Influence of Large South American Rivers of the Plata Basin on Distributional Patterns of Tropical Snakes: A Panbiogeographical Analysis

• Published in: Journal of biogeography 2009-09, Vol.36 (9), p.1739-1749
• Main Authors: Arzamendia, Vanesa, Giraudo, Alejandro R.
• Format: Article
• Language: English
• Subjects: Amphibia. Reptilia; Animal and plant ecology; Animal, plant and microbial ecology; Biodiversity conservation; Biogeographical corridor; Biogeography; Biological and medical sciences; Biological taxonomies; Freshwater ecology; Fundamental and applied biological sciences. Psychology; General aspects; Neotropical rivers; panbiogeography; Plata Basin; River basins; River deltas; Rivers; Snakes; South America; Synecology; Taxa; Tracks, Tectonics and Topography; Tropical regions; Vertebrates: general zoology, morphology, phylogeny, systematics, cytogenetics, geographical distribution
• ISSN: 0305-0270; 1365-2699
• DOI: 10.1111/j.1365-2699.2009.02116.x

Aim The main drainages of the Plata Basin–the Paraná, Paraguay and Uruguay rivers–begin in tropical latitudes and run in a north–south direction into subtropical–temperate latitudes. Consequently, the biota of these rivers has tropical elements that contrast with temperate biomes through which the rivers run. We apply a panbiogeographical approach, to test whether the large rivers of the Plata Basin have a differential influence on distributional patterns of tropical snakes in subtropical and temperate latitudes of South America. Location Subtropical and temperate sections of the major Plata Basin rivers, South America. Methods We compared the individual tracks of 94 snake taxa. The track analysis consisted of: (1) plotting the localities of each taxon on maps, (2) connecting the localities of each taxon using a minimal geographical proximity determinant of the 'individual tracks', and (3) superimposing the individual tracks to determine generalized tracks. To detect tropical snakes that reach higher latitudes through the rivers we used the preferential direction of distribution concept. For each taxon we measured the angular deviations between the line of its individual track and the course of the rivers in a 100 x 100 km scaled grid. Average angular values < 45° indicated a positive association with the rivers. Results Thirty-five of 94 taxa showed distributions associated with the major rivers of the Plata Basin, including fauna from distinct biogeographical lineages, supported by the occurrence of five generalized tracks as follows: (1) the Paraguay-Middle Parana, (2) the Paraguay-Paraná fluvial axis, Upper Parana and Middle Parana to Upper Delta, (3) the Lower Paraguay, Paraná and Uruguay rivers, excluding the sectors High Parana and High Uruguay, (4) the Uruguay River and Upper Paraná, and (5) the High Paraná. The Atlantic species occurred with significantly higher frequency in the Uruguay River and High Paraná river sections, the Amazon species were found with significantly higher frequency in the Paraguay and Middle Paraná sections, and the species with a Pantanal distribution were found in all sections. Main conclusions The observed distributional patterns may be explained by the interaction of ecological, geographical and historical factors. Previous authors have developed ecological (hydrological or environmental similarity) or dispersalist (effect of rivers as migration routes) explanations. The coincidence between generalized tracks and past g