What can be learnt from a snail?

Abstract

The marine snail Littorina saxatilis is a common inhabitant of intertidal shores of the north Atlantic. It is amazingly polymorphic and forms reproductively isolated ecotypes in microhabitats where crabs are either present and wave action is less furious, or where waves are strong and crabs are absent. Decades of research have unveiled much of the ecological and demographic context of the formation of crab‐ and wave‐ecotype snails showing important phenotypic differences being inherited, differential selection being strong over adjacent microhabitats, local dispersal being restricted, and long‐distance transports of individuals being rare. In addition, strong assortative mating of ecotypes has been shown to include a component of male mate preference based on female size. Several studies support ecotypes being diverged locally and under gene flow in a parallel and highly replicated fashion. The high level of replication at various levels of independence (from local to pan‐European scale) provides excellent opportunities to investigate the detailed mechanisms of microevolution, including the formation of barriers to gene flow. Current investigations benefit from a draft reference genome and an integration of genomic approaches, modelling and experiments to unveil molecular and ecological components of speciation and their interactions.

Is embryo abortion a post‐zygotic barrier to gene flow between Littorina ecotypes?

“…Although several ecotypes of Littorina saxatilis exist (Reid, ), this study focused on Crab and Wave ecotypes that are adapted to specific rocky‐shore microhabitats (Johannesson, ; Johannesson et al, ). The Crab ecotype has a large adult size (10–15 mm), thick shell and a shy behaviour: traits that are favoured in patches with crabs.…”

“…In this species, strong barriers to gene flow have evolved in contact zones between ecotypes, mainly by divergent selection (Johannesson et al, ), and evidence suggests that ecotypes repeatedly diverge without prior spatial isolation (Butlin et al, ; Panova, Hollander, & Johannesson, ). The divergent ecotypes differ in a range of independent, quantitative (and presumably polygenic) traits (reviewed in Johannesson, ), and this offers an excellent system to look for genetic incompatibilities or other types of maladaptation appearing in contact zones. Incompatibilities, if present, might have evolved as by‐products of strong divergent selection under gene flow (Kulmuni & Westram, ) and/or during short periods of allopatry (Bierne, Welch, Loire, Bonhomme, & David, ).…”

Women in evolution – highlighting the changing face of evolutionary biology

“…), evolution of cooperation (Aktipis ), diversification and speciation (Charmantier et al. ; Johannesson ; Qvarnström et al. ; Servedio ; Wellenreuther and Sánchez‐Guillén ), host–parasite interactions (Leftwich et al.…”

“…; Sork ), genomics and genome evolution (Aitken and Bemmels ; Charlesworth ; Charmantier et al. ; Johannesson ; Sork ), and climate change (Aitken and Bemmels ; Qvarnström et al. ).…”

“…The life‐long intellectual stimulation from students, collaborators and research discovery is another tremendous privilege. Johannesson () urges us to remember ‘that the most important driver in research is to have fun at work’, and many contributors expressed how much they love what they do. The rewards of collaboration and working as a part of a team were also frequently raised.

‘This is our experience of research, as female scientists at various stages of their career: we feel very lucky having worked in an environment where cooperation was always valued above competition, and where friendship was intricately mixed with high intellectual stimulation’.

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