Notice bibliographique
Résumé
Ecological communities are complex, and this complexity can obscure their underlying patterns and natural laws. One way to understand communities is to summarize their most important characteristics using consistent measures. Community structure is a set of measures of composition, abundance, distribution, and interaction that describe an ecological community over space and time. Trophic structure is an important aspect of community structure, and relates to energy and nutrient flow, especially the distribution of organisms across trophic levels. Trophic level is the energetic distance of an organism from the base of production – its average position in the food chains to which it belongs. Due to energetic inefficiencies, we generally predict that organisms decrease in number and biomass with trophic level, forming trophic pyramids (known as "pyramids of numbers" and "pyramids of biomass", respectively). Other, non-pyramidal trophic structures are also common, and trophic structure is affected by variables at multiple ecological scales. The objective of this thesis is to investigate determinants of trophic and community structure, including latitude, ecosystem type, biome transition, community composition, and body size. While pyramids of numbers and pyramids of biomass are well-studied, few have investigated the trophic distribution of diversity. Using a meta-analysis approach, I found that, on average, large published food webs form pyramids of species richness, with a decrease in number of species as trophic level increased. Trophic diversity structure was correlated to centrality, latitude, ecosystem type, and study identity.Community structure varies spatially, as can be seen even by a casual observer at interfaces between biomes. I studied how macroinvertebrate and soil prokaryote communities changed latitudinally along the forest-tundra biome transition in the Yukon, and how the communities responded to other environmental variables. I found that the communities differed between sites, changed along the latitudinal transect, and responded to environmental variables at multiple scales, including active layer depth, lichen cover, and road proximity. Loss of predators can have profound effects on community structure. I used an experimental approach to investigate the effect of spider assemblage composition and diversity on prey consumption. I hypothesized that diverse assemblages would consume more prey due to niche complementarity and sampling effects. I found, however, that the spiders were generalist and intraguild predators, and that the one-species assemblage consumed the most prey. Spider body size affects its trophic niche, energy requirements, and interspecific interactions, and as a result, body size mediates the relationship between spider assemblage composition and prey consumption. The body size of an organism affects how it interacts with other organisms and its biological rates. I used a meta-analytic approach to test several prediction regarding the relationship between body mass and trophic properties of terrestrial vertebrate predators: Accipitridae (hawks, eagles, and their relatives), Felidae (cats), and Serpentes (snakes). I found that the predators chose prey smaller than themselves, within a predictable mass range. Prey taxonomic diversity increased with Serpentes mass. Counter to theory, Felidae trophic level decreased with body mass, and Felidae and Accipitridae predator-prey body mass ratio increased with trophic level. We currently live in the Anthropocene, an epoch characterized by anthropogenic geological, atmospheric, and biological change. These changes are affecting community structure, which in turn is affecting human access to the benefits provided by nature. Therefore, it is important that we continue to study community structure and the variables that affect it, so that we can predict and respond to ecological change in the Anthropocene.
Récupéré en direct depuis OpenAlex et désinversé. Les résumés ne sont pas conservés dans cette base de données : les index inversés représentent 8,6 Go des 9,3 Go de texte de la base, et le serveur dispose de 13 Go libres.
Comment cette classification a été obtenuedéplier
Prédiction machine sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Le volet Gemma est une étiquette directe du modèle pour chaque travail de la base, lue sur la notice réduite au titre. Le volet Codex est un classifieur appris des 10 348 étiquettes directes de Codex et calibré sur les taux pondérés de l'échantillon; les champs sans appui suffisant ne portent aucun appel Codex. Le mode candidate est l'union des deux volets; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont pas des étiquettes humaines.
Scores du classifieur distillé par catégorie (deux têtes)
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,001 | 0,008 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,001 |
| Bibliométrie | 0,002 | 0,002 |
| Études des sciences et des technologies | 0,001 | 0,001 |
| Communication savante | 0,002 | 0,001 |
| Science ouverte | 0,000 | 0,001 |
| Intégrité de la recherche | 0,000 | 0,001 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,003 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule source (Gemma direct ou Codex distillé), pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».