Anatomical variation in cryptic mudsnail species: Statistical discrimination and evolutionary significance

Abstract

Abstract In the present paper, the brackish-water mudsnail genus Hydrobia is used to assess the degree of anatomical differentiation among cryptic species. Detailed anatomical data for seven populations from four taxa are compared to genetic data in order to test whether there are discrete anatomical differences among taxa, whether it is possible to partition the total anatomical variation into hierarchical among-taxa and among-population components, to find those anatomical characters that statistically discriminate taxa, and to make inferences about the mode of evolution. A qualitative anatomical analysis did not yield any character states that could be used to differentiate among taxa, and a PCA of quantitative anatomical characters did not discriminate among species. Moreover, no significant variance component could be detected in the nested analysis of morphological variance among lineages and/or populations. However, discriminant analyses (DA) with mtDNA lineages as grouping variables resulted in hi...