Time to abandon the loss of dispersal ability hypothesis in island plants: A comment on García-Verdugo, Mairal, Monroy, Sajeva and Caujapé-Castells (2017)

Abstract

García-Verdugo et al. (2017) recently tested the loss of dispersal ability hypothesis in a wind-dispersed shrub from Southern Europe. Although the hypothesis has guided research for over 150 years, García-Verdugo et al. (2017) results failed to substantiate its central prediction—the loss of seed dispersal potential in island populations. Here, I highlight several additional limitations of the hypothesis. First, García-Verdugo et al. (2017) results are not unusual. Empirical support for the hypothesis is equivocal. Second, when reduced dispersal potential is documented, it may often evolve as a passive by-product of selection for large seeds, for reasons that are wholly unrelated to their dispersal. Third, the hypothesis does not readily apply to all plant dispersal modes, particularly plants that produce fleshy fruits. These issues advocate a fresh approach to the study of how selection shapes the evolution of dispersal potential on islands.