Fruit Size Determines the Role of Three Scatter-Hoarding Rodents as Dispersers or Seed Predators of a Fleshy-Fruited Atacama Desert Shrub

Luna, Claudia A.; Loayza, Andrea P.; Squeo, Francisco A.

doi:10.1371/journal.pone.0166824

Cited by 14 publications

(16 citation statements)

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“…The actual outcome of the interaction may be more related to the ratio of seed to disperser size rather than seed size alone (Muñoz and Bonal 2008a). However, three species of rodents varying 4-fold in mass all preferentially selected and dispersed larger fruits of the Chilean desert shrub Myrcianthes coquimbensis (Luna et al 2016).…”

Section: Intrinsic Variation: Plant Traitsmentioning

confidence: 99%

Intrinsic and extrinsic drivers of intraspecific variation in seed dispersal are diverse and pervasive

et al. 2019

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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.

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Section: Intrinsic Variation: Plant Traitsmentioning

confidence: 99%

Intrinsic and extrinsic drivers of intraspecific variation in seed dispersal are diverse and pervasive

et al. 2019

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“…This shrub produces large (2.5 × 3.5 cm), red, fleshy fruits bearing a sugar-and water-rich pulp. Each fruit typically bears a single seed ranging in mass between 0.05 and 14.58 g; however, a single fruit can have up to four seeds 31 . Fruits are consumed solely by three species of seed caching rodents: Abrothrix olivaceus [ 17 .…”

Section: Methodsmentioning

confidence: 99%

“…Rodent behaviour. We assessed rodent foraging behaviour by conducting cafeteria experiments, which are detailed in Luna et al 31 . Briefly, 10 rodents of each species were captured in the field, taken to Universidad de la Serena and individually placed in 2.5 × 2.5 × 0.5 m experimental arenas.…”

Section: Model Parameterizationmentioning

confidence: 99%

“…The only vertebrates that consume M. coquimbensis fruits are three species of scatter-hoarding rodents (differing in body size and behaviour) that feed on the pulp and seed; consequently, they act both as predators and dispersers 17 . Foraging behaviour of these rodents is strongly influenced by M. coquimbensis seed size, with larger fruits/seeds having higher probabilities of being harvested and cached 31 . Seed size exhibits large intraspecific variation (0.03-14.6 g) and is positively related to emergence probability.…”

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Predators and dispersers: Context-dependent outcomes of the interactions between rodents and a megafaunal fruit plant

Loayza

Luna

Calviño‐Cancela

2020

Sci Rep

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Many plant species bear fruits that suggest adaptation to seed dispersal by extinct megafauna. presentday seed dispersal of these megafaunal plants is carried out by rodents, which can act as predators or dispersers; whether this interaction is primarily positive or negative can depend on the context. Here, we parameterized a stochastic model using data from the field and experimental arenas to estimate the effect of rodents on the recruitment of Myrcianthes coquimbensis-an Atacama Desert shrub with megafaunal fruits-and examine whether environmental conditions can alter the sign and strength of these rodent-plant interactions. We show that the outcome of these interactions is contextdependent: in wet conditions seed removal by rodents negatively impacts the recruitment probability of M. coquimbensis; in contrast, in dry conditions, the interaction with rodents increases recruitment success. In all cases, the strength of the effect of rodents on the recruitment success was determined mainly by their role as dispersers, which could be positive or negative. This study demonstrates that by caching seeds, rodents can be effective dispersers of a megafaunal fruit plant, but that the sign and magnitude of their effect on recruitment changes as a function of the environmental context in which the interaction occurs. Many New World plant species bear fruits with trait combinations that suggest adaptation for seed dispersal by the megafauna that went extinct during the Pleistocene-Holocene transition 1-5. Plants with this megafaunal dispersal syndrome bear fleshy fruits too large to be swallowed and dispersed by extant frugivores; hence they are believed to represent seed dispersal anachronisms 2. In present times, seed dispersal of Neotropical anachronic plants is carried out by surrogate dispersers; smaller-bodied animals, such as scatter-hoarding rodents 4,6 , which can benefit not only from the seed, but also from the fleshy pulp of some anachronic fruits, which provides a sugar-and water-rich reward not produced by typical rodent-dispersed, nutlike fruits 7,8. Although it is hypothesized that these smaller, surrogate dispersers are unlikely to compensate for the loss of the dispersal services provided by the extinct megafauna 9 , few empirical studies have examined their effectiveness as dispersers of anachronic plants 6,10,11. Scatter-hoarding rodents store intact fruits and/or seeds in many separate, shallow caches in the soil 12-15 , and because they generally store more food than they require 16 , they forget or neglect some of the caches 6,15. Moreover, during the caching and re-caching process, seeds can be moved far from the parent plant 6 and to habitats with high probabilities of seedling establishment 10,17. Therefore, seed dispersal by scatter-hoarding rodents can positively contribute to the recruitment of megafaunal fruit plants 4,6,17. The interaction between these plants and scatter-hoarding rodents, however, also comes with a cost because rodents are seed predators 18 that eventually recover many of t...

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“…, Luna et al . ), but whether the seed dispersal they provide is effective or not seems to be species‐specific. For example, agoutis provide effective dispersal to Astrocaryum standleyanum, a large‐seeded palm with a megafaunal dispersal syndrome (Hirsch et al .…”

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Are pulp consumers effective seed dispersers? Tests with a large‐seeded tropical relict tree

2018

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Several plant species in the Neotropics bear large, fleshy fruits that suggest adaptation to endozoochorous seed dispersal by large vertebrates. Many of these plants occur in areas where large vertebrates are no longer present; consequently, their seeds are dispersed by pulp consumers; small vertebrates that only ingest the pulp reward because they are uncapable of swallowing the fruits whole. Few studies have examined the role of these pulp consumers on the regeneration of large-fruited/seeded plants. Here, we assessed seed disperser effectiveness (SDE) and context-dependence in SDE of pulp consumers of Pouteria splendens, a large-seeded tree, considered a tropical relict in Mediterranean Chile. We found that P. splendens fruits are consumed by six species of non-flying vertebrates; four of which act as dispersers with very low effectiveness. Low SDE resulted from the quantitative, rather than the qualitative component, specifically from low visitation rates. Most seeds remained under P. splendens trees, either from being dispersed there or because they were not dispersed at all. However, both emergence and establishment probabilities were higher under conspecific plants than in other habitats, suggesting no negative density-dependent effects on P. splendens recruitment. Although the absence of more effective dispersers does not seem to affect local recruitment probabilities, it results in the absence of long-distance dispersal, further isolating the remnant P. splendens populations. Finally, although pulp consumers have very low disperser effectiveness, the key functional role of these species is to remove the fleshy pulp from P. splendens' seed as its presence significantly reduces germination probability.Abstract in Spanish is available with online material.

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Fruit Size Determines the Role of Three Scatter-Hoarding Rodents as Dispersers or Seed Predators of a Fleshy-Fruited Atacama Desert Shrub

Cited by 14 publications

References 49 publications

Intrinsic and extrinsic drivers of intraspecific variation in seed dispersal are diverse and pervasive

Intrinsic and extrinsic drivers of intraspecific variation in seed dispersal are diverse and pervasive

Predators and dispersers: Context-dependent outcomes of the interactions between rodents and a megafaunal fruit plant

Are pulp consumers effective seed dispersers? Tests with a large‐seeded tropical relict tree

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