Ecological Context Shapes Resistance Selection Under Antibiotic Pollution

Anthropogenic activities such as pharmaceutical manufacturing, antibiotic use, and waste disposal have increased environmental antibiotic contamination, exposing natural microbial communities to concentrations ranging from sub-inhibitory to strongly selective levels. While antibiotic pollution is widely assumed to promote antimicrobial resistance (AMR), the ecological conditions under which environmental exposure leads to measurable community-level selection remain poorly understood. Here, we integrate eco-evolutionary principles with measured environmental antibiotic concentrations to examine how ecological context shapes the emergence, maintenance, and spread of resistance across environments. We discuss how environmental conditions modulate mutation, horizontal gene transfer, fitness costs, epistasis, and compensatory evolution under antibiotic exposure, and how microbial interactions can either buffer or amplify resistance selection within communities. We further examine how co-selection, environmental heterogeneity, antibiotic degradation products, and alternative ecological functions of antibiotics influence resistance dynamics. Together, these observations support the view that resistance selection thresholds are not fixed concentrations, but ecologically dependent properties shaped by environmental conditions, community composition, and microbial interactions.