Signals of range expansions and contractions of vascular plants in the high Alps: observations (1994–2004) at the GLORIA* master site Schrankogel,Tyrol, Austria

High mountain ecosystems are defined by low temperatures and are therefore considered to react sensitively to climate warming. Responding to observed changes in plant species richness on high peaks of the European Alps, an extensive setup of 1 m × 1 m permanent plots was established at the alpine‐nival ecotone (between 2900 and 3450 m) on Mount Schrankogel, a GLORIA master site in the central Tyrolean Alps, Austria, in 1994. Recording was repeated in a representative selection of 362 quadrats in 2004. Ten years after the first recording, we observed an average change in vascular plant species richness from 11.4 to 12.7 species per plot, an increase of 11.8% (or of at least 10.6% at a 95% confidence level). The increase in species richness involved 23 species (about 43% of all taxa found at the ecotone), comprising both alpine and nival species and was pronouncedly higher in plots with subnival/nival vegetation than in plots with alpine grassland vegetation. Only three species showed a decrease in plot occupancy: one was an annual species, one was rare, and one a common nival plant that decreased in one part of the area but increased in the uppermost part. Species cover changed in relation to altitudinal preferences of species, showing significant declines of all subnival to nival plants, whereas alpine pioneer species increased in cover. Recent climate warming in the Alps, which has been twice as high as the global average, is considered to be the primary driver of the observed differential changes in species cover. Our results indicate an ongoing range contraction of subnival to nival species at their rear (i.e. lower) edge and a concurrent expansion of alpine pioneer species at their leading edge. Although this was expected from predictive distribution models and different temperature‐related habitat preferences of alpine and nival species, we provide first evidence on – most likely – warming‐induced species declines in the high European Alps. The projected acceleration of climate warming raises concerns that this phenomenon could become the major threat to biodiversity in high mountains.     

Identifying fern gametophytes using DNA sequences

Identification of fern gametophytes is generally hampered by low morphological complexity. Here we explore an alternative: DNA‐based identification. We obtained a plastid rbcL sequence from a sterile gametophyte of unknown origin (cultivated for more than 30 years) and employed blast to determine its affinities. Using this approach, we identified the gametophyte as Osmunda regalis. To evaluate the robustness of this determination, and the usefulness of rbcL in differentiating among species, we conducted a phylogenetic analysis of osmundaceous fern sequences. Based on our results, it is evident that DNA‐based identification has considerable potential in exploring the ecology of fern gametophytes.     

Expanding forests and changing growth forms of Siberian larch at the Polar Urals treeline during the 20th century

The ongoing climatic changes potentially affect plant growth and the functioning of temperature‐limited high‐altitude and high‐latitude ecosystems; the rate and magnitude of these biotic changes are, however, uncertain. The aim of this study was to reconstruct stand structure and growth forms of Larix sibirica (Ledeb.) in undisturbed forest–tundra ecotones of the remote Polar Urals on a centennial time scale. Comparisons of the current ecotone with historic photographs from the 1960s clearly document that forests have significantly expanded since then. Similarly, the analysis of forest age structure based on more than 300 trees sampled along three altitudinal gradients reaching from forests in the valleys to the tundra indicate that more than 70% of the currently upright‐growing trees are <80 years old. Because thousands of more than 500‐year‐old subfossil trees occur in the same area but tree remnants of the 15–19th century are lacking almost entirely, we conclude that the forest has been expanding upwards into the formerly tree‐free tundra during the last century by about 20–60 m in altitude. This upward shift of forests was accompanied by significant changes in tree growth forms: while 36% of the few trees that are more than 100 years old were multi‐stem tree clusters, 90% of the trees emerging after 1950 were single‐stemmed. Tree‐ring analysis of horizontal and vertical stems of multi‐stemmed larch trees showed that these trees had been growing in a creeping form since the 15th century. In the early 20th century, they started to grow upright with 5–20 stems per tree individual. The incipient vertical growth led to an abrupt tripling in radial growth and thus, in biomass production. Based on above‐ and belowground biomass measurements of 33 trees that were dug out and the mapping of tree height and diameter, we estimated that forest expansion led to a biomass increase by 40–75 t ha^?1 and a carbon accumulation of approximately 20–40 g C m^?2 yr^?1 during the last century. The forest expansion and change in growth forms coincided with significant summer warming by 0.9 °C and a doubling of winter precipitation during the 20th century. In summary, our results indicate that the ongoing climatic changes are already leaving a fingerprint on the appearance, structure, and productivity of the treeline ecotone in the Polar Urals.     

Water availability controls microbial temperature responses in frozen soil CO2 production

Soil processes in high-latitude regions during winter are important contributors to global carbon circulation, but our understanding of the mechanisms controlling these processes is poor and observed temperature response coefficients of CO₂ production in frozen soils deviate markedly from thermodynamically predicted responses (sometimes by several orders of magnitude). We investigated the temperature response of CO₂ production in 23 unfrozen and frozen surface soil samples from various types of boreal forests and peatland ecosystems and also measured changes in water content in them after freezing. We demonstrate that deviations in temperature responses at subzero temperatures primarily emanates from water deficiency caused by freezing of the soil water, and that the amount of unfrozen water is mainly determined by the quality of the soil organic matter, which is linked to the vegetation cover. Factoring out the contribution of water limitation to the CO₂ temperature responses yields response coefficients that agree well with expectations based on thermodynamic theory concerning biochemical temperature responses. This partitioning between a pure temperature response and the effect of water availability on the response of soil CO₂ production at low temperatures is crucial for a thorough understanding of low-temperature soil processes and for accurate predictions of C-balances in northern terrestrial ecosystems.     

Phylogenetics and biogeography of Nephrolepis – a tale of old settlers and young tramps

The phylogenetic relationships and biogeographical history of the tropical genus Nephrolepis, a popular ornamental fern, are investigated using plastid DNA data from three regions: rbcL, rps4 plus the rps4‐trnS intergenic spacer (IGS) and the trnG intron plus the trnG‐trnR IGS. Our taxon sampling includes all but one of the 19 species of the genus. We confirm the monophyly of Nephrolepis, resolve infrageneric relationships and propose monophyly of the widespread species Nephrolepis biserrata and Nephrolepis abrupta, awaiting a denser sampling of Nephrolepis cordifolia and Nephrolepis undulata. The controversial inclusion of Nephrolepis in Lomariopsidaceae is not clearly supported. With a view to identifying synapomorphies for the clades retrieved, we reconstruct the evolution in Nephrolepis of sorus position and indusium shape. Finally, based on an estimation of divergence times and reconstruction of ancestral distributions for the genus, we propose an origin of the crown group in the Eocene in the forests of the Laurasian tropical belt, from where two main lineages would have dispersed and become isolated, one in the Neotropics and the other in Asia–Australasia. From this clear biogeographical pattern, some species, probably of Asian–Australasian origin, show recent range expansions, now spanning the Palaeotropics or the pantropical zone. © 2010 The Linnean Society of London, Botanical Journal of the Linnean Society, 2010, 164 , 113–127.     

The Heart Ultrastructure in Two Species of Pycnogonids, and its Phylogenetic Implications

The heart of the pycnogonids Nymphon (Chaetonymphon) macronyx G. O. Sars and Boreonymphon cf. abyssorum Norman is pseudotubular and lacks an epicardium and an endocardium. The body wall forms the roof over the heart lumen. The myocardium is innvervated, and forms the lateral walls of the heart. Myofibres are absent in the midventral floor. This part is formed by cells of the horizontal septum attached to the gut complex. The myofibres are short. Interdigitating intercalated discs have not been observed, but lateral overlaps are common. Z-, I- and A-bands are seen in the sarcomere. The 2-bands are diffuse and irregular. The sarcolemma invaginates and forms a sparse system of clefts; a poorly developed T-system is indicated. Its presence supports the view that a T-system is inherent in the arthropod myocardium. Couplings are not related to any specific sarcomere band level. It is implied that the thin-walled pseudotubular heart in pycnogonids is a result of a reduction, and that it functions more like a channel than a heart.     

Karyotype differentiation in Chromaphyosemion killifishes (Cyprinodontiformes, Nothobranchiidae): patterns, mechanisms, and evolutionary implications

Chromaphyosemion killifishes are a karyotypically highly diverse group of small, sexually dimorphic fishes living in rainforest rivulets in tropical West and Central Africa. In the present study, we used various chromosome banding and staining techniques to analyse the karyotypes of 13 populations representing seven described species ( Chromaphyosemion loennbergii , Chromaphyosemion punctulatum , Chromaphyosemion splendopleure , Chromaphyosemion volcanum , Chromaphyosemion malumbresi , Chromaphyosemion melanogaster , Chromaphyosemion bitaeniatum ) and two undescribed forms ( Chromaphyosemion cf. lugens , Chromaphyosemion sp. Rio Muni GEMHS00/41). Diploid chromosome numbers (2 n ) and the number of chromosome arms (NF) ranged from 2 n  = 24 in C. malumbresi to 2 n  = 40 in C. bitaeniatum and from NF = 40 in C. volcanum and C. cf. lugens to NF = 54 in one population of C. loennbergii . A tentative XX/XY sex chromosome system was revealed in C. loennbergii , C. melanogaster , C. malumbresi , and Chromaphyosemion sp. Rio Muni GEMHS00/41. Mapping cytogenetic data for all described Chromaphyosemion species onto a recently published mitochondrial DNA phylogeny revealed a complex pattern of chromosomal evolution with several independent reductions of 2 n and independent modifications of NF and nucleolus organizer region phenotypes. Together with the results of preliminary crossing and mate choice experiments, the cytogenetic and molecular phylogenetic data suggest that, contrary to previous hypotheses, chromosomal rearrangements are probably not the most important and certainly not the only factor driving speciation in Chromaphyosemion killifishes.  © 2008 The Linnean Society of London, Biological Journal of the Linnean Society , 2008, 94 , 143–153.