1. Biology of invasive species

I was recently hired as a Visiting Research Associate by the Michigan State University Invasive Species Initiative. My primary responsibility is to conduct research on the ecology, management and policy implications of invasive species in the Great Lakes region. I am conducting an analysis of a unique database of non-indigenous biota found in Michigan, the aim of which is a greater understanding of factors that affect establishment success and spread of introduced organisms in all taxonomic groups. I am also responsible for coordinating research, grant-writing and outreach activities that are a part of the Invasive Species Initiative.

In addition to my work with the Invasive Species Initiative, I am a member of Doug Landis's lab group. I currently provide input and assistance for ongoing lab efforts, and we are in the process of identifying new systems and collaborations for the next generation of invasive species research.

2. Evolution of invasive species

My dissertation,'Phylogeography of an introduced insect pest and consequences of an insect introdcution' dealt, in part, with genetic and phenotypic consequences experienced by insects that are introduced into new habitats. Adelges cooleyi (Hemiptera: Adelgidae), a host-alternating gall-making insect pest native to the Rocky Mountains and Pacific Northwest and introduced into the eastern United States during the mid-19th century, was studied to address questions about phylogeography, to determine effects of introduction on genotypic and phenotypic variation, and to compare genetic variation associated with host use in native and introduced ranges. Sequence data from two mitochondrial (mtDNA) genes and amplified fragment length polymorphisms (AFLPs) were used to quantify the structure of genetic variation in the insect’s native range. Several well-supported, divergent mtDNA lineages were identified. The structure of genetic variation among sampled locations is consistent with patterns shaped by glaciations. Samples from the southern edge of the insect’s distribution are genetically isolated from the rest of the species, and hybridization of divergent mtDNA lineages via secondary contact was inferred from AFLP data.

Regarding introduced species, changes in genetic and phenotypic variation associated with introduction were quantified. Introduced insects had decreased genetic variation relative to samples collected in the native range. Variation in an ecologically important trait, host preference, was also significantly lower in introduced samples than in native samples. An association between mtDNA haplotypes and host preference was identified. Adelges cooleyi in the eastern US have low genetic and phenotypic variation but appear to be sufficiently adapted for persistence. My results call into question the utility of neutral genetic variation to assess the probability of persistence in new environments by introduced species.
Host-plants that A. cooleyi requires to complete its lifecycle are not native to the eastern US and occur together in patches that are often widely separated.

Analyses of mtDNA and AFLP genetic variation were conducted to determine the distribution of genetic variation within and among host plants in the native range and identify discrepancies that may be consistent with an incomplete lifecycle in the introduced range. Distribution of genetic variation within and among host-plants in the introduced range was not significantly different than that in the native range, as indicated by fixation indices, and I found no evidence for asexual populations in the introduced range.

3. Management of invasive species

Invasive species can pose unique challenges to those charged with managing pest populations, and damage caused by invasive insects can be extensive, especially in forests. Fiorinia externa, elongate hemlock scale, is a pest of hemlocks (Tsuga spp.) in the eastern United States. Hemlocks, already at risk due to attack by Adelges tsugae, hemlock woolly adelgid, are majestic trees, and riparian habitats are susceptible to irreversible change when hemlock stands die or are removed. In an attempt to identify viable control strategies, efficacy of six chemical treatments for control of F. externa was investigated during a three-year study conducted at the National Arboretum. This effort was lead by Mike Raupp and I managed the project and coordinated data analysis. In addition to measuring reductions in scale density, we quantified the effects of treatments on natural enemies, with particular attention paid to a specialist parasitoid. We found that several products provide good, long-term control of scale populations. Also, and importantly, movement and colonization by natural enemies and generalist predators did not appear to be affected by treatments. Our findings will hopefully be useful for forest managers charged with protecting important forest resources.

This work compliments work that I did for my Master's degree that dealt with control of Russian wheat aphid, Diuraphis noxia. In that project I found that habitat manipulations, in the form of increased vegetative diversity, led to increased control of aphids by parasitoids. Both projects deal with several of my long-term interests: Hemipteran pest insects, pest control tactics, and the role that parasitoids play in pest suppression.