a, The values of Φcrit are compared using two independent methods. The first (y axis) is determined from the peak in the F1-score for categorization into occupied and unoccupied sites (see Methods). The second (x axis) is determined from the bottom percentile (5–10%) of Φ values inhabited by the species. b, The histogram of Φcrit is not sensitive to the number of occurrence observations. c, For all species, waters with lower Φ values than Φcrit exist within the depth range of these species, but lack confirmed specimens. The dashed line indicates the 1:1 line.