Identification of ecophenotypic trends within three European freshwater mussel species (Bivalvia: Unionoida) using traditional and modern morphometric techniques

• Published in: Biological journal of the Linnean Society Vol. 98; no. 4; pp. 814 - 825
• Main Authors: ZIERITZ, ALEXANDRA, ALDRIDGE, DAVID C
• Format: Journal Article
• Language: English
• Published: Oxford, UK Oxford, UK : Blackwell Publishing Ltd 01-12-2009; Blackwell Publishing Ltd; Wiley-Blackwell
• Subjects: Animal and plant ecology; Animal, plant and microbial ecology; Animals; Autoecology; Biological and medical sciences; fourier shape analysis; Fundamental and applied biological sciences. Psychology; intraspecific variability; Invertebrates; Mollusca; palaeontological reconstruction; Protozoa. Invertebrata; Unionidae; Europe; Reconstruction; Shape analysis; Interspecific comparison; Biological evolution; Fresh water; palaeontological reconstruction; intraspecific variability; Morphotype; Phenotype; fourier shape analysis; Bivalvia; Morphology; Biotype; Habitat; Intraspecific comparison; Ecotype; River Thames; Invertebrata; Mollusca; Morphometry; Unionidae
• ISSN: 0024-4066; 1095-8312
• DOI: 10.1111/j.1095-8312.2009.01329.x

Most species of freshwater mussels (Unionoida) show a wide variability in shell form and size but an understanding of which factors determine unionoid morphology is poor. We identified ecophenotypic trends in shell and internal characters within three unionoid species from two habitat types (marinas and river) of the River Thames, UK, using traditional and modern morphometric techniques. In marinas, all species grew to larger maximum sizes than in the river, which might be a result of higher temperatures and phytoplankton densities in marinas. Unio pictorum in marinas was more elongated than in the river and Fourier shape analysis revealed a trend from dorsally arched river specimens to straight dorsal and pointed posterior margins in marina individuals. The degree of shell elongation and shape of dorso-posterior margin were not associated with sediment composition, but were associated with the different hydrological characters of the two habitat types. Relative shell width was a poor indicator of collection site and influenced by allometric growth. Unlike U. pictorum, a difference in shell elongation of marina and river mussels could not be detected in Unio tumidus and Anodonta anatina. However, all three species showed the same trends regarding the shape of the dorso-posterior shell margin. This shell character may thus have broad ecological significance and could have considerable utility to palaeontologists, taxonomists, and conservation biologists.