RESEARCH TOPICS

With more than 5000 species pleurocarpous mosses represent the largest monophyletic bryophyte lineage. The morphological diversity of pleurocarps and their recent rapid radiation is one of the most challenging problems in bryology as neither molecular nor morphological approaches were able to unravel the evolutionary history of pleurocarps so far. As current concepts of character evolution are largely misleading, thorough phylogenetic analyses combining molecular and morphological data are needed and crucial for understanding the evolution of pleurocarpous mosses. This site tries to provide a new platform for bryologists in order to coordinate joint research efforts on pleurocarps. Besides acting as a database for methods, primers, vouchers and references the main goal is trying to help revealing the pleurocarp phylogeny as well as a new system.

 


Molecular Phylogenetics

The backbone of pleurocarps

Character evolution in pleurocarpous mosses:
a phylogenetic study focusing on the Lembophyllaceae/Neckeraceae – clade

Evolution of the Meteoriaceae/Brachytheciaceae

The morphological evolution of epiphytic mosses

Evolution of dwarf males

 

Molecular Evolution

Structural evolution of the nuclear ribosomal spacers in pleurocarps

 

Biogeography

The genus Isothecium in Europe


 

 

 

 

 

 

 

 

 

The backbone of pleurocarps

 

Contact: Dietmar Quandt & Sanna Huttunen

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Character evolution in pleurocarpous mosses:
a phylogenetic study focusing on the Lembophyllaceae/Neckeraceae – clade

The morphological diversity of epiphytic pleurocarpous mosses and their recent rapid radiation is one of the most challenging problems in bryology. As current concepts of character evolution are largely misleading, thorough phylogenetic analyses combining molecular and morphological data are needed and crucial for understanding the evolution of pleurocarpous mosses. In this study we will focus on two closely related families, Lembophyllaceae and Neckeraceae. Aims of this study are: 1) to reconstruct well supported phylogenies of the families using both morphological and DNA sequence data 2) to pinpoint the ancestral clades of the Neckeraceae/Lembophyllaceae within pleurocarps, and 3) to study the evolution of morphological characters within this group. The phylogenetic analyses will clarify if the evolution of the currently used diagnostic morphological traits is a result of an independent adaptive evolution, especially to epiphytic habitats that occurred several times independently in the sampled lineages and perhaps in pleuocarpous mosses in general.

 

Thesis:

Volker Buchbender (Lembophyllaceae, PhD)
Sanna Olsson (Neckeraceae, PhD.)

Contact: Dietmar Quandt & Sanna Huttunen

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The morphological evolution of epiphytic mosses

When similar morphological traits evolve repeatedly under similar environmental conditions, it is reasonable to consider that they are beneficial for the survival of individuals in those environments. Thus individuals with those characters would be better adapted to their habitats. Inherited fitness differences between adapted and non-adapted phenotypes have in evolutionary theory been regarded as the most important factor leading to adaptive evolution, the emergence of new morphological character combinations and speciation. Studies that detect which morphological characteristics correlate with a certain environmental shift might thus bring us valuable information on morphological evolution and the role of adaptive evolution as a source of novel morphological character combinations.

Mosses are relatively simple organisms and therefore suitable for studies of how morphological adaptations evolve. Species from different moss lineages have repeatedly and independently conquest the epiphytic habitats (Buck et al. 2000, Huttunen et al. 2004, Quandt and Huttunen 2004). This habitat shift has been shown to correlate with the appearance of the similar combinations of morphological characters in different moss lineages (Hedenäs 2001, Vanderpoorten et al. 2002, Huttunen et al. 2004 ). Especially structures of the sporophyte generation are prone to adapt to new environmental conditions (Hedenäs 2001). Because the sporophytes are crucial for the reproduction success, their evolution in some species has a high potential to lead to fitness differences between phenotypes.

Despite the observed correlations, the evolutionary mechanisms behind them remain unknown. One likely explanation for morphological specializations is natural selection as a response to the physical environment, but the evidence of fitness differences between phenotypes is lacking. Some of the advantageous characters may also have originally evolved in response to other selective pressures before occupying the epiphytic habitats. Especially sporophytic character states are strongly intercorrelated with each other (Hedenäs 2002). This might indicate that some character states also result indirectly from selection due to pleiotropic connection with another, adaptive character. In the case of the peristome evolution, epiphytism normally seems to lead to a reduction in several structures. In other organisms such reductions were suggested to result from relaxation in maintaining selection.

 

Contact: Sanna Huttunen & Lars Hedenäs

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Evolution of the Meteoriaceae/Brachytheciaceae

 

Contact: Sanna Huttunen & Dietmar Quandt

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Evolution of dwarf males within the pleurocarpous moss family Ptychomniaceae

Phyllodioicy is a reproductive strategy in mosses where reduced male plants germinate from spores established on female plants. In this talk, we present the results of the first ever study of the evolution of moss dwarf males within a phylogenetic context.

The pleurocarpous moss family Ptychomniaceae is a well-supported monophyletic group sister to the remaining pleurocarps. The family comprises 12 genera and 44 species, of which 31 belong to the genera Ptychomnion (5 species), Euptychium (7 sp) and Garovaglia (19 sp). Of the remaining genera, one includes three species and the other eight are monotypic. This bias in species diversity becomes particularly interesting if compared with the distribution of dwarf males within the Ptychomniaceae. All species of Ptychomnion, Euptychium and Garovaglia have dwarf males, but among the remaining genera, dwarf males are only present in the monotypic Cladomnion. Furthermore, the largest genus, Garovaglia, contains species displaying unusually high levels of morphological variation, including G. angustifolia, G. plicata, G. powellii and G. elegans. These hypervariable species have many sub-specific taxa recognized and numerous names included in their synonymy, which is reflected in sometimes extreme levels of intraspecific character variation.

We evaluated the phylogenetic relationships within the Ptychomniacae using maximum likelihood and Bayesian inference of chloroplast and mitochondrial DNA sequence data. We then used maximum likelihood and maximum parsimony to study evolution of 18 morphological characters within the Ptychomniales, and maximum likelihood to test whether the evolution of dwarf males is correlated with morphological evolution and the epiphytic habitat. Reconstructions of morphological characters under maximum likelihood and maximum parsimony are mostly congruent although maximum likelihood reconstructions indicate high uncertainties at most internal nodes. Correlation tests using maximum likelihood suggest that the evolution of dwarf males is significantly correlated with twelve of the studied morphological characters. The correlation tests indicate that dorsal teeth are more likely to evolve when dwarf males are present whereas rugose leaves promote evolution of dwarf males. It is noteworthy that rugose leaves occur in the hypervariable G. angustifolia and G. plicata, and dorsal teeth in G. powellii and G. plicata. This may suggest that morphological plasticity is correlated with the expression of dwarf males, but studies based on extensive sampling of sub-specific taxa and varieties are needed to assess this.

 

Contact: Niklas Pedersen & Angela Newton

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Structural evolution of the nuclear ribosomal spacers in pleurocarps

 

Contact: Alexey Troitsky & Misha Ignatov

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The genus Isothecium in Europe

 

Contact: Isabel Draper & Lars Hedenäs

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