Heather M. Hines, Ph. D. - US grants

DESCRIPTION (provided by applicant): Comparative studies addressing the variation in how complex adaptive traits can be genetically regulated provide basic insights into the diverse diagnosis and treatments that may be needed to effectively target disease. Heliconius butterfly species H. erato and H. melpomene exhibit parallel color pattern diversifications across the Neotropics, forming up to 30 mimicry complexes. This highly tractable system provides numerous examples of color pattern convergence and divergence, and thus serves as a proxy for understanding the genetic regulation of rapidly evolving complex phenotypes. The genetic switches responsible for the diverse color patterns in these species have been narrowed to three loci, two of which have been refined to a genomic interval of ~400KB each. The proposed study seeks to hone in on the genes responsible for both divergent and convergent color pattern phenotypes in these butterflies. Towards this goal, microarrays containing both DNA tiled across these loci and whole-genomic transcripts will be hybridized to wing tissues across six developmental stages from five color pattern races of H. erato. Analyses of differential hybridization on these arrays will be used to assess the genes responsible for color pattern differences within each locus, the gene modules and hypothetical pathways elicited by these regulatory genes, and the genetic interactions between these pathways. Rapidly evolving traits may have high variance or even non-functionality in their underlying gene expression. Tissues of multiple individuals of each color pattern race will be hybridized to microarrays to explore the natural variation in gene expression across candidate genes. Genes implicated in color pattern will be analyzed further using spatial analysis of RNA and protein expression in wing tissue using in situ hybridization and antibodies. Public Health Relevance: By examining the genetics behind diverse mimetic color patterns of butterflies we gain a model system for understanding how genetic interactions and gene architecture govern changes in complex traits with a high impact on survival. This will enhance understanding of the genetic regulation of the complex adaptive traits of disease and disease resistance and, therefore, highlight the multitude of strategies that may be needed to both diagnose and treat disease.

The Frost Entomological Museum is an active research institution within the Department of Entomology at Penn State's flagship campus in University Park. The Museum houses a large collection of arthropods, estimated at almost 2 million specimens, and a public exhibition and educational space that receives >1,000 visitors per year. This project will unify the storage system onto a single standard, and move specimens to storage cabinets that are more protective - that is, built using archival materials and properly sealed from environmental elements and museum pests. Specimens will be imaged and their collected event data entered into a publically-accessible digital database. There will also be substantial training and outreach components aimed at raising awareness of the importance of insects. Individuals from a broad array of backgrounds - grade school students, undergrads, grad students, and non-expert adults - will be educated in museum practices and the importance of natural history collections. Outreach activities include 'Bug Camp' for kids aged 8-14, meet-the-curator events at the museum, graduate student training, summer internships for undergraduates, public exhibits at the museum, and the 'Great Insect Fair'.

The museum's holdings include one of the largest, most diverse collections of sucking lice (Anoplura, which includes the medically important lice) in the world, alongside renown collections of aphids (Hemiptera: Aphididae, including economically important pests), dragonflies and damselflies (Odonata), substantial collections of parasitic wasps (Hymenoptera, which includes species used to control pestiferous insects), native pollinators (including bees and butterflies), and Pennsylvania insects. Despite their extensive use in research and substantial investment in this resource by the University, the collection suffers from poor storage conditions, evident from an abundance of inadequate specimen cases, and the absence of a modern, accessible database. The activities proposed in this project are designed to remedy these problems by: replacing all specimen cabinets with a purpose-built archival system, increasing storage space, reorganizing the slide-mounted and ethanol-preserved specimens into appropriate storage, and setting up a Web-accessible specimen database. The data will be further disseminated through InvertNet and iDigBio. The database avails Frost Museum data for public data mining and fundamental research in areas such as epidemiology, invasive species biology, global climate change, pollinator declines, and the evolutionary history of insect lineages. More information can be found at the official Frost Entomological Museum website: http://ento.psu.edu/facilities/frost.

New advances in genomics allow for the discovery of the genes responsible for specific traits of organisms and for complex patterns of trait variation that have evolved in species across their geographic range. To better understand the evolutionary mechanisms that determine trait variation and that promote rapid adaptation to environmental change, studies are needed that can link traits to the genes that encode them, especially in species that show extraordinary trait variation. Bumble bees (Bombus) are especially suited for such research: the 250 species worldwide have evolved to exhibit >600 color patterns, in which similar color patterns evolve in different species when they live in the same geographical location. This project will explore how these different color patterns form in Bumble Bee species across North America by identifying the pigments that are responsible for color patterns and then identifying the genes responsible for those pigments and the observed geographic patterns of color variation. This research will provide general insights into how color variation arises in nature, and will also help to address a long standing question in evolutionary biology regarding the repeatability of evolution. Are the same genes in different species responsible for the same color patterns or are different genes able to produce the same color patterns? This research will directly address this question and in answering it help us understand whether evolution is truly repeatable or whether it just looks repeatable and that there are many evolutionary paths to get to the same outcome.

This CAREER project builds foundational knowledge on the genetic and evolutionary processes enabling the mimetic radiation of bumble bees. The project will address the mimetic process by characterizing the geographic distribution of color patterns in North America bumble bees and how they are impacted by climate. It will reveal how these bees are pigmented and the factors that influence their coloration, providing a foundation for further genetic work. Pigment discovery will extend to a diversity of insects through undergraduate research and classroom modules on insect pigment chemistry. As a primary aim, gene mapping and gene expression approaches will be used to identify genes driving red/black and yellow/black bumble bee color variation. Black and yellow pattern morphs of the subgenus Bombus will demonstrate how adaptive gene variants are transferred across species, populations, and sexes. The discovery of the genes behind black and red mimetic convergence in western U.S. bumble bees will inform on the genetic complexity underlying bumble bee mimicry. Identifying these genes will enable a broader comparative approach to examine how adaptive genes have been targeted and transferred across this replicate-rich radiation.

Hundreds of bumble bee species are important pollinators worldwide. They also have interesting behaviors and morphologies that tell us about evolution. Color pattern diversity is the most notable of these traits. These species have hundreds of different patterns of yellow, orange, black, and white hairs across their bodies. This diversity is related to mimicry, whereby species converge upon the same pattern to avoid predation. However, that dominant color pattern differs by region. This repeated evolution of color patterns can be used to understand how genes are targeted during evolution. In the Western United States, several bumble bee species undergo parallel changes across the landscape. This research will examine the genes that drive coloration shifts in each of these western species and provide a better understanding of how repeatable evolution is. Broader impacts of the research include training undergraduate students to develop functional genetics tools. The researchers will also share their gained knowledge outside the scientific community through several events for the public and develop color pattern field guides for bumble bees.

The study will compare genetic changes across color shifts to tell if the same genes are repeatedly targeted or if there are many ways to get to the same phenotype. The proposed research uses a combination of genome-wide trait association analysis and cross-developmental transcriptome comparisons to determine gene networks for color variation across five sets of mimetic species in the Western United States. This includes identifying genetic targets of selection and specific changes in final pigmentation genes. the work will determine which regions within genes are most likely to be targeted. It will determine if there are major developmental genes that get used in new functions or if downstream genes are more often targeted. It will also tell us how genetic variants inherited and transferred within and across species influence total diversity. This study will, in the process, provide genome sequences for several North American bumble bees, clarifying species boundaries hidden by mimicry. It will also improve understanding of the role of developmental and pigmentation genes in animals. Genomes will be sequenced for species across a clade of mimics to reveal how color-determining genes evolve. These objectives will provide a case study of how genetic variants and resulting changes in gene expression evolve across species under selection.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.