Measuring the demographic impact of conspecific negative density dependence

Fricke, Evan C.; Wright, S. Joseph

doi:10.1007/s00442-017-3863-y

Cited by 23 publications

(20 citation statements)

References 40 publications

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“…For example, Bagchi et al (2014) used a multi-trap design to quantify CNDD affecting the seed-to-seedling transition. The results in Bagchi et al (2014) dramatically differ from the results in H2000 and subsequent analyses (Wright et al 2005;Fricke & Wright 2017), as the former detected CNDD in few species only, whereas the latter reported CNDD in all the species. This can be explained by the multi-trap design's ability to correct for bias, which is consistent with our re-analysis of the data set used by H2000 informed by a newly available multi-trap estimate of collocation error ( Fig.…”

Section: Discussioncontrasting

confidence: 81%

Bias in the detection of negative density dependence in plant communities

et al. 2019

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Regression dilution is a statistical inference bias that causes underestimation of the strength of dependency between two variables when the predictors are error‐prone proxies (EPPs). EPPs are widely used in plant community studies focused on negative density‐dependence (NDD) to quantify competitive interactions. Because of the nature of the bias, conspecific NDD is often overestimated in recruitment analyses, and in some cases, can be erroneously detected when absent. In contrast, for survival analyses, EPPs typically cause NDD to be underestimated, but underestimation is more severe for abundant species and for heterospecific effects, thereby generating spurious negative relationships between the strength of NDD and the abundances of con‐ and heterospecifics. This can explain why many studies observed rare species to suffer more severely from conspecific NDD, and heterospecific effects to be disproportionally smaller than conspecific effects. In general, such species‐dependent bias is often related to traits associated with likely mechanisms of NDD, which creates false patterns and complicates the ecological interpretation of the analyses. Classic examples taken from literature and simulations demonstrate that this bias has been pervasive, which calls into question the emerging paradigm that intraspecific competition has been demonstrated by direct field measurements to be generally stronger than interspecific competition.

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Section: Discussioncontrasting

confidence: 81%

Bias in the detection of negative density dependence in plant communities

et al. 2019

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“…2c). SSMs provide insights on dispersal and recruitment limitation (Ribbens et al 1994, Clark et al 1998, Nathan and Muller-Landau 2000, Fricke and Wright 2017, gene flow and hybridization (Garant et al 2007, Jones and Muller-Landau 2008, Moran and Clark 2011, Moran et al 2012, migration potential , environmental controls on reproductive effort and sex ratio (Clark et al 2004, 2011, Uriarte et al 2005, 2012, Schurr et al 2008, Martinez and Gonzalez-Taboada 2009, Canham et al 2014, Detto et al 2018, and allocation (LaDeau and Clark 2006, Berdanier and. SSMs include a likelihood for seed-count data, such as a Poisson distribution with intensity expressed as expected seeds per trap…”

Section: Introductionmentioning

confidence: 99%

Foodwebs based on unreliable foundations: spatiotemporal masting merged with consumer movement, storage, and diet

Clark

Núñez

Tomasek

2019

Ecological Monographs

114

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Mast‐fruiting trees represent a pulsed resource that both supports and destabilizes consumer populations. Whereas a reliable resource is abundant on average and with limited variation in time and space, masting is volatile and localized, and that variability ramifies throughout food‐webs. Theory is developed to evaluate how the space–time structure of masting interacts with consumers who exploit alternative hosts, forage widely in space, and store reserves in time. We derive the space–time–species covariance in resource supply and combine it with the space–time–diet breadth of consumers, or ambit. Direct connection to data is made possible with Mast Inference and Forecasting (MASTIF), a state‐space autoregressive model that fits seed‐trap and canopy observations and predicts resource availability within the canopy and on the forest floor with full uncertainty. A resource score can be assigned to each consumer–habitat combination that integrates the benefits of a high mean supply weighed against the variance cost. As the consumer ambit increases, the volatility of an unreliable resource shifts from a variance cost to a mean benefit. Consumers foraging in the canopy (arboreal arthropods and rodents, song birds) experience space‐time covariance between host trees. Consumers on the forest floor (seed and damping‐off fungi, arthropods, rodents, ground‐nesting birds, mammals) experience instead a redistribution of that covariance by dispersal. For consumers lacking mobility, demographic storage in the form of episodic birth cohorts following mast years is important for population persistence. Consumers additionally compensate volatility with diet breadth. Depending on the dominant masting strategies of host tree species in the diet, habitats differentially limit consumers depending on the misalignment between consumer ambit and spatiotemporal covariance of hosts. The impact of adding or subtracting a diet item can be gauged with the standard error (SE) rule or the benefit of an added diet item balanced against the variance cost, both of which depend on the existing diet, the abundance of the new host, and the consumer's foraging ambit. Results rank habitats by their capacities to support wildlife and other consumers from a resource perspective. Results are connected directly to data, with full uncertainty, by MASTIF.

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“…Differences in the relative strength of CNDD regulation between common and rare species have been proposed to have an important effect on tree diversity and species composition (Comita et al., ; Hubbell, Ahumada, Condit & Foster, ; Miranda et al., ; Stump & Comita, ). Fricke and Wright () argue that in tropical forests, dominant tree species are expected to have weaker CNDD. The lack of CNDD regulation in Q. costaricensis correlates with its high abundance in montane forests and may result from different interacting life‐history traits (Comita et al., ; Zhu et al., ).…”

Section: Discussionmentioning

confidence: 99%

The effect of conspecific density, herbivory, and bamboo on seedling dynamics of a dominant oak in a Neotropical highland forest

et al. 2019

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Conspecific negative density dependence (CNDD) is one of the main mechanisms influencing diversity maintenance in tropical forests. Tropical highland forests, in contrast to most lowland forests, are commonly dominated by a few tree species, and testing the importance of density dependence effects on seedling establishment of dominant trees may provide insights on the mechanisms regulating population dynamics and forest composition of tropical highlands. We tested the effect of CNDD regulation on seedling survival and recruitment of Quercus costaricensis, a monodominant oak in the Talamanca highland forests of Costa Rica. We used Ripley's K and generalized linear mixed models to test the effects of conspecific density, distance to the nearest adult, density of Chusquea bamboo shoots, and herbivory on the annual survival probability of 3579 seedlings between 2014 and 2017. We did not find a significant effect of CNDD on seedling survival. However, bamboo density and herbivory both significantly decreased oak seedling survival. All seedlings had signs of herbivory and predator satiation may explain the lack of density dependent regulation in seedlings of this species. We argue that the lack of intraspecific density regulation at the seedling stage may contribute to explain the dominance of Q. costaricensis in the highland forests of Costa Rica. Local seedling dynamics of this endemic oak are instead regulated by herbivory and the density of Chusquea. Abstract in Spanish is available with online material.

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Measuring the demographic impact of conspecific negative density dependence

Cited by 23 publications

References 40 publications

Bias in the detection of negative density dependence in plant communities

Bias in the detection of negative density dependence in plant communities

Foodwebs based on unreliable foundations: spatiotemporal masting merged with consumer movement, storage, and diet

The effect of conspecific density, herbivory, and bamboo on seedling dynamics of a dominant oak in a Neotropical highland forest

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