Consequences of the Timing of Seed Release of Erythronium americanum (Liliaceae), a Deciduous Forest Myrmecochore

Ruhren, Scott; Dudash, Michele R.

doi:10.2307/2445923

Cited by 22 publications

(26 citation statements)

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“…Regardless of the mechanism, we found no evidence for soil nutrient-enrichment by ant nests in our study. The increase in seedling emergence in ant removal plots was an unexpected result in light of studies that have shown that when ants handle seeds and remove elaiosomes, seed germination rates increase (Christian 2001, Horvitz 1981, Lobstein and Rockwood 1993, Ruhren and Dudash 1996. However, some studies report the opposite trend and have proposed several possible explanations for the decrease in germination success.…”

Section: Discussionmentioning

confidence: 95%

“…In addition to reducing the effects of densitydependent processes, the deposition of seeds into nutrient-rich microsites, either within ant nests or into refuse piles, is another potential benefit of (Culver and Beattie 1983, Giladi 2006, Ruhren and Dudash 1996. While we did not directly design our study to address this hypothesis, we can make predictions about nutrient-enrichment based on the measurements we made.…”

Section: Discussionmentioning

confidence: 99%

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The mixed effects of experimental ant removal on seedling distribution, belowground invertebrates, and soil nutrients

Zelikova

Sanders²,

Dunn

2011

Ecosphere

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Abstract. Ants are ubiquitous members of most forest communities, where they disperse seeds, prey on other species, and influence the flow of nutrients. Their effects are often described as substantial, but few studies to date have simultaneously examined how the presence of ants affects both above and belowground processes. In this study, we experimentally reduced ant abundance in a suite of deciduous forest plots in northern Georgia, USA to assess the effects of ants on the spatial distribution of a common understory plant species, Hexastlylis arifolia, the structure of soil mesofaunal communities, and soil nitrogen dynamics. Over the course of several years, the removal of ants led to significant spatial aggregation of H. arifolia seedlings near the parent plant, most likely due to the absence of the keystone seed dispersal species, Aphaenogaster rudis. Seedling emergence was higher in ant removal plots, but seedling aggregation did not affect first or second year seedling mortality. Ammonium concentrations were 103 higher in ant removal plots relative to control plots where ants were present in the first year of the study, but this increase disappeared in the second and third years of the study. The effects of ant removal on the soil mesofauna were mixed: removal of ants apparently did not affect the abundance of Collembola, but the abundance of oribatid mites was significantly higher in ant removal plots by year two of the study. Taken together, these results provide some of the first experimental evidence of the diverse direct and indirect effects of ants on both above and belowground processes in forest ecosystems and demonstrate the potential consequences of losing an important seed dispersing ant species for the plants they disperse.

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Section: Discussionmentioning

confidence: 95%

Section: Discussionmentioning

confidence: 99%

The mixed effects of experimental ant removal on seedling distribution, belowground invertebrates, and soil nutrients

Zelikova

Sanders²,

Dunn

2011

Ecosphere

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“…They carry them into their mounds and deposit them there before they are found by rodents, so that at least a proportion of the seeds are protected from seed predation. As rodents orientate themselves mainly by odours, the seeds are harder to detect and less attractive to rodents after deposition on the ants' refuse pile, with the pulp removed but otherwise intact (Ruhren and Dudash 1996;Spehn and Ganzhorn 2000). Therefore, seeds dispersed by A. swammerdami are not only moved from directly under the parent tree, reducing clumping and parent tree-seedling conflicts, but should also be exposed to a substantially reduced predation risk.…”

Section: Discussionmentioning

confidence: 99%

Improved recruitment of a lemur-dispersed tree in Malagasy dry forests after the demise of vertebrates in forest fragments

et al. 2008

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The objective of this study was to examine how the processes of seed dispersal and seed predation were altered in forest fragments of the dry forest of Madagascar, where the usual seed dispersers and vertebrate seed predators were absent, using a lemur-dispersed tree species (Strychnos madagascariensis; Loganiaceae) as an example. We then assessed how the changes in vertebrate community composition alter the regeneration pattern and establishment of this tree species and thus, ultimately, the species composition of the forest fragments. By using size-selective exclosures, data from forest fragments were compared with results from continuous forest where vertebrate dispersers and predators were abundant. Visits to the exclosures by mammalian seed predators were monitored with hair traps. In the continuous forest up to 100% of the seeds were removed within the 7 days of the experiments. A substantial proportion of them was lost to seed predation by native rodents. In contrast, practically no predation took place in the forest fragments and almost all seeds removed were dispersed into the safety of ant nests by Aphaenogaster swammerdami, which improves chances of seedling establishment. In congruence with these findings, the abundance of S. madagascariensis in the forest fragments exceeded that of the continuous forest. Thus, the lack of vertebrate seed dispersers in these forest fragments did not lead to a decline in regeneration of this animal-dispersed tree species as would have been expected, but rather was counterbalanced by the concomitant demise of vertebrate seed predators and an increased activity of ants taking over the role of seed dispersers, and possibly even out-doing the original candidates. This study provides an example of a native vertebrate-dispersed species apparently profiting from fragmentation due to flexible animal-plant interactions in different facets, possibly resulting in an impoverished tree species community.

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“…It has been suggested, but not tested, that plants may stagger seed set to reduce competition for animal foragers that disperse their seeds (Beattie & Culver ; Handel, Fisch & Schatz ; Heithaus ; Smith et al . ; Ruhren & Dudash ).…”

Section: Introductionmentioning

confidence: 99%

Competition as a mechanism structuring mutualisms

2014

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Summary1. Hutchinsonian niche theory posits that organisms have fundamental abiotic resource requirements from which they are limited by competition. Organisms also have fundamental biotic requirements, such as mutualists, for which they also might compete. 2. We test this idea with a widespread ant-plant mutualism. Ant-mediated seed dispersal (myrmecochory) in eastern North America involves a few ant species that can effectively disperse the seeds of many plant species. This imbalance suggests that ant-dispersed plants (myrmecochores) might compete for ant dispersers. We hypothesized that, because larger seeds are more attractive to ants, myrmecochores might segregate the timing of seed release by size to relieve competition. 3. Comparative literature analysis across plant species reveals that myrmecochore seed size increases with the fruiting season in a staggered pattern so that small-and large-seeded co-occurring species do not release seeds at the same time -a pattern not observed in plants using other dispersal modes. 4. We then presented foraging ants with small and large seeds in field trials throughout the fruiting season to test whether the observed temporal segregation in myrmecochore seed size is consistent with plant competition for ant dispersers. 5. Our results show that dispersal rates for smaller seeds increase across the growing season, but only in the absence of large seeds. Our combined literature and field data suggest that myrmecochores stagger fruiting by seed size so that small seeds are set earlier to avoid competition for dispersal mutualists with larger seeds. 6. Synthesis. Ecological interactions are often treated as either positive or negative, but our data blur this distinction by revealing that a positive interaction (mutualism) might be structured by a negative interaction (competition). Moreover, the recognition of biotic resources as critical niche requirements blurs the classic dichotomy between the fundamental (abiotic) versus realized (biotic limited) niche.

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Consequences of the Timing of Seed Release of Erythronium americanum (Liliaceae), a Deciduous Forest Myrmecochore

Cited by 22 publications

References 0 publications

The mixed effects of experimental ant removal on seedling distribution, belowground invertebrates, and soil nutrients

The mixed effects of experimental ant removal on seedling distribution, belowground invertebrates, and soil nutrients

Improved recruitment of a lemur-dispersed tree in Malagasy dry forests after the demise of vertebrates in forest fragments

Competition as a mechanism structuring mutualisms

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