Tropical endophytes

Endophytic fungi, or endophytes, colonize roots or aboveground plant tissues and in some cases protect plants from pathogens and herbivores. We are studying how leaf traits influence endophyte colonization and community structure. We have also been exploring fascinating interactions among leaf-cutting ants, their fungal cultivar, and the diverse endophytic fungi that arrive at the ant’s nest in the leaves they cut. Here we are focusing on the intersection of two fungal mutualisms, one between the host plant and the foliar endophyte, and the other between the ants and their fungal cultivar. We have demonstrated that ants choose to cut leaf material with low relative to high endophyte densities, suggesting a host plant benefit for harboring endophytes. Leaf-cutting ants thrive in areas where land is cleared for human use, and the ants cause US $1 billion in damage annually for crop and timber production. This study could lead to environmentally friendly forms of biological control (specifically endophyte applications to crops or to ant colonies) that would lessen the economic impact of these ants. Please read more about our project here: (Tropical endophytes)

Coastal grasses

Can endophytic bacteria and fungi be used to increase the health and vigor of coastal grasses? Sea-level rise is a worldwide problem and is particularly severe in Louisiana and the Gulf region. One of the most important mechanisms for maintaining elevation is the contribution of below-ground plant growth to soil formation, which depends heavily on microbial activity. We are characterizing the fungi and bacteria that live in association with the roots and above-ground plant parts of Spartina alterniflora, an important salt marsh species in Louisiana. Our objective is to compare the microbial communities in natural, degraded and restored wetlands. This will provide baseline information on the microbiome changes in this essential plant under various levels of stress, and may lead to using endophytes as restoration tools in the future. You can read more about our projects here: (Oily soil website)

Baldcypress

How do endophytic bacteria and fungi increase the stress resilience of baldcypress trees as increasing salinity degrades coastal marshes? The Mississippi River Delta is experiencing some of the highest rates of sea-level rise in the U.S. and in most of the rest of the world. Sea level rise, combined with fewer pulses of freshwater from the Mississippi River, is resulting in formerly freshwater areas becoming brackish. Taxodium distichum (baldcypress) is a key species for wetland restoration efforts in the Mississippi Delta region, because the trees are moderately salt tolerant relative to other tree species. Cypress swamps throughout SE Louisiana, however, are becoming degraded and turning into marsh and open water. When this occurs, establishment of new trees is particularly difficult due to increased salinity and inundation stress. There is evidence that plant responses to environmental stressors of salt and inundation can be facilitated by endophytes. Little is known, however, about the role of endophytes in wetland trees. Because cypress restoration efforts are costly and their success has been mixed, it is crucial to understand how and if symbionts are contributing to success or failure of plant establishment and performance.

Sustainability

How can we use fungal symbionts in tropical agriculture and biofuel production? We have studied the endophytes of cacao, rice, yuca (cassava), cucumber and jatropha, a biofuel crop. We are especially turning our interest to jatropha because it is currently being planted throuhgout the tropics. Jatropha has the potential to advance developing nations by providing energy, and enabling remediation of deforested landscapes. Jatropha can help alleviate poverty because the plant can be harvested and processed by small-scale farmers on the farm for immediate use as a cooking fuel. Besides the benefits of oil production, jatropha offers additional ecological benefits. As a perennial shrub it stores carbon and may mitigate climate change. Plantings also prevent erosion and promote soil regeneration in lands heavily impacted by human use. Our research in Panama represents some of the first steps toward understanding the ecology and microbial ecology of jatropha in its native range.

Biodiversity

How do different land-use practices support the conservation of tropical biodiversity? The Agua Salud Ecosystem Services Project uses the Panama Canal’s central role in world commerce to focus global attention on Carbon storage, clean water, and biodiversity conservation (http://www.ctfs.si.edu/aguasalud/). Broadly, the project will quantify the effect of different land uses on (1) water quality, quantity, and temporal distribution; (2) Carbon storage; and (3) biodiversity. Specifically, our lab is involved in quantifying the biodiversity and evaluating the ecosystem services of birds and insects in the various land-use types. Two focal research catchments within the Canal Watershed have been planted with different mixes of native and non-native timber species, and two control catchments (one with forest preserve and one with degraded agricultural land) allow for comparisons of ecosystem services under different land uses. Cattle are currently being raised using slash-and-burn methods as well as other unsustainable techniques throughout Latin America. We are interested in the development of sustainable cattle grazing practices, or intensive silvopastoral systems. We have begun documenting the value of sustainable cattle pastures for biodiversity conservation. Our focus is on birds, which due to their bright colors and high diversity in Central America, receive a lot of attention from humans, especially tourists. Our project compares bird communities in sustainable cattle farms, traditional slash-and-burn farms, and nearby forest fragments.