Migration flows that refute the theory of ‘cul-de-sac’ islands

In order to determine the situation concerning the genetic structure of the different populations of Platyhypnidium riparioides populating the Azores, Madeira and the Canary Islands and those populating the continent, the scientists studied the nuclear microsatellite variation of this moss. ‘We used microsatellites, these genome motifs which are repeated very frequently within the latter, as markers,’ explains Alain Vanderpoorten. ‘These microsatellites have a mutation rate about one hundred times higher than other parts of the genome,’ he stresses. Thus, in detecting the mutations within the microsatellites of the various Platyhypnidium riparioides populations, the researchers have been able to determine to what extent these populations are similar from a genetic point of view.

Two principal results have emerged from this study, published in the Proceedings of the National Academy of Sciences (1). First of all, the genetic analyses have enabled the drawing up of a map of the migration flows of the moss’s spores from the continent to the islands and from the islands to the continent. ‘We have established that the migratory flows from the islands towards the continent are even slightly higher,’ points out Alain Vanderpoorten. ‘These results challenge the theory of cul-de-sac islands as far as the bryophytes of the Atlantic ocean islands are concerned,’ concludes the scientist.

Next, another important point brought to light by the researchers is that the Azores, Madeira and the Canary Islands served as a refuge for biodiversity over the course of the glaciations during the Quaternary era. In fact, it is thanks to the survival of species living on these islands that the continent was able to be recolonised by certain of them in the post-glacial period. ‘There was a huge loss of species amongst the continental populations during the last glacial periods. We do not observe such a loss of species on the Atlantic ocean islands over the course of the same period because the oceans have a buffer effect on the climate,’ explains Alain Vanderpoorten.

(1) Virginie Hutsemékers, Péter Szövényi, A. Jonathan Shaw, Juana-María González-Mancebo, Jesús Muñoz, and Alain Vanderpoorten. Oceanic islands are not sinks of biodiversity in spore-producing plants. Proceedings of the National Academy of Sciences, 108 (47): 18989-18994 NOV 22 2011.