Patiño, J., Sólymos, P., Carine, M., Weigelt, P., Kreft, H. & Vanderpoorten, A. (2015) Island floras are not necessarily more species-poor than continental ones.Journal of Biogeography, 42, 8-10. DOI:10.1111/jbi.12422 (IF2015 3,997; Q1 Ecology)
The fact that island spore-producing floras are not impoverished suggests that the shifts in the expression of reproductive traits observed in island bryophytes, such as the higher investment in asexual reproduction as well as the higher frequency of fertile shoots (Patiño et al., 2013), do not represent a response to empty niche space, as island biogeography theory predicts. Rather, such changes may reflect a response to the specific climate conditions that prevail on islands. Such environmental conditions may also be found on continents, but proportionally represent a smaller fraction of continental climates (Weigelt et al., 2013) and, hence, the emergence of a bias in life-history traits associated with such climates would not be linked to geographical isolation either. In seed plants, experimental support for the loss of dispersal capacity on islands is equivocal (contrast, e.g. Whittaker & Fernández-Palacios, 2007 and Talavera et al., 2012) and in spore-producing plants, a study on the dispersal capacity of the moss Rhynchostegium riparioides failed to demonstrate any significant difference in migration rates in insular and continental populations (Hutsemékers et al., 2011). This raises the question of whether other typical island syndromes, such as density compensation (e.g. Whittaker & Fernández-Palacios, 2007), which refers to the higher density of a species on an island as a result of the competitive release associated with lower overall species richness, prevail in highly dispersive organisms. Further research to investigate life-history traits associated with departures from the expectations of the island syndrome theory will contribute to the future development of the island biology paradigm.