The role of trait combinations in the conspicuousness of fruit display among bird-dispersed plants

Mariano Ordano, Pedro G Blendinger, Silvia B Lomáscolo, Natacha P Chacoff, Mariano S Sánchez, M Gabriela Núñez Montellano, Julieta Jiménez, Román A Ruggera & Mariana Valoy

At the grocery store, look at bins of fruit. You can see that conspicuousness of fruits is very important in this trade. Fruit choice is strongly driven by vision, and fruit sellers will increase benefits if their fruit displays look more conspicuous than the neighbouring store’s. Something similar occurs in communities of fleshy-fruited plants and animals searching for fruits, constituting the so-called seed dispersal mutualisms. These are natural exchange markets between plants and animals. The profitability of seed dispersal will increase in plants with more conspicuous fruits. There is no apparent novelty in this. In fact, fruit choice and consumption by seed dispersing animals have been broadly studied. But, how do different plant traits combine to enhance conspicuousness of the fruit display? Because the diverse strategies to maximize conspicuousness are expected to be costly, individual plant species will likely produce an efficient combination of traits.

We explored this prediction with 62 fleshy-fruited species of a subtropical Andean forest (Southern Yungas), using a large dataset of fruit consumption by birds. Conspicuousness of fruit display was characterized by both fruit and plant traits including colour contrast (the contrast of the fruit against its background), size, exposure, aggregation, and crop size. Very importantly, we determined fruit colours as birds see them.

We found that the greatest conspicuousness to birds was achieved by a combination of high fruit colour contrast and large crop size. These two fruit traits seem to amplify signals to communicate with animals that use visual perception, such as birds, and achieve high consumption rates. We also found that plants do not invest in more than one conspicuousness trait at the time, and that the combinations of fruit traits are mostly the result of natural selection, perhaps by seed-dispersing birds, and not merely inherited from the plant’s ancestor species.

As in the grocery store, the conspicuousness of fruit display appears to improve communication with mutualistic animals, and increase fruit consumption in a community context. The ultimate consequence will be to enhance the profitability of seed dispersal, a key process in nature.

Read the article in full here.

Image caption: Dusky-legged Guan (Penelope_obscura) looking for_fruits of Allophylus edulis – photo by RA Ruggera

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