Abstract
Harvestmen are a good taxon for biogeographic studies due to their low vagility and their dependence on environmental conditions which make most of them live in humid and shaded habitats. Current knowledge of the geographical distribution of Uruguayan opiliofauna suggests that no evident zoogeographic areas are present, mainly because of the apparent uniformity of the landscape of this country. Recent biogeographic studies indicate that Uruguay represents a biogeographical crossroad between three South American provinces, and the aim of this study is focused on determining if this fact is reflected in the distribution of the Uruguayan opiliofauna. To test this presumption, we used the species distribution model methodology. Distribution data about four harvestmen species from Uruguay and neighboring countries were analyzed. We used the maximum entropy principle to perform a distribution model for each species. We recognized Acanthopachylus aculeatus and Pachyloides thorellii as two Pampasic representatives of the Uruguayan opiliofauna. The other species studied, Discocyrtus prospicuus and Metalibitia paraguayensis, reflect Mesopotamian and Paranaense influences in the Uruguayan territory. Isothermality was the climatic variable with the best contribution in the models of the four species, reflecting constrained latitudinal ranges. Results of the present study suggest that two roughly different opiliological areas for Uruguay can be recognized, based on climatic variables.
Highlights
Harvestmen are a good taxon for biogeographic studies due to their low vagility and their dependence on environmental conditions which make most of them live in humid and shaded habitats
The database used for modeling consisted of 129 unique locality records for A. aculeatus, 68 for P. thorellii, and 65 for M. paraguayensis
Discocyrtus prospicuus The distribution of this species in Uruguay is restricted to a narrow corridor along the riparian forest of the coast of Uruguay and Río de la Plata rivers, showing a low probability of occurrence at the center of the country (Figure 1)
Summary
Harvestmen are a good taxon for biogeographic studies due to their low vagility and their dependence on environmental conditions which make most of them live in humid and shaded habitats. The latter paper (Capocasale 2003) consists of a catalogue, in which a total of 25 species belonging to 5 families were cited for the country In his contributions, Capocasale (1968, 2003) provided a coarse reference to the species distributions, either indicating the occurrence localities on a map (Capocasale 1968) or merely assigning them to the administrative divisions (departments) (Capocasale 2003). The biogeographical affinities between the Pampean Province in Argentina and Uruguay were already indicated for varied taxonomic groups, like Asteraceae (Crisci et al 2001), Pleistocene mammals (Carlini et al 2004), as well as harvestmen (Acosta 2002) and scorpions (Acosta 1993; Mattoni and Acosta 1997; Acosta et al 2008) This area is a part of the ‘peripampasic arc’ , a biogeographical track that comprises ancient mountain systems with biotic connections, where a high biodiversity and endemic species converge (Acosta 1993; Acosta and Maury 1998a, b; Acosta et al 2008; Ferretti et al 2012). This record represents new evidence that supports the proposal that this river acts as a biological corridor that allows the intromission of the Paranaense Forest and Chaco Provinces in Uruguay, as proposed by Grela (2004)
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