Tracing plant dispersal into the Pacific

Of fruits, seeds, and vectors – biogeographic processes and the impact of long-distance dispersal.

Above: Fruits and flowers of Epicharis cuneata (Hiern) Harms, which is a rainforest tree species from the Meliaceae. Photo credit: Alexandra N. Muellner-Riehl.

This study started with the aim to investigate the biogeographic history of Dysoxylum s.l., a polyphyletic group of rainforest trees in the Meliaceae. The distribution of genera lent itself for two main investigations: (1) whether Dysoxylum s.l. follows the known directional bias (West to East) of the Sunda-Sahul floristic exchange, and (2) by which means Didymocheton achieved its current distribution in the Southwest Pacific. As for the Sunda-Sahul floristic exchange, this study greatly profited from previous research, while plant dispersal in the Southwest Pacific is still insufficiently known. From this starting point, our focus also extended to the underlying biogeographic processes and testing the impact of long-distance dispersal.

Cover article: (open access)
Holzmeyer, L., Hauenschild, F., & Muellner-Riehl, A. N. (2023) Sunda–Sahul floristic exchange and pathways into the Southwest Pacific: New insights from wet tropical forest trees. Journal of Biogeography 50(7), 1257-1270.

Two dispersal routes were identified into the Southwest Pacific, from New Guinea through the Solomon Islands to Fiji, and from New Zealand directly to Fiji. While dispersal out of New Guinea is rather frequent, dispersal out of New Zealand was observed only once. Our insights on dispersal routes supported the impactful position Fiji holds as a secondary source for dispersal events in this region.

Area map displayed in Mercator projection. J: Australia, Asia, Africa, South America (non-Pacific); K: Solomon Islands; L: Vanuatu; M: New Caledonia; N: Fiji; O: Tonga; P: Samoa and Wallis et Futuna; Q: New Zealand; R: New Guinea. Arrows indicating the two dispersal routes identified by AAR.

While looking for information on dispersal vectors, I was astonished by the scarcity of species information on bird dispersers of Dysoxylum s.l. In order to better understand Pacific plant dispersal processes and routes, the relationship between fruits and seeds and their dispersal vectors needs to be studied in the future.

Fruits of Epicharis cuneata (Hiern) Harms. Photo credit: Alexandra N. Muellner-Riehl.

Written by:
Laura Holzmeyer
Department of Molecular Evolution and Plant Systematics & Herbarium (LZ), Institute of Biology, Leipzig University, D-04103 Leipzig, Germany

Published by jbiogeography

Contributing to the growth and societal relevance of the discipline of biogeography through dissemination of biogeographical research.

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