Thomisidae (Araneae) assemblages in different vegetation types in a ramsar site in the northeast of argentina

Abstract

The RAMSAR Chaco Wetland site is one of the three most diverse biomes in Argentina due to its very heterogeneous environment. Studies on the diversity of spiders on this biome are scarce and there is no study in relation to the diversity of Thomisidae Sundevall, 1833. We analyzed the Thomisidae assemblages in environments with different degrees of structural complexity (gallery forest-GF-, low open forest-LOF-, grassland-Grassl-and palm groves-Palm Grv-) on seven localities of RAMSAR site. The spiders were collected by foliage beating, hand collecting and vacuum sampling (G-vac). 464 individuals were collected, distributed in 34 species/morphospecies. Completeness of sampling was greater than 90% and more than 60% of the expected species were obtained according to the Chao 1 estimator. The highest abundance, richness, and diversity of order 1 and 2 were observed in the GF but these were not significant. The grassl had the lower richness, diversity and equitability. Tmarus pugnax (Mello-Leitão, 1929) dominated in the forests, while T. aff. humphreyi (Chickering, 1965) dominated in the Grassl, and Misumenops maculissparsus (Keyserling, 1891) with Uraarachne sp (Keyserling, 1880) in the Palm Grv. The NMDS separated two groups: the forests (GF and LOF) and the Grassl + Palm Grv (stress = 0.28) and the ANOSIM analysis indicated significant differences between groups (R = 0.38 p = 0.02). Likewise, the Chao-Jaccard index indicated greater similarity between forested environments and the Grassl + Palm Grv. The most richness and abundance of tomisids were obtained in forested environments, possibly due to greater plant complexity in these environments.