Ladislav Mucina

CONSPECTUS OF CLASSES OF EUROPEAN VEGETATION

This is a first approximation to a Conspectus of classes of European vegetation. European vegetation consists, according to the present scheme, of 73 classes. An attempt was made to compile all available names of classes which have ever appeared in European phytosociological literature. The names were checked for nomenclatural accuracy. Lists of synonyms and related names are given. The classes, are characterised by a brief diagnosis, a comprehensive list of diagnostic species, and a list of basic references. Several syntaxonomic problems are discussed in the form of short notes.

Phylogeny of Salicornioideae (Chenopodiaceae): diversification, biogeography, and evolutionary trends in leaf and flower morphology

Chenopodiaceae-Salicomioideae (14-16 gen./c. 90 spp.) are distributed worldwide in coastal and inland saline habitats. Most of them are easy to recognize by their succulent-articulated stem with strongly reduced leaves and by flowers aggregated in dense, thick spike-shaped thyrses. ITS and the atpB-rbcL spacer were sequenced for 67 species representing 14 genera of Salicomioideae and analysed with maximum parsimony and maximum likelihood, a fossil-calibrated molecular clock using the penalized likelihood method, and lineage through time plots. The evolution of stem, leaf, and flower morphology was traced using MacClade. Both molecular markers indicate that the monophyletic Salicomioideae originated in Eurasia during the Late Eocene/Early Oligocene (38.2- 28.7 Mya) and experienced a rapid radiation into its major lineages during the Early Oligocene with Allenrolfea/Heterostachys, Kalidium, Halopeplis and Halocnemum/Halostachys branching off early. Already in the Middle Miocene (19.6-14.6 Mya) all major lineages of Salicornioideae were present. These additionally include Arthrocnemum/Microcnemum, the Halosarcia lineage (which includes all Australian species except for the Australian Sarcocornia) and the Salicornia/Sarcocornia lineage. A high intercontinental dispersability can be observed in Salicomioideae in particular in the Salicornia/Sarcocornia lineage with multiple colonization events in America, Australia and South Africa linked to the global aridification during the Oligocene, Late Miocene and Pliocene. The comparatively low species number of many genera is explained by a low number of niches present in the extreme habitats of Salicomioideae, strong interspecific competition mainly by close relatives, and by Pleistocene extinctions. We detected an evolutionary trend towards increasing reduction of the leaf lamina in Salicomioideae, with an ovate or terete leaf with a decurrent base as the plesiomorphic condition. Opposite phyllotaxis has arisen at least two times in the subfamily and is strongly correlated with the pair-wise fusion of leaves (not bracts), the reduction of leaf lamina, and the articulation of stem. However, the articulated stems and reduced leaves also have evolved twice in lineages with alternate phyllotaxis, such as Allenrolfea and Kalidium caspicum. Only one shift from free to connate bracts occurred in Salicomioideae with at least one reversal within the Halosarcia lineage. The fusion of bracts is mostly accompanied by a partly or fully connation of bracts and axis resulting in club-shaped spikes in which the flowers are tightly embedded in cavities. Both molecular trees are conflicting with the traditional tribes indicating that their diagnostic characters have originated by convergent evolution. For reasons of stability and clarity we propose that only one tribe, Salicomieae, should be recognized. The traditional circumscription of most genera is supported by the molecular results except for the closely related genera of the Australian Halosarcia clade and the Sarcocornia/Salicornia complex. The monotypic Kalidiopsis clearly originated from within Kalidium, and it is therefore newly combined in Kalidium.

Twenty years of numerical syntaxonomy

The development of numerical syntaxonomy during its first 20 yr is reviewed. The use of methods of numerical classification and ordination is the dominating feature of the development. National and local phytosociological data banks were established, large data sets handled and many important vegetation monographs were methodically based on multivariate data analysis. Particularly the development in Italy, the Netherlands, Czechoslovakia, and Sweden contributed to new theoretical elements of numerical syntaxonomy. Ordination became a common tool of searching for reticulate synsystematic relations between community types. The most popular ordination techniques have been Principal Components Analysis and Detrended Correspondence Analysis. Hierarchical agglomerative techniques of clustering still prevail in classification, although the divisive strategy of TWINSPAN has also become an effective tool for phytosociological clustering and table sorting. Extensive program packages, also for personal computers have now become standard equipment for many vegetation scientists.

A taxonomic nightmare comes true: phylogeny and biogeography of glassworts (Salicornia L., Chenopodiaceae)

In this study we analysed ETS sequence data of 164 accessions belonging to 31 taxa of Salicornia, a widespread, hygrohalophytic genus of succulent, annual herbs of Chenopodiaceae subfam. Salicornioideae, to investigate phylogenetic and biogeographical patterns and hypothesise about the processes that shaped them. Furthermore, our aim was to understand the reasons for the notorious taxonomic difficulties in Salicornia. Salicornia probably originated during the Miocene somewhere between the Mediterranean and Central Asia from within the perennial Sarcocornia and started to diversify during Late Pliocene/Early Pleistocene. The climatic deterioration and landscape-evolution caused by orogenetic processes probably favoured the evolution and initial diversification of this annual, strongly inbreeding lineage from the perennial Sarcocornia that shows only very limited frost tolerance. The further diversification of Salicornia was promoted by at least five intercontinental dispersal events (2 x to South Africa, at least 3 x to North America) and at least two independent polyploidization events resulting in rapidly expanding tetraploid lineages, both of which are able to grow in lower belts of the saltmarshes than their diploid relatives. The diploid lineages of Salicornia also show rapid and effective range expansion resulting in both widespread genotypes and multiple genotypes in a given area. Reproductive isolation through geographical isolation after dispersal, inbreeding, and comparatively young age might be responsible for the large number of only weakly differentiated lineages. The sequence data show that the taxonomic confusion in Salicornia has two major reasons: (1) in the absence of a global revision and the presence of high phenotypic plasticity, the same widespread genotypes having been given different names in different regions, and (2) striking morphological parallelism and weak morphological differentiation led to the misapplication of the same name to different genotypes in one region.

Common data standards for recording releves in field survey for vegetation classification

. In the framework of the European Vegetation Survey common data standards are proposed for recording phytosociological releves for syntaxonomical classification. The authors wish to establish the notion that common data standards for recording phytosociological data can only be advantageous for advancing the credibility and application of vegetation science, and may stimulate other projects.

Vegetation of European springs: High‐rank syntaxa of the Montio‐Cardaminetea

. A survey of high-rank syntaxa of vegetation of European springs (class Montio-Cardaminetea) is presented. It shows the complexity of the class and the relations between the units. More than 1200 releves were arranged into six phytosociological tables, each representing an alliance. A synoptic table comprising all alliances is presented. Bryo-phytes are the most important group in most of the communities, both regarding biomass and cover. The Adiantetea and the Montio-Cardaminetea are combined into one class. As to floristics and ecology, there are no obvious reasons to distinguish more than one order in this class. The vegetation of European springs is divided into six alliances: (1) Adiantion, split into two new suballiances, Adiantenion and Lycopodo-Cratoneurenion; (2) Cratoneurion commutati; (3) Cardamino-Montion - incl. three new suballiances: Mniobryo-Epilobienion hornemannii, Swertio-Anisothecienion and Cardamino-Montenion; (4) Dermatocarpion; (5) Epilobio nutantis-Montion; (6) Caricion remotae - incl. two new suballiances: Caricenion remotae and Cratoneuro filicini-Calthenion laetae. The alliances are floristically and ecologically characterized and their distributions in Europe shown on maps.

Ecological and evolutionary significance of genomic GC content diversity in monocots

Significance Our large-scale survey of genomic nucleotide composition across monocots has enabled the first rigorous testing, to our knowledge, of its biological significance in plants. We show that genomic DNA base composition (GC content) is significantly associated with genome size and holocentric chromosomal structure. GC content may also have deep ecological relevance, because changes in GC content may have played a significant role in the evolution of Earth’s biota, especially the rise of grass-dominated biomes during the mid-Tertiary. The discovery of several groups with very unusual GC contents highlights the need for in-depth analysis to uncover the full extent of genomic diversity. Furthermore, our stratified sampling method of distribution data and quantile regression-like logic of phylogenetic analyses may find wider applications in the analysis of spatially heterogeneous data. Genomic DNA base composition (GC content) is predicted to significantly affect genome functioning and species ecology. Although several hypotheses have been put forward to address the biological impact of GC content variation in microbial and vertebrate organisms, the biological significance of GC content diversity in plants remains unclear because of a lack of sufficiently robust genomic data. Using flow cytometry, we report genomic GC contents for 239 species representing 70 of 78 monocot families and compare them with genomic characters, a suite of life history traits and climatic niche data using phylogeny-based statistics. GC content of monocots varied between 33.6% and 48.9%, with several groups exceeding the GC content known for any other vascular plant group, highlighting their unusual genome architecture and organization. GC content showed a quadratic relationship with genome size, with the decreases in GC content in larger genomes possibly being a consequence of the higher biochemical costs of GC base synthesis. Dramatic decreases in GC content were observed in species with holocentric chromosomes, whereas increased GC content was documented in species able to grow in seasonally cold and/or dry climates, possibly indicating an advantage of GC-rich DNA during cell freezing and desiccation. We also show that genomic adaptations associated with changing GC content might have played a significant role in the evolution of the Earth’s contemporary biota, such as the rise of grass-dominated biomes during the mid-Tertiary. One of the major selective advantages of GC-rich DNA is hypothesized to be facilitating more complex gene regulation.

European Vegetation Survey: Current state of some national programmes

Vegetation survey programmes in Austria, Great Britain, the Netherlands and Germany are described. The aims of these programmes are discussed and their origin and motivation elucidated against the historical background of the development of phytosociology (as part of vegetation science) in particular countries. The Austrian, British and Dutch national vegetation surveys have been logistically supported by either basic-research (Austria) or nature-conservation (Great Britain and the Netherlands) funding organisations. They are either being published (British Plant Communities) or heading for publication of their first volumes within the next two years. The German vegetation survey is a voluntarily-based enterprise expected to complete its work by the end of this century. The experience gained by the management of these national surveys is of fundamental importance in launching the European Vegetation Survey (a project under preparation)

Landscape age and soil fertility, climatic stability, and fire regime predictability: Beyond the OCBIL framework

Hopper (Plant Soil 322:49–86, 2009) introduced landscape age, climate buffering, and soil nutrient status as descriptors for a continuum between old, climatically buffered landscapes characterised by low soil fertility (OCBIL) and young, often disturbed landscapes characterised by fertile soils (YODFEL). Hopper (Plant Soil 322:49–86, 2009) provided an important framework for biodiversity and conservation. We argue that Hopper’s (Plant Soil 322:49–86, 2009) conceptual framework includes five areas worthy of further consideration. These include: (1) The appropriateness of the original three dimensions; (2) The need for deeper consideration of rejuvenation and disturbance within OCBILs. (3) Broadening the globally relevant range of environments. (4) Operationalising the definitions or dimensions. (5) Revisiting the scale and compatibility of the predictions. Here, we address the first four of these areas and offer an alternative conceptual framework based on the idea of Old Stable Landscapes (OSLs). We redefine Hopper’s climate buffering as a dimension of climate stability, identify soil-impoverishment as a function of landscape age, and recognise fire regime predictability as a large-scale, long-term evolutionarily important dimension. In so doing, we construct a globally-relevant, qualitative template to enable the testing of evolutionary-ecological hypotheses concerning biodiversity (e.g. species diversity, diversity gradients, endemism, speciation and extinction rates, cladogenesis, persistence of old lineages, refugial phenomena). Our template is characterised by having operationally defined dimensions, which can be used to design surveys and experiments to address the issues of biodiversity conservation, recovery, and restoration under variations in landscape age, climatic stability and fire regime.

Tree cover and biomass increase in a southern African savanna despite growing elephant population.

The growing elephant populations in many parts of southern Africa raise concerns of a detrimental loss of trees, resulting in overall reduction of biodiversity and ecosystem functioning. Elephant distribution and density can be steered through artificial waterpoints (AWPs). However, this leaves resident vegetation no relief during dry seasons. We studied how the introduction of eight AWPs in 1996 affected the spatiotemporal tree-structure dynamics in central Chobe National Park, an unfenced savanna area in northern Botswana with a dry-season elephant density of approximately 3.34 individuals per square kilometer. We hypothesized that the impact of these AWPs amplified over time and expanded in space, resulting in a decrease in average tree density, tree height, and canopy volume. We measured height and canopy dimensions of all woody plants around eight artificial and two seasonal waterpoints for 172 plots in 1997, 2000, and 2008. Plots, consisting of 50 x 2 m transects for small trees (0.20-3.00 m tall) nested within 50 x 20 m transects for large trees (> or = 3.0 m tall), were located at 100, 500, 1000, 2000, and 5000 m distance classes. A repeated-measures mixed-effect model showed that tree density, cover, and volume had increased over time throughout the area, caused by a combination of an increase of trees in lower size classes and a decrease in larger size classes. Our results indicate that the decrease of large trees can be attributed to a growing elephant population. Decrease or loss of particular tree size classes may have been caused by a loss of browser-preferred species while facilitating the competitiveness of less-preferred species. In spite of 12 years of artificial water supply and an annual elephant population growth of 6%, we found no evidence that the eight AWPs had a negative effect on tree biomass or tree structure. The decreasing large-tree component could be a remainder of a depleted but currently restoring elephant population.