Mantel test scriptR script permitting to compute Mantel testsMantel.ROrdination (NMDS) scriptR script permitting to compute and plot a Nonmetric Multidimensional Scaling (NMDS) ordinationOrdination.RPuccinellia maritima population assignment to DAPC regions (K=4)Puccinellia maritima input file for the implementation of the AMOVAP_4clusters.txtPuccinellia maritima population assignment to DAPC regions (K=5)Puccinellia maritima input file for the implementation of the AMOVAP_5clusters.txtPuccinellia maritima population assignment to DAPC regions (K=6)Puccinellia maritima input file for the implementation of the AMOVAP_6clusters.txtPuccinellia maritima AMOVA scriptR script permitting to compute AMOVA for Puccinellia maritimaP_amova.RPuccinellia maritima samples assignment to population of originPuccinellia maritima input file for the implementation of the AMOVAP_Populationdata.txtPuccinellia maritima DAPC scriptR script permitting to compute DAPC for Puccinellia maritimaP_Script DAPC.RCoastal distance between Puccinellia maritima populationsMatrix showing coastal distance between Puccinellia maritima populationsPdistcoast.txtPuccinellia maritima microsatellite datasetIndividuals are in row, microsatellite alleles in columns. Microsatellite alleles are coded as present or absent (1/0) in each individuals. NA for missing data.Pglobalpopgenbin.txtPairwise effective resistance between Puccinellia maritima population (TIDE model)Matrix of pairwise effective resistance (TIDE model) between Puccinellia maritima population inferred using the software Circuitscape. This matrix is inputted in R for Mantel test.Pres_100_linear_buffer.txtPairwise effective resistance between Puccinellia maritima population (SEDCELLS model)Matrix of pairwise effective resistance (SEDCELLS model) between Puccinellia maritima population inferred using the software Circuitscape. This matrix is inputted in R for Mantel test.Pres_100_sedcells_buffer.txtPairwise effective resistance between Puccinellia maritima population (TIDE_SEDCELLS model)Matrix of pairwise effective resistance (TIDE_SEDCELLS model) between Puccinellia maritima population inferred using the software Circuitscape. This matrix is inputted in R for Mantel test.Pres_100_sedcells_linear_buffer.txtTriglochin maritima population assignment to DAPC regions (K=4)Triglochin maritima input file for the implementation of the AMOVAT_4 clusters.txtTriglochin maritima population assignment to DAPC regions (K=5)Triglochin maritima input file for the implementation of the AMOVAT_5 clusters.txtTriglochin maritima population assignment to DAPC regions (K=6)Triglochin maritima input file for the implementation of the AMOVAT_6 clusters.txtTriglochin maritima AMOVA scriptR script permitting to compute AMOVA for Triglochin maritimaT_amova.RTriglochin maritima samples assignment to population of originTriglochin maritima input file for the implementation of the AMOVAT_Populationdata.txtTriglochin maritima DAPC scriptR script permitting to compute DAPC for Triglochin maritimaT_Script DAPC.RCoastal distance between Triglochin maritima populationsMatrix showing coastal distance between Triglochin maritima populationsTdistcoast.txtTriglochin maritima microsatellite datasetIndividuals are in row, microsatellite alleles in columns. Microsatellite alleles are coded as present or absent (1/0) in each individuals. NA for missing data.Tglobalpopgenbin.txtPairwise effective resistance between Triglochin maritima population (TIDE model)Matrix of pairwise effective resistance (TIDE model) between Triglochin maritima population inferred using the software Circuitscape. This matrix is inputted in R for Mantel test.Tres_100_linear_buffer.txtPairwise effective resistance between Triglochin maritima population (SEDCELLS model)Matrix of pairwise effective resistance (SEDCELLS model) between Triglochin maritima population inferred using the software Circuitscape. This matrix is inputted in R for Mantel test.Tres_100_sedcells_buffer.txtPairwise effective resistance between Triglochin maritima population (TIDE_SEDCELLS model)Matrix of pairwise effective resistance (TIDE_SEDCELLS model) between Triglochin maritima population inferred using the software Circuitscape. This matrix is inputted in R for Mantel test.Tres_100_sedcells_linear_buffer.txt

Little is known about the processes shaping population structure in saltmarshes. It is expected that the sea should act as a powerful agent of dispersal. Yet, in contrast, import of external propagules into a saltmarsh is thought to be small. To determine the level of connectivity between saltmarsh ecosystems at a macro-geographical scale, we characterised and compared the population structure of two polyploid saltmarsh species, Puccinellia maritima and Triglochin maritima based on a seascape genetics approach. A discriminant analysis of principal components highlighted a genetic structure for both species arranged according to a regional pattern. Subsequent analysis based on isolation by distance and isolation by resistance frameworks indicated a strong role of coastal sediment transport processes in delimiting regional structure in P. maritima while additional overland propagule dispersal was indicated for T. maritima. The identification and comparison of regional genetic structure and likely determining factors presented here allows us to understand the biogeographical units along the UK coast, between which barriers to connectivity occur not only at the species level but at the ecosystem scale. This information is valuable in plant conservation and community ecology and in the management and restoration of saltmarsh ecosystems.