Influence of large South American rivers of the Plata Basin on distributional patterns of tropical snakes: a panbiogeographical analysis

Abstract

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 · 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 Paraná, (2) the Paraguay-Paraná fluvial axis, Upper Paraná and Middle Paraná to Upper Delta, (3) the Lower Paraguay, Paraná and Uruguay rivers, excluding the sectors High Paraná 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 conclusionsThe 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 geomorphological events that caused displacements and changed relationships between the Paraguay, Paraná and Uruguay river sections supports hypotheses involving the strong influence of historical factors in the present configuration of tropical snake distribution in temperate latitudes.

Evolutionary biogeography of South American weevils of the tribe Naupactini (Coleoptera: Curculionidae)

“…Most of the Pampean Naupactini are flightless species adapted to environments of open communities that have certainly succeeded in extending their ranges southwards, towards more temperate areas. The margins of La Plata River are clearly subtropical (Ringuelet, ), as this area is inhabited by species also occurring in the Parana forest, which could expand southwards along the gallery forests of the Parana and Uruguay rivers (Menalled & Adámoli, ; Nores et al ., ; Arzamendia & Giraudo, ). Their effect as biogeographical corridors is a pattern previously described for several groups of aquatic (e.g.…”

Morphological variability of the cranium of Lontra longicaudis (Carnivora: Mustelidae): a morphometric and geographic analysis

“…In addition, this pattern of differentiation in shape may be influenced by the two biogeographically distinct regions in the La Plata Basin-tropical in the north and subtropical-temperate in the south-where climatic zoning has promoted changes in distribution and diversification patterns in both aquatic and terrestrial (Arzamendia and Giraudo 2009) species, and has possibly had the same effect on the Neotropical otter. Added to this effect is the presence of prairies that may be functioning as a barrier between the Amazon and La Plata during the dry season when bodies of water become scarce, preventing the Neotropical otter from migrating from one hydrological region to another.…”

A panbiogeographical model to prioritize areas for conservation along large rivers

“…The Neotropical region is characterized by the presence of large hydrographic basins (e.g. Amazon, Plata and Orinoco) that are considered areas of high diversity and endemism, and which play an important role in the distribution patterns and evolution of Neotropical biota (Haffer, 1997; Arzamendia & Giraudo, 2009). The Plata Basin is the second largest fluvial system in South America and includes the southernmost remains of the ‘Atlantic Forest Biodiversity Hotspot’, one of the most biodiverse and threatened ecosystems in the world (Galindo Leal & Câmara, 2003; Giraudo et al.…”

“…, 2009). The main drainages of the Plata Basin begin at tropical latitudes and run in a north–south direction into subtropical–temperate latitudes (Arzamendia & Giraudo, 2009). Consequently, the biota of these rivers has tropical elements that contrast with those of the xerophilous forests and temperate steppes through which the rivers run (Nores et al.…”

“…In fact, in the Plata Basin of South America, the fauna composition of one large river (i.e. the Paraná River) varies in different segments of the river in relation to historical, ecological and geographical factors (see Arzamendia & Giraudo, 2009 for a further discussion). The large Plata rivers serve as biogeographical corridors for tropical biota towards temperate latitudes (e.g.…”