Putative 'Dispersal Adaptations' Do Not Explain the Colonisation of a Volcanic Island by Vascular Plants, but Birds Can.

Dispersal syndromes based on traits assumed to be adaptations for specific dispersal mechanisms are routinely assigned to flowering plants. Using the colonisation record from a volcanic island formed in 1963, we assess whether dispersal syndromes predict which species establish on newly formed land. We evaluated the long-distance dispersal (LDD) syndromes of the 78 plant species using three European classification systems. Syndrome assignments were inconsistent between classifications (coinciding for ≤ 13% of species). Two systems showed no evidence that LDD syndromes conferred a colonisation advantage. The third classification suggested wind syndromes were favoured, but only assigned a minority of colonisers to LDD syndromes. 'Unassisted' species assumed to lack dispersal adaptations were dominant. However, empirical evidence supports endozoochory via aquatic birds for 62 colonisers. This suggests bird-dispersal is a major driver of colonisation for dry-fruited plants, and underscores the need for new approaches to plant dispersal that account for overlooked plant-animal interactions.