On the position of Uruguay in the South American biogeographical puzzle: insights from Ephemeroptera (Insecta)

Abstract

Aim To study the relationships between Uruguay and neighbouring geographical areas based on distributions of Ephemeroptera species (mayflies: an ancient order of aquatic insects). We wanted to evaluate whether Uruguay more closely represents (1) the southern limit of the tropical (Paranense and Amazonian) fauna or (2) the northern limit of the temperate (Pampean-Bonaerense) fauna.Location South America with an emphasis on Uruguay.Methods We compiled more than 5000 collection records of mayfly species throughout South America and evaluated these using current taxonomy and geographical validity. We used the Network Analysis Method (NAM) on these data to identify units of co-occurrence (UCs: mutually exclusive groups of codistributed species, with each group connected through strong links of sympatry and disconnected from the others). We focused solely on those UCs that included Uruguay in their spatial ranges and used these to infer the vicinity relationships.Results We recovered four UCs consisting of many species that link Uruguay with tropical areas of Brazil and NE Argentina. These groups followed a geographically nested pattern. The results contradict the previously held view that the Uruguayan fauna holds strong affinities to that of temperate grasslands that lie to the south in central oriental Argentina (i.e. the currently accepted concept of Pampas). A comparison of the genera known from Uruguay and Buenos Aires Province further reinforces the distinction between Uruguay and temperate areas to the south. Main conclusionsThe hypothesis that Uruguay represents the southern limit of tropical affinities is strongly supported by mayfly distributions, indicating that a reappraisal of the Pampas as a cohesive biogeographical province is needed. We suggest that Uruguay and Buenos Aires should belong to different provinces, the former aligned with tropical provinces and the latter aligned with more temperate areas.

Hidden areas of endemism: Small units in the South-eastern Neotropics

“…Despite the fact that many authors (Acosta, 2002;Arzamendia & Giraudo, 2009;Burkart, 1957;Cabrera, 1951;Cabrera & Dawson, 1944;Di Giacomo & Contreras, 2002;Dos Santos et al, 2016;Guerrero et al, 2018;Nores et al, 2005;Ringuelet, 1955Ringuelet, , 1959 established relationships of the biota of the Riverine district, its subdistricts, or of parts of its subdistricts, with that of the Paran a province, this relationship was not displayed in regionalization maps (e.g., Cabrera & Willink, 1973;Morrone, 2014). Furthermore, Burkart (1957) and Guerrero et al (2018) noted that the vegetation of the Paran a Delta subdistrict lacks elements of the other surrounding provinces, such as the Pampean and Chacoan, but it is strongly connected to the Paran a elements.…”

Análisis biogeográfico de los humedales del sistema fluvial del Río de la Plata basado en plantas trepadoras y epífitas

“…El área de endemismo selva Atlántica + río Uruguay, reconocida por Giraudo y Arzamendia (2018), es compatible con nuestros resultados y muestra la influencia de la provincia Paranaense hasta los ríos de la Plata y Uruguay. Esta influencia sobre el río Uruguay y sus afluentes se observa también en los patrones de distribución de los Ephemeroptera del Uruguay (Dos Santos et al, 2016). Si bien estos autores generalizan sus resultados atribuyendo una influencia Paranense a todos los ecosistemas del Uruguay, los insectos estudiados (cuyas etapas inmaduras están ligadas al ambiente acuático) probablemente estén reflejando la relación de los ríos y arroyos de dicho país con la provincia Paranaense.…”

“…En coincidencia, Cabrera (trabajos fitogeográficos de 1951, 1953, 1958 y 1976) considera a las selvas marginales de los ríos Paraná y Uruguay dentro del distrito de las selvas mixtas de la provincia Paranaense. Grela (2004) y Dos Santos et al (2016), para la República Oriental del Uruguay, manifiestan criterios similares, mapeando las galerías fluviales como parte de la provincia Paranaense, o considerando a todo el país en dicha provincia. En análisis recientes (Giraudo y Arzamendia, 2018) el río Paraná resultó estar vinculado con el Chaco Húmedo, mientras que el Río Uruguay lo está con la provincia Paranaense.…”

Biodiversidata: An Open-Access Biodiversity Database for Uruguay

“…The reptiles and amphibians, on the other hand, are the result of lineage radiations that come from subregions as contrasting as Patagonia and the Amazon (Pincheira-Donoso 2010). Given these unique biodiversity features, the geographic region, encompassed by the territory of Uruguay, has been proposed to represent a differentiated unit of Pampa, defined by the unique composition of its flora and fauna (Chebataroff 1942, Dos Santos et al 2016). Therefore, it is surprising that these biogeographic features, combined with the country’s small territorial area (176,220 km2) and its relatively uniform elevational topography (513 m maximum altitude), remain one of the poorest-known across the Americas as a whole.…”