Genome scans detect consistent divergent selection among subtidal vs. intertidal populations of the marine angiosperm Zostera marina

Abstract

Genome scans are a powerful tool to detect natural selection in natural populations among a larger sample of marker loci. We used replicated habitat comparisons to search for consistent signals of selection among contrasting populations of the seagrass Zostera marina, a marine flowering plant with important ecological functions. We compared two different habitat types in the North Frisian Wadden Sea, either permanently submerged (subtidal) or subjected to aerial exposure (intertidal). In three independent population pairs, each consisting of one tidal creek and one tidal flat population each, we carried out a genome scan with 14 expressed sequence tag (EST)-derived microsatellites situated in 5'- or 3'-untranslated regions of putative genes, in addition to 11 anonymous genomic microsatellites. By using two approaches for outlier identification, one anonymous and two EST-derived microsatellites showed population differentiation patterns not consistent with neutrality. These microsatellites were detected in several parallel population comparisons, suggesting that they are under diverging selection. One of these loci is linked to a putative nodulin gene, which is responsible for water channelling across cellular membranes, suggesting a functional link of the observed genetic divergence with habitat characteristics.

New evidence for habitat-specific selection in Wadden Sea Zostera marina populations revealed by genome scanning using SNP and microsatellite markers

“…The approach by Beaumont and Nichols detected only few loci which is consistent with earlier results (Vitalis et al 2001;Vasemagi et al 2005;Oetjen and Reusch 2007). The DetSel model developed by Vitalis et al (2001) detected several loci as being subject to selection.…”

“…The DetSel model developed by Vitalis et al (2001) detected several loci as being subject to selection. Reassuringly, all three loci that had been detected in an earlier study with far fewer loci (Oetjen and Reusch 2007;GA20, ZMC19066, ZMC01058) were also detected with the increased number of markers. The locus GA20, an anonymous microsatellite, was found to be an outlier in all three population pairs.…”

“…We extended the analysis of samples described in Oetjen and Reusch (2007) by reanalysing six populations sampled in 2005. Samples from three subtidal populations and three intertidal populations were reused, and no further sampling was done for this study.…”

“…Samples from three subtidal populations and three intertidal populations were reused, and no further sampling was done for this study. Sampling sites were located on three islands: Hallig Hooge, Hallig Langeness and Sylt island (for coordinates refer to Oetjen and Reusch 2007). While intertidal populations were located at the shores of the islands in the tidal Xat area (Langeness: ca 1 km from shoreline, Hooge: ca 100 m, Sylt: ca 100 m), subtidal populations grew in tidal creeks inland the islands.…”

“…AM408830-AM408843, AJ249303-AJ249307, AJ009 898, AJ009900, AJ009901 and AJ009904) (Oetjen and Reusch 2007). Of the gene-linked microsatellites (Table 1, accession numbers FN4353336-FN435350), 15 were newly developed from an EST database (http://drzompo.…”