Reproductive biology of Ranunculus weyleri (Ranunculaceae), a narrowly endemic plant from the Balearic Islands with disjunct populations

Ranunculus weyleri is a species endemic to Mallorca Island (western Mediterranean basin) that is currently threatened due to its reduced geographical distribution and disjunct, isolated populations. It is a small, perennial herb that inhabits rocky environments, together with other endemic plants with creeping life-forms. In the present study, for the first time the reproductive biology of the species was investigated in terms of its floral phenology (floral stages and times of formation), pollen/ovule (P/O) ratios, and fruit and seed setting under natural and pollen manipulation experiments, assessing the breeding system, pollination vectors and pollen limitations. Cross-pollinations among populations were performed to evaluate the levels of compatibility between populations. In addition, the floral displays and the reproductive outputs of four wild populations were determined. The observed high P/O ratios, results of the hand-pollination experiments, and flower traits indicate that this species is predominantly allogamous. Combinations of both insects (belonging to Coleoptera, Diptera, Lepidoptera and Hymenoptera) and wind (ambophily) constitute the main pollination vectors, and pollen limitation was observed. Interpopulation crossing was effective, and exogamic depression was not present, as evidenced by the fecundity levels. The predation of the floral stems by herbivores (mainly goats) severely limits the reproductive success of this endemic species in wild populations. Finally, several ways of action are proposed for R. weyleri conservation.