Vicariance or dispersal: the use of natural historical data to test competing hypotheses of disjunction on the Tyrrhenian coast

Aim To illustrate the use of natural historical data to evaluate vicariance and dispersal as hypotheses competing to explain disjunct populations. Location Nine disjunct areas on the margin of the Tyrrhenian basin of the M editerranean Sea. Methods First describe how each hypothesized mechanism might explain the ob served morphological variation in the model species complex, Genista ephedr oides (Fabaceae); then confront the hypotheses with natural historical data including geology, oxygen isotopes, palynology, macro-, micro- and nano-fo ssils, and sea level changes, and with the ecological tolerances of the mod el species complex. Results Dispersal seems the more credible explanation. Main conclusion Patterns of morphological (or other) variation among relate d disjunct taxa can fit both vicariance and dispersal hypotheses. However t hey can possibly be distinguished by considering natural historical data.