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Phylogeny of Woodsia (Woodsiaceae): recent speciation through polyploidization is common in old diploid stock.
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology.
Department of Biology, Duke University, , Durham, North Carolina, USA.
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology.
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Woodsia is a genus of small tufted ferns growing in rocky habitats. It is widely distributed in temperate and montane regions of the world. Through previous cytological studies and allozyme work it is known to have a complex evolutionary history and includes numerous polyploid taxa and hybrids. We present here for the first time detailed phylogenetic analyses of a wide range of taxa within Woodsia, including samples from many chromosome-counted specimens. Five plastid (atpA, atpB, matK, rbcL and trnG-R) and two nuclear (pgiC and RPA2) regions have been used from an ingroup of 188 samples representing 36 taxa and six hybrids. In a complementary expanded analysis the polyploid speciation frequency is estimated within the 10 families most closely related to Woodsiaceae (the Eupolypods II). Woodsia is monophyletic if the often segregated genera Protowoodsia, Cheilanthopsis and Hymenocystis are included. The genus comprises two major well-supported clades, one including the circumboreal and most of the Asian species, and the other including all American and the remaining Asian species. The split between these clades is estimated to 45 Ma. Woodsia × abbae is a remarkable triploid hybrid between members of these two clades. Most taxa in Woodsia are polyploid and polyploidization is the most common mode of speciation in the genus with an estimated polyploid speciation rate of 54%. The polyploids are mostly young. Some of the polyploid taxa, such as W. alpina and W. obtusa, seem to have been formed multiple times. The Eupolypod II study agrees with the Woodsia study in showing a high proportion of polyploids with a polyploid speciation rate of 46%. Old polyploid lineages are rare. The circumboreal species do not form a monophyletic group and are nested among various Asian species, whereas the "American clade" is monophyletic and nested among Asian species. Within the American clade W. montevidensis has its main distribution in South America, but also has made a recent leap to Southern Africa and Madagascar.

Keyword [en]
biogeography, chromosome numbers, Eupolypods II, hybrids, nuclear and plastid DNA, polyploid speciation
National Category
Botany
Research subject
Biology with specialization in Systematics
Identifiers
URN: urn:nbn:se:uu:diva-232232OAI: oai:DiVA.org:uu-232232DiVA: diva2:747143
Funder
Formas, 2006-429 and 2010-585
Available from: 2014-09-15 Created: 2014-09-15 Last updated: 2015-01-23
In thesis
1. Systematics of Woodsia: Ferns, bioinformatics and more
Open this publication in new window or tab >>Systematics of Woodsia: Ferns, bioinformatics and more
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Ferns are one of the three main clades of vascular plants. They have few easily studied morphological characters, reflected in a historically unstable classification. The fern genus Woodsia is known to have a complex evolutionary history including numerous polyploid taxa and hybrids. It is a cosmopolitan group of small rock loving ferns mainly found in montane areas.

This thesis aims at analyzing the patterns of diploid and polyploid evolution in Woodsia and to resolve and classify the relationships of Woodsiaceae and the other families in the large fern clade Eupolypods II.

The Eupolypods II family relationships were inferred with DNA sequences from 81 specimens representing all major lineages. This resulted in the first well supported phylogeny of this clade and revealed Woodsiaceae to be non-monophyletic. The genera previously placed in this family were reclassified into five new or resurrected families. Swedish fern genera that have changed family classification are Woodsia (hällebräknar), now in the monogeneric family Woodsiaceae, Athyrium (majbräknar), now  in Athyriaceeae and Cystopteris (stenbräknar) and Gymnocarpium (ekbräknar) now in Cystopteridaceae.

To analyze the evolution of Woodsia, phylogenies were produced from five plastid and two nuclear regions sequenced from 188 specimens. The results show that most taxa in Woodsia are polyploid. Polyploidization is the most common mode of speciation in the genus with an estimated polyploid speciation rate of 54%. The polyploids are mostly young and many of the polyploid taxa seem to have formed multiple times. The results also address several taxonomic and biogeographic questions.

In the process of the work we made methodological advancements and developed 20 new low copy nuclear marker regions as well as a software pipeline for finding primers in transcriptome datasets. The alignment editor software AliView was developed for handling the increasing size datasets in a user friendly way.

In conclusion this thesis provides new insights into the complexities of the evolution of a fern genus in which much of the diversity is accommodated in young species formed through polyploidization. It provides a framework of phylogenetic relationships at different levels that both answers long standing questions and generates new ones.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2014. 36 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1182
Keyword
ferns, Eupolypods II, Woodsia, phylogeny, biogeography, polyploidy, polyploid speciation, classification, alignment
National Category
Biological Systematics
Research subject
Biology with specialization in Systematics
Identifiers
urn:nbn:se:uu:diva-232233 (URN)978-91-554-9040-9 (ISBN)
Public defence
2014-10-31, Lindahlsalen, Norbyvägen 18B, Uppsala, 10:00 (English)
Opponent
Supervisors
Funder
Swedish Research Council Formas, 2006-429 and 2010-585
Available from: 2014-10-10 Created: 2014-09-15 Last updated: 2015-01-23

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