Greg Gilbert, Ingrid Parker, and Megan Saunders.
Locally rare species are expected to have a survival advantage over more abundant species, because rarity reduces their risk of damage from pathogens. This "rare-species advantage" may help maintain plant diversity in natural systems and explain how introduced plant species become invasive weeds. Usually, a plant species is considered rare if few individuals of that species are present; this assumes that pathogens are specialized on individual species. In fact, most pathogens are able to infect a variety of different hosts. Which hosts are susceptible is not a random assortment of species, because closely related species are more likely to share a pathogen than are more distantly related species. This means that rarity is not simply a function of species density (numerical rarity), but of the combined density of all species with which it shares a pathogen. A species with no closely related neighbors has the added benefit of "phylogenetic rarity". We are evaluating the relative importance of phylogeny and abundance in the rare-species advantage of plants in seven plant communities along the Central Coast of California. We will measure disease on different plant species, the host ranges of the responsible pathogens, and the ability of the pathogens to reproduce on different hosts. These results will be compared to the local host abundance and the relatedness between host species, in the first attempt to evaluate how the overall structure of a plant community affects the amount of disease suffered by each species in the community. (NSF DEB-084259)    related pubs...

Greg Gilbert and lots of other people.
The UCSC-FERP is a 6-ha mapped forest plot in Mediterranean-climate, mixed-evergreen coastal forest in the Santa Cruz mountains, along the Central Coast of California, USA.  Located in the Campus Natural Reserve on the University of California Santa Cruz Campus, it is both part of an extensive area of protected forest habitat and just a short walk or drive from the UCSC laboratories and classrooms.  It is meant to foster research and inquiry-based teaching about ecology and evolutionary biology in a changing world.  In 2007, the Gilbert lab (with support from NSF DEB-0515520) tagged, mapped, measured, and identified all the trees, shrubs, and vines on the plot that had a stem diameter larger than 1 cm.  We followed the standardized protocol established by CTFS to allow direct comparison to the established network of mapped plots.  Among the 8,180 woody individuals the 6 ha (~15 acres) UCSC-FERP, we found 31 woody species from 27 genera and 18 families. To facilitate research on the plot, we maintain grid-based biological and environmental monitoring programs that include litter-fall traps, micrometeorological stations, soil moisture, canopy openness, soil nutrients, and bird, small-mammal, and mushroom survey.  We welcome collaborating researchers from UCSC and elsewhere to use the plot for non-destructive research that complements ongoing efforts. See the UCSC FERP link for more information. (NSF DEB-0515520, DEB-084259, UCSC)    related pubs...

Greg Gilbert, Cam Webb, and Karen Garrett.
Some plant pathogens cause destructive epidemics in natural plant communities, but many others have limited impacts, or can even act as important agents in maintaining structure and diversity in species-rich plant communities. Predicting the spread and impacts of a particular plant pathogen depends on understanding the range of plant species it can infect as well as the spatial arrangement and abundance of host species in the landscape. Here we will work in both the moist tropical forest of lowland Panama and the mixed temperate forest on the central coast of California to examine how the composition and spatial patterns of plant species in the forest affects the potential for disease spread in high- and low-diversity plant communities. Through a series of cross inoculations we will measure directly the potential for pathogens to be shared among hosts that are evolutionarily closely or more distantly related. Using a spatially-explicit epidemiological simulation model, we will couple these empirical estimates of host range with the known spatial pattern of tree species in mapped plots in the forests, to examine the likelihood of spread through forest communities of pathogens with different life histories and different host breadths. The results of this research will inform issues of forest management, plant pest quarantine, and a basic understanding of the importance of host range in plant-pathogen interactions in natural communities. (NSF DEB-0515520)   related pubs...

Ingrid Parker and Greg Gilbert
In a long-term collaboration with Dr. Ingrid M. Parker (Dept. of Ecology and Evolutionary Biology, UCSC) and others, we are examining the role of pathogens and herbivores in regulating whether introduced plants become invasive weeds. We are evaluating two hypotheses central to invasion biology: The Escape from Natural Enemies Hypothesis (where plants become weeds when introduced to a new locale by escaping the natural enemies that kept their populations in check in their native range), and the Biotic Resistance Hypothesis (where introduced plants are unable to invade natural communities because they are particularly susceptible to the newly encountered pathogens and pests to which they are naïve). Additionally, we use greenhouse and laboratory experiments to evaluate how rapidly novel host-pathogen interactions change in virulence. Experimental work has been based primarily at the Bodega Marine Reserve and Laboratory, focused on a suite of 18 native and introduced clover species (Trifolium and Medicago) in the California coastal prairie. (NSF DEB-9806517, DEB-0096298)   related pubs...

Greg Gilbert, Ingrid Parker, Edgardo Soo, Nigel Harrison, and John Rogers
This long-term project focuses on the large-scale epidemiology of an emergent disease of coconut, "Porroca" or Little Leaf, that has spread rapidly across Panama, with potentially devastating impacts on the economy of the Kuna Indians, the principal indigenous community of the Caribbean coast of the isthmus. Since 1998 we have conducted regular surveys of more than 200,000 coconut palms in Panama and the Comarca of Kuna Yala. Ultimately, this project is aimed at helping to solve a potentially devastating socioeconomic problem for the Kuna community, with ongoing community-based experiments for control of the disease. Additionally, the project will contribute toward models for the spread of invasive new diseases across the landscape. Collaborative work with Nigel Harrison points to a Stolbur-group phytoplasma as the cause of the disease, and we are working to elucidate the basic biology of the disease and seek control options. This research is a collaboration with Kuna project coordinator Edgardo Soo, and the Kuna General Congress. This project also produced the first complete map of the more than 300 islands in the comarca of Kuna Yala. (Jane Carver Foundation) related pubs...

Greg Gilbert, Don Reynolds, Astrid Ferrer, and many more
I have a long-term interest in trying to understand what controls the diversity, composition, and structure of fungal (and bacterial) communities. I've taken a variety of approaches to teasing out the relative contributions of abiotic factors, host preferences, and dispersal limitation in shaping fungal communities. Most of the work has been with wood-decay polypore fungi, epifoliar fungi, foliar endophytes, and rhizosphere bacteria. Most of this work has been in moist tropical forests and mangrove forests, with studies in Panama, Costa Rica, Australia, and Micronesia. I've been particularly interested in how fungal communities vary vertically in the forests, and so a number of studies have employed canopy access cranes. This work is being extended to comparative work in California forests. (STRI, Mellon Foundation)    related pubs...

Greg Gilbert, Bárbara Ayala, Kyle Harms, Devon Bradley, Jen Martiny.
Perhaps the most fundamental question in tropical ecology is "what maintains high biological diversity?" I have a long-standing interest in how plant diseases affect host population dynamics, community structure, and conservation of forest ecosystems. Much of my work has focused on investigating the impacts of endemic diseases on host fecundity, survival, and spatial distribution. Past work has included tests of the Janzen-Connell hypothesis, where diseases of juvenile trees disproportionately affect trees at high densities and near mother trees. This makes resources available for non-susceptible species and can help maintain high diversity in the forest. I continue to look at the role diseases play in structuring both high- and low-diversity tropical forests, ranging from lowland moist tropical forests to mangrove forests.  (STRI) related pubs...

Greg Gilbert, Ernesto Méndez, CenTREAD Working Group
Much of my tropical work is intended to inform better conservation practices, particuarly in a landscape of mixed land-use types. The CenTREAD Working Group on the UCSC campus regularly publishes reviews or other collaborative papers in the area of tropical ecology, agriculture, and development. (Jane Carver Foundation, Pepper-Giberson Chair)    related pubs...