Zooplankton co-occurrence patterns in Amazon lotic systems along a forest cover gradient

Anthropic activities are expected to change species co-occurrence by altering niche availability and biotic interactions, which affects ecosystem functioning. We investigated the non-random co-occurrences of zooplankton species, which species have positive and negative co-occurrences, and which environmental factors (local and landscape) influence the species distribution and co-occurrences in Amazon lotic systems. We expected that variables related to intense changes in the landscape would influence species distribution and reduce positive and negative co-occurrences, increasing random associations. Our study was conducted in a river and twelve first- and second-order streams across three periods in the Amazon region of Brazil. We sampled zooplankton and physical and chemical variables and determined forest cover around the sampling sites. Co-occurrences were determined by probabilistic models. Total suspended solids, pH, and ammonium were the variables shaping zooplankton distribution. We observed 43 positive and six negative co-occurrences. Ammonium increased positive and negative co-occurrences and suspended solids decreased these associations. Our study provides insights into how environmental factors can alter niche availability and biotic interactions leading to different patterns of zooplankton co-occurrence in Amazon systems. This is the first study investigating such relationships in Amazon lotic systems and can help to understand risks to biodiversity and plan conservation strategies.