds19,56, all bioregions with statistical support were studied independently of their potential biogeographical hierarchical level58.
