Publication in: Spring 2023 Issue

Genetic Analysis of Geographically Distinct Curculio sayi Populations in the Northeastern United States
Cassius Guthrie
Faculty Mentor(s):
Camila Filgueiras and Graham Reynolds
Abstract / Summary:
The American Chestnut was a tree of vital ecological importance to the forests of the eastern United States before the accidental introduction of the pathogenic chestnut blight which killed all adult trees. Efforts to reintroduce the historic American Chestnut tree to its native range using blight-resistant hybrids have also had the effect of increasing the range and numbers of an unwanted pest. Curculio sayi, the lesser chestnut weevil, is a specialized seed predator that not only damages the nuts through the oviposition of eggs but also through its inadvertent ability to introduce toxic fungi to the plant. As the population of its host plant has been increasing, so have C. sayi populations. Developing a strategy of population control of C. sayi stands to directly support the commercial chestnut industry and the successful reintroduction of this historical tree. Trapping and monitoring efforts have revealed divergences in reported phenologies in northeastern C. sayi populations as well as distinct morphological differences. Such differences could indicate a possibility of at least two diverging species. It is currently unknown how C. sayi was introduced or what role humans have had in its dispersal. Therefore, characterization of C. sayi phylogeography and the northeastern population structure would directly improve the efficacy of pest management efforts. DNA barcoding analysis of the mitochondrial cytochrome c oxidase inhibitor subunit 1 (CO1), gene of two distinct populations of C. sayi showed that there is no phylogeographic signal present within the populations, indicating that these populations are not undergoing species divergence but are rather a product of recent shared ancestry, which suggests human-mediated movement. Although both populations were found to belong to the same species, when developing pest management strategies, the adaptation and spread capabilities of C. sayi should be considered to improve pest control efficacy.
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