| Species listed as endangered face extinction within their niche, and close relatives of these taxa should occupy similar niches, and thus, share similar risks of extinction. However, few comparative analyses of niche similarity (e.g., niche conservatism) exist for endangered and threatened taxa across a wide array of taxonomic groups. Using ecological niche modeling (ENM), I evaluated the modeled niches of 20 listed species in California and their sisters, together representing plant, snail, amphibian, reptile, bird and mammal lineages. Each pair was modeled in Maxent using extensive museum collections data and 16 topographic and bioclimatic variables. I employed Schoener's D to measure niche overlap and conducted background randomization tests in ENM Tools to examine whether niches were more different from one another than expected based on the environmental background available to them. Almost all (25 of 26) pairwise comparisons had niche overlap scores at the low end of the range (< 0.5). The randomization tests showed more conserved (12), than divergent (8) or indistinguishable (7) niche comparisons. These results were supported in that nearly 85% of the sister taxa (22 out of 26) were found to have some designation of rarity by governmental jurisdictions or non-profit and conservation organizations. For conservation purposes, my results support the use of ENM in evaluating rarity in close relatives of endangered taxa and as part of a management strategy for any endangered species. |
