Climate change is altering ecosystems at multiple scales. Globally, warming temperatures and increasing irregularity of precipitation will have large scale impacts on species distribution and success. Locally, understanding species response to fine scale microhabitat variation can provide key insights into population adaptation. Non-native plants represent an opportunity to investigate population level response and adaptation to relatively novel combinations of biotic and abiotic environments. Subalpine meadows are at the intersection of biotic and abiotic change, as large-scale climatic shifts alter water and temperature regimes and species range shifts become increasingly common and larger in scale. This dissertation addresses these questions of biological change and local adaptation through field and greenhouse studies on the plant Thlaspi arvense (Brassicaceae) in the Rocky Mountains of Colorado, USA. Thlaspi arvense is a non-native mustard plant that is becoming more prevalent in subalpine meadows, where biological invasions have been relatively. In the subalpine ecosystems of the Rocky Mountains, climate change is predicted to fluctuate precipitation, alter snowmelt timing, vi and increase disturbance regimes. These factors can exert selection pressure to adapt to new conditions, and/or lead to a shift in the spatial distribution of plant species and communities. T. arvense produces secondary chemicals called glucosinolates, which can alter soil microbial composition, impede the growth of neighboring plants, and deter herbivory. The continued expansion of T. arvense into the Rocky Mountains poses a threat to native subalpine ecosystems but is also an opportunity to study the interface between microevolution and ecology of this species as it spreads across a changing landscape. We surveyed ten subalpine meadow sites over a three year span and conducted common garden experiments with two populations of T. arvense to investigate population adaptation and divergence of morphology and phytochemical production. We found evidence of directional selection at early snowmelt sites in the field, morphological differences between populations in a common garden, and significant increase of glucosinolate production in response to water limitation in the greenhouse. These results indicate that T. arvense is adapting to microsite variation in subalpine meadows and may retain the ability to upregulate glucosinolate production in response to stress across populations