Concordia University
Postdoctoral fellow candidate
Supervisor: Pedro Peres-Neto
Start: 2024-03-01
End: 2025-03-01

Project

Integrating the Top-down and Bottom-up Controls of Community Assembly
Community assembly theory investigates the mechanisms through which species from a broader pool of potential colonizers form local communities at finer spatiotemporal scales. The theory is heuristic because it reduces the large number of possible mechanisms shaping communities into a tractable number of fundamental high-level processes. However, despite its heuristic value, community assembly theory is inherently context-dependent, i.e., its predictions regarding community dynamics are only valid within specific ecological conditions. Thus, a synthetic understanding of community assembly relies on identifying a few influential ecological axes that regulate the context-dependent nature of community dynamics. In my research, I investigate community assembly along two latent ecological axes that determine the context of community dynamics. The first represents the top-down control of species pools on the membership of local communities. The second represents the bottom-up control of landscape features on species movement and interactions. By employing process-based simulation models that replicated community assembly across varied landscape structures and species pool compositions, I generated theoretical predictions about the isolated and interactive effects of both forms of control on: (i) spatiotemporal patterns in community composition; (ii) the ecological selection of prevailing life-history strategies observed in (meta)communities; (iii) the relative importance of assembly processes across space and time and throughout large-scale ecological gradients; and (iv) the trajectories of communities (towards differentiation or homogenization) in response to natural or anthropogenic disturbances. I provide empirical validation for these theoretical predictions by investigating the assembly of insect communities in distinct (bio)geographic contexts or by contrasting model predictions with empirical patterns observed in the literature. In parallel, I introduced new analytical frameworks that allowed the testing of the predictions outlined in this thesis and can be used to address other pertinent questions in community ecology. My research derives a mechanistic understanding of causal links between landscape-mediated bottom-up control, species pool-mediated top-down control, and the context-dependent nature of community assembly. Beyond its theoretical significance, this knowledge is crucial for predicting how the impact of human activities on landscapes and species pools can alter the structure, dynamics, and regulation of ecological communities

Keywords

community assembly, metacommunity, entomology, Light Pollution

Publications

1- Reciprocal inhibition and competitive hierarchy cause negative biodiversity‐ecosystem function relationships
D'Andrea, Rafael, Gabriel Khattar, Thomas Koffel, Veronica F. Frans, Leonora S. Bittleston, Catalina Cuellar‐Gempeler
2024 Ecology Letters

2- The Geography of Metacommunities: Landscape Characteristics Drive Geographic Variation in the Assembly Process through Selecting Species Pool Attributes
Khattar, Gabriel, Pedro R. Peres-Neto
2024 The American Naturalist

3- Life history traits modulate the influence of environmental stressors on biodiversity: The case of fireflies, climate and artificial light at night
Khattar, Gabriel, Stephanie Vaz, Pedro Henrique Pereira Braga, Margarete Macedo, Luiz Felipe Lima da Silveira,
2022 Diversity and Distributions

4- Determinism and stochasticity in the spatial–temporal continuum of ecological communities: the case of tropical mountains
Khattar, Gabriel, Margarete Macedo, Ricardo Monteiro, Pedro Peres‐Neto
2021 Ecography

5- Global meta-analysis of urbanization stressors on insect abundance, richness, and traits
Vaz, Stephanie, Stella Manes, Gabriel Khattar, Mariana Mendes, Luiz Silveira, Eduardo Mendes, Erimágna de Morais Rodrigues, Danielle Gama-Maia, Maria Lucia Lorini, Margarete Macedo, Paulo Cesar Paiva
2023 Science of The Total Environment

6- Natural history of the fireflies of the Serra dos Órgãos mountain range (Brazil: Rio de Janeiro) – one of the ‘hottest’ firefly spots on Earth, with a key to genera (Coleoptera: Lampyridae)
Silveira, Luiz F L, Gabriel Khattar, Stephanie Vaz, Vinicius A. Wilson, Paula M. Souto, José R. M. Mermudes, Kathrin F. Stanger-Hall, Margarete V. Macedo, Ricardo F. Monteiro
2020 Journal of Natural History