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Kim HT, Park SH, Kim JS. Dynamic hybridization between two spleenworts, Asplenium incisum and Asplenium ruprechtii in Korea. FRONTIERS IN PLANT SCIENCE 2023; 14:1116040. [PMID: 37476173 PMCID: PMC10354290 DOI: 10.3389/fpls.2023.1116040] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/05/2022] [Accepted: 05/31/2023] [Indexed: 07/22/2023]
Abstract
Natural hybridization between Asplenium incisum and A. ruprechtii has been observed in Northeast Asia and its allotetraploid species, A. castaneoviride, was reported. However, the hybridization process between the parental species and the origin of the allotetraploid taxon remains obscure. Additionally, the systematic affinities of the recently described hybrid A. bimixtum, considered to have originated from the hybridization of A. ruprechtii, A. trichomanes, and A. incisum, is unresolved owing to its similarity to A. castaneoviride. The goals of this study were to (1) investigate the hybridization between A. ruprechtii and A. incisum; (2) verify the origin of A. castaneoviride occurring in Korea, whether it independently arose from 2x sterile hybrids; and (3) elucidate the reliability of identifying A. bimixtum. Three genotypes, A. incisum, A. ruprechtii, and their hybrid, were identified based on the nuclear gene pgiC sequence and finally divided them into six types by ploidy levels: diploid A. incisum, A. ruprechtii, and four hybrid types (diploid A. × castaneoviride, triploid A. × castaneoviride, allotetraploid A. castaneoviride, and A. bimixtum). In the analyses of plastid DNA, all hybrids had an A. ruprechtii-type rbcL gene. In addition, the four plastomes of A. ruprechtii and the hybrids had high pairwise sequence identities greater than 98.48%. They increased up to 99.88% when a large deletion of A. x castaneoriviride (2x) collected from Buramsan populations was ignored. Notably, this large deletion was also found in triploid A. × castaneoviride and allotetraploid A. castaneoviride in the same populations. Sequence data of the nuclear and plastid genes showed that hybridization is unidirectional, and A. ruprechtii is the maternal parent. The large deletion of rpoC2-rps2 commonly found in the different ploidy hybrids of the Buramsan population suggests that the allotetraploid A. castaneoviride can be created independently from sterile hybrids. We assume that both polyploidization driving allopolyploidy and minority cytotype exclusion took place independently in the population, since A castaenoviride co-occurs with A. ruprechtii in small populations. Furthermore, it was also observed that an enlarged noncoding region in fern organelle (ENRIFO) of the plastome was found in the genus Asplenium.
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Affiliation(s)
- Hyoung Tae Kim
- Department of Ecological and Environmental System, Kyungpook National University, Sangju, Republic of Korea
| | - Sang Hee Park
- Department of Forest Science, Chungbuk National University, Cheongju, Republic of Korea
| | - Jung Sung Kim
- Department of Forest Science, Chungbuk National University, Cheongju, Republic of Korea
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Windham MD, Huiet L, Metzgar JS, Ranker TA, Yatskievych G, Haufler CH, Pryer KM. Once more unto the breach, dear friends: Resolving the origins and relationships of the Pellaea wrightiana hybrid complex. AMERICAN JOURNAL OF BOTANY 2022; 109:821-850. [PMID: 35568966 DOI: 10.1002/ajb2.1850] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/05/2022] [Revised: 03/09/2022] [Accepted: 03/10/2022] [Indexed: 06/15/2023]
Abstract
PREMISE The taxonomic status of Wright's cliff brake fern, Pellaea wrightiana, has been in dispute ever since it was first described by Hooker in 1858. Previously published evidence suggested that this "taxon" may represent a polyploid complex rather than a single discrete species, a hypothesis tested here using a multifaceted analytical approach. METHODS Data derived from cytogenetics, spore analyses, leaf morphometrics, enzyme electrophoresis, and phylogenetic analyses of plastid and nuclear DNA sequences are used to elucidate the origin, relationships, and taxonomic circumscription of P. wrightiana. RESULTS Plants traditionally assigned to this taxon represent three distinct polyploids. The most widespread, P. wrightiana, is a fertile allotetraploid that arose through hybridization between two divergent diploid species, P. truncata and P. ternifolia. Sterile triploids commonly identified as P. wrightiana, were found to be backcross hybrids between this fertile tetraploid and diploid P. truncata. Relatively common across Arizona and New Mexico, they are here assigned to P. ×wagneri hyb. nov. In addition, occasional sterile tetraploid plants assigned to P. wrightiana are shown here to be hybrids between the fertile allotetraploid and the tetraploid P. ternifolia subsp. arizonica. These tetraploid hybrids originated independently in two regions of parental sympatry (southern Arizona and west Texas) and are here assigned to P. ×gooddingii hyb. nov. CONCLUSIONS Weaving together data from a diversity of taxonomic approaches, we show that plants identified as P. wrightiana represent three morphologically distinguishable polyploids that have arisen through repeated hybridization events involving the divergent sexual taxa P. ternifolia and P. truncata.
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Affiliation(s)
| | - Layne Huiet
- Department of Biology, Duke University, Durham, 27708, NC, USA
| | - Jordan S Metzgar
- Department of Biological Sciences, Virginia Tech, Blacksburg, 24061, VA, USA
| | - Tom A Ranker
- School of Life Sciences, University of Hawai'i at Mānoa, Honolulu, 96822, HI, USA
| | - George Yatskievych
- Billie L. Turner Plant Resources Center, University of Texas, Austin, 78712, TX, USA
| | - Christopher H Haufler
- Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, 66045, KS, USA
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Hornych O, Férová A, Hori K, Košnar J, Ekrt L. Apomictic fern fathers: an experimental approach to the reproductive characteristics of sexual, apomict, and hybrid fern gametophytes. AMERICAN JOURNAL OF BOTANY 2022; 109:628-644. [PMID: 35072270 DOI: 10.1002/ajb2.1817] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/05/2021] [Revised: 01/05/2022] [Accepted: 01/13/2022] [Indexed: 06/14/2023]
Abstract
PREMISE Apomixis and hybridization are two essential and complementary factors in the evolution of plants, including ferns. Hybridization combines characteristics from different species, while apomixis conserves features within a lineage. When combined, these two processes result in apo-sex hybrids. The conditions leading to the formation of these hybrids are poorly understood in ferns. METHODS We cultivated spores from 66 fern samples (43 apomicts, 7 apo-sex hybrids, and 16 sexuals), and measured their development in vitro over 16 weeks. We evaluated germination, lateral meristem formation rates, sexual expression, and production of sporophytes and then compared ontogenetic patterns among the three groups. RESULTS The three examined groups formed antheridia (male gametangia) but differed in overall gametophyte development. Sexual species created archegonia (female, 86% of viable samples), but no sporophytes. Apomicts rarely created nonfunctional archegonia (8%) but usually produced apogamous sporophytes (75%). Surprisingly, apomictic and sexual species showed similar development speed. The sexually reproducing parents of viable studied hybrids formed about twice as many meristic gametophytes as the apomictic parents (39% vs. 20%, respectively). CONCLUSIONS We present the most thorough comparison of gametangial development of sexual and apomictic ferns, to date. Despite expectations, apomictic reproduction might not lead to earlier sporophyte formation. Apomicts produce functional sperm and thus can contribute this type of gamete to their hybrids. The development patterns found in the parents of hybrids indicate a possible increase of hybridization rates by antheridiogens. The apo-sex hybrids always inherit the apomictic reproductive strategy and are thus capable of self-perpetuation.
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Affiliation(s)
- Ondřej Hornych
- Department of Botany, Faculty of Science, University of South Bohemia, Branišovská 1760, České Budějovice, CZ-37005, Czech Republic
| | - Alžběta Férová
- Department of Botany, Faculty of Science, University of South Bohemia, Branišovská 1760, České Budějovice, CZ-37005, Czech Republic
| | - Kiyotaka Hori
- The Kochi prefectural Makino Botanical Garden, Godaisan 4200-6, Kochi, 781-8125, Japan
| | - Jiří Košnar
- Department of Botany, Faculty of Science, University of South Bohemia, Branišovská 1760, České Budějovice, CZ-37005, Czech Republic
| | - Libor Ekrt
- Department of Botany, Faculty of Science, University of South Bohemia, Branišovská 1760, České Budějovice, CZ-37005, Czech Republic
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Wang J, Dong S, Yang L, Harris A, Schneider H, Kang M. Allopolyploid Speciation Accompanied by Gene Flow in a Tree Fern. Mol Biol Evol 2021; 37:2487-2502. [PMID: 32302390 DOI: 10.1093/molbev/msaa097] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Hybridization in plants may result in hybrid speciation or introgression and, thus, is now widely understood to be an important mechanism of species diversity on an evolutionary timescale. Hybridization is particularly common in ferns, as is polyploidy, which often results from hybrid crosses. Nevertheless, hybrid speciation as an evolutionary process in fern lineages remains poorly understood. Here, we employ flow cytometry, phylogeny, genomewide single nucleotide polymorphism data sets, and admixture and coalescent modeling to show that the scaly tree fern, Gymnosphaera metteniana is a naturally occurring allotetraploid species derived from hybridization between the diploids, G. denticulata and G. gigantea. Moreover, we detected ongoing gene flow between the hybrid species and its progenitors, and we found that G. gigantea and G. metteniana inhabit distinct niches, whereas climatic niches of G. denticulata and G. metteniana largely overlap. Taken together, these results suggest that either some degree of intrinsic genetic isolation between the hybrid species and its parental progenitors or ecological isolation over short distances may be playing an important role in the evolution of reproductive barriers. Historical climate change may have facilitated the origin of G. metteniana, with the timing of hybridization coinciding with a period of intensification of the East Asian monsoon during the Pliocene and Pleistocene periods in southern China. Our study of allotetraploid G. metteniana represents the first genomic-level documentation of hybrid speciation in scaly tree ferns and, thus, provides a new perspective on evolution in the lineage.
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Affiliation(s)
- Jing Wang
- Key Laboratory of Plant Resources Conservation and Sustainable Utilization, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou, China.,Center of Conservation Biology, Core Botanical Gardens, Chinese Academy of Sciences, Guangzhou, China
| | - Shiyong Dong
- Key Laboratory of Plant Resources Conservation and Sustainable Utilization, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou, China.,Center of Conservation Biology, Core Botanical Gardens, Chinese Academy of Sciences, Guangzhou, China
| | - Lihua Yang
- Key Laboratory of Plant Resources Conservation and Sustainable Utilization, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou, China.,Center of Conservation Biology, Core Botanical Gardens, Chinese Academy of Sciences, Guangzhou, China
| | - Aj Harris
- Key Laboratory of Plant Resources Conservation and Sustainable Utilization, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou, China.,Department of Biology, Oberlin College, Oberlin, OH
| | - Harald Schneider
- Center for Integrative Conservation, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Menglun, China
| | - Ming Kang
- Key Laboratory of Plant Resources Conservation and Sustainable Utilization, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou, China.,Center of Conservation Biology, Core Botanical Gardens, Chinese Academy of Sciences, Guangzhou, China
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Hornych O, Ekrt L, Riedel F, Koutecký P, Košnar J. Asymmetric hybridization in Central European populations of the Dryopteris carthusiana group. AMERICAN JOURNAL OF BOTANY 2019; 106:1477-1486. [PMID: 31634425 DOI: 10.1002/ajb2.1369] [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: 04/03/2019] [Accepted: 08/30/2019] [Indexed: 06/10/2023]
Abstract
PREMISE Hybridization is a key process in plant speciation. Despite its importance, there is no detailed study of hybridization rates in fern populations. A proper estimate of hybridization rates is needed to understand factors regulating hybridization. METHODS We studied hybridization in the European Dryopteris carthusiana group, represented by one diploid and two tetraploid species and their hybrids. We sampled ~100 individuals per population in 40 mixed populations of the D. carthusiana group across Europe. All plants were identified by measuring genome size (DAPI staining) using flow cytometry. To determine the maternal parentage of hybrids, we sequenced the chloroplast region trnL-trnF of all taxa involved. RESULTS We found hybrids in 85% of populations. Triploid D. ×ambroseae occurred in every population that included both parent species and is most abundant when the parent species are equally abundant. By contrast, tetraploid D. ×deweveri was rare (15 individuals total) and triploid D. ×sarvelae was absent. The parentage of hybrid taxa is asymmetric. Despite expectations from previous studies, tetraploid D. dilatata is the predominant male parent of its triploid hybrid. CONCLUSIONS This is a thorough investigation of hybridization rates in natural populations of ferns. Hybridization rates differ greatly even among closely related fern taxa. In contrast to angiosperms, our data suggest that hybridization rates are highest in balanced parent populations and support the notion that some ferns possess very weak barriers to hybridization. Our results from sequencing cpDNA challenge established notions about the correlation of ploidy level and mating tendencies.
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Affiliation(s)
- Ondřej Hornych
- Faculty of Science, University of South Bohemia, Branišovská 1760, České Budějovice, CZ-37005, Czech Republic
| | - Libor Ekrt
- Faculty of Science, University of South Bohemia, Branišovská 1760, České Budějovice, CZ-37005, Czech Republic
| | - Felix Riedel
- Botanischer Garten der Universität Potsdam, Maulbeerallee 3, Potsdam, D-14469, Germany
- Arboretum der Humboldt-Universität zu Berlin, Späthstrasse 80/81, Berlin, D-12437, Germany
| | - Petr Koutecký
- Faculty of Science, University of South Bohemia, Branišovská 1760, České Budějovice, CZ-37005, Czech Republic
| | - Jiří Košnar
- Faculty of Science, University of South Bohemia, Branišovská 1760, České Budějovice, CZ-37005, Czech Republic
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Testo WL, Watkins JE, Barrington DS. Dynamics of asymmetrical hybridization in North American wood ferns: reconciling patterns of inheritance with gametophyte reproductive biology. THE NEW PHYTOLOGIST 2015; 206:785-795. [PMID: 25443156 DOI: 10.1111/nph.13213] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/26/2014] [Accepted: 11/11/2014] [Indexed: 06/04/2023]
Abstract
Hybridization is an important evolutionary force in plants, but the mechanisms underlying it have not been well studied for many groups. In particular, the drivers of non-random patterns of interspecific gene flow (asymmetrical hybridization) remain poorly understood, especially in the seed-free vascular plants. Here, we examine patterns of asymmetrical hybridization in two widespread fern hybrids from eastern North America and study the role of gametophyte ecology in the determination of hybridization bias. We characterized the maternal parentage of > 140 hybrid sporophytes by sequencing a c. 350-bp region of chloroplast DNA (cpDNA). To identify factors contributing to patterns of asymmetrical hybridization, we cultured gametophytes of the parental species and evaluated critical aspects of their reproductive biology. We found that asymmetrical hybridization was prevalent across the populations of both hybrids. Reproductive traits varied across species and suggest that selfing potential, antheridiogen responsiveness, sperm dispersal capacity and gamete size all contribute to the mediation of the direction of hybridization in this group. Our findings suggest that asymmetrical hybridization in ferns is driven by an array of reproductive traits. This study helps to sharpen and define a mechanistic understanding of patterns of hybridization in this group and demonstrates the importance of considering gametophyte biology when studying evolutionary processes in ferns.
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Affiliation(s)
- Weston L Testo
- Department of Plant Biology, University of Vermont, 111 Jeffords Hall, 63 Carrigan Drive, Burlington, VT, 05405, USA
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Zhang R, Liu T, Wu W, Li Y, Chao L, Huang L, Huang Y, Shi S, Zhou R. Molecular evidence for natural hybridization in the mangrove fern genus Acrostichum. BMC PLANT BIOLOGY 2013; 13:74. [PMID: 23634934 PMCID: PMC3668252 DOI: 10.1186/1471-2229-13-74] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/06/2012] [Accepted: 04/26/2013] [Indexed: 05/12/2023]
Abstract
BACKGROUND Natural hybridization is prevalent in ferns, and plays an important role in fern evolution and speciation. In the Indo West-Pacific region, the mangrove fern genus Acrostichum consists of two largely sympatric species, A. aureum and A. speciosum. Although there has been no report of interspecific hybridization before, we found some individuals morphologically intermediate between them in Guangdong and Hainan, China, for the first time, which were suspected to be hybrids. In this study, we aimed to test the hypothesis of natural hybridization between A. aureum and A. speciosum in Guangdong and Hainan using three low-copy nuclear genes. A chloroplast intergenic spacer was used to infer the hybridization direction once the hybrid status was confirmed. In addition, we examined spore shapes and germination for these taxa. RESULTS Both A. aureum and A. speciosum showed a low level of polymorphism at all three nuclear genes; however, they were well separated at these loci. At both locations, each individual of the putative hybrid showed additivity in chromatograms at all sites where the two species showed fixed differences. Haplotype analysis at all three nuclear genes indicated that each individual of the putative hybrid possessed two haplotypes, matching with those of A. aureum and A. speciosum, respectively. Sequencing of the chloroplast trnV-trnM regions showed that A. aureum differed from A. speciosum by eleven nucleotide substitutions and three indels (insertions/deletions), and all sampled individuals of the putative hybrid had the identical sequences with A. speciosum. Compared with A. aureum and A. speciosum, the putative hybrid had much reduced spore germination rate. CONCLUSIONS Sequence data of the three nuclear genes provide compelling evidence for natural hybridization between A. aureum and A. speciosum, and all the hybrid individuals are likely F1s. The hybridization is unidirectional and A. speciosum is the maternal parent of the hybrid based on the assumption of maternal inheritance of chloroplast DNA. Human disturbance on mangrove habitats may facilitate the establishment of hybrids of Acrostichum.
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Affiliation(s)
- Rongshu Zhang
- State Key Laboratory of Biocontrol and Guangdong Key Laboratory of Plant Resources, Sun Yat-sen University, Guangzhou, 510275, China
| | - Ting Liu
- State Key Laboratory of Biocontrol and Guangdong Key Laboratory of Plant Resources, Sun Yat-sen University, Guangzhou, 510275, China
| | - Wei Wu
- Key Laboratory of Plant Resources Conservation and Sustainable Utilization, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou, 510650, China
| | - Yunqin Li
- Experimental Center of Fundamental Teaching, Zhuhai Campus, Sun Yat-sen University, Zhuhai, 519802, China
| | - Lifang Chao
- State Key Laboratory of Biocontrol and Guangdong Key Laboratory of Plant Resources, Sun Yat-sen University, Guangzhou, 510275, China
| | - Lishi Huang
- State Key Laboratory of Biocontrol and Guangdong Key Laboratory of Plant Resources, Sun Yat-sen University, Guangzhou, 510275, China
| | - Yelin Huang
- State Key Laboratory of Biocontrol and Guangdong Key Laboratory of Plant Resources, Sun Yat-sen University, Guangzhou, 510275, China
| | - Suhua Shi
- State Key Laboratory of Biocontrol and Guangdong Key Laboratory of Plant Resources, Sun Yat-sen University, Guangzhou, 510275, China
| | - Renchao Zhou
- State Key Laboratory of Biocontrol and Guangdong Key Laboratory of Plant Resources, Sun Yat-sen University, Guangzhou, 510275, China
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Affiliation(s)
- Rama S Talluri
- School of Biological Sciences, The University of Auckland, Private Bag 92019, Auckland Mail Centre, Auckland 1142, New Zealand.
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Hunt HV, Ansell SW, Russell SJ, Schneider H, Vogel JC. Dynamics of polyploid formation and establishment in the allotetraploid rock fern Asplenium majoricum. ANNALS OF BOTANY 2011; 108:143-57. [PMID: 21593062 PMCID: PMC3119625 DOI: 10.1093/aob/mcr118] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/11/2011] [Accepted: 03/28/2011] [Indexed: 05/29/2023]
Abstract
BACKGROUND AND AIMS Successful establishment of newly formed polyploid species depends on several interlinked genetic and ecological factors. These include genetic diversity within and among individuals, chromosome behaviour and fertility, novel phenotypes resulting from novel genomic make-up and expression, intercytotypic and interspecific competition, and adaptation to distinct habitats. The allotetraploid rock fern Asplenium majoricum is known from one small population in Valencia, Spain, and several larger populations on the Balearic island of Majorca. In Valencia, it occurs sympatrically with its diploid parents, A. fontanum subsp. fontanum and A. petrarchae subsp. bivalens, and their diploid hybrid A. × protomajoricum. This highly unusual situation allowed the study of polyploid genetic diversity and its relationship to the formation and establishment of nascent polyploid lineages. METHODS Genetic variation for isozyme and chloroplast DNA markers was determined for A. majoricum and A. × protomajoricum sampled thoroughly from known sites in Majorca and Valencia. Results were compared with variation determined previously for the diploid parent taxa. KEY RESULTS A highly dynamic system with recurring diploid hybrid and allotetraploid formation was discovered. High diversity in the small Valencian A. majoricum population indicates multiple de novo origins from diverse parental genotypes, but most of these lineages become extinct without becoming established. The populations on Majorca most probably represent colonization(s) from Valencia rather than an in situ origin. Low genetic diversity suggests that this colonization may have occurred only once. CONCLUSIONS There is a striking contrast in success of establishment of the Majorcan and Valencian populations of A. majoricum. Chance founding of populations in a habitat where neither A. fontanum subsp. fontanum nor A. petrarchae subsp. bivalens occurs appears to have been a key factor enabling the establishment of A. majoricum on Majorca. Successful establishment of this polyploid is probably dependent on geographic isolation from diploid progenitor competition.
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Affiliation(s)
- Harriet V Hunt
- Department of Botany, Natural History Museum, London SW7 5BD, UK.
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Ekrt L, Holubová R, Trávnícek P, Suda J. Species boundaries and frequency of hybridization in the Dryopteris carthusiana (Dryopteridaceae) complex: A taxonomic puzzle resolved using genome size data. AMERICAN JOURNAL OF BOTANY 2010; 97:1208-19. [PMID: 21616872 DOI: 10.3732/ajb.0900206] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
PREMISE OF THE STUDY Genome duplication and interspecific hybridization are important evolutionary processes that significantly influence phenotypic variation, ecological behavior, and reproductive biology of land plants. These processes played a major role in the evolution of the Dryopteris carthusiana complex. This taxonomically intricate group composed of one diploid (D. expansa) and two allotetraploid (D. carthusiana and D. dilatata) species in Central Europe. Overall phenotypic similarity, great plasticity, and the incidence of interspecific hybrids have led to a continuous dispute concerning species circumscription and delimitation. • METHODS We used flow cytometry and multivariate morphometrics to assess the level of phenotypic variation and the frequency of hybridization in a representative set covering all recognized species and hybrids. • KEY RESULTS Flow cytometric measurements revealed unique genome sizes in all species and hybrids, allowing their easy and reliable identification for subsequent morphometric analyses. Different species often formed mixed populations, providing the opportunity for interspecific hybridization. Different frequencies of particular hybrid combinations depended primarily on evolutionary relationships, reproductive biology, and co-occurrence of progenitors. • CONCLUSIONS Our study shows that genome size is a powerful marker for taxonomic decisions about the D. carthusiana complex and that genome size data may help to resolve taxonomic complexities in this important component of the temperate fern flora.
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Affiliation(s)
- Libor Ekrt
- Department of Botany, Faculty of Science, University of South Bohemia, Branišovská 31, CZ-370 05 České Budějovice, Czech Republic
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Wu W, Zhou R, Huang Y, Boufford DE, Shi S. Molecular evidence for natural intergeneric hybridization between Liquidambar and Altingia. JOURNAL OF PLANT RESEARCH 2010; 123:231-9. [PMID: 19941029 DOI: 10.1007/s10265-009-0275-z] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/27/2008] [Accepted: 10/06/2009] [Indexed: 05/16/2023]
Abstract
Since its establishment, a hybrid origin for Semiliquidambar has been proposed based on morphological intermediacy and sympatric distribution with Altingia and Liquidambar. This hypothesis, however, has lacked convincing molecular evidence. In this study, two nuclear genes, pin2 and cab4, and a chloroplast gene, matK, from Semiliquidambar cathayensis and its putative parental species Liquidambar and Altingia in Jianfengling, Hainan, and Heishiding and Nanling, Guangdong, China, were sequenced to test this hypothesis. Our results showed that L. formosana and L. acalycina were closely related and constituted an inseparable clade in the phylogenetic trees of both pin2 and cab4 genes. Phylogenetic analyses revealed two types of sequences for S. cathayensis, which were clustered with its putative parents, L. formosana-L. acalycina and A. obovata in Jianfengling, and with L. formosana-L. acalycina and A. chinensis in Heishiding and Nanling. The partial chloroplast matK gene sequences showed four nucleotide substitutions between L. formosana and A. obovata in Jianfengling; the sequences of the two individuals of S. cathayensis were identical with those of A. obovata. No diagnostic chloroplast markers including matK and three other chloroplast genes were found to distinguish L. formosana and A. chinensis in Heishiding and Nanling. Molecular data clearly demonstrated that S. cathayensis is of intergeneric hybrid origin between L. formosana-L. acalycina and A. obovata or A. chinensis and that A. obovata functions as the maternal parent in the hybridization event in Jianfengling, Hainan.
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Affiliation(s)
- Wei Wu
- State Key Laboratory of Biocontrol, Key Laboratory of Gene Engineering of the Ministry of Education, School of Life Science, Sun Yat-Sen University, Xinggangxi Road No 135, 510275 Guangzhou, China
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Ebert D, Peakall R. Chloroplast simple sequence repeats (cpSSRs): technical resources and recommendations for expanding cpSSR discovery and applications to a wide array of plant species. Mol Ecol Resour 2009; 9:673-90. [PMID: 21564725 DOI: 10.1111/j.1755-0998.2008.02319.x] [Citation(s) in RCA: 137] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Chloroplast microsatellites, or simple sequence repeats (cpSSRs), are typically mononucleotide tandem repeats. When located in the noncoding regions of the chloroplast genome (cpDNA), they commonly show intraspecific variation in repeat number. Despite the growing number of studies applying cpSSRs, studies of economically important plants and their relatives remain over-represented. Thus, the potential of cpSSRs to offer unique insights into ecological and evolutionary processes in wild plant species has yet to be fully realized. This review provides an overview of the technical resources available to aid cpSSR discovery including a list of cpSSR primer sets available and cpDNA sequencing resources. Our updated analysis of 99 whole chloroplast genomes downloaded from GenBank confirms that potentially variable cpSSRs are abundant in the noncoding cpDNA of plants. Overall variation in the frequency of cpSSRs was extreme, ranging from one to 700 per genome (median = 93), while in 81 vascular plants, between 35 and 160 cpSSRs were detected per genome (median = 86). We offer five recommendations to aid wider development and application of cpSSRs: (i) When genus-specific cpSSR primers are available, cross-species amplification can often be fruitful. (ii) While potentially useful, universal cpSSR primers at best provide access to only a small number of variable markers. (iii) De novo sequencing of noncoding cpDNA is the most effective and efficient way to develop cpSSR markers in wild species. (iv) DNA sequencing of cpSSR alleles is essential, given the complex nature of the genetic variation associated with hypervariable cpDNA regions. (v) The reliability of cpSSR length based genetic assays need to be validated in all studies.
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Affiliation(s)
- Daniel Ebert
- School of Botany and Zoology, The Australian National University, Canberra ACT 0200, Australia
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Fazekas AJ, Burgess KS, Kesanakurti PR, Graham SW, Newmaster SG, Husband BC, Percy DM, Hajibabaei M, Barrett SCH. Multiple multilocus DNA barcodes from the plastid genome discriminate plant species equally well. PLoS One 2008; 3:e2802. [PMID: 18665273 PMCID: PMC2475660 DOI: 10.1371/journal.pone.0002802] [Citation(s) in RCA: 340] [Impact Index Per Article: 21.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2008] [Accepted: 06/23/2008] [Indexed: 12/03/2022] Open
Abstract
A universal barcode system for land plants would be a valuable resource, with potential utility in fields as diverse as ecology, floristics, law enforcement and industry. However, the application of plant barcoding has been constrained by a lack of consensus regarding the most variable and technically practical DNA region(s). We compared eight candidate plant barcoding regions from the plastome and one from the mitochondrial genome for how well they discriminated the monophyly of 92 species in 32 diverse genera of land plants (N = 251 samples). The plastid markers comprise portions of five coding (rpoB, rpoC1, rbcL, matK and 23S rDNA) and three non-coding (trnH-psbA, atpF-atpH, and psbK-psbI) loci. Our survey included several taxonomically complex groups, and in all cases we examined multiple populations and species. The regions differed in their ability to discriminate species, and in ease of retrieval, in terms of amplification and sequencing success. Single locus resolution ranged from 7% (23S rDNA) to 59% (trnH-psbA) of species with well-supported monophyly. Sequence recovery rates were related primarily to amplification success (85-100% for plastid loci), with matK requiring the greatest effort to achieve reasonable recovery (88% using 10 primer pairs). Several loci (matK, psbK-psbI, trnH-psbA) were problematic for generating fully bidirectional sequences. Setting aside technical issues related to amplification and sequencing, combining the more variable plastid markers provided clear benefits for resolving species, although with diminishing returns, as all combinations assessed using four to seven regions had only marginally different success rates (69-71%; values that were approached by several two- and three-region combinations). This performance plateau may indicate fundamental upper limits on the precision of species discrimination that is possible with DNA barcoding systems that include moderate numbers of plastid markers. Resolution to the contentious debate on plant barcoding should therefore involve increased attention to practical issues related to the ease of sequence recovery, global alignability, and marker redundancy in multilocus plant DNA barcoding systems.
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Affiliation(s)
- Aron J Fazekas
- Department of Integrative Biology, University of Guelph, Guelph, Ontario, Canada.
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Zhou R, Gong X, Boufford D, Wu CI, Shi S. Testing a hypothesis of unidirectional hybridization in plants: observations on Sonneratia, Bruguiera and Ligularia. BMC Evol Biol 2008; 8:149. [PMID: 18485207 PMCID: PMC2409324 DOI: 10.1186/1471-2148-8-149] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2007] [Accepted: 05/16/2008] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND When natural hybridization occurs at sites where the hybridizing species differ in abundance, the pollen load delivered to the rare species should be predominantly from the common species. Previous authors have therefore proposed a hypothesis on the direction of hybridization: interspecific hybrids are more likely to have the female parent from the rare species and the male parent from the common species. We wish to test this hypothesis using data of plant hybridizations both from our own experimentation and from the literature. RESULTS By examining the maternally inherited chloroplast DNA of 6 cases of F1 hybridization from four genera of plants, we infer unidirectional hybridization in most cases. In all 5 cases where the relative abundance of the parental species deviates from parity, however, the direction is predominantly in the direction opposite of the prediction based strictly on numerical abundance. CONCLUSION Our results show that the observed direction of hybridization is almost always opposite of the predicted direction based on the relative abundance of the hybridizing species. Several alternative hypotheses, including unidirectional postmating isolation and reinforcement of premating isolation, were discussed.
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Affiliation(s)
- Renchao Zhou
- State Key Laboratory of Biocontrol and Key Laboratory of Gene Engineering of the Ministry of Education, Sun Yat-Sen University, Guangzhou 510275, PR China
| | - Xun Gong
- Kunming Institute of Botany, Chinese Academy of Sciences, Kunming 650204, PR China
| | - David Boufford
- Harvard University Herbaria, 22 Divinity Ave, Cambridge, Massachusetts 02138, USA
| | - Chung-I Wu
- Department of Ecology and Evolution, University of Chicago, Chicago, Illinois 60637, USA
| | - Suhua Shi
- State Key Laboratory of Biocontrol and Key Laboratory of Gene Engineering of the Ministry of Education, Sun Yat-Sen University, Guangzhou 510275, PR China
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Sperm cell architecture, insemination, and fertilization in the model fern, Ceratopteris richardii. ACTA ACUST UNITED AC 2008. [DOI: 10.1007/s00497-008-0068-x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Adjie B, Masuyama S, Ishikawa H, Watano Y. Independent origins of tetraploid cryptic species in the fern Ceratopteris thalictroides. JOURNAL OF PLANT RESEARCH 2007; 120:129-38. [PMID: 16955374 DOI: 10.1007/s10265-006-0032-5] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/18/2006] [Accepted: 07/20/2006] [Indexed: 05/07/2023]
Abstract
Ceratopteris thalictroides (L.) Brongn is a tetraploid fern species that contains at least three cryptic species, the south, the north and the third type. In this study we combined data from both chloroplast DNA (cpDNA) and nuclear DNA sequences of three diploid species and three cryptic species of C. thalictroides to unravel the origin of the cryptic species, particularly of the reticulate relationships among the diploid and tetraploid taxa in the genus Ceratopteris. Of the three diploid species examined, C. cornuta had cpDNA identical to that of the tetraploid third type plants, and this diploid species is a possible maternal ancestor of the tetraploid third type. Analysis of the homologue of the Arabidopsis thaliana LEAFY gene (CLFY1) identified ten alleles in the genus Ceratopteris, with six alleles found in C. thalictroides. The unrooted tree of the CLFY1 gene revealed four clusters. Each cryptic species showed fixed heterozygosity at the CLFY1 locus and had two alleles from different clusters of the CLFY1 tree. Consideration of the cpDNA sequences, CLFY1 genotypes of the cryptic species and CLFY1 gene tree in concert suggested that the cryptic species of C. thalictroides had originated through independent allopolyploidization events involving C. cornuta and two unknown hypothetical diploid species.
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Affiliation(s)
- Bayu Adjie
- Graduate School of Science and Technology, Chiba University, Yayoi 1-33, Inage, Chiba 263-8522, Japan.
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Tessier JT, Bornn MP. Old fronds serve as a vernal carbon source in the wintergreen fern Dryopteris intermedia (Aspleniaceae). AMERICAN JOURNAL OF BOTANY 2007; 94:25-28. [PMID: 21642204 DOI: 10.3732/ajb.94.1.25] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Maintaining green leaves beyond the growing season has been hypothesized to benefit plants by supplying either a nutrient or a carbon source. Understanding such ecophysiological aspects of plants will help us to appreciate how a species functions in its environment and predict how it might be affected by future changes in that environment. The wintergreen fern species Dryopteris intermedia does not retranslocate nitrogen and phosphorus from old fronds in spring, but photosynthesis does take place in the old fronds during this season. To determine if carbon fixed in the old fronds is translocated to other parts of the plant, we labeled old fronds with (13)C via photosynthetic uptake and examined old fronds, new fronds, fine roots, and rhizomes for (13)C content 1 day and 1 month after labeling the old fronds. Vernally fixed carbon was translocated to the new fronds but not significantly to the below ground tissues. Old fronds in this species, therefore, serve as a carbon source for vernal growth of new fronds. This is the first study in which a fern was labeled with (13)C to track vernally fixed carbon from old fronds to the rest of the plant in a wintergreen species. Future research should examine the precise timing of this carbon movement and examine other species for a similar or contrasting strategy.
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Wu CA, Campbell DR. Cytoplasmic and nuclear markers reveal contrasting patterns of spatial genetic structure in a natural Ipomopsis hybrid zone. Mol Ecol 2005; 14:781-92. [PMID: 15723669 DOI: 10.1111/j.1365-294x.2005.02441.x] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Spatial variation in natural selection may play an important role in determining the genetic structure of hybridizing populations. Previous studies have found that F1 hybrids between naturally hybridizing Ipomopsis aggregata and Ipomopsis tenuituba in central Colorado differ in fitness depending on both genotype and environment: hybrids had higher survival when I. aggregata was the maternal parent, except in the centre of the hybrid zone where both hybrid types had high survival. Here, we developed both maternally (cpDNA PCR-RFLP) and biparentally inherited (nuclear AFLP) species-diagnostic markers to characterize the spatial genetic structure of the natural Ipomopsis hybrid zone, and tested the prediction that the majority of natural hybrids have I. aggregata cytoplasm, except in areas near the centre of the hybrid zone. Analyses of 352 individuals from across the hybrid zone indicate that cytoplasmic gene flow is bidirectional, but contrary to expectation, most plants in the hybrid zone have I. tenuituba cytoplasm. This cytotype distribution is consistent with a hybrid zone in historical transition, with I. aggregata nuclear genes advancing into the contact zone. Further, nuclear data show a much more gradual cline than cpDNA markers that is consistent with morphological patterns across the hybrid populations. A mixture of environment- and pollinator-mediated selection may contribute to the current genetic structure of this hybrid system.
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Affiliation(s)
- Carrie A Wu
- Department of Ecology and Evolutionary Biology, University of California, Irvine, CA 92697, USA.
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