What is it about?
Members of the relict tree genus Zelkova (Ulmaceae) possess a unique dispersal mechanism: mature fruits fall with the entire twig, and the dried leaves, still attached, behave as a drag-enhancing appendage, almost like a parachute. This singular adaptation has never been investigated previously with modern methods.
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Why is it important?
Our results clearly demonstrate the flying capacities of the Z. abelicea dispersal units. Much more surprising is, however, that the dispersal behaviour is virtually the same as in its East Asiatic relatives. Members of the genus Zelkova, growing today in areas thousands of kilometres apart, show evolutionary conservation of the velocity and flight mode of their dispersal units. The Mediterranean and East Asiatic Zelkova species have been separated at least 15–20 mya. Zelkova abelicea, although growing under a completely different forest structure, still uses the same dispersal mechanism.
Perspectives
The dispersal capacity of the genus Zelkova is less efficient than that of other wind-dispersed trees, and it presumably evolved for short-distance ecological spread and not for long-distance biogeographical dispersal. Once long-distance disjunctions are formed (water or orographic barriers) the new areas are not conquerable by Zelkova species. This had important implications for the genetic pattern of Z. abelicea on Crete. Populations inhabiting each of the Cretan mountain chains (separated by a distance of 50-100 km), possess a unique genetic pattern, indicating no genetic exchange for probably several millions of years. And this will have an implication in the future: the recolonization of Europe of this relict from Crete will never happen via natural dispersal.
Daniele Certini
Lund University
Read the Original
This page is a summary of: Velocity of the falling dispersal units in
Zelkova abelicea
: remarkable evolutionary conservation within the relict tree genus, American Journal of Botany, December 2020, Wiley,
DOI: 10.1002/ajb2.1581.
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