Conspecific negative density dependence and why its study should not be abandoned

LaManna, Joseph A.; Mangan, Scott A.; Myers, Jonathan A.

doi:10.1002/ecs2.3322

Cited by 24 publications

(12 citation statements)

References 38 publications

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“…Second, NDD tends to decrease with ontogeny rather than increase [25]. Finally, studies of NDD at the recruitment level may overestimate NDD due to regression dilution ( [26]; but see [4]).…”

Section: Discussionmentioning

confidence: 99%

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Are we missing the forest for the trees? Conspecific negative density dependence in a temperate deciduous forest

Barry

Schnitzer

2021

PLoS ONE

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One of the central goals of ecology is to determine the mechanisms that enable coexistence among species. Evidence is accruing that conspecific negative density dependence (CNDD), the process by which plant seedlings are unable to survive in the area surrounding adults of their same species, is a major contributor to tree species coexistence. However, for CNDD to maintain community-level diversity, three conditions must be met. First, CNDD must maintain diversity for the majority of the woody plant community (rather than merely specific groups). Second, the pattern of repelled recruitment must increase in with plant size. Third, CNDD should extend to the majority of plant life history strategies. These three conditions are rarely tested simultaneously. In this study, we simultaneously test all three conditions in a woody plant community in a North American temperate forest. We examined whether understory and canopy woody species across height categories and dispersal syndromes were overdispersed–a spatial pattern indicative of CNDD–using spatial point pattern analysis across life history stages and strategies. We found that there was a strong signal of overdispersal at the community level. Across the whole community, larger individuals were more overdispersed than smaller individuals. The overdispersion of large individuals, however, was driven by canopy trees. By contrast, understory woody species were not overdispersed as adults. This finding indicates that the focus on trees for the vast majority of CNDD studies may have biased the perception of the prevalence of CNDD as a dominant mechanism that maintains community-level diversity when, according to our data, CNDD may be restricted largely to trees.

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Section: Discussionmentioning

confidence: 99%

“…Conspecific negative density dependence (CNDD) is one of the most empirically supported mechanisms for the maintenance of plant species diversity [1][2][3][4]. Conspecific negative density dependence occurs when small individuals have relatively low rates of growth and survival near adult members of their own species (conspecifics).…”

Section: Introductionmentioning

confidence: 99%

Are we missing the forest for the trees? Conspecific negative density dependence in a temperate deciduous forest

Barry

Schnitzer

2021

PLoS ONE

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“…To further account for the possibility that our CNDD coeff estimate could be produced by underlying spatial or other factors not accounted for in this simple statistical model, we additionally performed null model testing (LaManna et al, 2021). Using the same model structure as above, we recalculated values of NCI con and NCI het for each sapling after randomizing the observed proportion of the total NCI that was conspecific: effectively keeping the total neighborhood density the same as the observed, but randomizing the density of conspecific neighbors.…”

Section: Observational Sapling Survivalmentioning

confidence: 99%

Experimental and observational evidence of negative conspecific density dependence in temperate ectomycorrhizal trees

Jevon

Cruz

LaManna

et al. 2022

Ecology

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Conspecific negative density dependence (CNDD) promotes tree species diversity by reducing recruitment near conspecific adults due to biotic feedbacks from herbivores, pathogens, or competitors. While this process is well-described in tropical forests, tests of temperate tree species range from strong positive to strong negative density dependence. To explain this, several studies have suggested that tree species traits may help predict the strength and direction of density dependence: for example, ectomycorrhizal-associated tree species typically exhibit either positive or weaker negative conspecific density dependence. More generally, the strength of density dependence may be predictably related to other species-specific ecological attributes such as shade tolerance, or the relative local abundance of a species. To test the strength of density dependence and whether it affects seedling community diversity in a temperate forest, we tracked the survival of seedlings of three ectomycorrhizal-associated species experimentally planted beneath conspecific and heterospecific adults on the Prospect Hill tract of the Harvard Forest, in Massachusetts, USA. Experimental seedling survival was always lower under conspecific adults, which increased seedling community diversity in one of six treatments. We compared these results to evidence of CNDD from observed sapling survival patterns of 28 species over approximately 8 years in an adjacent 35-ha forest plot. We tested whether species-specific estimates of CNDD were associated with mycorrhizal association, shade tolerance, and local abundance. We found evidence of significant, negative conspecific density dependence (CNDD) in 23 of 28 species, and positive conspecific

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“…Considerable evidence has been presented for CNDD acting on early life stages in tropical and temperate forests, and variation in CNDD has been hypothesized to underlie the latitudinal gradient from high tree species diversity at the equator to lower diversity at higher latitudes (3,(5)(6)(7). For example, the abundance of seedlings, seeds and adults have been shown by numerous works to reduce the number and survival of seedlings and saplings (8)(9)(10)(11) and several works have also presented evidence that CNDD is stronger than HNDD (8,11).…”

Section: Main Textmentioning

confidence: 99%

Pervasive species-specific repulsion among adult tropical trees

Kalyuzhny

Lake

Wright

et al. 2022

Preprint

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For multiple species to stably coexist, it is necessary that, as species increase in abundance, they suffer from Conspecific Negative Density Dependence (CNDD). For trees, there is ample evidence for such negative effects of abundance on the survival and frequency of juveniles, typically on small spatial scales. Despite this short distance 'repulsion' of juveniles, adult trees are generally spatially aggregated, and there is little evidence that CNDD acting on juveniles propagates to the adult stage, casting doubt on its importance for coexistence. However, evidence of aggregation was previously obtained by comparing the spatial distribution of adults to a random placement across the landscape, ignoring dispersal limitation. Here we show that, when compared to the predictions of a calibrated null model of stochastic birth, death and limited dispersal, the adults of dozens of tropical forest species are almost ubiquitously and strongly overdispersed, often up to distances of ~100 meters. We also show that such strong overdispersion can only occur if CNDD considerably exceeds Heterospecific Negative Density Dependence, creating stabilizing niche differences, which are an important requirement for stable coexistence. Together these findings suggest that CNDD propagates from juveniles to adults, strongly influencing adult spatial distribution. Furthermore, these results refine our view of the fundamental nature of species spatial distributions, a key interest in ecology, and demonstrate the power of using limited dispersal null models to detect biotic interactions and habitat associations from spatial distributions.

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Conspecific negative density dependence and why its study should not be abandoned

Cited by 24 publications

References 38 publications

Are we missing the forest for the trees? Conspecific negative density dependence in a temperate deciduous forest

Are we missing the forest for the trees? Conspecific negative density dependence in a temperate deciduous forest

Experimental and observational evidence of negative conspecific density dependence in temperate ectomycorrhizal trees

Pervasive species-specific repulsion among adult tropical trees

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