Evaluating Completeness of Species Lists for Conservation and Macroecology: a Case Study of Mexican Land Birds

Abstract

Studies of species diversity, macroecology, and conservation are usually based 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 undertaking an analysis. Species-richness estimators are useful for judging the completeness of species lists but have limitations. To add rigor to studies based on species lists, we propose that species lists should test for " omnipresent" taxa-species, genera, and families that occur throughout the region concerned-and for a minimum number of species and families. As a case study, we compared species assemblages in diverse habitats in Mexico and found that 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 land birds from Mexico that lacks any of these omnipresent taxa or that contains 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 combination with other existing criteria, such as species-richness functions, to better evaluate the completeness of species lists. Realistic results may be produced in macroecological and conservation studies only if they are based on reasonably complete species lists.Evaluación para Determinar si las Listas de Especies para Conservación y Macroecología son Completas: Caso de Estudio de Aves Terrestres Mexicanas Resumen: Los estudios sobre diversidad, macroecología y conservación emplean listas de especies, pero en la literatura científica y en los bancos de datos suelen estar mezcladas listas completas e incompletas de especies. El uso de datos heterogéneos puede generar resultados engañosos y es recomendable reconocer y eliminar las listas incompletas antes de llevar a cabo un análisis. Los estimadores de riqueza de especies son útiles para juzgar cuán completa es una lista determinada, pero éstos tienen limitaciones. Para agregar rigor a los estudios basados en listas de especies proponemos que las listas sean evaluadas con criterios adicionales: se pueden reconocer listas incompletas cuando faltan taxones "omnipresentes" (especies, géneros y familias que ocurren en la totalidad de la región) y si contienen menos de un cierto número mínimo de especies y familias. Por ejemplo, estudiamos ensamblajes de aves en diversos hábitats de México y encontramos que siete familias y dos géneros de aves terrestres son omnipresentes en México (excluyendo islas y hábitats desprovistos de árboles) y que la comunidad con menor riqueza conocida tiene 35 especies de aves pertenecientes a 21 familias. Concluimos que cualquier lista de aves terrestres de México que le falte algunos de estos taxones omnipresentes o tenga menor número de especies o familias se puede reconocer rápidamen...

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