Disparate biomes within the Caatinga region are not part of the same evolutionary community: A reply to Araujo et al. (2022)

In recent attempts to estimate plant and bird species diversity in the Caatinga, the largest nucleus of the Seasonally Dry Tropical Forest and Woodland biome in South America, we called into question a widely used delimitation of this region that includes areas of disparate biomes. We argued that the Caatinga is best delimited without rainforest and savanna enclaves that exist in the region, and that such enclaves should be treated as part of those other biomes rather than part of the Caatinga. In a response to our proposal, Araujo et al. (2022) advocated the continued adoption of that broader delimitation. Here we review Araujo et al.’s (2022) criticism and elaborate on this problem. We demonstrate that using a delimitation of the Caatinga that includes areas of disparate biomes precludes measures of biome-specific information, cross-biome comparisons, and large-scale syntheses, and we argue that such a delimitation is a poor framework for both studies of biological phenomena and regional conservation planning.