We are interested in understanding how environmental variation modulates developmental processes and resulting phenotypic variation. As a study system, we focus on the C. elegans germline, a molecularly well-tractable system that shows a high degree of environmental sensitivity. We have characterized how germline proliferation and differentiation as well as resulting reproductive output are modified in animals exposed to various experimental conditions mimicking ecologically relevant environments. Here we present how one specific environment – high temperature exposure (27°C) - affects germline and reproductive properties. In addition to previously reported deleterious effects on sperm function and fertility, we found that high temperature significantly impacts germline proliferation and differentiation, apparently through modifications of Distal Tip Cell (DTC) morphology and signalling through the Delta/Notch pathway controlling germline proliferation. We are now using this experimental paradigm to explore how environmental factors impact the C. elegans germ stem cell niche and how germline integrity is maintained in variable environments.