Toward a better understanding of the native-nonnative status of mytilus mussels in the Southwestern Atlantic: Comparing pre-european middens and modern populations

Abstract

The aim of this study is to determine the degree of similarity of the Mytilus mussels currently found along the Patagonian coast of Argentina to those found in pre-European colonization middens, in order to approach an understanding of whether the former are native or not. An elliptic Fourier analysis between pre-European archaeological (native) and modern mussels (cryptogenic) was performed, and the resulting data were analyzed with multivariate approaches (principal component analysis, discriminant function analysis, and cluster analysis). Our results showed that when all samples belonging to the Patagonian coast were included on a single analysis, modern and archaeological mussels were clustered in two major groups, matching the macroregional marine biogeographic scheme. In addition, morphometric differences were detected when modern and archaeological mussels from similar latitudes were compared. We discuss these results in light of the natural and anthropogenic changes that occurred along the Argentinean coast together with the environmental changes occurring between the biogeographic provinces along the SW Atlantic coast.

El objetivo del presente trabajo es realizar un estudio morfológico entre valvas de mejillones Mytilus actuales y arqueológicos de la costa patagónica de Argentina, a fin de brindar una nueva perspectiva que permita mejorar el conocimiento sobre el origen nativo o invasor de los mejillones Mytilus actuales. Valvas arqueológicas (nativas) y actuales (criptogénicas) se estudiaron mediante el análisis elíptico de Fourier, y los datos obtenidos se analizaron con análisis multivariados (análisis de componentes principales, análisis de función discriminante, análisis de conglomerados y MANOVAs). Por un lado, los resultados muestran que en un análisis conjunto de todas las muestras (i.e. actuales y arqueológicas) éstas se agruparon siguiendo el esquema biogeográfico del mar argentino. Por otro lado, las valvas actuales y arqueológicas procedentes de latitudes similares de la costa patagónica se diferenciaron morfométricamente. Los resultados se discuten a la luz de los cambios naturales y antropogénicos ocurridos a lo largo de la costa argentina, y considerando además las diferencias ambientales entre ambas provincias biogeográficas del mar argentino.