Macroscopic sexual dimorphism in Fucus radicans (Phaeophyceae) with implications for its reproductive ecology
(English)Manuscript (preprint) (Other academic)
Sexual dimorphism on a macroscopic scale is unusual within Phaeophyceae. In this paper we report for the first time on macroscopic sexual dimorphism in F. radicans. During field collections it was possible to tell the two sexes of F. radicans apart on size, as both receptacles and thallus seemed smaller in males than females. A set of morphological characters were therefore measured on three dioecious Fucus species, F. radicans, F. serratus and F. vesiculosus, with the aim of determining if sexual dimorphism occurs in the recently described endemic F. radicans in the Baltic Sea and if it also is found in the other fucoids. Here F. radicans was sampled from highly clonal populations of the Bothnian Sea and from the populations in Väinameri Sea where no clones have been found yet. Regardless of origin, a macroscopic sexual dimorphism was recorded in F. radicans regarding receptacle size (length, width and height) and weight (DW/WW ratio). The receptacle DW/WW ratio was higher in males than 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 in thallus width and Fertility Index (F.I.) between the sexes also were present. This has not been shown for any member of the genus Fucus before, but seem to be a species specific character in F. radicans, as there was no differences between the sexes in either F. serratus or F. vesiculosus. Observed differences in F. I. and reproductive allocation between F. radicans and F. vesiculosus and F. serratus may have implications for recruitment success in marginal populations of the three species.
Fertility Index, Reproductive Allocation, receptacles, morphology, clonality
Research subject Plant Ecology
IdentifiersURN: urn:nbn:se:su:diva-117575OAI: oai:DiVA.org:su-117575DiVA: diva2:813711