The group of pleurocarpous mosses comprises approximately 5000 species, which corresponds to about half of all mosses. The pleurocarpous mosses (i.e. “the Core Pleurocarps”) form a monophylum, which consists typically of perennial mosses with creeping stems and abundant lateral branches. In pleurocarpous mosses the archegonium and thus also sporophyte development is restricted to the apices of short, specialized lateral branches, in contrast to most other mosses, where archegonia and sporophytes develop terminally on the main axis (acrocarpous) or on major branches (cladocarpous). Traditionally, pleurocarpous mosses have been divided into three orders based mainly on their sporophytic characters. Brotherus described the Neckeraceae in 1925 and placed it into the Leucodontales, later the family has alternatively been divided into two or three separate families: the Thamnobryaceae, the Neckeraceae and the Leptodontaceae. These families have been placed even in different orders (Neckeraceae and Leptodontaceae among the leucodontalean mosses and Thamnobryaceae among hypnalean mosses) according to their peristome structure and the grade of peristome reduction. A growing amount of evidence indicates that a grouping based on sporophytic characters is artificial and based on convergent evolution. According to the latest phylogenetic studies of pleurocarpous mosses, based on molecular data, the Neckeraceae belong to the order Hypnales and share a sister group relationship with the Lembophyllaceae. In the most recent comprehensive classification 28 genera were included in the Neckeraceae family. This classification was based on both morphological and molecular data, but done with limited taxon sampling that did not cover all species of the family. Some previous studies based on molecular data have challenged the family concept of the Neckeraceae, indicating the need for a revision of the family. Here the family concept of the Neckeraceae is revisited, the closest relatives of the family are resolved and its position within pleurocarpous mosses is shown. In addition, new insights into the morphological evolution of the family are provided. Previous phylogenetic studies indicated that branch lengths among pleurocarpous mosses are usually extremely short. Therefore we chose to use mainly non-coding DNA sequences from rapidly evolving DNA regions. The phylogenetic reconstructions are based on extensive sequence data from all genomes: plastid trnS-trnF and rpl16, nuclear ITS1 & 2 and mitochondrial nad5. Both parsimony (PAUP and PRAP2) and Bayesian statistics (MrBayes) were employed for phylogenetic reconstructions. In order to use the information provided by length mutations indels were included in the analyses as binary data using a simple indel coding approach. No severe conflicts appeared between the different methods used, but the indel coding affected the support values of the inferred topologies. Therefore, all support values resulting from different methods are shown along the phylogenetic trees. The morphological features are studied and synapomorphies for each clade formed in the phylogenetic analyses are interpreted. A new delimitation of the family makes it necessary to reconsider the relevance of the morphological description and the morphological features characteristic of the family need to be reconsidered. Due to new groupings, some changes in the morphological circumscriptions of the genera are necessary, resulting in two new genera and several new combinations. Chapter 1 gives a broad overview of the relationships of the pleurocarpous mosses and shows the need for changes in the definition of genera, families and the corresponding nomenclature in this group. Chapter 2 is a population genetic study on the genus Thamnobryum. The main aim of this chapter is to test the species concept in Thamnobryum that are endemic to strictly restricted regions showing only minor differences in the morphological features in comparison to some more common species. In Chapter 3 the monophyly of the Neckeraceae is tested. In addition, in this chapter the ancestral character states of some morphological characters within the Neckeraceae are reconstructed. Chapters 4 and 5 resolve the genus composition and the relationships within the family in more detail. The results of this thesis show that the Neckeraceae need re-circumscription; this includes changes in the genus composition. The Lembophyllaceae is confirmed to be the sister group of the Neckeraceae. In addition to the new phylogeny, the potential evolution of several characters as a result of environmental selection pressures is analyzed. From the ancestral state reconstructions made (using BayesTraits) for both the habitat and a selection of morphological characters, character state distributions and habitat shift appear congruent, peristome reduction being a good example. However, some character states do not correlate with the habitat, suggesting very complex evolutionary patterns underlying these morphological characters. Many widely distributed genera that are composed of several species and seem to be morphologically coherent (Echinodium, Homalia, Thamnobryum, partly Neckera), are shown in this thesis to be polyphyletic. They are replaced by smaller, geographically more restricted genera that at least in some cases (e.g. Thamnomalia, Homalia s.str., Neckera s.str.) seem to form morphologically heterogeneous genera. In other words, morphology can be misleading in the family Neckeraceae even at the genus level and convergent evolution in both morphological and sequence level characters are common within the family. Special habitat conditions have been shown to result in similar morphological structures also in several other moss groups. This kind of convergent evolution occurs in aquatic mosses, and seems to have occurred among the neckeraceous species Thamnobryum alopecurum and its allies. However, similar morphological structure in similar aquatic habitats can also be due to true phylogenetic relationships as is the case within the Neckeraceae for Handeliobryum sikkimense and Hydrocryphae wardii, or the members of Touwia. The geographical grouping seems to be more strongly correlated with the phylogenetic grouping than thought before.
| Identifer | oai:union.ndltd.org:DRESDEN/oai:qucosa:de:qucosa:23645 |
| Date | 27 February 2009 |
| Creators | Olsson, Sanna |
| Contributors | Neinhuis, Christoph, Quandt, Dietmar, Huttunen, Sanna |
| Publisher | Technische Universität Dresden |
| Source Sets | Hochschulschriftenserver (HSSS) der SLUB Dresden |
| Language | English |
| Detected Language | English |
| Type | doc-type:doctoralThesis, info:eu-repo/semantics/doctoralThesis, doc-type:Text |
| Rights | info:eu-repo/semantics/openAccess |
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