Understanding movement capabilities of individuals within a landscape is essential to identifying the effects of habitat boundaries on species abundances, ranges, and spread rates. Movement barriers due to habitat fragmentation may reduce mate-finding ability in some species, particularly in heterogeneous landscapes containing low-density populations. This study focuses on the effects of habitat type and edge on mate-finding in an invasive defoliator, the European gypsy moth. Adult European gypsy moth males locate mates by following pheromones released by flightless females. Reduced mate-finding was expected in fields and near forest edges based on geographic variation in invasion rates and pheromone plume dynamics. A male release-recapture experiment using female-baited traps in fields, at forest edges, and in the forest interior showed that mate-finding was highest at forest edges, reduced in fields, and lowest within the forest interior. This suggests that forest edges and moderate habitat fragmentation enhance mate-finding in the gypsy moth.

Invasive insects are considered one of the most serious threats affecting forests today; however, surprisingly little research has addressed the impacts of invasive species establishment on native forest insect communities. Such information is lacking for even the most thoroughly studied invasive forest insect, the gypsy moth. Using gypsy moth as a case study, my thesis addresses the questions: What are the ecological impacts of an exotic forest insect upon its establishment in a new community of native species? Does the community shift after the invasive establishes, and if so, what are the drivers in this realignment? I used multivariate analysis to assess native caterpillar communities collected in forest stands with and without a history of gypsy moth outbreak. I found that gypsy moth outbreak history had no significant effects on native caterpillar communities; however, current gypsy moth abundance was related to shifts in the structure of late season caterpillar assemblages. These results suggest that gypsy moth may affect native caterpillar communities through short-term mechanisms but not through long-term ecological changes. I used quantitative food webs to investigate the effects of gypsy moth on native host-parasitoid webs from the same caterpillar communities, and found that food web structure was resilient to both gypsy moth outbreak history and current abundance. The gypsy moth shared few parasitoids with native species in my study sites, none of numerical significance, thus minimizing the opportunity for enemy-mediated indirect interactions. Finally, I conducted a greenhouse experiment and found that early spring feeding by forest tent caterpillar can indirectly influence gypsy moth susceptibility to its virus, demonstrating that the complex interactions that can occur between native and exotic species do not always benefit the invader. Overall, I argue that the establishment of the gypsy moth into North American forests will not cause major changes in native caterpillar communities.

Invasive insects are considered one of the most serious threats affecting forests today; however, surprisingly little research has addressed the impacts of invasive species establishment on native forest insect communities. Such information is lacking for even the most thoroughly studied invasive forest insect, the gypsy moth. Using gypsy moth as a case study, my thesis addresses the questions: What are the ecological impacts of an exotic forest insect upon its establishment in a new community of native species? Does the community shift after the invasive establishes, and if so, what are the drivers in this realignment? I used multivariate analysis to assess native caterpillar communities collected in forest stands with and without a history of gypsy moth outbreak. I found that gypsy moth outbreak history had no significant effects on native caterpillar communities; however, current gypsy moth abundance was related to shifts in the structure of late season caterpillar assemblages. These results suggest that gypsy moth may affect native caterpillar communities through short-term mechanisms but not through long-term ecological changes. I used quantitative food webs to investigate the effects of gypsy moth on native host-parasitoid webs from the same caterpillar communities, and found that food web structure was resilient to both gypsy moth outbreak history and current abundance. The gypsy moth shared few parasitoids with native species in my study sites, none of numerical significance, thus minimizing the opportunity for enemy-mediated indirect interactions. Finally, I conducted a greenhouse experiment and found that early spring feeding by forest tent caterpillar can indirectly influence gypsy moth susceptibility to its virus, demonstrating that the complex interactions that can occur between native and exotic species do not always benefit the invader. Overall, I argue that the establishment of the gypsy moth into North American forests will not cause major changes in native caterpillar communities.

2 spread sheets included. Title from title page of PDF (University of Missouri--St. Louis, viewed February 8, 2010). Includes bibliographical references.

The study of biological invasions is not only essential to regulate their vast potential for ecological and economical harm, they offer a unique opportunity to study adaptive evolution in the context of recent range expansions into novel environments. The North American invasion of the gypsy moth, Lymantria dispar L., since its introduction in 1869 to Massachusetts, has expanded westward to Minnesota, northward to Canada, and southward to North Carolina. Fluctuating range dynamics at the southern invasive edge are heavily influenced by heat exposure over their optimal (supraoptimal) during the larval stage of development. We coupled genomic sequencing with reciprocal transplant and laboratory-rearing experiments to examine the interactions of phenotypic, genetic, and environmental variation under selective supraoptimal regimes. We demonstrate that while there is no evidence to support local adaptation in the fitness-related physiological traits we measured, there are clear genomic patterns of adaptation due to differential survival in higher temperatures. Mapping of loci identified as contributing to local adaptation in a selective environment and those associated with phenotypic variation highlighted that variation in larval development time is partly driven by pleiotropic loci also affecting survival. Overall, I highlight the necessity and inferential power gained through replicating environmental conditions using both phenotypic and genome-wide analyses.

Data for this study were collected by the US Forest Service and the Pennsylvania Bureau of Forestry on nearly 600 plots in central Pennsylvania. Tree and stand characteristics recorded between 1978 and 1985 include estimates of percent defoliation on individual trees. Logistic regression using maximum likelihood estimation was employed to model individual-tree mortality of 15 species in central Pennsylvania that had been defoliated by the gypsy moth. Defoliation was estimated to the nearest ten percent for individual trees. Other variables used for prediction included stand basal area and an individual-tree relative basal area index. Success ranged from no fit for three of the species to an R value (a derivation of Akaike's information criterion) of .613 for white oak. The inclusion of defoliation in the models had a varied effect. For four of the species percent defoliation was not significant. For hickory and white oak respectively, percent defoliation raised the R value by .305 and .290 percentage points. As many as five models for each species were developed: one or two models with no defoliation measure in the model and one each for one, two or three consecutive years of defoliation measures. A beta and gamma function were used to model individual· tree basal area growth for the same 15 species. The models were fit using nonlinear least squares. Variables used include the relative basal area index, stand basal area, site index and a defoliation index that incorporated three years of individual-tree, percent defoliation. The beta and gamma functions fit equally well with values of (1 - relative mean square error) ranging from .1967 to .6290. Results for both models are presented for each species. The defoliation index was a significant variable for five of the fifteen species: white, chestnut, red, and black oak and sassafras. / Master of Science

The effects of gypsy moth defoliation on acorn production (the seed source for oak regeneration), and the forest floor regeneration environment were investigated. Parameters measured included: acorn quantity, weight, development, and viability; litterfall; and forest floor depth and biomass. Nineteen plots in north-central Virginia and western Maryland on which trees suffered heavy, moderate, or no defoliation were monitored over a two-year period. / Master of Science

An instructional guide for high school science and agricultural education courses was designed around the topic of integrated pest management (IPM) and the gypsy moth (Lymantria dispar [L.]) problem in Virginia. Construction of the guide followed three phases—design, development, and evaluation—of the Instructional Development Institute (IDI) model of instructional design. Lessons were developed using information from Virginia agricultural education course competencies, national science standards, a conceptual model of IPM, and gypsy moth management references and contacts. A validation panel consisting of two educators and two gypsy moth managers provided a review of the guide. / Master of Science

The objective of this study was to determine differences in small mammal assemblage structure and population dynamics among four oak dominated sites at four different stages of gypsy moth disturbance: a high tree mortality site, a disturbance in process site, a disturbance recovery site, and an undisturbed reference site. More specifically, the study was designed to identify changes in habitat structure that would influence small mammal microdistributions and determine the quality of habitat created by gypsy moth herbivory using demographic structure of <i>Peromyscus</i> populations as an indicator of habitat quality. <i>Peromyscus leucopus</i>, Peromyscus maniculatus, the Soricids, and <i>Clethrionomys gapperi</i> had greater abundances at the disturbed sites relative to the reference site. Gypsy moth disturbance increased the abundance of small mammals and the number of coexisting species within a given area, which was attributed to several changes in habitat structure. The disturbed sites were characterized as having more fallen logs and standing dead snags, greater shrub and herbaceous cover, and higher invertebrate abundances relative to the reference site. These changes in habitat structure provided small mammals with increased cover from avian predators, more food resources, and potential nesting cavities. <i>P. leucopus</i> populations at the high mortality site exhibited greater demographic stability than the reference Site populations. This was marked by higher proportions of females, smaller density fluctuations, more fall recruitment of young, higher residency, and lower proportions of males. Strong evidence for density-dependent population regulation was observed for <i>P. leucopus</i> populations at the high mortality site and the <i>P. maniculatus</i> population at the recovery site. At high densities these populations exhibited extensive intraspecific microhabitat segregation. Female adults segregated from juveniles and male adults into more optimal microhabitats. Male adult microhabitat use significantly differed from male juvenile microhabitat use. The exclusion of young mice from optimal microhabitats by adults may be a mechanism by which adults limit over-exploitation of resources by subordinate members of the population at high densities. The results of this study suggest that gypsy moth disturbance of areas dominated by chestnut oaks at least temporarily improves habitat quality for small mammals. / Master of Science

The effects of gypsy moth infestation on the Shenandoah National Park (SNP) black bear population and habitat were studied during 1985 - 1991 by comparing radio telemetry, population, and behavioral data from preinfestation years (1982 - 1986) and years with extensive defoliation (1987 - 1991). Gypsy moth defoliation (> 60% canopy loss) increased from 546 ha in 1986 (1 % of the study area), to 2,304 ha in 1987 (4%), 6,227 ha in 1988 (12%), and 17,736 ha in 1989 (34%). Chestnut oak and red oak habitat types received the greatest defoliation; 60% and 45% of these habitat types suffered greater than 60 % canopy loss in the North and Central Districts, respectively. Infestation resulted in a 99% reduction in acorn production in defoliated stands. Maximum daily temperatures 0.5 m above the ground in defoliated stands averaged 4.7 ± 0.3 C, 4.3 ± 0.4 C, and 2.5 ± 0.3 C warmer (P < 0.01) than in nondefoliated stands during peak defoliation, refoliation, and post-refoliation periods, respectively. Bear / Ph. D.