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Homoploid hybridization in Central European Diphasiastrum (Lycopodiaceae).
Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Department of Evolution, Genomics and Systematics.
(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.

Keyword [en]
admixture analysis, Bayesian clustering, Diphasiastrum, homoploid hybridization, Lycopodiaceae, Lycopodium, NewHybrids.
National Category
Biological Systematics
Research subject
Systematic Botany; Population Biology
URN: urn:nbn:se:uu:diva-99579OAI: oai:DiVA.org:uu-99579DiVA: diva2:208222
Available from: 2009-03-16 Created: 2009-03-16 Last updated: 2010-01-14
In thesis
1. Reticulate Evolution in Diphasiastrum (Lycopodiaceae)
Open this publication in new window or tab >>Reticulate Evolution in Diphasiastrum (Lycopodiaceae)
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. 35 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 623
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
urn:nbn:se:uu:diva-99584 (URN)978-91-554-7470-6 (ISBN)
Public defence
2009-04-29, Lindahlsalen, Norbyvägen 18, Uppsala University, 10:00 (English)
Available from: 2009-04-08 Created: 2009-03-16 Last updated: 2009-09-14Bibliographically approved

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Aagaard, Sunniva M.D.
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