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Delineation of Structural Complexity in Above and Belowground Forest Food Webs
Department of Entomology
Arthropod natural enemies frequently forage within dense and tangled microhabitats, making observations of their interactions with prey or host species, and interpretation of the data thus obtained, difficult. Such behaviors dictate the need for alternative technologies for the study of their biocontrol potential in complex habitats, such as forest ecosystems throughout Kentucky, which are replete with pest and non-pest prey.
This research will therefore focus on identifying the structure of arthropod communities in Kentucky forest ecosystems. Particular attention will be given to identifying the role of diversity, non-prey food availability and pest species on the foraging dynamics of arthropod predators. The structure of above and belowground food webs in forest ecosystems will be identified, with a view to establishing a framework for food web function and the capacity to respond to changing pest control needs within such systems.
This ability to respond requires a fundamental knowledge of existing food web structure, something that has been quantitatively examined only occasionally. This project will exploit natural spatial and temporal differences in prey communities within Kentucky forests, and will merge organismal and molecular approaches. This study will yield results of immediate relevance to pest management in forest ecosystems, focusing on pests of critical importance in Kentucky, while simultaneously fostering a fundamental understanding of how predator foraging behavior impacts pest suppression.
2011 Project Description
This McIntire-Stennis project, which started in October 2010, has made significant progress towards establishing research projects that examine the primary goals that are to be addressed. Through the recruitment of a graduate student who is working towards addressing these goals, the following projects have been established and are ongoing.
1. Examination of foraging activity of generalist predators (spiders are being used as the model predator in this system because they are numerically dominant and potentially exhibit seasonal variations in foraging behavior in relation to prey availability). Collections have commenced, and will be undertaken over 24 consecutive months, to reveal specific mechanisms of foraging as resource availability changes with shifting patterns of weather. Research sites have been established in Berea Forest, KY, and collections started to examine whether (i) they exhibit foraging activity that is dependent upon prey density throughout the season and (ii) quantify whether they resort to intra-guild predation during prey scarcity. Pitfall trapping is ongoing to mass collect predators and examine, through molecular gut-content analysis, feeding behavior. (iii) No-choice feeding trials will also be undertaken to examine how low-temperatures impact prey choice and selection in generalist predators. This aspect of the project therefore addresses primary objective (1): characterize the structure of above and below ground food webs in forest ecosystems, by delineating foraging decisions of generalist predators under open-field conditions of naturally fluctuating prey densities.
2. Food quality experiments have also commenced to quantify the nutritive quality of prey to generalist predators. These will be undertaken to examine (i) how prey nutrition affects predator fitness and (ii) how prey nutritive quality affects feeding decisions in forest-floor spiders. The graduate student will, in 2012, disseminate these results widely by presenting results at regional and national conferences.
The primary aspect of this research is to relate what predators are actually eating to the spectrum of prey available to them. This is of fundamental importance in food web ecology and pest management, in that a changing pattern of foraging under open field conditions can have a profound impact on the structure and function of terrestrial ecosystems. Delineating how and, crucially, why predators shift foraging activity in relation to resource availability can help further advance our understanding of the role of generalist predators in biological control.
Undertaking the research over a 24 month cycle encompasses all life stages of predators and prey, thereby seeks to understand how dominant invertebrate predators are sustained through periods of food shortage and adverse weather conditions. Quantifying winter foraging in predators is crucial for fully understanding aspects of population growth given the high mortality experienced during these months. Mitigating the effect of winter mortality, through habitat management, could provide a framework for natural population enhancement that could provide valuable benefits in pest management.