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Abstract Plant secondary metabolites are key mechanistic drivers of species interactions. These metabolites have primarily been studied for their role in defense, but they can also have important consequences for mutualisms, including seed dispersal. Although the primary function of fleshy fruits is to attract seed‐dispersing animals, fruits often contain complex mixtures of toxic or deterrent secondary metabolites that can reduce the quantity or quality of seed dispersal mutualisms. Furthermore, because seeds are often dispersed across multiple stages by several dispersers, the net consequences of fruit secondary metabolites for the effectiveness of seed dispersal and ultimately plant fitness are poorly understood. Here, we tested the effects of amides, nitrogen‐based defensive compounds common in fruits of the neotropical plant genusPiper(Piperaceae), on seed dispersal effectiveness (SDE) by ants, which are common secondary seed dispersers. We experimentally added amide extracts toPiperfruits both in the field and lab, finding that amides reduced the quantity of secondary seed dispersal by reducing ant recruitment (87%) and fruit removal rates (58% and 66% in the field and lab, respectively). Moreover, amides not only reduced dispersal quantity but also altered seed dispersal quality by shifting the community composition of recruiting ants (notably by reducing the recruitment of the most effective disperser by 90% but having no detectable effect on the recruitment of a cheater species that removes fruit pulp without dispersing seeds). Although amides did not affect the distance ants initially carried seeds, they altered the quality of seed dispersal by reducing the likelihood of ants cleaning seeds (67%) and increasing their likelihood of ants redispersing seeds outside of the nest (200%). Overall, these results demonstrate that secondary metabolites can alter the effectiveness of plant mutualisms, by both reducing mutualism quantity and altering mutualism quality through multiple mechanisms. These findings present a critical step in understanding the factors mediating the outcomes of seed dispersal and, more broadly, demonstrate the importance of considering how defensive secondary metabolites influence the outcomes of mutualisms surrounding plants.
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Dispersers and environment drive global variation in fruit colour syndromes
Abstract The colours of fleshy fruits play a critical role in plant dispersal by advertising ripe fruits to consumers. Fruit colours have long been classified into syndromes attributed to selection by animal dispersers, despite weak evidence for this hypothesis. Here, we test the relative importance of biotic (bird and mammal frugivory) and abiotic (wet season temperatures, growing season length and UV‐B radiation) factors in determining fruit colour syndrome in 3163 species of fleshy‐fruited plants. We find that both dispersers and environment are important, and they interact. In warm areas, contrastive, bird‐associated fruit colours increase withrelative bird frugivore prevalence, whereas in cold places these colours dominate even where mammalian dispersers are prevalent. We present near‐global maps of predicted fruit colour syndrome based on our species‐level model and our newly developed characterisations of relative importance of bird and mammal frugivores.
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- Award ID(s):
- 1907293
- PAR ID:
- 10448417
- Publisher / Repository:
- Wiley-Blackwell
- Date Published:
- Journal Name:
- Ecology Letters
- Volume:
- 24
- Issue:
- 7
- ISSN:
- 1461-023X
- Page Range / eLocation ID:
- p. 1387-1399
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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