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Your search keyword '"Smith DJB"' showing total 3 results
Start Over Author "Smith DJB" Publication Type Academic Journals
3 results on '"Smith DJB"'

1. Consequences of Local Conspecific Density Effects for Plant Diversity and Community Dynamics.

Author

LaManna JA, Hartig F, Myers JA, Freckleton RP, Detto M, Surendra A, Doolittle CJ, Bachelot B, Bagchi R, Comita LS, DeFilippis DM, Huanca-Nunez N, Hülsmann L, Jevon FV, Johnson DJ, Krishnadas M, Magee LJ, Mangan SA, Milici VR, Murengera ALB, Schnitzer SA, Smith DJB, Stein C, Sullivan MK, Torres E, Umaña MN, and Delavaux CS

Subjects
Population Dynamics, Plant Physiological Phenomena, Symbiosis, Ecosystem, Biodiversity, Population Density, Plants
Abstract

Conspecific density dependence (CDD) in plant populations is widespread, most likely caused by local-scale biotic interactions, and has potentially important implications for biodiversity, community composition, and ecosystem processes. However, progress in this important area of ecology has been hindered by differing viewpoints on CDD across subfields in ecology, lack of synthesis across CDD-related frameworks, and misunderstandings about how empirical measurements of local CDD fit within the context of broader ecological theories on community assembly and diversity maintenance. Here, we propose a conceptual synthesis of local-scale CDD and its causes, including species-specific antagonistic and mutualistic interactions. First, we compare and clarify different uses of CDD and related concepts across subfields within ecology. We suggest the use of local stabilizing/destabilizing CDD to refer to the scenario where local conspecific density effects are more negative/positive than heterospecific effects. Second, we discuss different mechanisms for local stabilizing and destabilizing CDD, how those mechanisms are interrelated, and how they cut across several fields of study within ecology. Third, we place local stabilizing/destabilizing CDD within the context of broader ecological theories and discuss implications and challenges related to scaling up the effects of local CDD on populations, communities, and metacommunities. The ultimate goal of this synthesis is to provide a conceptual roadmap for researchers studying local CDD and its implications for population and community dynamics., (© 2024 John Wiley & Sons Ltd.)

Published
2024
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2. The unexpected influence of legacy conspecific density dependence.

Author

Magee LJ, LaManna JA, Wolf AT, Howe RW, Lu Y, Valle D, Smith DJB, Bagchi R, Bauman D, and Johnson DJ

Subjects
Population Dynamics, Models, Biological, Biodiversity, Trees physiology, Population Density, Forests
Abstract

When plants die, neighbours escape competition. Living conspecifics could disproportionately benefit because they are freed from negative intraspecific processes; however, if the negative effects of past conspecific neighbours persist, other species might be advantaged, and diversity might be maintained through legacy effects. We examined legacy effects in a mapped forest by modelling the survival of 37,212 trees of 23 species using four neighbourhood properties: living conspecific, living heterospecific, legacy conspecific (dead conspecifics) and legacy heterospecific densities. Legacy conspecific effects proved nearly four times stronger than living conspecific effects; changes in annual survival associated with legacy conspecific density were 1.5% greater than living conspecific effects. Over 90% of species were negatively impacted by legacy conspecific density, compared to 47% by living conspecific density. Our results emphasize that legacies of trees alter community dynamics, revealing that prior research may have underestimated the strength of density dependent interactions by not considering legacy effects., (© 2024 John Wiley & Sons Ltd.)

Published
2024
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3. The functional form of specialised predation affects whether Janzen-Connell effects can prevent competitive exclusion.

Author

Smith DJB

Subjects
Animals, Models, Theoretical, Seedlings, Seeds, Tropical Climate, Predatory Behavior, Trees
Abstract

Janzen-Connell effects (JCEs), specialised predation of seeds and seedlings near conspecific trees, are hypothesised to maintain species richness. While previous studies show JCEs can maintain high richness relative to neutral communities, recent theoretical work indicates JCEs may weakly inhibit competitive exclusion when species exhibit interspecific fitness variation. However, recent models make somewhat restrictive assumptions about the functional form of specialised predation-that JCEs occur at a fixed rate when offspring are within a fixed distance of a conspecific tree. Using a theoretical model, I show that the functional form of JCEs largely impacts their ability to maintain coexistence. If predation pressure increases additively with adult tree density and decays exponentially with distance, JCEs maintain considerably higher species richness than predicted by recent models. Loosely parameterising the model with data from a Panamanian tree community, I elucidate the conditions under which JCEs are capable of maintaining high species richness., (© 2022 The Authors. Ecology Letters published by John Wiley & Sons Ltd.)

Published
2022
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