The species of Plagiodontes living southern Buenos Aires Province (Gastropoda, Odontostominae)

CAZZANIGA NÉSTOR J.; PIZÁ JULIA; GHEZZI NATALIA S

Sau Paulo

Congreso; V Congreso Latinoamericano de Malacología; 2002

Instituto Butantan-USP

Three out of the eight nominal species of Plagiodontes are known to live in southern Buenos Aires province, i.e., P. patagonicus, P. magnus and P. rocae. Their taxonomic characterization did not include any quantitative analysis of variability for an accurate discrimination. Shell measurements and angles, and quantitative data on the terminal male genitalia were studied by multivariate analysis (discriminant analysis, VARIMAX). Shell morphometry revealed that, even if its qualitative distinct characteristics (shell ribs, color) are kept aside, P. rocae morphometrically differs from all other snails in the area, so that its identity as a separate morphospecies is warranted. Instead, P. patagonicus and P. magnus showed an almost continuous pattern of shell variation over a geographical gradient, which is here interpreted as a size-form cline that does not allow to objectively delimit different morphospecies. Data from the genital system also arranged as a geographical gradient within the P. patagonicus, P. magnus continuum, but they do not differentiate P. rocae.