Fd. Menalled et Jm. Adamoli, A QUANTITATIVE PHYTOGEOGRAPHIC ANALYSIS OF SPECIES RICHNESS IN FORESTCOMMUNITIES OF THE PARANA RIVER DELTA, ARGENTINA, Vegetatio, 120(1), 1995, pp. 81-90
A biogeographic analysis of 26 species of trees and shrubs occurring i
n the Parana River Delta (32 degrees to 34 degrees 30' South latitude,
58 degrees to 61 degrees West longitude, Argentina) was performed to
study the floristic and structural differences among deltaic woodland
communities. Traditionally these variations have been interpreted as a
consequence of the differential influence of local island geomorpholo
gy and flood dynamics on floristic successions. We performed a cluster
analysis of collection site, obtained maps showing the joint occurren
ce of the species of each community, and related species ranges with t
he presence of possible migration corridors. Results suggest that, in
addition to local variations in topography and flood persistence, chan
ges in floristic richness can be understood as a consequence of the di
fferential efficiency of the Parana and Uruguay Rivers as migration co
rridors for tropical species into temperate latitudes. Geomorphical st
ability of riverbeds and fluvial dynamic differences between rivers ar
e discussed in relation to how they may explain the more efficient mig
ration of species along the flood plain of the Uruguay River compared
to the Parana River. Results allow us to re-interpret the relative imp
ortance of both rivers in the establishment of tropical and subtropica
l species in temperate latitudes, and to add a regional explanation fo
r the observed floristic heterogeneity.