The niche‐width variation hypothesis reconfirmed: Validation by genetic diversity in the sessile intertidal cirripedes Chthamalus stellatus and Euraphia depressa (Crustacea, Chthamalidae)

Genetic diversity in a pair of cirripede species, based on electrophoretic analysis of 25 gene loci, is higher for Chthamalus stellatus, the species with a broader biogeographical distribution, and hence, with a broader ecological niche, than that of Euraphia depressa. Comparing the genetic diversity within E. depressa we again report a higher genetic diversity among the specimens exposed to solar radiation (living in the wider ecological niche) versus the specimens confined to the sheltered dark environments in caves or under boulders. The indices of genetic diversity used in this study are polymorphism, heterozygosity, mean number of alleles per locus and gene diversity. We conclude that the niche‐width variation hypothesis has been confirmed in this pair of species: genetic diversity is positively correlated with niche breadth.