Spiders (Arachnida: Araneae) of the tropical mountain cloud forest from El Triunfo Biosphere Reserve, Mexico

Abstract

We carried out an intensive and systematized sampling of the spider fauna of the tropical mountain cloud forest (TMCF) in El Triunfo Biosphere Reserve, Chiapas, Mexico, in order to analyze their composition, species richness, abundance, and proportion of undescribed species, and to compare these results with those found in other TMCFs. We sampled ten plots in two seasons (dry and rainy) using different sampling techniques on two strata (ground and understory). A total of 7,432 specimens were collected corresponding to 28 families, 78 genera and 111 morphospecies. A high proportion of total species (58.6%) were undescribed species. For 11 species originally described from a single sex, we found the other sex. Five species and one genus were new records for the Mexican spider fauna. Understory stratum had higher numbers of species and individuals than ground stratum, and there was a high species turnover, with only 17% of the total species shared between strata. The spider fauna of El Triunfo shows similarities with other TMCFs (especially that on the same mountain range) concerning the identities of dominant and species-rich families, family and genera composition, the presence and relevance (in abundance or richness) of families that are uncommon in lowland tropical habitats (Linyphiidae and Theridiosomatidae), and in the high proportion of undescribed species. However, there is a high species turnover among sites (only 16% species shared), even at relatively short distances, that seems derived in part from the relative high proportions of endemic species. Our results suggest that high abundance of Theridiosomatidae and Linyphiidae, together with high species richness of this last family, could be used as conservation indicators for the Mexican TMCFs. The high numbers of undescribed species in the analyzed TMCFs, and their relatively high endemicity levels, support that TMCFs could be regarded as hotspots for the order Araneae.