Earthworms, good indicators for palaeogeographical studies? Testing the genetic structure and demographic history in the peregrine earthworm Aporrectodea trapezoides (Dugès, 1828) in southern Europe

It has been traditionally assumed that earthworms tend to remain in their areas of origin due to their low vagility, thus following the geological fate of the regions that they inhabit. Following this, many authors have correlated palaeogeographical events with earthworm distribution in several species to date diversification processes or to explain phylogenetic and phylogeographic patterns. Nonetheless, this correlation has been poorly tested, thus there is no scientific evidence supporting this assumption. This study aimed to test if widespread earthworm species are good indicators of geological changes by means of checking the population genetic structure at different levels (lineages, clades and populations). The results of the AMOVA supported the existence of strong population structure at the level of clades and populations. In some cases, substructure within populations was also observed. In addition, FST values indicated a lack of genetic flow between populations. Correlation between demographic history in the main Mediterranean clades and past Iberian palaeogeographical events was congruent, thus showing that it was a ‘good’ the candidate for this kind of studies.