Research

We are primarily interested in how plant population dynamics respond to chronic anthropogenic disturbance, and the mediating role played by a/biotic drivers. Most of the systems we study are affected by humans. Studying these plant-human interactions is critical to our understanding of and ability to project the nature and intensity of future interactions and their biological consequences. This interdisciplinary approach is at the core of modern ecology and conservation biology. We now learn that in tropical regions, most systems that are previously considered as pristine have been disturbed in the past by humans. Therefore, we can study these systems without considering the role of human and the drivers of local ecological knowledge. Our research is focused on most common conservation biology problems: harvest, fire, deforestation and fragmentation, invasive species, and rare endemic species. Our study sites are in Africa, the Pacific, and Latin America. We investigate the ecological implications of wild plants harvest with a particular emphasis on the role of stochasticity in environmental conditions and in harvesters' behavior on the transient and long-term responses of plant populations. In West Africa, we are investigating the response of a tree species (Pentadesma butyraceae) with clonal and sexual reproduction to disturbance in fragmented ecosystems. We are also exploring the effects of anthropogenic activities on tritrophic interactions and potential trade-offs between chemical and biological defenses on African mahogany. In Hawaii, we are investigating the effects of multiple stressors on the dynamics and viability of endangered plants (Cyrtandra dentata, Schiedea obovata), and the effects of forest fragmentation and NTFP harvest on plant population dynamics. Our ethnoecology research focuses on the dynamics of local ecological knowledge of patterns and processes in ecology.

Anthropogenic influence on plant-ant interactions and chemical defense

Plant chemical/physical defense and plant-insect mutualism are strategies by which plants can respond to herbivory or biomass damage. The allocation of resources to chemical defense may be favored in high quality environments and mutualism is expected to be more frequent in low quality environments. We are using the Khaya-Fulani system in West Africa, to investigate the effect of human disturbance (foliage harvest by Fulani) and environmental quality (soil fertility, moisture, rainfall) on plant-ant mutualism. Khaya senegalensis is colonized by weaver ants which control the populations of shoot borer (Hypsipyla robusta). K. senegalensis has also developed chemical defenses locally recognized by indigenous people from the bitterness of its leaves and bark. As a result the bark is harvested for traditional medicine. The foliage serves as fodder-medicine for Fulani cattle during critical dry season. We are testing how foliage harvesting by the Fulani and differences in habitat quality affect the trade-offs between chemical and biological defense and how this varies with ontogeny. We are investigating how harvesting affect the dynamics of Khaya and its interactions weaver ant and shoot borer.

Can clonal reproduction successfully compensate the short- and long term cost of disturbance?

Some plants can reproduce asexually (clonal production) as well as sexually (production of fruits/seeds). This includes several wild plants whose organs (e.g., fruits, leaves, bark, roots) are harvested as non-timber forest products. The direct energy cost of asexual reproduction is often lower than that of sexual reproduction. However, the long-term consequences of asexual reproduction on populations' ability to withstand environmental stochasticity are expected to be greater. The genetic 'homogenization' caused by high allocation to asexual reproduction can lead to reduced population fitness and stability. Given that it is easier to produce clonal than seeds, it is expected that in stressful conditions, plants that can reproduce via seeds and clonal would allocate more resources to clonal reproduction. It is unclear how does habitat fragmentation mediate this response; and the short- and long-term consequences on population dynamics are also poorly understood. We are investigating if and how clonal reproduction buffers the combined effects of fruits harvesting and reduction in habitat size on Pentadesma butyracea (Clusiaceae).

Ethnobiology : How does who you know shape what you know and what you do?

Theories in ethnobiology suggest that local people have extensive ecological knowledge of their environment and they use this knowledge to adapt to environmental changes. We seek to directly test these theories by using hypothesis-driven ethnographic research to understand how local people acquire and transmit knowledge and how they use this knowledge. I am interested in the dynamics of local ecological knowledge (what you know) and how it is shaped by the characteristics of the social network (who you know) at the individual, village and community levels. I am particularly interested in local knowledge about biological processes (e.g., plant response to perturbation, mechanisms of adaptation to perturbation) and how ecological knowledge is used (or not used) in decision-making and to develop and implement management practices (what you do) that are sustainable (or not). I borrow tools from ecology, applied mathematics and econometrics to test simple hypotheses about the drivers and dynamics local ecological knowledge.