Influence of biotic and abiotic factors on the population ecology of the spiny spider Micrathena nigrichelis (Araneidae)

• Grant number: 24/13109-5
• Support Opportunities: Scholarships in Brazil - Master
• Start date: December 01, 2024
• End date: November 30, 2026
• Field of knowledge: Biological Sciences - Ecology - Theoretical Ecology
• Principal Investigator: João Vasconcellos Neto
• Grantee: Lílian de Andrade Santiago
• Host Institution: Instituto de Biologia (IB). Universidade Estadual de Campinas (UNICAMP). Campinas , SP, Brazil

Abstract

Understanding how intrinsic and extrinsic variables of abiotic and biotic nature influence the population variability of species helps to understand the mechanisms underlying population dynamics. Spiders are considered excellent model organisms for population studies, mainly due to their high diversity, abundance, wide distribution and important role within terrestrial ecosystems. Therefore, our study aims to describe the population variability and phenology of the orbitella spider Micrathena nigrichelis (Araneidae), correlating the variation in the number of individuals and the age structure of the spiders over time with climatic variables and prey availability. We hypothesize that the population density of M. nigrichelis is greater in periods of higher temperatures and precipitation, when there is also greater availability of food resources (e.g. flying insects). Furthermore, we will investigate whether the distribution of the species occurs randomly in the environment or whether spiders occur more frequently in a specific microhabitat. We expect that the distribution of M. nigrichelis is not random, with a higher frequency of spiders on host plants that share specific structures and architecture, with sufficient space for the anchoring of the web's supporting threads. To test our hypotheses, we will carry out monthly data collections in Serra do Japi (Jundiaí, São Paulo, Brazil) for two years, in which we will count the number of individuals of the species and classify each spider based on its developmental stage. Additionally, we will compare the frequencies of food resources available in the environment with the frequencies of prey actually consumed by spiders. Finally, we will carry out a similar methodology regarding habitat selection, comparing the frequencies of species and plant architectures available in the environment with the frequencies of plants occupied by spiders. With this project, we intend to advance knowledge about population ecology and reveal how biotic and environmental mechanisms can modulate spider population fluctuations in neotropical forests.