ABSTRACT

Several studies have proposed that a group of morpho-functional traits are key factors in determining the ecological strategy of plant species. Among these, five leaf morpho-functional traits are considered to be relevant in determining a plant's ecological strategy: leaf length, width, thickness, area, and specific leaf area (SLA). Here, I studied the variation in leaf functional traits within and between species of two genera of understory shrubs commonly found in the tropical rain forests of Costa Rica. In addition, I examined how these traits varied in two different light environments: forest-covered and full-light. I hypothesized that light availability has a direct impact on leaf functional traits and that the response of each genus is independent of the other. Leaves from Miconia and Piper species were collected in both forest-covered and full-light environments along two trails located in Alberto Manuel Brenes Biological Reserve, Costa Rica. Leaf length (F1,163=5.51, p=0.0201), leaf weight (F1,163=4.82, p=0.0296), and leaf area (F1,163=6.24, p=0.0135) varied significantly between genera and environment. Leaf length (F1,163=4.42, p=0.0370) and surface leaf weight (F1,163=4.59, p= 0.0336) varied significantly between forest-covered and full-light environments for both genera. Overall, the results show that leaf functional traits can vary as a result of phenotypic plasticity to varying amounts of light. Variance in other abiotic conditions, such as soil type and water availability may also have similar effects on phenological variation between different functional traits in plant communities of different environments.

Key Words: Functional trait, Piper, Miconia, Costa Rica, plasticity, light availability, abiotic