On islands, evolutionary but not functional originality is rare

Functionally and evolutionary originalspecies are those whose traits or evolutionary history are shared by few others in a given set. These originalspecies promote ecosystem multifunctionality, the ability to cope with an uncertain future, future benefits to society and therefore have a high conservation value. A potential signal of their extinction risks is their rarity (stating for geographic range-restriction in this study). In islands life in isolation conducted to the rise of a multitude of originalforms and functions as well as to high rates of endemism. Not only patterns and processes of insular originalityare unexplained but the relationship between originalityand rarity is still unknown. The aim of this study is to assess how originalinsular species are, to explore whether originalspecies are rare or not and to investigate the factors that may explain the rarity of originalspecies. We first compared the functional and evolutionary originalityof monocotyledonspecies and whether continental or insular species were more original. We found that species restricted to islands were more originalthan continental species and, although functionally and evolutionary originalspecies were dissimilar, many occurred on similar territories so that regional conservation strategies may allow to conserve these distinct forms. Yet, evolutionary originalspecies were significantly more range-restricted than those which were distinct in their traits. Reflecting their rarity, evolutionary originalspecies had low dispersal abilities and were found on islands where settlement may have been facilitated. On the opposite, functionally originalspecies could reach a wider set of islands by being transported on long-distances. While some mechanisms may both explain rarity and originalitysuch as extinctions, others may be specific to each of these biodiversity facets, in particular diversification, niche shift and expansion, and dispersal power. Implications for conservation are huge: originalspecies are range-restricted and mostly found in the most threatened systems of the world, i.e. islands, endangering the reservoir of features against an uncertain future.