Terrestrial growth and marine dispersal? Comparative phylogeography of five coastal plant species at a European scale

Abstract

AbstractThe phylogeography of five flowering plant species (Cakile maritima, Eryngium maritimum, Salsola kali, Halimione portulacoides, Crithmum maritimum) widespread along the European coasts was investigated across their entire European range using AFLP evidence. Both similarities and dissimilarities were found. All species contain a distinct Black Sea/Aegean Sea cluster, and all except E. maritimum contain a distinct Adriatic Sea cluster or group of genetically very similar clusters. All species except Cr. maritimum contain a distinct Atlantic Ocean/North Sea/Baltic Sea cluster clearly separate from the Mediterranean material. In Ca. maritima a distinct Baltic Sea subcluster was found. In the western Mediterranean, two species groups can be recognized. Whereas in S. kali and E. maritimum material from this area falls into only one cluster or a group of genetically very similar clusters, it falls into two clusters or groups of clusters of either more Atlantic or more central Mediterranean similarity in Ca. maritima, H. portulacoides and Cr. maritimum. Similarities and dissimilarities in patterns found are discussed in terms of a combination of historical and extant abiotic and biotic factors. Thus, the distribution range of all species in the eastern Mediterranean area was not affected by Quaternary temperature changes, resulting in phylogeographic congruency here. The existence of distinct Black Sea/Aegean Sea and Adriatic Sea clusters or groups of clusters is the result of sea currents isolating these regions from each other. In the western Mediterranean basin the more cold‐sensitive species (H. portulacoides, Cr. maritimum) but not the less cold‐sensitive species (S. kali, E. maritimum) had to retreat from northern coasts. Re‐colonization of these areas from two different directions is implied by their phylogeographic pattern. The existence of a distinct Gibraltar gap is explained in terms of extant sea currents. Comparison of phylogeographic patterns found with those observed in either marine or terrestrial organisms leads to the conclusion that marine dispersal is of overriding importance in these coastal plants.