Geographical distribution of Discocyrtus prospicuus (Arachnida: Opiliones: Gonyleptidae): Is there a pattern?

Abstract

The environmental constraints determining the distribution of the harvestman Discocyrtus prospicuus in Argentina and Uruguay are addressed. Habitat observations across the entire range (Río de la Plata-Atlantic coast area; Córdoba sierras; northwestern Argentina) are provided. Previous published localities (verified for accuracy), new records and bioclimatic predictors were used to characterize the species bioclimatic profile and to build predictive distributional models with BIOCLIM and MAXENT algorithms. Relative importance of each bioclimatic variable in the final models is assessed. It was determined that D. prospicuus is primarily a gallery forest dweller, with preferred climate temperate to temperate-cold; variables related to thermic uniformity rank among the most influential. Results consistently support the alleged yungas- Mesopotamian disjunction; but the link between the Río de la Plata and Córdoba sierras areas shows disagreement between methods (predicted continuous with BIOCLIM, separate with MAXENT). It is suggested that the need for constant air humidity (favored in the core area by its proximity to large rivers and the seacoast) and competitive exclusion with congener D. testudineus may represent additional limiting factors. Some observations on the species tolerance to human activity are also given.