CONSIDERACIONES ACERCA DE LA DIVERSIDAD DE LAS AVES EN RELACIÓN CON EL EJE FLUVIAL PARAGUAY-PARANÁ, EN SUDAMÉRICA

DI GIACOMO, ADRIÁN S.; CONTRERAS, JULIO R.

Historia Natural (Segunda Serie)

Fundación de Historia Natural "Felix de Azara"

Lugar: Buenos Aires; Año: 2002 vol. 1 p. 23 - 29

0326-1778

Bird diversity was studied along the fluvial axis of the rivers Paraguay-Paraná. Bird-atlasing methods with a grid for each species with a square unit of 0,5 x 0,5 geographic degree superimposed over a map of the Rio de La Plata Basin were used for to carry out analysis. Main results are: 1) The avian richness is higher along the Paraguay-Paraná axis than in out of the flood valley area in the same latitude, excepting the tract between 23º and 30º S; 2) There is a gradient North-South in richness, from 536 species at 16º to 238 at the neighbourhood of the Río de la Plata; 3) The slope of the gadient is non-linear because of two "steps" of decreasing diversity; 4) Range borders of many species inflected to south, extending its distributions along the valley. The gradient of richness could be a pattern reflecting the dispersal in response to valley. A possible hypothesis is that the fluvial axis and the adjacent flood valley constitute a functional area/biota unit not belonging at any biogeographic category but highly operative in the natural balance of biotic diversity of southern South America.