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Edwards TP, Trigiano RN, Ownley BH, Windham AS, Wyman CR, Wadl PA, Hadziabdic D. Genetic Diversity and Conservation Status of Helianthus verticillatus, an Endangered Sunflower of the Southern United States. Front Genet 2020; 11:410. [PMID: 32499812 PMCID: PMC7243268 DOI: 10.3389/fgene.2020.00410] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2019] [Accepted: 03/31/2020] [Indexed: 11/13/2022] Open
Abstract
Evaluating species diversity and patterns of population genetic variation is an essential aspect of conservation biology to determine appropriate management strategies and preserve the biodiversity of native plants. Habitat fragmentation and potential habitat loss are often an outcome of a reduction in naturally occurring wildfires and controlled prescribed burning, as seen in Helianthus verticillatus (whorled sunflower). This endangered, wild relative of the common sunflower, Helianthus annuus, is endemic to four locations in Alabama, Georgia, and Tennessee, United States. Despite its endangered status, there is no recovery plan for H. verticillatus, and knowledge related to its basic plant biology and importance in ecosystem services is mostly unknown. In this study, we utilized 14 microsatellite loci to investigate fine-scale population structure and genetic diversity of H. verticillatus individuals found on two sampling sites within the Georgia population. Our results indicated moderate genetic diversity and the presence of two distinct genetic clusters. Analyses of molecular variance indicated that the majority of variance was individually based, thus confirming high genetic differentiation and limited gene flow between H. verticillatus collection sites. The evidence of a population bottleneck in these sites suggests a recent reduction in population size that could be explained by habitat loss and population fragmentation. Also, high levels of linkage disequilibrium were detected, putatively suggesting clonal reproduction among these individuals. Our study provides a better understanding of fine-scale genetic diversity and spatial distribution of H. verticillatus populations in Georgia. Our results can underpin an original recovery plan for H. verticillatus that could be utilized for the conservation of this endangered species and to promote its persistence in the wild.
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Affiliation(s)
- Tyler P Edwards
- Department of Entomology and Plant Pathology, The University of Tennessee, Knoxville, Knoxville, TN, United States
| | - Robert N Trigiano
- Department of Entomology and Plant Pathology, The University of Tennessee, Knoxville, Knoxville, TN, United States
| | - Bonnie H Ownley
- Department of Entomology and Plant Pathology, The University of Tennessee, Knoxville, Knoxville, TN, United States
| | - Alan S Windham
- Department of Entomology and Plant Pathology, The University of Tennessee, Knoxville, Knoxville, TN, United States
| | - Christopher R Wyman
- Department of Plant Sciences, The University of Tennessee, Knoxville, Knoxville, TN, United States
| | - Phillip A Wadl
- United States Department of Agriculture, Agriculture Research Service, U.S. Vegetable Laboratory, Charleston, SC, United States
| | - Denita Hadziabdic
- Department of Entomology and Plant Pathology, The University of Tennessee, Knoxville, Knoxville, TN, United States
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Zhang JQ, Imerovski I, Borkowski K, Huang K, Burge D, Rieseberg LH. Intraspecific genetic divergence within Helianthus niveus and the status of two new morphotypes from Mexico. AMERICAN JOURNAL OF BOTANY 2019; 106:1229-1239. [PMID: 31461165 DOI: 10.1002/ajb2.1349] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/23/2019] [Accepted: 07/17/2019] [Indexed: 05/12/2023]
Abstract
PREMISE Collecting and characterizing the genetic diversity of wild relatives of crops can contribute importantly to sustainable crop production and food security. Wild sunflower, Helianthus niveus, occurs in arid regions in western North America and is partially cross-compatible with the cultivated sunflower (H. annuus). We assessed phylogenetic relationships and patterns of genetic divergence among three previously described subspecies (subsp. niveus, subsp. canescens, and subsp. tephrodes) as well as two new morphotypes of H. niveus recently discovered in extreme drought and dune habitats in Baja California, Mexico. METHODS We measured 50 plants growing in a common garden for 27 morphological traits and conducted principal component analysis to assess patterns of phenotypic variation. Genome size of each accession was determined using flow cytometry. Pollen viability of first generation hybrids between taxa was tested to infer the strength of intrinsic postzygotic reproductive barriers. Finally, genotyping-by-sequencing data were used to investigate the genetic structure and phylogenetic relationships among the previously described subspecies and new morphotypes. RESULTS The intraspecific genetic and phenotypic divergence of H. niveus populations closely tracks their geographical distribution. Subspecies niveus is phenotypically, genetically, and reproductively distinct from the other two subspecies and has a larger genome. Therefore, H. niveus as currently circumscribed should be considered to contain two distinct species, H. niveus and H. tephrodes. ABBA-BABA tests revealed substantial introgression between subsp. canescens and its sympatric congener H. petiolaris, which might contribute to their morphological similarities. The two new morphotypes collected in Mexico represent local ecotypes of subsp. niveus that occur in extreme drought and dune environments. Mantel tests showed a strong positive correlation between genetic and geographic distances. CONCLUSIONS We conclude that geographic isolation is primarily responsible for intraspecific genomic divergence within H. niveus, while patterns of phenotypic variation appear to have been shaped by ecological selection and interspecific introgression.
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Affiliation(s)
- Jian-Qiang Zhang
- College of Life Sciences, Shaanxi Normal University, Xi'an, 710119, China
- Department of Botany, University of British Columbia, Vancouver, British Columbia, V6T1Z4, Canada
| | - Ivana Imerovski
- Department of Botany, University of British Columbia, Vancouver, British Columbia, V6T1Z4, Canada
| | - Kelly Borkowski
- Department of Botany, University of British Columbia, Vancouver, British Columbia, V6T1Z4, Canada
| | - Kaichi Huang
- Department of Botany, University of British Columbia, Vancouver, British Columbia, V6T1Z4, Canada
| | - Dylan Burge
- Department of Botany, University of British Columbia, Vancouver, British Columbia, V6T1Z4, Canada
| | - Loren H Rieseberg
- Department of Botany, University of British Columbia, Vancouver, British Columbia, V6T1Z4, Canada
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Mandel JR, Ramsey AJ, Iorizzo M, Simon PW. Patterns of Gene Flow between Crop and Wild Carrot, Daucus carota (Apiaceae) in the United States. PLoS One 2016; 11:e0161971. [PMID: 27603516 PMCID: PMC5014312 DOI: 10.1371/journal.pone.0161971] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2016] [Accepted: 08/15/2016] [Indexed: 11/18/2022] Open
Abstract
Studies of gene flow between crops and their wild relatives have implications for both management practices for cultivation and understanding the risk of transgene escape. These types of studies may also yield insight into population dynamics and the evolutionary consequences of gene flow for wild relatives of crop species. Moreover, the comparison of genetic markers with different modes of inheritance, or transmission, such as those of the nuclear and chloroplast genomes, can inform the relative risk of transgene escape via pollen versus seed. Here we investigate patterns of gene flow between crop and wild carrot, Daucus carota (Apiaceae) in two regions of the United States. We employed 15 nuclear simple sequence repeat (SSR) markers and one polymorphic chloroplast marker. Further, we utilized both conventional population genetic metrics along with Shannon diversity indices as the latter have been proposed to be more sensitive to allele frequency changes and differentiation. We found that populations in both regions that were proximal to crop fields showed lower levels of differentiation to the crops than populations that were located farther away. We also found that Shannon measures were more sensitive to differences in both genetic diversity and differentiation in our study. Finally, we found indirect evidence of paternal transmission of chloroplast DNA and accompanying lower than expected levels of chloroplast genetic structure amongst populations as might be expected if chloroplast DNA genes flow through both seed and pollen. Our findings of substantial gene flow for both nuclear and chloroplast markers demonstrate the efficiency of both pollen and seed to transfer genetic information amongst populations of carrot.
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Affiliation(s)
- Jennifer R. Mandel
- Department of Biological Sciences, The University of Memphis, Memphis, Tennessee, United States of America
- W. Harry Feinstone Center for Genomic Research, The University of Memphis, Memphis, Tennessee, United States of America
- * E-mail:
| | - Adam J. Ramsey
- Department of Biological Sciences, The University of Memphis, Memphis, Tennessee, United States of America
| | - Massimo Iorizzo
- Plants for Human Health Institute, Department of Horticultural Science, North Carolina State University, Kannapolis, North Carolina, United States of America
| | - Philipp W. Simon
- USDA-Agricultural Research Service, Vegetable Crops Unit, University of Wisconsin-Madison, Wisconsin, United States of America
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Lesica P, Adams B, Smith CT. Can physiographic regions substitute for genetically-determined conservation units? A case study with the threatened plant, Silene spaldingii. CONSERV GENET 2016. [DOI: 10.1007/s10592-016-0842-5] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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Environmental requirements trump genetic factors in explaining narrow endemism in two imperiled Florida sunflowers. CONSERV GENET 2015. [DOI: 10.1007/s10592-015-0739-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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Brouillette LC, Mason CM, Shirk RY, Donovan LA. Adaptive differentiation of traits related to resource use in a desert annual along a resource gradient. THE NEW PHYTOLOGIST 2014; 201:1316-1327. [PMID: 24325125 DOI: 10.1111/nph.12628] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/13/2013] [Accepted: 10/21/2013] [Indexed: 05/15/2023]
Abstract
• Plant resource-use traits are generally hypothesized to be adaptively differentiated for populations distributed along resource gradients. Although nutrient limitations are expected to select for resource-conservative strategies, water limitations may select for either resource-conservative or -acquisitive strategies. We test whether population differentiation reflects local adaptation for traits associated with resource-use strategies in a desert annual (Helianthus anomalus) distributed along a gradient of positively covarying water and nutrient availability. • We compared quantitative trait variation (Q(ST)) with neutral genetic differentiation (F(ST)), in a common garden glasshouse study, for leaf economics spectrum (LES) and related traits: photosynthesis (A(mass), A(area)), leaf nitrogen (N(mass), N(area)), leaf lifetime (LL), leaf mass per area (LMA), leaf water content (LWC), water-use efficiency (WUE, estimated as δ(13)C) and days to first flower (DFF). • Q(ST)-F(ST) differences support adaptive differentiation for Amass , N(mass), N(area), LWC and DFF. The trait combinations associated with drier and lower fertility sites represent correlated trait evolution consistent with the more resource-acquisitive end of the LES. There was no evidence for adaptive differentiation for A(area), LMA and WUE. • These results demonstrate that hot dry environments can selectively favor correlated evolution of traits contributing to a resource-acquisitive and earlier reproduction 'escape' strategy, despite lower fertility.
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Affiliation(s)
- Larry C Brouillette
- Department of Plant Biology, University of Georgia, 2502 Miller Plant Sciences, Athens, GA, 30602, USA
| | - Chase M Mason
- Department of Plant Biology, University of Georgia, 2502 Miller Plant Sciences, Athens, GA, 30602, USA
| | - Rebecca Y Shirk
- Department of Plant Biology, University of Georgia, 2502 Miller Plant Sciences, Athens, GA, 30602, USA
| | - Lisa A Donovan
- Department of Plant Biology, University of Georgia, 2502 Miller Plant Sciences, Athens, GA, 30602, USA
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