Diversidad de Theridiidae (Araneae) en la Reserva Natural e Histórica Isla Martín García (Buenos Aires-Argentina)

Spiders are considered important for studies of biodiversity, conservation and succession. They readily disperse and become established in new habitats and are considered good colonizers of islands. The Theridiidae is one of the most diverse spider families, characterized by great morphological, ethological and ecological diversity. In Argentina, there are no studies of island theridiids, therefore, this study comprises the first record of the family in these environments. The Martin Garcia Island is a Natural and Historical Reserve located in the northwest of the La Plata River and presents environmental and floristic variability. In order to analyse the species richness, relative abundance and alpha and beta diversity of theridiids, sampling was performed over three consecutive years, by beating net and manual sampling. We recorded 1173 spiders, belonging to 9 genera and 21 morphospecies. The most abundant species in all environments was Cryptachaea hirta (61.68%) The forest was the habitat with highest diversity (H' = 1.9, J = 0.67) (S = 16), providing extensive vegetation, with vast resources for the survival of these spiders. The island is not an important area with regard to species singularity. Three new records were found for Argentina: C. altiventer, Theridion positivum and T. tinctorium.