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Spikemoss patterns: Systematics and historical biogeography of Selaginellaceae
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Systematic Biology.
2016 (English)Doctoral thesis, comprehensive summary (Other academic)Alternative title
Mosslummermönster : Systematik och historisk biogeografi hos Selaginellaceae (Swedish)
Abstract [en]

Selaginellaceae, spikemosses, is a heterosporous plant family belonging to the lycophytes. With an estimated age of some 350 million years, the family is historically important as one of the oldest known groups of vascular plants. Selaginellaceae is herbaceous with a worldwide distribution. However, the majority of the ca. 750 species in the single genus Selaginella are found in the tropics and subtropics.

This thesis aims at elucidating the systematics and historical biogeography of Selaginellaceae. The evolutionary relationships of the family were inferred from DNA sequence data (plastid and single-copy nuclear) of one-third of the species richness in the group. Attention was paid to cover the previously undersampled taxonomic, morphological, and geographical diversity. Morphological features were studied and mapped onto the phylogeny. The results show an overall well-supported phylogeny and even more complex morphological patterns than previously reported. Despite this, many clades can be distinguished by unique suites of morphological features.

With the phylogeny as a basis, together with the thorough morphological studies, a new subgeneric classification with seven subgenera, representing strongly supported monophyletic groups, is presented for Selaginella. By mainly using gross morphological features, easily studied by the naked eye or with a hand lens, the intention is that the classification should be useful to a broader audience.

During the work with species determinations, it was revealed that the correct name for an endemic Madagascan Selaginella species is S. pectinata Spring, not S. polymorpha Badré as previously proposed.

The robust phylogeny of Selaginellaceae allowed for a historical biogeographical analysis of the group. A time-calibrated phylogeny, together with extant species distribution data, formed the basis. The results show pre-Pangean diversification patterns, Gondwanan vicariance, and more recent Cenozoic long-distance dispersals. The many inferred transoceanic dispersals during the last 50 million years are surprising considering Selaginella’s large megaspores that are thought to have a negative effect on dispersal.

In conclusion, this thesis presents a well-founded hypothesis of the evolutionary history of Selaginellaceae including its phylogeny, morphology, and historical biogeography. The thesis forms a firm basis for further studies on Selaginellaceae in particular, and gives us a better understanding of early land plant evolution in general.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2016. , 50 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1401
Keyword [en]
classification, historical biogeography, lycophytes, nomenclature, phylogeny, Selaginella, Selaginellaceae, systematics
Keyword [sv]
fylogeni, historisk biogeografi, klassifikation, lummerväxter, nomenklatur, Selaginella, Selaginellaceae, systematik
National Category
Biological Systematics Botany
Research subject
Biology with specialization in Systematics
Identifiers
URN: urn:nbn:se:uu:diva-300734ISBN: 978-91-554-9647-0 (print)OAI: oai:DiVA.org:uu-300734DiVA: diva2:952218
Public defence
2016-09-30, Zootissalen, Evolutionsbiologiskt centrum, Villavägen 9, Uppsala, 09:15 (English)
Opponent
Supervisors
Available from: 2016-09-07 Created: 2016-08-12 Last updated: 2016-09-13
List of papers
1. Phylogeny of Selaginellaceae: There is value in morphology after all!
Open this publication in new window or tab >>Phylogeny of Selaginellaceae: There is value in morphology after all!
2016 (English)In: American Journal of Botany, ISSN 0002-9122, E-ISSN 1537-2197, Vol. 103, no 12, 2136-2159 p.Article in journal (Refereed) Published
Abstract [en]

PREMISE OF THE STUDY: The cosmopolitan lycophyte family Selaginellaceae, dating back to the Late Devonian–Early Carboniferous, is notorious for its many species with a seemingly undifferentiated gross morphology. This morphological stasis has for a long time hampered our understanding of the evolutionary history of the single genus Selaginella. Here we present a large-scale phylogenetic analysis of Selaginella, and based on the resulting phylogeny, we discuss morphological evolution in the group.

METHODS: We sampled about one-third of the approximately 750 recognized Selaginella species. Evolutionary relationships were inferred from both chloroplast (rbcL) and single-copy nuclear gene data (pgiC and SQD1) using a Bayesian inference approach. The morphology of the group was studied and important features mapped onto the phylogeny.

KEY RESULTS: We present an overall well-supported phylogeny of Selaginella, and the phylogenetic positions of some previously problematic taxa (i.e., S. sinensis and allies) are now resolved with strong support. We show that even though the evolution of most morphological characters involves reversals and/or parallelisms, several characters are phylogenetically informative. Seven major clades are identified, which each can be uniquely diagnosed by a suite of morphological features. There is value in morphology after all!

CONCLUSIONS: Our hypothesis of the evolutionary relationships of Selaginella is well founded based on DNA sequence data, as well as morphology, and is in line with previous findings. It will serve as a firm basis for further studies on Selaginella with respect to, e.g., the poorly known alpha taxonomy, as well as evolutionary questions such as historical biogeographic reconstructions.

Keyword
lycophytes, morphology, pgiC, phylogeny, rbcL, Selaginella, Selaginellaceae, SQD1
National Category
Botany Biological Systematics
Identifiers
urn:nbn:se:uu:diva-300730 (URN)10.3732/ajb.1600156 (DOI)000391736600013 ()27999082 (PubMedID)
Funder
Swedish Research Council Formas, 2006-429 2010-585Helge Ax:son Johnsons stiftelse
Available from: 2016-08-12 Created: 2016-08-12 Last updated: 2017-11-28Bibliographically approved
2. A subgeneric classification of Selaginella (Selaginellaceae)
Open this publication in new window or tab >>A subgeneric classification of Selaginella (Selaginellaceae)
2016 (English)In: American Journal of Botany, ISSN 0002-9122, E-ISSN 1537-2197, Vol. 103, no 12, 2160-2169 p.Article in journal (Refereed) Published
Abstract [en]

PREMISE OF THE STUDY: The lycophyte family Selaginellaceae includes approximately 750 herbaceous species worldwide, with the main species richness in the tropics and subtropics. We recently presented a phylogenetic analysis of Selaginellaceae based on DNA sequence data and, with the phylogeny as a framework, the study discussed the character evolution of the group focusing on gross morphology. Here we translate these findings into a new classification.

METHODS: To present a robust and useful classification, we identified well-supported monophyletic groups from our previous phylogenetic analysis of 223 species, which together represent the diversity of the family with respect to morphology, taxonomy, and geographical distribution. Care was taken to choose groups with supporting morphology.

KEY RESULTS: In this classification, we recognize a single genus Selaginella and seven subgenera: Selaginella, Rupestrae, Lepidophyllae, Gymnogynum, Exaltatae, Ericetorum, and Stachygynandrum. The subgenera are all well supported based on analysis of DNA sequence data and morphology. A key to the subgenera is presented.

CONCLUSIONS: Our new classification is based on a well-founded hypothesis of the evolutionary relationships of Selaginella, and each subgenus can be identified by a suite of morphological features, most of them possible to study in the field. Our intention is that the classification will be useful not only to experts in the field, but also to a broader audience.

Keyword
classification, key, lycophytes, morphology, phylogeny, Selaginellaceae, subgenera
National Category
Botany Biological Systematics
Identifiers
urn:nbn:se:uu:diva-300731 (URN)10.3732/ajb.1600288 (DOI)000391736600014 ()27999080 (PubMedID)
Funder
Swedish Research Council Formas, 2006-429 2010-585Helge Ax:son Johnsons stiftelse
Available from: 2016-08-12 Created: 2016-08-12 Last updated: 2017-11-28Bibliographically approved
3. Selaginella pectinata resurrected: The correct name for an unusual endemic spikemoss from Madagascar
Open this publication in new window or tab >>Selaginella pectinata resurrected: The correct name for an unusual endemic spikemoss from Madagascar
2016 (English)In: American Fern Journal, ISSN 0002-8444, E-ISSN 1938-422X, Vol. 106, no 2, 131-134 p.Article in journal (Refereed) Published
Abstract [en]

We review the nomenclature of Selaginella polymorpha Badre, endemic to Madagascar, and conclude that this name is illegitimate by superfluity under the International Code of Nomenclature. The name should be rejected and replaced by the older S. pectinata Spring, coined in 1843.

Keyword
lycophytes, nomenclature, Selaginella polymorpha, Selaginellaceae
National Category
Botany Biological Systematics
Identifiers
urn:nbn:se:uu:diva-299519 (URN)10.1640/0002-8444-106.2.131.1 (DOI)000377575900004 ()
Available from: 2016-07-22 Created: 2016-07-22 Last updated: 2017-11-28Bibliographically approved
4. Historical biogeography of the heterosporous Selaginellaceae: A tale of pre-Pangean diversifications, Gondwanan vicariance, and Cenozoic long-distance dispersals
Open this publication in new window or tab >>Historical biogeography of the heterosporous Selaginellaceae: A tale of pre-Pangean diversifications, Gondwanan vicariance, and Cenozoic long-distance dispersals
(English)Manuscript (preprint) (Other academic)
National Category
Botany Biological Systematics
Identifiers
urn:nbn:se:uu:diva-300732 (URN)
Available from: 2016-08-12 Created: 2016-08-12 Last updated: 2016-09-02

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