skip to main content

Explore Research Products in the NSF-PAR

Title: Intrinsic and extrinsic drivers of intraspecific variation in seed dispersal are diverse and pervasive
Abstract There is growing realization that intraspecific variation in seed dispersal can have important ecological and evolutionary consequences. However, we do not have a good understanding of the drivers or causes of intraspecific variation in dispersal, how strong an effect these drivers have, and how widespread they are across dispersal modes. As a first step to developing a better understanding, we present a broad, but not exhaustive, review of what is known about the drivers of intraspecific variation in seed dispersal, and what remains uncertain. We start by decomposing ‘drivers of intraspecific variation in seed dispersal’ into intrinsic drivers (i.e. variation in traits of individual plants) and extrinsic drivers (i.e. variation in ecological context). For intrinsic traits, we further decompose intraspecific variation into variation among individuals and variation of trait values within individuals. We then review our understanding of the major intrinsic and extrinsic drivers of intraspecific variation in seed dispersal, with an emphasis on variation among individuals. Crop size is the best-supported and best-understood intrinsic driver of variation across dispersal modes; overall, more seeds are dispersed as more seeds are produced, even in cases where per seed dispersal rates decline. Fruit/seed size is the second most widely studied intrinsic driver, and is also relevant to a broad range of seed dispersal modes. Remaining intrinsic drivers are poorly understood, and range from effects that are probably widespread, such as plant height, to drivers that are most likely sporadic, such as fruit or seed colour polymorphism. Primary extrinsic drivers of variation in seed dispersal include local environmental conditions and habitat structure. Finally, we present a selection of outstanding questions as a starting point to advance our understanding of individual variation in seed dispersal.  more » « less
Award ID(s):
1548194
NSF-PAR ID:
10324926
Author(s) / Creator(s):
; ; ; ; ; ; ; ; ; ; ; ; ;
Editor(s):
McConkey, Kim
Date Published:
Journal Name:
AoB PLANTS
Volume:
11
Issue:
6
ISSN:
2041-2851
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. ; ; ; ; ; ; ; ; ; ; 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
  2. ; ; ( , Ecosphere)
    Abstract

    Small mammals are key scatter hoarders in forest ecosystems, acting as both seed predators and dispersers. The outcome of their interactions (i.e., predation vs. dispersal) is determined by a series of decisions made by small mammals, such as the choice of seed, whether the seed is immediately consumed or cached, and where it is cached. These decisions are influenced by a variety of factors, including the intrinsic traits of the seed, the individual personality of the scatter hoarder, and the perceived risk of predation while foraging. Furthermore, these factors may all interact to dictate the fate of the seed, with consequences for forest regeneration. Nevertheless, the ways in which perceived predation risk and personality interact to affect the seed dispersal decisions of scatter hoarders are still poorly understood. To contribute in filling this knowledge gap, we tested the hypotheses that southern red‐backed voles (Myodes gapperi), an important scatter hoarder in forest ecosystems, would exhibit personality‐mediated foraging and that predation risk would alter associations between personality and seed dispersal. We conducted a large‐scale field experiment, offering seed trays at stations with altered risk levels and recorded foraging decisions of free‐ranging voles with known personalities. We found that personality and perceived predation risk influenced decisions made by foraging voles. Specifically, docility, and boldness predicted foraging site selection, boldness predicted seed species selection and the number of seeds individuals selected, and the tendency to explore of an individual predicted whether voles would remove or consume seeds. Predation risk, mediated by the amount of cover at a site and by moon illumination, affected which foraging site individuals chose, seed species selection, and the probability of removal versus consumption. We did not find support for an interaction between personality and predation risk in predicting foraging decisions. These findings highlight the importance of scatter hoarder personality and perceived predation risk in affecting foraging decisions, with important consequences for seed dispersal and implications for altered patterns of forest regeneration in areas with different small mammal personality distributions or landscapes of fear.

     
    more » « less
  3. ; ; ( , Functional Ecology)
    Abstract

    Dispersal is one of the primary mechanisms by which organisms adapt to spatial and temporal variation in the environment. Theory predicts that increasing spatiotemporal variation drives selection for offspring dispersal away from their natal habitat and one another. However, due to inherent difficulties in measuring dispersal in plant systems, there are few empirical tests of the extent to which this hypothesis can explain variation in seed dispersal strategies.

    In this study, we characterized and compared the dispersal patterns of three closely related plant species that segregate across gradients in spatiotemporal variation in seasonal wetlands.

    We tracked individual seeds as they dispersed in their natural habitats to measure seed dispersal distance (the distance travelled from the maternal plant) and inter‐seed spread (distances between dispersed seeds) and to identify the plant traits causing within‐species variation in seed dispersal. We also evaluated the seed traits causing within‐species variation in seed flight distance and terminal velocity in a wind tunnel and a drop tube, respectively.

    We found that average seed dispersal distance was lowest in the species that occupies the most spatiotemporally variable habitat, contradicting our predictions; however, inter‐seed spread was lowest in the species from the least variable habitat, which aligned with our expectations.

    The maternal plant and seed traits explaining intraspecific variation in seed dispersal varied among species as well as the method used to measure dispersal potential. Two traits had non‐intuitive effects on dispersal, including pappus size, which reduced seed flight distance in two of the focal taxa.

    Overall, our results indicate that the differences we detected in seed dispersal among three closely related plant taxa can be only partially explained by current patterns of environmental variability in their respective habitats and that the traits driving within‐species variation in seed dispersal can evolve rapidly and change with the environmental context in which they are measured.

    Read the freePlain Language Summaryfor this article on the Journal blog.

     
    more » « less
  4. ; ( , Proceedings of the National Academy of Sciences)
    Mutualisms are foundational components of ecosystems with the capacity to generate biodiversity through adaptation and coevolution and give rise to essential services such as pollination and seed dispersal. To understand how mutualistic interactions shape communities and ecosystems, we must identify the mechanisms that underlie their functioning. One mechanism that may drive mutualisms to vary in space and time is the unique behavioral types, or personalities, of the individuals involved. Here, our goal was to examine interindividual variation in the seed dispersal mutualism and identify the role that different personalities play. In a field experiment, we observed individual deer mice ( Peromyscus maniculatus ) with known personality traits predating and dispersing seeds in a natural environment and classified all observed interactions made by individuals as either positive or negative. We then scored mice on a continuum from antagonistic to mutualistic and found that within a population of scatter hoarders, some individuals are more mutualistic than others and that one factor driving this distinction is animal personality. Through this empirical work, we provide a conceptual advancement to the study of mutualism by integrating it with the study of intraspecific behavioral variation. These findings indicate that animal personality is a previously overlooked mechanism generating context dependence in plant–animal interactions and suggest that behavioral diversity may have important consequences for the functioning of mutualisms. 
    more » « less
  5. ; ; ( , Biotropica)
    Abstract

    Through frugivory and seed dispersal, vertebrates influence plant demography and forest regeneration. Variation in local habitat surrounding fruiting plants can influence frugivore foraging decisions, thereby creating intraspecific variation in seed dispersal services. However, we have little knowledge of drivers of local variation in frugivory. Here, we investigate factors that may influence frugivore diversity and fruit removal at the level of individual plants. We focus on a common understory palm within a continuous Chocó forest with mixed land‐use histories in Ecuador. The density of pioneer tree species in the genusCecropiaaround focal palms was negatively related to fruit removal and the diversity of frugivores visiting palms. This may relate to the fact that the presence and abundance ofCecropiaspecies often indicate the existence and severity of past disturbances. LocalCecropiadensity was also related to an overall shift in the frugivore community that corresponded with an increase in fruit removal by lower‐quality seed dispersers (rodents). We also found that the local density of fruiting conspecifics was positively related to frugivore diversity, but not fruit removal. Our results provide information on drivers of intraspecific inequalities in plant populations across tropical forest landscapes. The reduction in fruit removal and frugivore diversity associated with localCecropiaabundance suggests that seed dispersal services can be sensitive to fine‐scale variation in habitat structure. Furthermore, becauseCecropiaare often indicative of past disturbances, this indicates that even small‐scale habitat degradation by humans can have lasting effects by creating localized pockets of forest unfavored by frugivores.

    Abstract in Spanish is available with online material.

     
    more » « less
  • Citation Formats
  • MLA
  • APA
  • Chicago
  • BibTeX
  • Save / Share this Record
  • Send to Email