| Understanding the mechanisms behind adaptation to different climates is key to understanding the prevalent phenomenon of local adaptation in plants. Variation among sites in seasonal patterns of temperature and precipitation is thought to select functional strategies that work locally but not range-wide. These strategies tend to involve the concerted evolution of suites of traits including life history, acquisition and allocation resources. I studied adaptive differentiation due to climate in Arabidopsis thaliana. I examine natural genetic variation in this genome-sequenced species, because it provides insight into the functional ecology of annual plants generally, while providing context for future research on adaptation genetics. I investigated plants collected along an altitudinal gradient where hot, dry low contrasts cold, wet high elevation climates. Heating and drying in a growth chamber during reproduction favored plants from low elevations where conditions are most similar to the experiment. I found that stress avoidance traits like earlier flowering and faster fruit ripening were advantageous in this setting. Subsequently, I focused on how variation in the lifespan-dependent balance between carbon income and investment adapt plants across the climate gradient. Leaves generally fall along a continuum between short lives with rapid photosynthesis and long lives with slow photosynthesis, a pattern known as the worldwide leaf economic spectrum. Under seasonal hot, dry growth chamber conditions simulating low elevation climate, I demonstrated for the first time natural variation in an economic spectrum at the rosette level. Low elevation plants had short-lived economies compared to plants from colder, wetter locations. I then considered the whole plant including photosynthetic inflorescences, which were previously ignored. I discovered that earlier flowering led to a majority of the whole plant economy depending on the contribution of the inflorescence. Plants as a whole exhibited the same trade-offs observed at lower levels of organization, with inflorescence-centric life adapting plants for avoidance of spring stress. My work supports the general hypothesis that avoidance of stress at low elevation, which requires a fast life, is traded off with a strategy of delay and tolerance associated with winter in high altitude populations, leading to local adaptation. |
