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Reticulate Evolution in Diphasiastrum (Lycopodiaceae)
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Evolution, Genomics and Systematics.
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In this thesis relationships and the occurrence of reticulate evolutionary events in the club moss genus Diphasiastrum are investigated. Diphasiastrum is initially established as a monophyletic group within Lycopodiaceae using non recombinant chloroplast sequence data. Support is obtained for eight distinct parental lineages in Diphasiastrum, and relationships among the putative parent taxa in the hypothesized hybrid complexes; D. alpinum, D. complanatum, D. digitatum, D. multispicatum, D. sitchense, D. tristachyum and D. veitchii are presented.

Feulgen DNA image densitometry data and sequence data obtained from three nuclear regions, RPB2, LEAFY and LAMB4, were used to infer the origins of three different taxa confirmed to be allopolyploid; D. zanclophyllum from South Africa, D. wightianum from Malaysia and an undescribed taxon from China. The two Asian polyploids have originated from two different hybrid combinations, D. multispicatum x D. veitchii and D. tristachyum x D. veitchii. Diphasiastrum zanclophyllum originates from a cross between D. digitatum and an unidentified diploid taxon.

The occurrence of three homoploid hybrid combinations commonly recognized in Europe, D. alpinum x D. complanatum, D. alpinum x D. tristachyum and D. complanatum x D. tristachyum, are verified using the same three nuclear regions. Two of the three hybrid combinations are also shown to have originated from reciprocal crosses. Admixture analyses performed on an extended, dataset similarly identified predominately F1 hybrids and backcrosses. The observations and common recognition of hybrid species in the included populations are hence most likely due to frequent observations of neohybrids in hybrid zones. Reticulate patterns are, however, prominent in the presented dataset. Hence future studies addressing evolutionary and ecological questions in Diphasiastrum should emphasize the impact of gene flow between parent lineages rather than speciation as the result of hybridization.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis , 2009. , p. 35
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 623
Keywords [en]
admixture analysis, Bayesian clustering, Diphasiastrum, Feulgen DNA image densitometry, homoploid hybridization, Lycopodiaceae, phylogenetic analysis, polyploidy, reticulate evolution
National Category
Biological Systematics
Research subject
Systematic Botany
Identifiers
URN: urn:nbn:se:uu:diva-99584ISBN: 978-91-554-7470-6 (print)OAI: oai:DiVA.org:uu-99584DiVA, id: diva2:208250
Public defence
2009-04-29, Lindahlsalen, Norbyvägen 18, Uppsala University, 10:00 (English)
Opponent
Supervisors
Available from: 2009-04-08 Created: 2009-03-16 Last updated: 2009-09-14Bibliographically approved
List of papers
1. Resolving maternal relationships in the clubmoss genus Diphasiastrum (Lycopodiaceae)
Open this publication in new window or tab >>Resolving maternal relationships in the clubmoss genus Diphasiastrum (Lycopodiaceae)
2009 (English)In: Taxon, ISSN 0040-0262, E-ISSN 1996-8175, Vol. 58, no 3, p. 835-848Article in journal (Refereed) Published
Abstract [en]

Diphasiastrum comprises 20-30 species. In addition to a number of species with a circumboreal distribution, several island endemics and putative diploid hybrid species contribute to the diversity of the group. To assess the integrity and relationships of the recognized species, a global phylogeny of Diphasiastrum is constructed using five chloroplast regions comprising ~9000 bp. Six monophyletic groups are identified. Accessions identified as hybrid species cluster in all but one case together with one of its putative parents. Two microsatellite loci are identified, and allelic information combined with sequence information is found diagnostic for the three putative parental taxa in the Central Europe hybrid complexes. Haplotype screening is performed on six Central European populations, from where one or more putative diploid hybrid species have been reported to grow in sympatry with their parent species. The most common parental haplotypes are identified in all populations. Additional intraspecific variation, restricted to single populations, is identified in all sympatric populations at very low frequencies. Taking the low degree of sequence and microsatellite variation into consideration, the acknowledged morphological diversity in Central Europe is probably best explained by phenotypic plasticity, ancestral polymorphisms or relatively recent events of reticulate evolution.

Keywords
Chloroplast microsatellites, Diphasiastrum, Diploid hybrid species, Lycopodium, Lycopodiaceae, Plastid phylogeny
National Category
Biological Sciences
Research subject
Systematic Botany
Identifiers
urn:nbn:se:uu:diva-99576 (URN)000269774900012 ()
Available from: 2009-03-16 Created: 2009-03-16 Last updated: 2017-12-13Bibliographically approved
2. Occurrence and evolutionary origins of polyploids in the club moss genus Diphasiastrum (Lycopodiaceae)
Open this publication in new window or tab >>Occurrence and evolutionary origins of polyploids in the club moss genus Diphasiastrum (Lycopodiaceae)
2009 (English)In: Molecular Phylogenetics and Evolution, ISSN 1055-7903, E-ISSN 1095-9513, Vol. 52, no 3, p. 746-754Article in journal (Refereed) Published
Abstract [en]

Two polyploid taxa are commonly recognized in the genus Diphasiastrum, D. wightianum from Asia and D. zanclophyllum from South Africa and Madagascar. Here we present results from Feulgen DNA image densitometry analyses providing the first evidence for the polyploid origin of D. zanclophyllum. Reported for the first time is also data confirming that D. multispicatum and D. veitchii, representing putative parent lineages for D. wightianum, are diploids. Phylogenetic analyses of nuclear regions RPB2, LEAFY and LAMB4 reveal that putative tetraploid accessions are of allopolyploid origin. Diphasiastrum zanclophyllum shows close relationships to the North American taxon D. digitatum on the maternal side, but the paternal relationship is less clear. Two accessions from Asia, both found to be polyploid, have D. veitchii as maternal parent, whereas the paternal paralogs show relationships to D. multispicatum and D. tristachyum, respectively. None of these parental combinations have previously been hypothesized.

Keywords
Diphasiastrum, Feulgen DNA image densitometry, Lycopodium, Lycopodiaceae, low-copy nuclear genes, phylogenies, polyploidy
National Category
Biological Sciences
Research subject
Systematic Botany
Identifiers
urn:nbn:se:uu:diva-99577 (URN)10.1016/j.ympev.2009.05.004 (DOI)000268265800016 ()
Available from: 2009-03-16 Created: 2009-03-16 Last updated: 2017-12-13Bibliographically approved
3. Reticulate phylogenetic patterns in diploid European Diphasiastrum (Lycopodiaceae).
Open this publication in new window or tab >>Reticulate phylogenetic patterns in diploid European Diphasiastrum (Lycopodiaceae).
(English)Manuscript (Other academic)
Abstract [en]

In Central Europe, three species belonging to Diphasiastrum are considered to be of homoploid hybrid origin. Diphasiastrum issleri is suggested to have originated from a cross between D. alpinum and D. complanatum, D. oellgaardii from D. alpinum and D. tristachyum, and D. zeilleri from D. complanatum and D. tristachyum. Variation at three nuclear regions and two chloroplast microsatellites verify the presence of all three putative parental combinations in Europe. Data obtained with Feulgen DNA image densitometry confirms that all specimens displaying such pattern are diploid. Also, two of three parental combinations have probably arisen repeatedly, implied by the occurrence of chloroplast haplotypes associated with different parents. The presented dataset cannot be used as argument for the existence of independent evolutionary entities hybrid origin. This is nonetheless an important first step in order to address the influence of reticulate evolutionary events in European Diphasiastrum

Keywords
Keywords – Diphasiastrum, homoploid hybridization, Lycopodiaceae, Lycopodium, low copy nuclear genes, phylogenies, Feulgen DNA image densitometry
Identifiers
urn:nbn:se:uu:diva-99578 (URN)
Available from: 2009-03-16 Created: 2009-03-16 Last updated: 2010-01-14
4. Homoploid hybridization in Central European Diphasiastrum (Lycopodiaceae).
Open this publication in new window or tab >>Homoploid hybridization in Central European Diphasiastrum (Lycopodiaceae).
(English)Manuscript (Other academic)
Abstract [en]

Three species of homoploid hybrid origin are commonly recognized among Central European Diphasiastrum, and reticulate evolutionary events have for a long time been acknowledged as an important factor contributing to the species count in the genus. Presented evidence obtained from molecular data has until recently been scarce and inconclusive. Recent studies have, however, documented reticulate phylogenetic patterns involving all putative parental combinations reported from Central Europe. Reciprocal crosses involving the same parental combinations have also been confirmed. In order to further explore these putative reticulate events, admixture analyses using a Bayesian approach as implemented in the program NewHybrids are conducted on an expanded dataset obtained from six Central European populations from where putative hybrid taxa are reported. A majority of the accessions included in the analyses were inferred to represent pure bred D. alpinum, D. complanatum, D. tristachyum, F1 hybrids, F2 hybrids or backcrosses with one of the parent species. Accessions displaying ambiguous classification were found in both allopatric parent populations as well as in Central European hybrid populations. Presented results indicate the presence of frequently occurring hybrid zones with first and second generation hybrids as well as backcrosses.

Keywords
admixture analysis, Bayesian clustering, Diphasiastrum, homoploid hybridization, Lycopodiaceae, Lycopodium, NewHybrids.
National Category
Biological Systematics
Research subject
Systematic Botany; Population Biology
Identifiers
urn:nbn:se:uu:diva-99579 (URN)
Available from: 2009-03-16 Created: 2009-03-16 Last updated: 2010-01-14
5. Revised lectotypification of Lycopodium complanatum L. (Lycopodiaceae)
Open this publication in new window or tab >>Revised lectotypification of Lycopodium complanatum L. (Lycopodiaceae)
2009 (English)In: Taxon, ISSN 0040-0262, E-ISSN 1996-8175, Vol. 58, no 3, p. 974-976Article in journal (Refereed) Published
Abstract [en]

The currently accepted lectotype of the circumboreal species Lycopodium complanatum L., or Diphasiastrum complanatum (L.) Holub, is a specimen of the related species L. tristachyum Pursh, or D. tristachyum (Pursh) Holub, mainly distributed in eastern North America and Europe. This lectotype, in LINN, is here superseded in favour of an alternative original element in the Celsius herbarium in Uppsala, supported by an epitype, on the grounds of conflict with the protologue. Thereby the traditional usage of the well-known name L. complanatum can be maintained.

Keywords
Diphasiastrum, nomenclature, Lycopodium, Lycopodiaceae, typification.
National Category
Biological Systematics
Research subject
Systematic Botany; Biology with specialization in Systematics
Identifiers
urn:nbn:se:uu:diva-99572 (URN)000269774900026 ()
Available from: 2009-03-16 Created: 2009-03-16 Last updated: 2017-12-13Bibliographically approved

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