Intraspecific morphological variation across climatic gradients in cloud forest epiphytes


The purpose of this trip was to carry out preliminary fieldwork for a project focused on understanding the functional morphology of cloud forest epiphytes. Cloud forest is a unique forest type that occurs on tropical mountains, where the daily upslope flow of moist air drives the formation of clouds at a certain elevation, above which the forest is regularly immersed in clouds. This radically alters forest climate by reducing solar radiation, evaporation, and temperature and depositing mist onto the leaves. The mist thus deposited makes these forests especially hospitable to many species of epiphytes, which are plants that grow on the limbs and trunks of trees, far above the soils of the forest floor. We believe that climate change is changing the dynamics of montane cloud formation, pushing the clouds higher upslope and drying out cloud forests. The long-term implications of this, especially for the atmospherically dependent epiphytes that are highly adapted to procuring and preserving airborne water, are uncertain. I collected nail polish leaf impressions from a handful of species of epiphytes in the Bromeliad family (relatives of the pineapple) across a wide variety of forest sites, in order to quantify the variation in the microscopic leaf-surface traits (trichomes and stomates) responsible for managing water relations in these plants and to assess its relation to the climatic variation across these sites. RESULTS HERE. These results suggest that IMPLICATIONS HERE. Furthermore, my field observations this summer suggest that the climatology of cloud immersion (and the other factors it influences, e.g. solar radiation, evapotranspiration, temperature) is extremely variable in tropical mountains, with major implications for the evolution (what species arose were in the past), distribution (what species live where now), and conservation (how species might persist, adapt, or move in the future) of tropical montane biodiversity. I hope that in my future work, and that of others, we can continue to document the distributions and adaptations of cloud forest vegetative communities and the complex montane climatologies that circumscribe them.

Drew Hart
Publication date: 
August 18, 2017
Publication type: 
Student Research