Morphological and genetic variation of Fucus in the eastern Gulf of Bothnia, northern Baltic Sea

A1 Journal article (refereed)

Internal Authors/Editors

Publication Details

List of Authors: Henna Rinne, Ulrika Björkman, Conny Sjöqvist, Sonja Salovius-Laurén, Johanna Mattila
Publication year: 2018
Journal: European Journal of Phycology
Volume number: 53
Issue number: 3
Start page: 369
End page: 380


Fucus vesiculosus and F. radicans (Phaeophyceae) are
important habitat-formers on rocky shores in the Bothnian Sea. While
both species occur sympatrically along the entire western Bothnian Sea
coast, F. radicans has been found only in the northern part of
the eastern coast. According to previous studies, the two species can be
distinguished based on morphology, F. radicans having narrower
thalli and a bushier appearance. However, marine mapping in the eastern
Bothnian Sea has revealed that high morphological variation in Fucus,
partly caused by gradients in salinity and exposure, makes
differentiation between the two species difficult. We studied
morphological and genetic variation to find out whether the two Fucus species can be differentiated in the south-eastern Bothnian Sea, and if F. radicans
occurs in the area. The study was carried out in six subareas including
350 km of coast, with a salinity gradient of 3.5–6.5 PSU, and varying
wave exposure. We found a gradual change towards smaller and narrower
thalli and a higher number of holdfasts in Fucus populations when moving northwards to lower salinities. Distinct Fucus
morphs were often found within the study sites but the morphs were
genetically differentiated only at one study site in the Skaftung
subarea, suggesting the occurrence of both species. However, in the Vasa
subarea the sample size for analysing genetic differentiation was low
due to high clonality. In the Luvia subarea south of Skaftung, Fucus morphology corresponded to that of F. radicans in earlier studies but the population was genetically more similar to F. vesiculosus
in the southern subareas. We conclude that by using only morphological
characteristics it is not possible to differentiate between the two
species in central and northern parts of the eastern Bothnian Sea. Based
on genetic analyses, the southernmost known occurrence of F. radicans in the eastern Bothnian Sea is in Skaftung.

Last updated on 2020-08-04 at 08:21