Insect Ecology @ Long Island University

    Research at the lab centers on the following question: How do anthropogenic activities influence insect populations, communities, and ultimately biodiversity and ecosystem function? Insects and related arthropods can serve as an excellent tool to measure environmental response to any number of exogenous factors. Additionally, insects are the primary drivers of a wide array of ecosystem services (e.g., pollination, biological control), and wise stewardship of insect diversity can be a means of managing ecosystems toward sustainability. Thus, the goal of our research is to identify management tools or environmental variables that can support both biological conservation and ecosystem function.
    Our field-based research is conducted in a range of managed ecosystems, including agricultural lands and highly urbanized landscapes, which are characterized by habitat fragmentation and high levels of external inputs. Robust sampling programs, high levels of taxonomic resolution, and creative statistical approaches are used to best identify patterns in insect diversity and dynamics.
    Ongoing research projects are detailed below:

    Non-target effects of insecticidal transgenic (Bt) crops
    Genetically engineered, or transgenic, crops have been rapidly adopted in U.S. agroecosystems, most often to assist in the management of insect pests and weeds. Some of these crops contain genetic sequences from the soil bacterium, Bacillus thuringiensis (Bt), which encode for the production of Cry proteins toxic to specific insect pest taxa. In maize, this includes Cry3Bb and Cry1A/c toxin, directed at corn rootworm and European corn borer, respectively. Seeds of these crops now come treated with fungicides and systemic insecticides to provide further control of pests and disease.
    Using a tiered approach, a series of experiments were conducted to examine the relative influence of Bt toxins and seed treatments on non-target ground beetle communities, as compared to conventional pest management techniques. This work has produced a series of papers, of which three are currently published in the ‘Transgenic Plants and Insects’ section of Environmental Entomology.

    Conservation of beneficial insect communities
    The lab is involved in several projects aimed at promoting diverse communities of insects that provide essential ecosystem services, such as pollination and biological control:
    1. Reduced risk IPM and beneficial insect communities. The global decline of insect pollinators, in conjunction with the dramatic losses of commercial honeybees due to Colony Collapse Disorder (CCD), has placed great emphasis on the conservation of native insect pollinators. In agricultural settings, the pollination deficit may translate into severe economic losses (pollination from honey bees is valued at over $15 billion for U.S. agriculture). Through collaboration with researchers at the Penn State Fruit Research and Extension Center, we are examining the effects of reduced risk insecticide IPM programs and landscape context on insect pollinator communities, especially native bees. Other beneficial taxa, such as spiders, hymenopterous parasitoids, and predatory mites, are also being studied.
    2. Urbanization and native bees. Habitat loss and fragmentation associated with urbanization can also threaten native bee communities. During the 2009 field season, our lab will be establishing research sites at community gardens throughout the NYC area where we will begin sampling the native bee communities. Bee abundance and diversity measures will be compared to environmental variables at both the local (e.g., floral diversity) and landscape (e.g., habitat patch size and isolation) level, to identify the best tools for conserving native bees in urban areas.
    3. Forested field margins and ground beetle communities. Field margins can be important reservoirs for beneficial insects in agricultural lands. The northeastern U.S. is embedded in a landscape mosaic of agricultural fields, natural and semi-natural habitats, and urban areas. Thus, the vegetation composition of agricultural field margins can vary greatly from one site to the next. Many agricultural sites consist of farms located directly adjacent to forest patches. Therefore, an experiment in central Pennsylvania was conducted in an attempt to quantify the influence of forest patches on ground beetle communities in adjacent fields of maize. At the landscape scale, dissimilarity indices were used to compare ground beetle communities between fields of maize that differed in proximity to forest. At the local scale, transects of traps running from interior forest to interior maize fields were established to examine community gradients across and ag-forest ecotone. A novel adaptation of principle response curve (PRC) was developed to quantify community shifts across a spatial gradient, and a manuscript is currently in preparation.

    Long-term population dynamics of insect pests
    Long-term data sets of population densities can provide valuable information and a statistical foothold from which to discern pattern and process order in dynamics. Hypotheses regarding which exogenous or endogenous factors that may be regulating these fluctuations can be tested using regression-based modeling. We currently have two projects utilizing long-term data sets to better understand the ecology and management of several economically important insect pests.
    1. Aphids in winter wheat. Through collaboration with researchers at Wageningen University in the Netherlands and the Crop Research Institute in Prague, Czech Republic, we recently examined an 18-year data set of aphid population densities (3 spp: Metapolophium dirhodum, Sitobion avenae, and Rhopilasiphum padi) recorded in winter wheat fields. In addition to the aphid data, we also had access to regional density estimates of the aphids’ primary predator, Coccinella septempunctata, and weather data (temperature and rainfall) for the same time period. While the aphids displayed no long-term patterns in dynamics, it was possible to predict C. septempunctata densities using the aphid data, indicating a predator-prey linkage. A combined model using the predator and the weather factors, could be used to predict densities for some of the aphid species. A resultant manuscript recently has been published in Agricultural and Forest Entomology. We are currently using our empirical data set to test theoretical models found within the literature.
    2. European corn borer in maize. There has been interest in how the adoption of Bt crops may influence the regional densities of their target pests. Some studies have shown that in areas of high Bt crop adoption, regional suppression of specialist pests (e.g., cotton bollworm) is possible. However, little is known as to whether polyphagous pests, such as European corn borer (ECB), may show the same response. Using a 42-year data set of European corn borer overwintering densities in the Midwestern U.S., we looked for evidence of regional suppression in this region where large acreages of Bt maize are planted. Autocorrelation analyses showed a distinct 7-year cycle in ECB dynamics, likely driven by a density-dependent relationship with a Nosema pathogen. We quantified a significant reduction in the amplitude of these dynamics during the post-Bt adoption portion of the time series, indicating a regional suppression of the pest due to widescale adoption of Bt maize. A manuscript is currently in preparation.


Copyright © 2008 Timothy Leslie. All rights reserved.