The evolution of tropical fruit traits associated with long-distance dispersal by mammals or birds, has contributed to the disjunct tropical biogeographical distribution of rain forest plants. This is the main conclusion of a new study published in the Journal of Biogeography by an international research team, including Daniel Kissling who is a researcher at the Institute for Biodiversity and Ecosystem Dynamics at the University of Amsterdam.
Each fruit has specific characteristics called fruit traits: e.g. fruit size, shape and colour. In the newly published study, led by former UvA postdoctoral researcher Renske Onstein, it was studied how these fruit traits relate to long-distance dispersal by birds and mammals. Onstein: ‘We tested this in the Annonaceae plant family which has globally around 2400 species, and has historically colonised all continents and their rainforests. It is an important family for fruit-eating (frugivorous) animals, because most species have fleshy fruits.’
In October 2015 a team of researchers, including Renske Onstein, travelled to the rain forest in Borneo, to collect Annonaceae plants (see below standing video). Afterwards the researchers combined their field knowledge and the compiled trait data with a phylogenetic framework to infer historical biogeography and long-distance dispersals of these tropical plants. What they found is that sets of correlated fruit traits (dispersal syndromes) relate well to historical long-distance dispersal events by animals. They showed for instance that historical long-distance dispersal events are characteristic for plants with large fruits that have dull colours, typically dispersed by large mammals.
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Traditionally, the disjunct biogeographic distribution of rain forest plants on different continents has been explained by ‘vicariance’, i.e. the break-up of the Gondwanan supercontinent. ‘In contrast to this traditional view, our study shows that over-land and across water dispersal of more than 1,000 km is a plausible scenario to explain much of the disjunct distributions of tropical plant lineages in the world’, says UvA researcher Daniel Kissling. ‘Hence, our study sheds light on the dispersal mechanism and potentially the animals that may have facilitated these long-distance dispersals’, continues Kissling.
Long-distance dispersal is important for plant survival, and may also play an important role in escaping current and future global warming. For tropical plants that rely on frugivorous animals for seed dispersal, it may be difficult to survive ongoing global changes if large-bodied animal dispersers in the tropics continue to decline. Onstein: ‘Some of the traits we identified in this study may provide insights into which plants depend on which types of animal disperses to move across long distances, and thus can help species to survive under global warming if considerable amounts of habitat continue to remain.’
Renske E. Onstein, W. Daniel Kissling, Lars W. Chatrou, Thomas L. P. Couvreur, Hélène Morlon, Hervé Sauquet (2019). Which frugivory‐related traits facilitated historical long‐distance dispersal in the custard apple family (Annonaceae)? Journal of Biogeography. DOI: https://doi.org/10.1111/jbi.13552