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 yungasMesopotamian 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.

The Northern region of Buenos Aires province, in Argentina, suffered an uninterrupted increase in rainfall and temperature values during the last decades. The aim of the present contribution is to analyze the effects of such climatic change in the distribution of local flora and fauna. The analysis resulted in the recognition of distributional shifts in a total of 115 species. These changes represented the progressive southern expansion of species typically present in subtropical areas. Because all these changes have a similar orientation and direction, and included a large number of plant and animals with different ecological requirements, it is here postulated that those geographical changes are probably a response to climatic alteration.

This study aimed to establish if the Lower R ıo de la Plata Basin (LRPB) wetlands can be considered a biogeographic unit. The species of this area were compiled and segregated according to the habitat, selecting only 87 endemic taxa restricted to the LRPB and linked to wetlands. Distributional data of species obtained from the literature, web databases, biological collections, and field trips were georeferenced. The areas of endemism were established as those areas where the distribution of two or more taxa overlaps in groups of rivers' sections with geographic continuity and were tested with a cluster analysis. This congruence is due to ecological, geomorphological, and historical factors. Four areas of endemism were found: a broad area that comprises the whole study area (Riverine district), which is divided into three nested smaller areas (Paraguay-Paran a Flooding Valleys, Uruguay Basin, and Paran a Delta subdistricts). Then, we analysed 170 taxa distributions to evaluate the relationship between the study area and the neighbouring biogeographic units. According to the results, the study area belongs to the Paran a biogeographic province. Some areas of endemism are hidden inside broader areas and are hardly detected with the currently used biogeographic grid-methods. We propose to combine the information about ecological requirements of each taxon with its georeferenced records to estimate their areas of distribution as a primary step for searching areas of endemism in intracontinental studies.

La asociación denominada selva marginal de Punta Lara está ubicada al sureste de la ciudad de La Plata, en el partido de Ensenada, a los 34° 47’ 31’’ Sur y 57° 59’ 51’’ Oeste. En esta asociación se destacan especies arbóreas como Blepharocalyx salicifolius, Allophylus edulis, Ocotea acutifolia, Pouteria salicifolia y Lonchocarpus nitidus, acompañadas de numerosas especies trepadoras, epífitas, hierbas y arbustos típicos de las selvas del sur de Brasil y noreste de Argentina. A fines de la primera mitad del siglo XX, los aportes de Cabrera & Dawson en 1944 y de Cabrera en 1949 constituyeron el marco teórico que siguió la comunidad científica para reconocer el estado “primitivo” de área costera del Río de la Plata. Desde ese momento la calificación de “relicto” para la selva marginal de Punta Lara quedó fuertemente arraigada en la literatura científica, técnica y de divulgación. El objetivo de este trabajo es poner a prueba ese marco teórico, sobre el cual se basan algunas de las principales prácticas conservacionistas de la provincia de Buenos Aires. Para ello, se utilizaron cinco fuentes de información: 1) cartografía de los siglos XVIII y XIX, 2) relatos de viajeros de esa época, obtenidas de diversas fuentes bibliográficas, 3) bases de datos de plantas vasculares herborizadas antes del siglo XX, 4) los hongos xilófilos herborizados a fines del siglo XIX en la costa platense y 5) el registro paleoclimático reciente. Como resultado del presente trabajo se propone una nueva hipótesis: la selva marginal de Punta Lara no constituye un relicto sino una asociación instalada recientemente, establecida a mediados del siglo XIX cuando el clima de la región del Río de la Plata manifestó un incremento en las precipitaciones y la temperatura mínima, tendencia que se mantiene hasta el presente.