Unravelling conflicting density‐ and distance‐dependent effects on plant reproduction using a spatially explicit approach

Fedriani, José M.; Wiegand, Thorsten; Calvo, Gemma; Suárez‐Esteban, Alberto; Jácome, Miguel; Żywiec, Magdalena; Delibes, Miguel

doi:10.1111/1365-2745.12454

Cited by 43 publications

(81 citation statements)

References 54 publications

(133 reference statements)

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“…Therefore, it is possible that the positive density-dependent effects of predator satiation in years of high seed predation may be offset later by negative density-dependent recruitment of seedlings, which can cause large impacts on plant population dynamics and tree diversity (Hammond and Brown, 1998;Wright, 2002). As shown by Fedriani et al (2015), such antagonistic density-dependent effects may operate at multiple stages of plant reproduction. They found that fruit initiation was higher for individuals with more neighbours at small distances, but fruit development decreased with an increasing number of nearby neighbours leading to density-independent overall fruitset.…”

Section: Discussionmentioning

confidence: 99%

Seed–predator satiation and Janzen–Connell effects vary with spatial scales for seed-feeding insects

Xiao

Holyoak³

et al. 2016

Ann Bot

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Background and AimsThe Janzen-Connell model predicts that common species suffer high seed predation from specialized natural enemies as a function of distance from parent trees, and consequently as a function of conspecific density, whereas the predator satiation hypothesis predicts that seed attack is reduced due to predator satiation at high seed densities. Pre-dispersal predation by insects was studied while seeds are still on parent trees, which represents a frequently overlooked stage in which seed predation occurs.Methods Reproductive tree density and seed production were investigated from ten Quercus serrata populations located in south-west China, quantifying density-dependent pre-dispersal seed predation over two years by three insect groups.Key Results Acorn infestation was nearly twice as high in the low-seed year as that in the high-seed year, with considerable spatio-temporal variation in the direction and magnitude of density-dependent pre-dispersal seed predation evident. Across whole populations of trees, a high density of reproductive trees caused predator satiation and reduced insect attack in the high-seed year. Within individual trees, and consistent with the Janzen-Connell model, overall insect seed predation was positively correlated with seed production in the low-seed year. In addition, there was variation among insect taxa, with positive density-dependent seed predation by Curculio weevils in the high-seed year and moths in the low-seed year, but apparent density independence by Cyllorhynchites weevils in both years.Conclusions The overall trend of negative density-dependent, pre-dispersal seed predation suggests that predator satiation limited the occurrence of Janzen-Connell effects across Q. serrata populations. Such effects may have large impacts on plant population dynamics and tree diversity, depending on the extent to which they are reduced by counteracting positive density-dependent predation for seeds on individual trees and other factors affecting successful recruitment.

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Section: Discussionmentioning

confidence: 99%

Seed–predator satiation and Janzen–Connell effects vary with spatial scales for seed-feeding insects

Xiao

Holyoak³

et al. 2016

Ann Bot

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“…Another possibility is that because fruit crop size is the outcome of numerous processes operating at several ontogenic stages, opposing DDD processes could in fact be operating but neutralising each other (e.g. Fedriani et al., ; Jones & Comita, ).…”

Section: Discussionmentioning

confidence: 99%

“…Finally, we use the density correlation function C m,K ( r ) developed by Fedriani et al. (), which directly relates the crop size of a rowan tree to the density of its conspecific neighbours. C m,K ( r ) estimates the classical Pearson correlation between the crop size success m i of a tree and the number of neighbours within distance r [=λ K i ( r )].…”

Section: Methodsmentioning

confidence: 99%

“…It estimates the classical Pearson correlation coefficient between the fruit crop of a tree and the number of neighbours within distance r. Nonetheless, both statistics (i.e. k m ( r ) and C m,K ( r )) can be interpreted in terms of both density and distance dependence (Fedriani et al., ). Specifically, for the r‐mark correlation function, k m ( r ) > 1 and k m ( r ) < 1 indicate positive and negative DDD respectively.…”

Section: Methodsmentioning

confidence: 99%

“…For k m ( r ) and C m,K ( r ), departures above the superior limit of the simulation envelopes indicate positive distance and density dependence respectively. Departures below the inferior limit of the simulation envelopes indicate negative distance and density dependence respectively (Fedriani et al., ). For I mm ( r ), although departures above the superior limit of the simulation envelopes indicate higher than expected spatial covariance (similarity) of the marks (i.e.…”

Section: Methodsmentioning

confidence: 99%

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Rare events of massive plant reproductive investment lead to long‐term density‐dependent reproductive success

et al. 2017

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The level of reproductive investment and density‐ and distance‐dependent (DDD) processes are major determinants of plant reproductive output. The reproductive investment of a plant population varies temporally, but whether and how DDD processes are affected by population‐level reproductive investment is a puzzle. We used a spatially explicit approach in order to examine DDD effects on Sorbus aucuparia crop sizes for a continuous period of 16 years. Our special interest was to investigate whether and how DDD processes affect long‐term individual plant reproductive success (PRS) and whether such processes vary between years of relatively high and low population‐level reproductive investment, measured as fruit crop size. Our study revealed that DDD processes of fruit crop relate to population‐level reproductive investment. In most years, including all years with low and most years with moderate reproductive investment, no positive or negative DDD was found for PRS. However, significant negative density‐dependent effects were found during most years of high and some years of moderate reproductive investment. During these years, the individual reproductive success decreased with increasing density of conspecifics. The overall accumulated long‐term negative density‐dependent pattern of PRS was determined by few sporadic years of high reproductive investment, rather than by the most frequent years of low or moderate reproductive investment, when the DDD effects were usually weak. Synthesis. Our study highlights the ecological relevance of relatively infrequent processes which affect plant reproductive success, stressing thus the importance of long‐term ecological research.

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Interactions between large‐scale and local factors influence seed predation rates and seed loss

Calixto

Maron

Hahn

2023

Ecology and Evolution

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Herbivores often have highly variable impacts on plant fecundity. The relative contribution of different environmental factors operating at varying spatial scales in affecting this variability is often unclear. We examined how density‐dependent seed predation at local scales and regional differences in primary productivity are associated with variation in the magnitude of pre‐dispersal seed predation on Monarda fistulosa (Lamiaceae). Within M. fistulosa populations growing in a low‐productivity region (LPR), Montana, USA, and a high‐productivity region (HPR), Wisconsin, USA, we quantified the magnitude of pre‐dispersal seed predation among individual plants differing in seed head densities. Out of a total of 303 M. fistulosa plants that were surveyed, we found half as many herbivores in seed heads in the LPR (n = 133 herbivores) compared to the HPR (n = 316). In the LPR, 30% of the seed heads were damaged in plants with low seed head density, while 61% of seed heads were damaged in plants with high seed head density. Seed head damage was consistently high in the HPR (about 49% across the range of seed head density) compared to the LPR (45% across a range of seed head density). However, the proportion of seeds per seed head that were destroyed by herbivores was nearly two times higher (~38% loss) in the LPR compared to HPR (22% loss). Considering the combined effects of probability of damage and seed loss per seed head, the proportion seed loss per plant was consistently higher in the HPR regardless of seed head density. Nevertheless, because of greater seed head production, the total number of viable seeds produced per plant was higher in HPR and high‐density plants, despite being exposed to greater herbivore pressure. These findings show how large‐scale factors can interact with local‐scale factors to influence how strongly herbivores suppress plant fecundity.

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Unravelling conflicting density‐ and distance‐dependent effects on plant reproduction using a spatially explicit approach

Cited by 43 publications

References 54 publications

Seed–predator satiation and Janzen–Connell effects vary with spatial scales for seed-feeding insects

Seed–predator satiation and Janzen–Connell effects vary with spatial scales for seed-feeding insects

Rare events of massive plant reproductive investment lead to long‐term density‐dependent reproductive success

Interactions between large‐scale and local factors influence seed predation rates and seed loss

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