Investigating spatiotemporal patterns, spatial density dependence and fruit quality in a plant-bruchine-parasitoids system

Author(s)

Rossi, Marcelo N. ; Rodrigues, Ligia M. S.

• Document type: Journal article
• Source: ECOSCIENCE; v. N/A, p. 17-pg., 2023-07-22.

Abstract

Many of the spatial patterns observed in nature are governed by interactions between species and between species and their environment, providing valuable information about which processes are determinants in shaping ecological communities. In a system composed of Mimosa bimucronata, the bruchine Acanthoscelides schrankie and its parasitoids, we examined the spatial distribution patterns of these insects and fruit quality. We tested the hypothesis that an aggregate pattern of parasitism is predominant, characterizing a direct density-dependent pattern. Because nitrogen, water, and phenols are crucial fruit traits that can affect the fitness of many insects, we also tested the hypothesis that the spatial distribution of A. schrankie and its parasitoids is positively associated with water and nitrogen content in the fruits and negatively associated (i.e., dissociation) with phenols. The distribution of bruchine and its parasitoids varied over time, from random to aggregated. The spatial patterns of parasitism varied between direct density dependence, inverse density dependence, and density independence. Dissociations were found between the abundance of A. schrankiae and the phenolic content, and similar results were found for the parasitoids. Our results suggest that a combination of bottom-up and top-down effects may drive spatiotemporal dynamics between A. schrankiae and its parasitoids. ResumePlusieurs des patrons spatiaux observes dans la nature sont regis par des interactions entre les especes et entre les especes et l'environnement, ce qui fournit de l'information utile sur les processus importants dans la structuration des communautes ecologiques. Dans un systeme compose de Mimosa bimucronata, de la bruche Acanthoscelides schrankie et de ses parasitoides, nous avons etudie les patrons de repartition spatiale des insectes et de la qualite des fruits. Nous avons teste l'hypothese de predominance d'un patron agrege de parasitisme indiquant une dependance directe a la densite. Puisque l'azote, l'eau et les phenols sont d'importants traits des fruits qui peuvent influencer l'aptitude de plusieurs insectes, nous avons aussi teste l'hypothese selon laquelle la repartition de A. schrankie et de ses parasitoides est positivement associee au contenu en eau et en azote des fruits, et negativement associee (dissociation) au contenu en phenols. La repartition de la bruche et de ses parasitoides variait dans le temps, d'aleatoire a agregee. Le patron spatial de parasitisme variait entre la dependance directe a la densite, la dependance inverse a la densite, et la non-dependance a la densite. La dissociation a ete observee entre l'abondance de A. schrankiae et de ses parasitoides et le contenu en phenols. Nos resultats suggerent qu'une combinaison d'effets ascendants et descendants pourrait expliquer la dynamique spatiale de A. schrankiae et de ses parasitoides. (AU)