Date of Award


Document Type

Masters Thesis

Degree Name


Organizational Unit

College of Natural Science and Mathematics, Biological Sciences

First Advisor

Erica Larson

Second Advisor

Shannon Murphy

Third Advisor

Jon Velotta

Fourth Advisor

Rebecca Powell


Community science, Hybrid zone, Local adaptation, Morphology, Orthoptera, Speciation


Patterns of morphological divergence across species’ ranges provide insight into local adaptation and speciation. Here, we compare phenotypic divergence among 4,221 crickets from 337 populations of two related species of field cricket, Gryllus firmus and G. pennsylvanicus and their hybrids. We find that these species differ across their geographic range in key morphological traits, such as body size and ovipositor length, and we directly compare phenotype with genotype for a subset of crickets demonstrating nuclear genetic introgression, phenotypic intermediacy of hybrids, and essentially unidirectional mitochondrial introgression. We discuss how these morphological traits relate to life history differences between the species. Our comparisons across geographic areas support prior research suggesting cryptic variation within G. firmus that may represent different species. Overall, our study highlights how variable morphology can be across wide ranging species, and the importance of studying reproductive barriers in more than one or two transects of a hybrid zone.

Publication Statement

Copyright is held by the author. User is responsible for all copyright compliance.

Rights Holder

Amy Byerly


Received from ProQuest

File Format




File Size

73 pgs


Evolution and development