Biogeographic and species richness patterns of Gastropoda on the southwestern Atlantic

Abstract

Patterns of richness and biogeography of Gastropoda molluscs were determined based on lists of species from five sites along the southwestern Atlantic. The analysis of the distribution patterns of these sites confirmed the existence of a broader transition zone between southern Espírito Santo State (21 degrees S) and Rio Grande do Sul State (32 degrees S). This zone is very heterogeneous, presenting a low endemism rate and a significant number of species common to the near provinces, and does not show enough consistency to be considered as an independent biogeographic province as proposed by Palacio (1980). Observing the distribution of species along the southwestern Atlantic we find an increase in the proportion of species with greatest latitudinal ranges (occurring from the tropics to Patagonia) from lowest to highest latitudes, following Rappoport's rule.

Biogeography and biodiversity of gastropod molluscs from the eastern Brazilian continental shelf and slope

“…Furthermore, on the Uruguayan coast (Scarabino, 2004), 16 among 182 gastropods were the same as the species reported in this study (carried out in the Tropical and Paulista provinces). The presence of species that are considered to be endemic to the Paulista Province (i.e., Anachis fenelli Radwin, 1968;Favartia varimutabilis Houart, 1991;Olivella defiorei Klappenbach, 1964) and subtropical species from the Patagonic Province in the north region (Tropical Province) corroborate the notion of a broader transition zone between tropical and temperate waters (Van nucci, 1964;Lana, 1987;Miyaji, 1995;Floeter & Soares-Gomes, 1999).…”

“…The disappearance of some tropical species towards the south suggests that the southernmost limit of the Tropical Province is located close to 21°S, according to the results found for gastropods (Floeter & Soares-Gomes, 1999); cirripeds (Young, 1995), and polychaetes (Lana, 1987). Nevertheless, the location of that limit remains uncertain (Absalão, 1989;Mello, 1993;Briggs, 1995).…”

Introduced ascidians in Paranaguá Bay, Paraná, southern Brazil

“…The Caribbean fauna should extend only to the Brazilian state of Espírito Santo, following PALÁCIO (1982), who considered the region between Espírito Santo and the southernmost Brazilian state of Rio Grande do Sul, as a region of high endemism and therefore a biogeographical province. However, a study of the gastropod community did not support this hypothesis, since endemism was not high within these latitudes, which should therefore only be considered a region of transition (FLOETER & SOARES-GOMES 1999). Also, the Brazilian Current reaches the state of Santa Catarina, providing a dispersal route and explaining southern ascidian distributions.…”

Potencial atrator de tubarões costeiros em recife artificial no litoral norte do estado do Rio de Janeiro, Brasil

“…A região entre o estado do Espírito Santo e a cidade de Cabo Frio -Rio de Janeiro é considerada de grande importância na distribuição zoogeográfica no Atlântico Sul, sendo indicada como o início de transição entre as faunas nectônicas tropical e subtropical (PALAClO 1982;FLOETER & SOARES-GOMES 1999). Inserida nesta área, a região norte do estado do Rio de Janeiro justifica a condição de zona de transição, sendo banhada ao norte por águas oligotróficas da Corrente do Brasi I e inJluenciada ao sul pela ressurgência daÁgua Central do Atlântico Sul (VALENTlN & Mo TEIRO-RIBAS 1993;EKAU & K OPPERS 1999).…”