Journal Article

Divergence within and among Seaweed Siblings (Fucus vesiculosus and F. radicans) in the Baltic Sea

Ardehed, Angelica, Bergström, Lena, Kautsky, Lena, Rafajlovic, Marina, Pereyra, Ricardo T., Johannesson, Kerstin, Johansson, Daniel, Sundqvist, Lisa, Kovaltchouk, Nikolaj A., Zagrodzka, Zuzanna, Schagerström, Ellen

2016

Overview

Closely related taxa provide significant case studies for understanding evolution of new species but may simultaneously challenge species identification and definition. In the Baltic Sea, two dominant and perennial brown algae share a very recent ancestry. Fucus vesiculosus invaded this recently formed postglacial sea 8000 years ago and shortly thereafter Fucus radicans diverged from this lineage as an endemic species. In the Baltic Sea both species reproduce sexually but also recruit fully fertile new individuals by asexual fragmentation. Earlier studies have shown local differences in morphology and genetics between the two taxa in the northern and western Bothnian Sea, and around the island of Saaremaa in Estonia, but geographic patterns seem in conflict with a single origin of F. radicans. To investigate the relationship between northern and Estonian distributions, we analysed the genetic variation using 9 microsatellite loci in populations from eastern Bothnian Sea, Archipelago Sea and the Gulf of Finland. These populations are located in between earlier studied populations. However, instead of bridging the disparate genetic gap between N-W Bothnian Sea and Estonia, as expected from a simple isolation-by-distance model, the new populations substantially increased overall genetic diversity and showed to be strongly divergent from the two earlier analysed regions, showing signs of additional distinct populations. Contrasting earlier findings of increased asexual recruitment in low salinity in the Bothnian Sea, we found high levels of sexual reproduction in some of the Gulf of Finland populations that inhabit extremely low salinity. The new data generated in this study supports the earlier conclusion of two reproductively isolated but very closely related species. However, the new results also add considerable genetic and morphological complexity within species. This makes species separation at geographic scales more demanding and suggests a need for more comprehensive approaches to further disentangle the intriguing relationship and history of the Baltic Sea fucoids.

• Publisher: Public Library of Science,Public Library of Science (PLoS)
• Subject: Algae / Analysis / Animal reproduction / Archipelagoes / Biologi / Biological evolution / Biological Sciences / Biology and Life Sciences / Bladderwrack / Botanik / Botany / Case studies / differentiation / Divergence / Divergent evolution / Earth sciences / Endemic species / Environmental science / Europe / evanescens / Evolution / Evolutionary biology / fucaceae / Fucus / Fucus - classification / Fucus - genetics / Fucus radicans / Fucus vesiculosus / Gene flow / Gene Frequency / Genes / Genetic aspects / Genetic diversity / Genetic Variation / Genetics / Genetik / Genotype / heterokontophyta / hybridization / Hypotheses / Microsatellite Repeats - genetics / Microsatellites / morphological variation / Morphology / New species / Oceans and Seas / People and Places / Phaeophyceae / Physical Sciences / Plant sciences / Poison ivy / Population / Population genetics / Population studies / population-structure / Populations / Principal components analysis / Recruitment / Reproduction (biology) / Reproductive isolation / Salinity / Salinity effects / Science & Technology - Other Topics / serratus / Sexual reproduction / speciation / Studies / Taxa