Overcoming the Wallacean shortfall in sky-islands of central Mexico: the case of copro-necrophagous beetles and two national parks.

Insects are the most diverse group of organisms, but their large number of species and the lack of specialists to study them have made this group particularly vulnerable to the main limitations in biological diversity, such as the Wallacean deficit. This study will contribute to the geographical knowledge of an insect trophic guild that has been widely used as an indicator group, the Scarabaeoidea and Silphidae copro-necrophagous beetles, emphasizing their geographical distribution in two Mexican national parks (Iztaccíhuatl-Popocatepetl and La Malinche) and the intermediate region, which includes sky-island ecosystems in central Mexico. Geographic records of the 32 species that have been previously recorded in the study region were compiled and used to generate potential distribution models aiming to generate potential alpha (species richness) and beta (total beta diversity, nestedness and replacement) diversity maps. The greatest predicted species richness was found between 3,000 and 3,500 m a.s.l. in the study region. Potential species richness ranged from 2 to 24 species. Total beta diversity was low in the study region (mean 0.1), while nestedness was the most important component of beta diversity (0.8). The maximum alpha and beta diversity values were predicted outside the national parks. Consequently, we consider that the studied national parks are not able to protect completely the regional alpha and beta diversities by themselves. Implications for insect conservation: Our results show that the highest alfa and beta diversity values of copro-necrophagous beetles might occur outside the national parks, and a suitable way to protect them could be the Archipelago reserve model as an alternative to protect the regional diversity. [ABSTRACT FROM AUTHOR]