Morphological and genetic characterization of the invasive rayed pearl oyster Pinctada imbricata radiata (Mollusca: Bivalvia: Pteriidae) populations from contrasting environments along the Tunisian coast

ABSTRACT

To understand patterns of genetic and morphological variability, population structure and dispersal dynamics of the invasive bivalve Pinctada imbricata radiata (Leach, 1814) in Tunisian waters, we studied 200 individuals from five different sites (natural, polluted and/or subjected to environmental and anthropogenic pressures) using 10 enzymatic systems and six shell measurements. In this study, we attempt to elucidate the relationship between the spreading ability and the adaptive potential of the species under various environmental stresses. Fourteen putative enzyme-coding loci were resolved, six of which were polymorphic at the level of 99%. P. imbricata radiata maintains a relatively consistent level of polymorphism at the genetic markers studied, since 10% of individuals were heterozygous. The mean F_IS value was positive and significant in two samples. However, the remaining samples collected from the disturbed marine sites (polluted, urban and lagoon areas) were at Hardy–Weinberg equilibrium. Highly significant genetic (mean F_ST = 0.022, P < 0.001) and morphological (Wilks’ lambda = 0.0814, approximate F_{20, 627} = 35.484, P < 0.001) differentiations between samples were observed, with no evidence of isolation caused by geographic distance. However, the Mantel test performed between genetic and morphological distances revealed a significant correlation. Our results indicate that natural selection seems to have a greater influence on genetic differentiation in P. imbricata radiata than genetic drift. The combination of genetic and morphological data provided important theoretical information for determining the invasion mechanisms of the species.

KEYWORDS:

• Bioinvasion
• genetic diversity
• connectivity
• shell morphometry
• population structure
• environmental stress

Acknowledgements

The authors gratefully thank the editors and the three anonymous reviewers for their careful reading of the manuscript and their many insightful comments and suggestions. We are grateful to the teams from the Ecosystems and Aquatic Resources Research Unit (UR13AGRO1, INAT/University of Carthage) for their valuable collaboration.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This study was financially supported by the French National Research Institute for Sustainable Development (Institut de Recherche pour le Développement - IRD, JEAI GAMBAS project).