Explore Research Products in the PAR
It may take a few hours for recently added research products to appear in PAR search results.


Title: Rates of premature fruit drop for 201 plant species on Barro Colorado Island, Panama
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
Award ID(s):
1754632
PAR ID:
10626729
Author(s) / Creator(s):
; ; ;
Publisher / Repository:
Dryad
Date Published:
Subject(s) / Keyword(s):
FOS: Biological sciences FOS: Biological sciences plant–herbivore interactions plant traits seed predation Tropical forests tropical rainforest Plant communities insect herbivory
Format(s):
Medium: X Size: 1342125 bytes
Size(s):
1342125 bytes
Right(s):
Creative Commons Zero v1.0 Universal
Sponsoring Org:
National Science Foundation
More Like this
  1. ; (, Annals of the Missouri Botanical Garden)
    null (Ed.)
    Over the past five decades, many studies have examined the Janzen-Connell hypothesis, which posits that host-specific natural enemies, such as insect herbivores and fungal pathogens, promote plant species coexistence by providing a recruitment advantage to rare plant species. Recently, researchers have been exploring new and exciting angles on plant-enemy interactions that have yielded novel insights into this long-standing hypothesis. Here, we highlight some empirical advances in our understanding of plant-enemy interactions in tropical forests, including improved understanding of variation in plant species’ susceptibility to enemy effects, as well as insect and pathogen host ranges. We then review recent advances in related ecological theory. These theoretical studies have confirmed that specialist natural enemies can promote tree diversity. However, they have also shown that the impact of natural enemies may be weakened, or that natural enemies could even cause species exclusion, depending on enemy host range, the spatial extent of enemy effects, and variation among plant species in seed dispersal or enemy susceptibility. Finally, we end by discussing how human impacts on tropical forests, such as fragmentation, hunting, and climate change, may alter the plant-enemy interactions that contribute to tropical forest diversity. 
    more » « less
  2. ; ; ; ; ; ; (, Oikos)
    Plant demography is heavily influenced by individual survival at local scales, with host‐specific natural enemies potentially reducing the survival of seeds and seedlings in high density patches near conspecific adults, favoring heterospecific recruitment, and ultimately increasing local plant diversity. Natural enemy pressure should differ 1) between sites directly beneath and away from their hosts' crowns, 2) between sites where their hosts are abundant versus rare, and 3) among potentially competing plant species. Assessing the potential pathways by which natural enemies affect diversity at local scales requires coupling experimental approaches that track plant performance with characterization of their natural enemy communities. Here, we focused on the fate of individuals at the seed stage, a critical demographic bottleneck in the plant life cycle. We tested how seed germination is affected by fungal infection, distance from the adult tree, burial duration, and host tree identity. We conducted a seed burial experiment on Barro Colorado Island, Panama, using four pioneer tree species (Jacaranda copaia,Cecropia insignis,C. peltataandC. longipes). Seeds were buried beneath and 30 m away from adultC. insignisandJ. copaiatrees and retrieved after 3 and 12 months. We measured germination, cultured seed‐infecting fungi, and evaluated fungal communities using a culture‐independent approach. Germination rates of all tree species declined with burial time. Germination of seeds buried below versus away from focal trees also did not differ. Fungal isolation frequency and richness increased after burial but did not change with distance or identity of the adult tree. Fungal communities in seeds differed markedly among tree species, but distance, burial duration, and seed viability status had little effect on community composition. Consequently, we found limited evidence that distance from conspecifics drives seed mortality in the soil. Nonetheless, seed exposure to the soil increases fungal infections and decreases seed survival, highlighting the role of fungi in seed demography. We recommend that future research explore the mechanisms by which host‐generalist soilborne fungi may drive seed mortality in plant communities. 
    more » « less
  3. ; ; ; ; ; ; ; ; ; ; et al (, Frontiers in Ecology and Evolution)
    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. 
    more » « less
  4. ; ; ; (, Biotropica)
    ABSTRACT Tropical soil seed banks under isolated trees in pastures remain relatively understudied despite their important role in forest regeneration. Here, we investigated patterns of plant species diversity, abundance, and composition in the soil seed banks of cattle pastures, under fleshy‐fruited, and nonfleshy‐fruited trees within pastures, and in secondary forest patches at ten study sites in Brazil. We also examined how the fruit traits of isolated trees affected seed bank communities, predicting that fleshy‐fruited trees are more connected to frugivory and seed dispersal networks than trees without fruit resources, and would therefore have richer seed banks. We found that the species richness and diversity of seed bank communities were higher in secondary forest patches and under fleshy and nonfleshy‐fruited trees compared to soil samples from open pastures, although early successional plants were dominant across all habitats. The fruit traits of isolated trees also affected the richness of seeds dispersed by animals and abiotically. Seed banks under fleshy‐fruited trees had more seeds of bird‐dispersed plants compared to nonfleshy‐fruited trees. Overall, our results show that soil seed banks under isolated trees are more similar to those in secondary forest patch seed banks, especially trees bearing attractive fruit resources that likely increase connectivity to frugivory and seed dispersal networks active in fragmented landscapes. 
    more » « less
  5. ; ; (, American journal of physical anthropology)
    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 GRAF 
    more » « less
  • Citation Formats
  • MLA
  • APA
  • Chicago
  • BibTeX
  • Text Encoded Conversion
  • XML
  • Save / Share this Record
  • Send to Email