Aim: Two main biogeographic hypotheses have been proposed to explain the Mediterranean-Turanian disjunct distributions exhibited by numerous steppe-dwelling organisms, namely (i) dispersal during the Messinian salinity crisis (∼5.96-5.33 Ma) followed by range fragmentation and vicariance, and (ii) Pleistocene colonization and recent processes of population subdivision (<2 Ma). Despite the two hypotheses postulate the role of climatic alterations and changes in landmass configuration on determining such disjunct distributions, estimates of the timing of lineage diversification have not been complemented so far with spatially-explicit tests providing independent evidence on the proximate processes underlying geographical patterns of population genetic connectivity/fragmentation.

Location: Mediterranean-Turanian region

Taxon: Saltmarsh band-winged grasshopper (Mioscirtus wagneri)

Methods: We integrate different sources of genetic (mtDNA and ddRADseq) and spatial information (configuration of emerged lands and niche modelling) to evaluate competing hypotheses of lineage diversification in the saltmarsh band-winged grasshopper, a halophile species showing a classical Mediterranean-Turanian disjunct distribution.

Results: Phylogenomic analyses reveal the presence of two North African cryptic lineages and support that trans-Mediterranean populations of the species diverged in the Pleistocene, with evidence of post-Messinian permeability of the Strait of Gibraltar to gene flow likely associated with sea level drops during glacial periods. Accordingly, spatial patterns of genetic differentiation are best explained by a scenario of population connectivity defined by the configuration of emerged landmasses and environmentally suitable habitats during glacial periods, a time when effective population sizes of the species peaked as inferred by genomic-based demographic reconstructions.

Main conclusions: Our results support post-Messinian colonization and Pleistocene diversification as the biogeographic scenario best explaining the trans-Mediterranean disjunct distributions of halophilous organisms.

Sampled populations and individuals
Description of individual and population codes used in the different analyses and genomic datasets.
Samples.xlsx

BEAST input file
Input file (NEXUS format) used for phylogenetic analyses in BEAST based on a concatenated database containing 12S and 16S mitochondrial gene fragments
InputFile_BEAST_mtDNA.nex

SVDquartets input file
Input file (NEXUS format) used for phylogenomic analyses in SVDquartets
InputFile_SVDquartets.nex

FASTSTRUCTURE input file
Input file (str. format) used for analyses of genetic structure in FASTSTRUCTURE
InputFile_FastStructure.str

DNAsp input file
Input file (alleles. format) used for calculating nucleotide diversity per population in DNAsp
InputFile_DnaSP_DEF.alleles

BPP input files
This ZIP folder contains the input files (genetic datasets and control and map files) to perform BPP analyses
BPP.zip

StarwayPlot input files
This ZIP folder contains the "blueprint" files to perform StarwayPlot analyses for each population
StarwayPlot.zip

Isolation-by-resistance (IBR) scenarios
This ZIP folder contains the “ASC.” files corresponding to the isolation by resistance (IBR) scenarios based on the spatial configuration
of emerged lands (sea level) during the present-day, last glacial maximum (LGM), and Messinian, and the spatial configuration of
climatically suitable habitats as inferred from projections of an environmental niche model (ENM) to present-day and LGM bioclimatic conditions.
This folder also contains a “flat landscape” scenario (equivalent to an isolation-by-distance scenario) whose pixels (including sea water and emerged lands)
have a fixed resistance (=1) value.
IBR_scenarios.zip