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Molecular data and ploidal levels indicate several putative allopolyploidization events in the genus Potentilla (Rosaceae)
Stockholm University, Faculty of Science, Department of Botany.
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Several naturally occurring hybrids in Potentilla (Rosaceae) have been reported, but no molecular evidence has so far been available to test these hypotheses of hybridization. We have compared a nuclear and a chloroplast gene tree to identify topological incongruences that may indicate hybridization events in the genus. Furthermore, the monophyly and phylogenetic position of the proposed segregated genera Argentina, Ivesia and Horkelia have been tested. The systematic signal from the two morphological characters, style- and anther shape, has also been investigated by ancestral state reconstruction, to elucidate how well these characters concur with the results of the molecular phylogenies. Six major clades, Anserina, Alba, Fragarioides, Reptans, ivesioid Potentilleae and Argentea, have been identified within genus Potentilla. The ivesioid Potentilleae (Horkelia, Ivesia and Horkeliella) form a monophyletic group nested within Potentilla. Furthermore, the origin of the proposed segregated genus Argentina (the Anserina clade) is uncertain but not in conflict with a new generic status of the group. We also found style morphology to be an informative character that reflects the phylogenetic relationships within Potentilla. Four well supported incongruences were found between the nuclear and the chloroplast phylogenies, where the involved taxa were polyploids. However, further investigations using low copy molecular markers are required to infer the phylogeny of these species and to test the hypothesis of hybrid origin.

Keyword [en]
Allopolyploidy, Potentilla, molecular phylogeny, Rosaceae, hybridization
National Category
Biological Systematics
Research subject
Systematic Botany
Identifiers
URN: urn:nbn:se:su:diva-56686OAI: oai:DiVA.org:su-56686DiVA: diva2:412169
Available from: 2011-04-26 Created: 2011-04-20 Last updated: 2011-04-26Bibliographically approved
In thesis
1. Systematics and polyploid evolution in Potentilleae (Rosaceae)
Open this publication in new window or tab >>Systematics and polyploid evolution in Potentilleae (Rosaceae)
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis comprises studies of the phylogenetic relationships in the flowering plant clade Potentilleae in Rosaceae. The relationships were elucidated by using DNA sequence data from the nuclear genome as well as from the plastid genome. In particular, the focus of the studies was the investigation of allopolyploidy, i.e. speciation as a result of hybridization and subsequent chromosome doubling. A phylogenetic method was used for identifying allopolyploidy through comparison of trees resulting from the analyses of different DNA sequences. Five sub-clades were investigated. First, both the sister clades that together contain all of Potentilleae: Fragariinae and Potentilla. Secondly, three subclades of Fragariinae, namely Alchemilla in wide sense, Sibbaldia and relatives, and Fragaria. The aim was to unravel the phylogenetic relationships, including instances of allopolyploidy. Classification issues were discussed in relation to the phylogenetic results. The split between Potentilla (=Potentillinae) and Fragariinae received better support than in previous studies. The phylogeny of Fragariinae was found to be consistent with classifying ten genera: Alchemilla in wide sense (incl. Aphanes and Lachemilla), Comarum, Sibbaldia, Sibbaldianthe, Sibbaldiopsis, Chamaerhodos, Drymocallis, Dasiphora, Potaninia, Fragaria, and also including a few orphan Potentilla species. The segregated genera Ivesia, Horkelia, Horkeliella and Duchesnea were found to be nested within Potentilla, corroborating earlier studies, while the segregated genus Argentina (P. anserina and close relatives) showed an ambiguous position. Plastid and nuclear (ribosomal) phylogenies were compared and incongruences were detected as potential instances of allopolyploid speciation. Five strongly supported incongruences were detected in Fragariinae and four of them were considered to be potentially caused by allopolyploidy. In addition, five supported incongruences were found in Potentilla. Alchemilla in the wide sense was found to contain four major clades, African Alchemilla, Eurasian Alchemilla, Lachemilla and Aphanes. Both Lachemilla and Aphanes were nested within Alchemilla and it was suggested that the name Alchemilla should be used in the wide sense, i.e. including both the genera Lachemilla and Aphanes. The genus Sibbaldia as commonly classified was shown to be polyphyletic in five different places in Potentilleae. Three Sibbaldia clades ended up in Fragariinae and two in Potentilla. A phylogeny of Fragaria, based on a nuclear low/single copy DNA region was estimated. The gene copy phylogeny was used to construct a reticulate tree hypothesizing allopolyploid speciation events. The evolution of Fragaria was shown to have been shaped by polyploidy.

Place, publisher, year, edition, pages
Stockholm: Department of Botany, Stockholm University, 2011. 28 p.
Keyword
Potentilleae, Fragariinae, Potentilla, Sibbaldia, Fragaria, Alchemilla, systematics, phylogeny, polyploidy, autopolyploidy, allopolyploidy, reticulate evolution
National Category
Biological Systematics
Research subject
Plant Systematics
Identifiers
urn:nbn:se:su:diva-53967 (URN)978-91-7447-227-1 (ISBN)
Public defence
2011-05-20, föreläsningssalen, Botanicum, Lilla Frescativägen 5, Stockholm, 10:00 (English)
Opponent
Supervisors
Note
At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Manuscript. Paper 4: Manuscript. Paper 5: Manuscript.Available from: 2011-04-28 Created: 2011-01-25 Last updated: 2011-04-26Bibliographically approved

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