9 March: Sanna Huttunen

Phylogeny of moss order Hypnales - current state of knowledge and future challenges

Sanna Huttunen

Department of Biology, University of Turku, Finland

The Hypnales are the largest moss order comprising circa 4200 species, i.e. 1/3 of all mosses. Phylogenetic reconstruction of the group has proven to be difficult due to rapid radiation at an early stage of their evolution, but the most studies applying molecular systematic methods favor its position as a crown clade in the phylogeny of mosses. Within the order, however, relationships among groups have remained poorly resolved. The most recent phylogenetic inference is based on four sequence regions, namely, nuclear ITS1-5.8S-ITS2, plastid trnL-F and rps4, and mitochondrial nad5, for 122 Hypnalean species and 34 species from closely related groups. Tree topologies resolve the order as monophyletic, although monophyly, as well as the backbone nodes within the Hypnales, gained significant support only under Bayesian inferences. The phylogenetic tree differs only in few details from recent classifications, but familial relationships especially among the apical crown clade within the Hypnales were mainly unsupported. Ancestral distribution based on Bayesian dispersal-vicariance analysis support a Gondwanan origin of the Hypnales and subsequent geographical radiation in the area of the former Laurasian supercontinent. Reconstruction of historical biogeography is congruent with mainly tropical and Gondwanan distributions in the sister groups Hypnodendrales, Ptychomniales, and Hookeriales, and with the dating for the oldest pleurocarp and Hypnalean fossils. Scattered fossil data, unique character combinations in some of the fossil pleurocarps and lack of a well-supported phylogeny, however, still hamper testing diversification events using molecular dating. In the presentation I will summarize current knowledge on the evolutionary history and relationships among the Hypnales and present an overview of the recent fossil data on pleurocarpous mosses. In light of these two sources of the information I aim at discussing evolution of the Hypnales and point out potential directions for future research.

24 February: Tamara van Mölken

Three-way interactions between pathogens, plants and herbivores: consequences for herbivore feeding, disease development and plant fitness. 

Tamara van Mölken 

Department of Agriculture and Ecology, University of Copenhagen, Denmark. 

Under natural conditions plants are often simultaneously exposed to pathogen attack and damage by insect herbivores. As a consequence of sharing the same host plant, interactions between pathogens and herbivores are bound to occur. The plant plays a central role in mediating such interactions, whereby pathogen induced changes in the host plant can affect herbivory and vice versa. Mechanisms underlying these effects include pathogen induced changes in: secondary metabolite levels; nutritional value; plant volatile emissions; and crosstalk between defence pathways. In turn, these biochemical changes may affect herbivore feeding and behaviour. Given that both pathogens and herbivores can impair plant performance, reciprocal effects between pathogens and herbivores are expected to result in altered plant growth and reproduction. To gain more insight into the ecological implications of pathogen infection for plant-herbivore interactions, we need a better understanding of the tripartite interactions between plants originating from wild populations and their naturally associated pathogens and herbivores. Barbarea vulgaris is well studied for its chemical defences against a range of herbivores. This herbaceous plant is susceptible to Phyllotreta nemorum flea beetles and the oomycete pathogen Albugo candida which both occur in wild B. vulgaris populations. In a series of experiments we have addressed the following questions: (i) does infection with the oomycete have an effect on flea beetle induced changes in plant nitrogen, glucosinolate and saponin levels; (ii) what are the effects of the pathogen on herbivore preference, consumption and fitness; and (iii) how do biochemical changes and variation in pathogen and herbivore damage affect plant growth, development and fitness?

10 February: Bjarne Larsen

Botanisk indsamlingstur 2011: Crocus oreocreticus på Kreta

Bjarne Larsen

dept. Agriculture and Ecology, Copenhagen University

8 February: Marco Thines

Diversity, evolution, and ecology of white blister rusts 

Marco Thines 

Biodiversity and Climate Research Centre Frankfurt, Germany

White blister rusts are a cosmopolitan group of obligate biotrophic oomycetes and are not related to true fungi, but to diatoms and other members of the Straminipila. While the host spectrum of the white blister rusts encompasses a wide range of flowering plants, recent investigations have revealed that some white blister rusts are highly host specific. Until five years ago it was believed that the Brassicaceae are parasitised by a single species, Albugo candida, which has a broad host range, encompassing several hundred species in this family. Recent molecular and morphological studies have revealed that in addition to Albugo candida, which has indeed a very broad host range, extending even to related families like Cleomaceae and Capparaceae, several specialized species exist. These include a specialized species on Arabidopsis thaliana, at least four distinct species in the genus Cardamine, and a specialized species on Barbarea. Based on the current knowledge, it seems likely that in Brassicaceae alone a few dozen species await their discovery. This could also extend to predominantly endophytic species, as we could recently demonstrate that Albugo candida can infest host plants asymptomatically and can potentially be transmitted vertically to the next generation of host plants. Potential factors influencing pathogenic development of asymptomatic endophytes will be shortly discussed on the example of two oomycete pathogens (Protobremia sphaerosperma and Pustula obtusata) infecting goatsbeard (Tragopogon pratensis agg.).