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By dispersing seeds long distances, large, fruit-eating animals influence plant population spread and community dynamics. After fruit consumption, animal gut passage time and movement determine seed dispersal patterns and distances. These, in turn, are influenced by extrinsic, environmental variables and intrinsic, individual-level variables. We simulated seed dispersal by forest elephants ( Loxodonta cyclotis ) by integrating gut passage data from wild elephants with movement data from 96 individuals. On average, elephants dispersed seeds 5.3 km, with 89% of seeds dispersed farther than 1 km. The longest simulated seed dispersal distance was 101 km, with an average maximum dispersal distance of 40.1 km. Seed dispersal distances varied among national parks, perhaps due to unmeasured environmental differences such as habitat heterogeneity and configuration, but not with human disturbance or habitat openness. On average, male elephants dispersed seeds farther than females. Elephant behavioral traits strongly influenced dispersal distances, with bold, exploratory elephants dispersing seeds 1.1 km farther than shy, idler elephants. Protection of forest elephants, particularly males and highly mobile, exploratory individuals, is critical to maintaining long distance seed dispersal services that shape plant communities and tropical forest habitat.
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Putting a New Spin on the Flight of Jabillo Seeds
Synopsis Our article describes the explosive seed dispersal of the Hura crepitans fruit. Through high-speed video analysis of an exploding fruit, we observe that the seeds fly with backspin as opposed to topspin, which was previously assumed. Backspin orients seeds to minimize drag during flight and consequently increases dispersal distance. The seeds’ dispersal distance is estimated by using results from the seeds of Ruellia ciliatiflora, which are similarly shaped but ∼10 times smaller than those of H. crepitans. We note that the effects of lowering drag on the dispersal distance are more pronounced at higher speeds. We also see that the effect of launch height on the dispersal distance of the seeds becomes less consequential at higher launch speeds. We conclude that the increased dispersal distance due to flying with backspin should improve fitness in colonizing new habitats or escaping disease or predation and that comparisons of the seed dispersal mechanisms across species within the Euphorbiaceae and Acanthaceae might help reveal the adaptive significance of this behavior.
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- Award ID(s):
- 1930744
- PAR ID:
- 10206558
- Date Published:
- Journal Name:
- Integrative and Comparative Biology
- Volume:
- 60
- Issue:
- 4
- ISSN:
- 1540-7063
- Page Range / eLocation ID:
- 919 to 924
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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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.more » « less
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null (Ed.)Seed dispersal is important for forest growth, maintenance, and regeneration. Orangutans are large-bodied frugivores with ecological roles as seed predators and seed dispersers. However, little is known about orangutans’ ecological roles and how they relate to orangutans’ patterns of frugivory. We investigated Bornean orangutans’ (Pongo pygmaeus wurmbii) ecological roles at the Cabang Panti Research Station in Gunung Palung National Park, Indonesian Borneo. We collected orangutan feces (n=401) and analyzed them for intact seeds (August 2018 to March 2020). We observed orangutan fruit handling behavior for 306 feeding bouts for 53 fruit genera to measure how often orangutans swallow, spit, or predate seeds. We used Ivlev’s Electivity Index to analyze fruit preference using long-term feeding data and phenology data (2014-2019). Lastly, we combined fruit preference with fruit handling behavior using the seed dispersal effectiveness framework to identify which fruit taxa were most effectively dispersed. Orangutans dispersed seeds in 71.8% of fecal samples with a mean of 27.9 ±4.5 (SD=0.95) seeds (>2mm) per fecal sample. Orangutans predated seeds more often than spitting or swallowing seeds (predating= 42.1% of fruit feeding time; spitting= 21.8%; swallowing= 12.5%; mixed behaviors= 10.6%, not observed=12.0%). Additionally, the top five preferred fruit genera, (Dialium, Sindora, Scaphium, Magnifera, and Spatholobus) were highly predated (0 to 5% of seeds dispersed). We identified Alangium and Tetramerista as the most effectively dispersed genera, orangutans frequently dispersed and preferred these fruits. We found orangutans are frequent seed predators, but this overlaps with their seed dispersal role, and we describe orangutans’ seed dispersal contribution. Funders: NSF (9414388, BCS-1638823, BCS-0936199); National Geographic; USFish/Wildlife (F18AP00898, F15AP00812, F13AP00920, 96200-0-G249, 96200-9-G110); Leakey; Disney Conservation Fund; Wenner-Gren; Nacey-Maggioncalda; Conservation-Food-Health; Orangutan Conservancy; Woodland Park Zoo; Boston University GRAFmore » « less
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null (Ed.)Seed dispersal is important for forest growth, maintenance, and regeneration. Orangutans are large-bodied frugivores with ecological roles as seed predators and seed dispersers. However, little is known about orangutans’ ecological roles and how they relate to orangutans’ patterns of frugivory. We investigated Bornean orangutans’ (Pongo pygmaeus wurmbii) ecological roles at the Cabang Panti Research Station in Gunung Palung National Park, Indonesian Borneo. We collected orangutan feces (n=401) and analyzed them for intact seeds (August 2018 to March 2020). We observed orangutan fruit handling behavior for 306 feeding bouts for 53 fruit genera to measure how often orangutans swallow, spit, or predate seeds. We used Ivlev’s Electivity Index to analyze fruit preference using long-term feeding data and phenology data (2014-2019). Lastly, we combined fruit preference with fruit handling behavior using the seed dispersal effectiveness framework to identify which fruit taxa were most effectively dispersed. Orangutans dispersed seeds in 71.8% of fecal samples with a mean of 27.9 ±4.5 (SD=0.95) seeds (>2mm) per fecal sample. Orangutans predated seeds more often than spitting or swallowing seeds (predating= 42.1% of fruit feeding time; spitting= 21.8%; swallowing= 12.5%; mixed behaviors= 10.6%, not observed=12.0%). Additionally, the top five preferred fruit genera, (Dialium, Sindora, Scaphium, Magnifera, and Spatholobus) were highly predated (0 to 5% of seeds dispersed). We identified Alangium and Tetramerista as the most effectively dispersed genera, orangutans frequently dispersed and preferred these fruits. We found orangutans are frequent seed predators, but this overlaps with their seed dispersal role, and we describe orangutans’ seed dispersal contribution. Funders: NSF (9414388, BCS-1638823, BCS-0936199); National Geographic; USFish/Wildlife (F18AP00898, F15AP00812, F13AP00920, 96200-0-G249, 96200-9-G110); Leakey; Disney Conservation Fund; Wenner-Gren; Nacey-Maggioncalda; Conservation-Food-Health; Orangutan Conservancy; Woodland Park Zoo; Boston University GRAFmore » « less
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Pre-dispersal seed mortality caused by premature fruit drop is a potentially important source of plant mortality, but one which has rarely been studied in the context of tropical forest plants. Of particular interest is premature fruit drop triggered by enemies, which – if density-dependent – could contribute to species co-existence in tropical forest plant communities. We used a long-term (31 year) dataset on seed and fruit fall obtained through weekly collections from a network of seed traps in a lowland tropical forest (Barro Colorado Island, Panama) to estimate the proportion of seeds prematurely abscised for 201 woody plant species. To determine whether enemy attack might contribute to premature fruit drop we tested whether plant species abscise more of their fruit prematurely if they: (1) have attributes hypothesised to be associated with high levels of enemy attack, and (2) are known to be attacked by one enemy-group (insect seed predators). We also tested (3) whether mean rates of premature fruit drop for plant species are phylogenetically conserved. Overall rates of premature fruit drop were high in the plant community. Across all species, 39% of seeds were abscised before completing their development. Rates of premature seed abscission varied considerably among species and could not be explained by phylogeny. Premature seed abscission rates were higher in species which are known to host pre-dispersal insect seed predators and species with attributes that were hypothesised to make them more susceptible to attack by pre-dispersal enemies, namely species which (1) have larger seeds, (2) have a greater average height, (3) have temporally predictable fruiting patterns, and (4) are more abundant at the study site. Synthesis. Premature fruit drop is likely to be a major source of seed mortality for many plant species on Barro Colorado Island. It is plausible that pre-dispersal seed enemies, such as insect seed predators, contribute to community-level patterns of premature fruit drop and have the potential to mediate species co-existence through stabilising negative density dependence. Our study suggests that the role of pre-dispersal enemies in structuring tropical plant communities should be considered alongside the more commonly studied post-dispersal seed and seedling enemies.more » « less
- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1093/icb/icaa117
