Sexual dimorphism on a macroscopic scale is unusual within the Phaeophyceae. We report for the first time macroscopic sexual dimorphism in Fucus radicans. A set of morphological characters was measured on three dioecious Fucus species, F. radicans, Fucus serratus and Fucus vesiculosus, to determine if sexual dimorphism occurs in the endemic F. radicans in the Baltic Sea and if it also is found in the other fucoids. F. radicans was sampled from highly clonal populations of the Bothnian Sea and from populations in the Väinameri Sea where no clones have been found. In both locations, sexual dimorphism was recorded in receptacle size and weight in F. radicans. Also, the receptacle dry weight to wet weight ratio was higher in males than in females, showing that male receptacles have a lower water content than females. The dimorphism was more pronounced in the Bothnian Sea populations, where further differences between the sexes in thallus width and fertility index also were present. This has not been shown for any member of the genus Fucus before, but seems to be a species-specific character in F. radicans, as there were no differences between the sexes in either F. serratus or F. vesiculosus.
About the authors
Ellen Schagerström has a PhD in Plant Ecology and is a researcher at Stockholm University, Department of Ecology, Environment and Plant Science and at the Baltic Sea Centre. Her research expertise is within the field of marine ecology focusing on biodiversity both at the genetic and species level in Fucus communities as well as adaptation and speciation. Furthermore, her research covers studies of dynamics of benthic vegetation as well as restoration of shallow benthic communities.
Lena Kautsky is Professor Emeritus in Marine Plant Ecology at Stockholm University, Department of Ecology, Environment and Plant Science and senior advisor at the Baltic Sea Centre. Her research expertise is within the field of marine ecology focusing on benthic vegetation and dynamics in Fucus communities. Furthermore, her research covers studies of biodiversity both at the genetic and species level, as well as effects and impact of pollution on benthic vegetation and issues on integrated aquaculture and restoration of shallow benthic communities.
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