Unexpected diversity: the Mygalomorph spider community from a natural reserve representing the dry Chaco region in Argentina

Abstract

Most species of Mygalomorphae spiders are known to be habitat specialists, have a sedentary lifestyle with restricted geographic distributions. The dry Chaco ecoregion in Argentina is an extensive region located northern in the provinces of Chaco, Córdoba, Formosa, Salta and Santiago del Estero. This habitat is characterized by a xeric vegetation composed of small shrubs and iconic tree species such as “quebracho-blanco” over a sandy soil. The climate at the region is temperate with extreme temperatures above 40°C during summer. The only Natural Reserve that preserves an undisturbed area of the dry Chaco is the Copo National Park located northeastern Santiago del Estero province. Recent surveys carried out during two sampling dates at this area revealed a remarkable diversity of mygalomorphs spiders not expected to be found in a such dry habitat with lack of suitable refuges (e.g. logs, rocks). We performed two surveys in spring and autumn, during which we were collecting the spiders during both day and night. We registered 10 mygalomorph species belonging to the families Actinopodidae, Idiopidae, Theraphosidae (Theraphosinae and Ischnocolinae) and Pycnothelidae. All specimens were found inhabiting burrows with open entrances, with small turrets or closed with a trapdoor. From this work, we present new distribution records for Santiago del Estero province, first citations for Argentina, and new species discovered for science. This spider community is relevant for future conservation studies in the area because it comprises a diversity hotspot of these threatened spiders, even highest that some of the richest areas in tropical regions.