Evaluating completeness of species lists for conservation and macroecology: a case study of Mexican land birds

Studies of species diversity, macroecology, and conservation are usually ba sed on lists of species, but lists found in the scientific literature vary in completeness. The use of such data sets can produce misleading results, making it necessary to test species lists for completeness before undertaki ng an analysis. Species-richness estimators are useful for judging the comp leteness of species lists but have limitations. To add rigor to studies bas ed on species lists, we propose that species lists should test for "omnipre sent" taxa-species, genera, and families that occur throughout the region c oncerned-and for a minimum number of species and families. As a case study, we compared species assemblages in diverse habitats in Mexico and found th at seven families and two genera of land birds are omnipresent In mainland Mexico (excluding treeless areas) and that the most depauperate assemblage known contains 35 species from 21 families. We concluded that a list of lan d birds from Mexico that lacks any of these omnipresent taxa or that contai ns fewer than 35 species or 21 families is incomplete. Similar analyses can be done for other taxa and other parts of the world. Tests for omnipresent taxa and for a minimum number of species and families can be used in combi nation with other existing criteria, such as species-richness functions, to better evaluate the completeness of species lists. Realistic results may b e produced in macroecological and conservation studies only if they are bas ed on reasonably complete species lists.