Scientists used DNA to track how a group of tropical plants travelled across continents over millions of years and found that they were able to spread because they attracted a variety of animals to eat their fruits and excrete their seeds.

The disjunct distribution of plant species, in which seemingly similar populations are found in geographically distant locations, has long fascinated scientists. A new study by Jenifer Lopes and colleagues, published in Annals of Botany, investigated the long-distance dispersal pathways of plant tribe Bocageeae across continents and within South America revealing that their success resulted from their ability to attract a diverse range of frugivore dispersers. 

Members of the Bocageeae. (C) Cardiopetalum calophyllum Schltdl., fruit, dehiscent monocarps. (D, E) Cymbopetalum brasiliense (Vell.) Benth. ex Baill. (D) Flower. (E) Apocarpous fruit. (F) Mkilua fragrans Verdc. Flower. (G) Hornschuchia myrtillus Nee; flowers. (H, I) Porcelia macrocarpa (Warm.) R.E. Fr. (H) Flowers. (I) Apocarpous fruit. Photographs by: Kuhlmann (2018) (C); Tarcísio Leão (D, E); Thomas L. P. Couvreur (F); Renato Mello-Silva (G); and Otávio Marques (H, I). Source Lopes et al. 2023.

Bocageeae is a diverse lineage of flowering plants native to the tropics. These plants, characterized by their large, fleshy fruits, have managed to move between Africa and the Americas, establishing themselves across the Neotropics, the tropical region of the Americas. 

To unravel the evolutionary history and dispersal mechanisms of Bocageeae, Jenifer Lopes and colleagues reconstructed a detailed family tree using genetic data from 70% of the tribe’s species. Their analysis revealed that the tribe originated in Africa during the Early Eocene, around 55 million years ago. From there, they embarked on a journey, crossing the ancient Atlantic Ocean via the Boreotropics land bridge to reach South America, where they became firmly established. 

Interestingly, the researchers discovered that the ancestral Bocageeae plants had large, dehiscent fruits, a characteristic that suggests they were adapted for dispersal by large mammals that could swallow and then defecate the intact seeds. This dispersal mode, known as endozoochory, is particularly effective for long-distance dispersal, as seeds can travel long distances within an animal’s digestive system. 

Over time, the Bocageeae lineage diversified, giving rise to distinct groups adapted to different Neotropical regions and biomes. These adaptations included transitions in fruit morphology, such as the evolution of smaller, indehiscent fruits that were more attractive to smaller frugivores like birds and bats. 

The reconstructed ancestral fruit of Bocageeae suggests that both the mammal trait syndrome with large fruits and seeds and few monocarps; or the bird trait syndrome with dehiscent with bright coloured fruits may have been possible.

Lopes et al. 2023

The research team concluded that the long-distance dispersal of Bocageeae was likely facilitated by a variety of frugivores, which in their constant search for food, played a crucial role in transporting seeds across vast distances, enabling plants to conquer new territories. 

The story of Bocageeae highlights the ability of plants to overcome geographical barriers and establish themselves in distant lands and sheds new light on the interconnected history of plant evolution, dispersal ability, and frugivore-mediated migration.

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Lopes, J.C., Fonseca, L.H.M., Johnson, D.M., Luebert, F., Murray, N., Nge, F.J., Rodrigues-Vaz, C., Soulé, V., Onstein, R.E., Lohmann, L.G. and Couvreur, T.L.P. (2023) “Dispersal from Africa to the Neotropics was followed by multiple transitions across Neotropical biomes facilitated by frugivores,” Annals of Botany. Available at: https://doi.org/10.1093/aob/mcad175.

Cover: Cardiopetalum calophyllum by M/ Kuhlmann.

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