Do community and food-web metrics temporally change in tropical systems? Responses from a four-trophic level food web

Abstract

Most research reports changes in biological communities and environmental stability by using community estimators (e.g. species richness and relative abundance) and food-web metrics (e.g. connectance and vulnerability), yet only a few studies have examined how both community and food-web estimators temporally change in tropical terrestrial environments. Here, we sampled 1399 fruits and 12,647 seeds from the climbing shrub Senegalia tenuifolia (Fabaceae: Mimosoideae) across eight fragments in three areas of Brazilian savannah sampled annually during 4 years to assess the temporal variation within community and food-web metrics commonly used in the tropical research. While resource availability and the abundance of insects from the second and third trophic levels changed with time, species richness from all trophic levels and food-web metrics remained temporally stable. We found that α-diversity was the most important diversity-component influencing the herbivore communities when partitioning the diversity using raw species richness and the Shannon entropy, while for parasitoids the contributions of α and ß varied. These findings provide insights into the temporal variation of terrestrial food webs, while highlighting the need for further research considering both community metrics and food-web estimators to better understand the stability of tropical environments. We bring empirical evidence that communities within plant–herbivore–parasitoid networks may be dynamic, but food-web metrics are likely to remain temporally stable within undisturbed environments.