Temperature and nutrients drive complex eco-phenotypic dynamics in a microbial food web

Abstract

Anthropogenic increases in temperature and nutrient loads will likely impact food web structure and stability. Though their independent effects have been well studied, their joint effects— particularly on coupled ecological and phenotypic dynamics—remain poorly understood. Here we experimentally manipulated temperature and nutrient levels in microbial food webs and used time-series analysis to quantify the strength and causality of reciprocal effects between ecological and phenotypic dynamics across species. We found that i) temperature and nutrients have more complex effects on ecological dynamics at higher trophic levels, ii) temperature and nutrients interact antagonistically to shift the relative strength of top-down vs. bottom-up control, iii) phenotypic dynamics have stronger impacts on ecological dynamics than vice versa (especially at higher temperature), and iv) rapid phenotypic change mediates observed ecological responses to changes in temperature and nutrients. Our results expose how feedbacks between ecological and phenotypic dynamics mediate food web responses to environmental change.