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

DOS SANTOS DA, EMMERICH D, MOLINERI C, NIETO C & E DOMÍNGUEZ

JOURNAL OF BIOGEOGRAPHY

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2016 vol. 43 p. 361 - 371

0305-0270

Aim To study the relationships between Uruguay and neighbouring geographicalareas based on distributions of Ephemeroptera species (mayflies: an ancientorder of aquatic insects). We wanted to evaluate whether Uruguay more closelyrepresents (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 speciesthroughout South America and evaluated these using current taxonomy andgeographical validity. We used the Network Analysis Method (NAM) on thesedata to identify units of co-occurrence (UCs: mutually exclusive groups of codistributedspecies, with each group connected through strong links of sympatryand disconnected from the others). We focused solely on those UCs thatincluded Uruguay in their spatial ranges and used these to infer the vicinityrelationships.Results We recovered four UCs consisting of many species that link Uruguaywith tropical areas of Brazil and NE Argentina. These groups followed a geographicallynested pattern. The results contradict the previously held view thatthe Uruguayan fauna holds strong affinities to that of temperate grasslands thatlie to the south in central oriental Argentina (i.e. the currently accepted conceptof Pampas). A comparison of the genera known from Uruguay and BuenosAires Province further reinforces the distinction between Uruguay andtemperate areas to the south.Main conclusions The hypothesis that Uruguay represents the southern limitof tropical affinities is strongly supported by mayfly distributions, indicatingthat a reappraisal of the Pampas as a cohesive biogeographical province isneeded. We suggest that Uruguay and Buenos Aires should belong to differentprovinces, the former aligned with tropical provinces and the latter alignedwith more temperate areas.