Taxonomic diversity of Thomisidae (Araneae) in heterogeneous environments of the Ramsar site Chaco Wetlands, Argentina

Abstract

The Ramsar site Chaco Wetlands is characterized by its environmental heterogeneity and high diversity of flora and fauna. However, fragmentation and homogenization of environments tend to negatively affect taxa with low abundance or richness like the Thomisidae spiders. In this work, taxonomic diversity is analyzed for Thomisidae assemblages in those environments with varying degrees of plant complexity. The samples were carried out in grasslands, palm groves, open forests, and gallery forests of seven localities, during the years 2013 to 2016, by the techniques of foliage beating, vacuum sam-pling, and direct observation. A total of 464 individuals and 34 species/morphospecies were obtained. These samples belong to five subfamilies, seven tribes, and ten genera. Forested environments showed low taxonomic diversity (Δ +) and high values of taxonomic variation (Λ +), this reflects a phylogenetic tree of Thomisidae non-uniform due to an overrepresentation of species of the genus Tmarus. The high species richness of this genus in forests suggests that environmental filters possibly mediate the mechanism of assembly, where biotic conditions favor the coexistence of species, which allow them to survive in certain habitats. In the grasslands and palm groves, the species were uniformly represented in the phylogenetic tree. The degraded forests presented a specific and taxonomic structure closer to the grassland and palm grove environments. The inclusion of phylogenetic relationships in diversity analyzes could be key in implementing management and conservation plans.