Research

 RESEARCH AREAS

Agroecology: herbivores and natural enemies                                                                   

How do arthropods respond to habitat vegetation structure, composition, and spatial scale? These questions are central to understanding both basic and applied aspects of many plant-animal interactions, and serve nicely as a starting point for developing sustainable methods in organic farming as well as laying the groundwork for bridging small organic production with larger scale IPM-based agriculture. I use a combination of field experiments and mathematical models to explore how  increased vegetation diversity (e.g., intercropping/trap-cropping) and other interventions may be deployed across spatial scales to manage crop pest populations. I am also interested in the compatibility of biological control and pesticide use (see Ecotoxicology research below). My fieldwork approaches include working with farmers to explore sustainability in commercial crop systems, as well as conducting manipulative field experiments. Furthermore, I explore population dynamics and herbivore/natural enemy movement behavior using models parameterized with life history traits and dispersal measurements. In the past few years I have collaborated with colleagues from the Swedish University of Agricultural Sciences (SLU) addressing these issues in the context of food web ecology as part of their Ecosystem Services Research team. More recently, I have been collaborating with Dr. Amanda Laubmeier (Texas Tech) in developing models of insect mobility and farm spatial scale, and with Annabel Meade and Natalie Cody (NC State University) and colleagues at UC Riverside modelling biological control of glassy-winged sharp shooter (Homalodisca vitripennis) on unsprayed citrus over a ten-year period in southern California.

Ecotoxicology/ Risk assessment/ Population dynamics modeling     

The effects of toxicants such as pesticides on both target and non-target organisms have historically been studied with little consideration of ecological factors such as population age-structure and sublethal effects.  Together with Dr. John Stark, an environmental  toxicologist from Washington State University (where I am also an Adjunct Faculty member in the Department of Entomology), I have been working on evaluating methodologies used in toxicological risk assessment. In particular, we have been examining the merits of considering  population-level endpoints  (as opposed to more traditional approaches such as use of the LC50) in determining the effects of pesticides and other contaminants on biological populations and communities.  In addition to conducting lab and field experiments, we have an ongoing collaboration with mathematicians from North Carolina State University, exploring the use of different mathematical models to  describe population dynamics in risk assessment data. Most recently we have been exploring how bumble bee populations are affected by pesticide exposure.

More generally, I am interested in how factors such as competition and disturbance interact with life history traits to affect population dynamics for a variety of organisms, with a focus on applications to agriculture and conservation.  I have a long-term collaboration with colleagues at Washington State University, the University of Louisiana at Lafayette, and USDA-ARS Hilo to better understand how the use of common species as surrogates in risk assessment may mislead us in our efforts to protect beneficial or rare/endangered species in both natural and managed systems.

Tropical ecology        

    Biological control of mango pests in Senegal

In 2018 I began collaborating with colleagues in Senegal, USDA-ARS in Hilo, and North Carolina State University on a project aiming to control the spread of B. dorsalis, a recently introduced tephritid fruit fly pest of mango in Senegal. Following releases of a parasitoid wasp biocontrol agent (Fopius arisanus)  that has proven effective against B. dorsalis in other parts of the world, we are using field data to parameterize models that explore how environmental and other factors affect the efficacy of biocontrol in different regions of Senegal. 

  Coffee & biodiversity

Starting in 2007,  I embarked on a five-year collaborative project with scientists from Earthwatch Institute and Coopetarrazú, a coffee grower cooperative in the Tarrazú region of Costa Rica aimed at better understanding how farmer practices influence coffee yields and quality as well as environmental health.  There I worked with undergraduate and graduate students  along with colleagues from the Earthwatch Institute and local Costa Rican scientists to analyze the effects of varying levels of herbicide, fertilizer, density of shade trees, and other practices on coffee plant yields and farm condition/characteristics. As part of this effort, we compared arthropod biodiversity across a wide range of coffee grower practices and landscape characteristics. Most recently we focused on the role that forest fragments have on pollinator populations and coffee yields, working in the spring and summer with teams of Earthwatch citizen-scientist volunteers to collect data.

Farms, forests, & biodiversity

How are agricultural and forested areas linked, and what do land use decisions mean for biodiversity conservation in the tropics? Together with undergraduate research assistants,  for the past 20 years I have been sampling arthropod diversity in farmland and forest habitats as well as nearby  La Cangreja National Park in and around the rural farming village of Mastatal, near Santiago de Puriscal, Costa Rica, a few hours west and south of San Jose.  I'm particularly interested in the relationship between forest condition and arthropod diversity, and how how land use affects and possibly provides benefits (ecosystem services) to both habitats. By comparing arthropod diversity across habitats, we hope to better understand the role different habitats in landscapes traditionally regarded as "marginal" (such as agroecosystems) may play in terms of both production and conservation. Some of our data from Mastatal have been incorporated into a large international database project (PREDICTS) linking biodiversity with land use. More recently, I have been working with teams of CSU students to compare biodiversity in agricultural and forest habitats, revisiting sites that we sampled 20 years ago.

Birds, arthropods, and elephants

The past decade I have been exploring the link between a suite of endangered bird species (most of which are insectivorous) and their arthropod prey in East Africa. My first project there concerned the distribution of a Near-Threatened Afrotropical thrush, the East Coast Akalat (Sheppardia gunningi), and its prey in the Arabuko-Sokoke Forest in coastal Kenya.  Working with Colin Jackson, a local ornithologist at the Mwamba Field Study Centre and Bird Observatory in Watamu, University of Washington undergraduates, and colleagues from ICIPE and National Museums of Kenya, we compared the spatial distributions of the insectivorous Akalat with arthropod diversity in different habitat types within Arabuko-Sokoke  (the UW Columns magazine featured this work in one of their stories in 2010).  More generally, I'm interested in how disturbance caused by African elephants (Loxodonta africana) and others species within a managed reserve may influence distributions and abundance of both birds and arthropods -- see our latest (2017) publication on bird diversity in Arabuko. I'm currently working with recently graduated CSUMB student Liz Reyes-Gallegos on data collected from Gede National Monument; we published a 2019 entry on arthropod diversity data collected in the Kenyan coastal area to the Global Biodiversity Information Facility (GBIF). More recently, we have worked with colleagues at the National Museums of Kenya on a paper describing the effects of habitat restoration on arthropod biodiversity in Gede, Kenya, which was published in Spring 2022.

Elsewhere, I have been collaborating with David MacFarlane (Michigan State University) assessing the restoration efforts in Gede Ruins National Monument. Working in a forest that was planted with native trees some twenty years ago, we are looking at how plant, arthropod, and bird populations have recovered relative to nearby reference sites - and how different planting techniques (e.g., direct seeding, natural regeneration, etc.) have fared.  Read a summary of our 2015 paper about this work.