@article{373289749cea47c4985aa29c078a18aa,
title = "Incomplete reproductive isolation and low genetic differentiation despite floral divergence across varying geographic scales in Castilleja",
abstract = "Premise: Divergence depends on the strength of selection and frequency of gene flow between taxa, while reproductive isolation relies on mating barriers and geographic distance. Less is known about how these processes interact at early stages of speciation. Here, we compared population-level differentiation in floral phenotype and genetic sequence variation among recently diverged Castilleja to explore patterns of diversification under different scenarios of reproductive isolation. Methods: Using target enrichment enabled by the Angiosperms353 probe set, we assessed genetic distance among 50 populations of four Castilleja species. We investigated whether patterns of genetic divergence are explained by floral trait variation or geographic distance in two focal groups: the widespread C. sessiliflora and the more restricted C. purpurea species complex. Results: We document that C. sessiliflora and the C. purpurea complex are characterized by high diversity in floral color across varying geographic scales. Despite phenotypic divergence, groups were not well supported in phylogenetic analyses, and little genetic differentiation was found across targeted Angiosperms353 loci. Nonetheless, a principal coordinate analysis of single nucleotide polymorphisms revealed differentiation within C. sessiliflora across floral morphs and geography and less differentiation among species of the C. purpurea complex. Conclusions: Patterns of genetic distance in C. sessiliflora suggest species cohesion maintained over long distances despite variation in floral traits. In the C. purpurea complex, divergence in floral color across narrow geographic clines may be driven by recent selection on floral color. These contrasting patterns of floral and genetic differentiation reveal that divergence can arise via multiple eco-evolutionary paths.",
keywords = "Orobanchaceae, flower color, gene flow, selection, speciation, species cohesion, target enrichment sequencing",
author = "Wenzell, {Katherine E.} and McDonnell, {Angela J.} and Wickett, {Norman J.} and Fant, {Jeremie B.} and Skogen, {Krissa A.}",
note = "Funding Information: The authors thank the members of the Skogen-Fant lab group and two anonymous reviewers for feedback on previous versions of this manuscript. D. Tank provided leaf tissue for outgroup species, and both he and M. Egger provided initial guidance on the C. purpurea species complex. We are grateful for field assistance from S. Deans, K. Bonefont, A. Cisternas Fuentes, C. Woolridge, A. Gruver, E. Lewis, and A. Morgan, as well as assistance in the field and laboratory from K. Manion, M. Malone, and G. Perez Cartagena. We also thank the following landowning agencies for permission and access to study sites: The Nature Conservancy Chapters of Texas, Oklahoma, and Illinois; the Native Prairies Association of Texas; Cities of Lubbock and Ft. Worth, Texas, and Tulsa, Oklahoma; Texas Parks and Wildlife Department; New Mexico Energy, Minerals and Natural Resources Department; Minnesota Department of Natural Resources; Illinois Nature Preserves Commission; Illinois Department of Natural Resources; U.S. Fish and Wildlife Services; U.S. Forest Service; U.S. Bureau of Land Management; U.S. Army Corps of Engineers; and U.S. National Park Service. Funding was provided by the Botanical Society of America, American Society of Plant Taxonomists, American Philosophical Society Lewis and Clark Grant, Friends of Nachusa Grasslands, Northwestern University Program in Plant Biology and Conservation, and an NSF Graduate Research Fellowship award (DGE-1842165; to K.E.W.). Undergraduate students were supported by an NSF Research Experience for Undergraduates site award to J.B.F. (DBI-461007 and DBI-1757800). Funding was provided, in part, from NSF award DEB-1752785 to N.J.W., and additional support was provided by the Negaunee Institute for Plant Conservation and Action at the Chicago Botanic Garden. Funding Information: The authors thank the members of the Skogen‐Fant lab group and two anonymous reviewers for feedback on previous versions of this manuscript. D. Tank provided leaf tissue for outgroup species, and both he and M. Egger provided initial guidance on the species complex. We are grateful for field assistance from S. Deans, K. Bonefont, A. Cisternas Fuentes, C. Woolridge, A. Gruver, E. Lewis, and A. Morgan, as well as assistance in the field and laboratory from K. Manion, M. Malone, and G. Perez Cartagena. We also thank the following landowning agencies for permission and access to study sites: The Nature Conservancy Chapters of Texas, Oklahoma, and Illinois; the Native Prairies Association of Texas; Cities of Lubbock and Ft. Worth, Texas, and Tulsa, Oklahoma; Texas Parks and Wildlife Department; New Mexico Energy, Minerals and Natural Resources Department; Minnesota Department of Natural Resources; Illinois Nature Preserves Commission; Illinois Department of Natural Resources; U.S. Fish and Wildlife Services; U.S. Forest Service; U.S. Bureau of Land Management; U.S. Army Corps of Engineers; and U.S. National Park Service. Funding was provided by the Botanical Society of America, American Society of Plant Taxonomists, American Philosophical Society Lewis and Clark Grant, Friends of Nachusa Grasslands, Northwestern University Program in Plant Biology and Conservation, and an NSF Graduate Research Fellowship award (DGE‐1842165; to K.E.W.). Undergraduate students were supported by an NSF Research Experience for Undergraduates site award to J.B.F. (DBI‐461007 and DBI‐1757800). Funding was provided, in part, from NSF award DEB‐1752785 to N.J.W., and additional support was provided by the Negaunee Institute for Plant Conservation and Action at the Chicago Botanic Garden. C. purpurea Publisher Copyright: {\textcopyright} 2021 The Authors. American Journal of Botany published by Wiley Periodicals LLC on behalf of Botanical Society of America",
year = "2021",
month = jul,
doi = "10.1002/ajb2.1700",
language = "English (US)",
volume = "108",
pages = "1270--1288",
journal = "American Journal of Botany",
issn = "0002-9122",
publisher = "John Wiley & Sons Inc.",
number = "7",
}