Data for Geographic variation in phenotypic divergence between two hybridizing field cricket species

<p><span>Patterns of morphological divergence across species' ranges can provide insight into local adaptation and speciation. In this study, we compare phenotypic divergence among 4,221 crickets from 337 populations of two closely related species of field cricket, <em>Gryllus firmus</em> and <em>G. pennsylvanicus </em>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 to demonstrate nuclear genetic introgression, phenotypic intermediacy of hybrids, and essentially unidirectional mitochondrial introgression. We discuss how these morphological traits relate to life history differences between these two species. Our comparisons across geographic areas support prior research that suggested that cryptic variation within <em>G. firmus</em> 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.</span></p>