The geographic distribution of metazoan microfauna on East Antarctic nunataks

The abundance and distribution of nematodes, rotifers and tardigrades in samples from nunataks in continental Antarctica were investigated during four Antarctic expeditions in the austral summers of 1991/92, 1993/94, 1996/97 and 2001/02. Altogether 368 samples were collected from 14 nunataks and one oasis in East Antarctica. Nematodes were found in 35%, rotifers in 67% and tardigrades in 40% of all samples. Fifty-four microfaunal taxa were identified. Of these, 27 were nematodes, 8 tardigrades and 19 rotifers. The size and geographic location of the nunatak and oasis influenced the abundance and taxonomic composition of the microfauna. The highest abundance and diversity of nematodes were found on large nunataks close to the coast. Nematodes were not found on small inland nunataks. Very high population densities of tardigrades and rotifers were found on two small and isolated nunataks. No microfauna was found on the two southernmost nunataks (Okkenhaugrusta and Vardeklettane), or on the smallest one (Utsikta). The Sørensens Quotient of Similarity was generally low, especially between faunas on nunataks in different mountain ridges. The results indicate rather limited rates of dispersal and colonization between nunataks.     

On the uptake of ornithogenic products by plants on the inland mountains of Dronning Maud Land, Antarctica, using stable isotopes

Breeding snow petrels (Pagodroma nivea) may be a major source of nutrients for the ecosystems on the inland nunataks (mountain outcrops) of continental Antarctica. To test this theory, the δ¹⁵N and δ¹³C values of soil and plants (moss, lichen and algae) from 11 nunataks with and without breeding snow petrels in northwestern Dronning Maud Land were compared. High δ¹⁵N values in all samples from nunataks with breeding birds provide a strong indication of the presence of breeding birds, as well as the use of bird-derived nitrogen by the plants of these ecosystems. The δ¹³C values showed little difference between the nunataks and are not a useful indicator of bird effects on ecosystem development. Received: 3 March 1997 / Accepted: 30 March 1998     

Corridor or drift fence? The role of medial moraines for fly dispersal over glacier

Corridors are often considered to promote dispersal between habitat patches. In this paper, we study whether or not corridors induce colonisation of nunataks (ice-free areas in glacier surroundings) by promoting dispersal from lowland to the nunataks. On outlet glaciers, debris originating from nunataks forms the so-called medial moraines that stretch from the nunataks down-glacier to the lowland, forming corridors of debris on the glacier. Aerial dispersal was determined with yellow sticky traps on the moraines, bare glacier and glacier foreland. Dipterans were sampled in pitfall traps on the nunataks. Flying insects that were present on the vegetated glacier foreland belonged to five orders, that is, Diptera, Hemiptera, Hymenoptera, Lepidoptera and Trichoptera. On the glacier and medial moraines, however, mainly dipterans were present, with the majority of individuals found on the moraines. Hoverflies (Syrphidae) were abundant on the moraines and on the edges of nunataks close to the moraines, but were not present on the vegetated foreland. The origin of the hoverflies is thus not the nunataks and not the lowland. Rather, they are brought in by air currents towards the glacier, where they aggregate on a land type where they have a chance of survival, although it is not habitable. Thus, we conclude that the medial moraines do not function as regular corridors but as drift fences that direct the dispersal towards the adjacent land types, that is, the nunataks and the glacier foreland.     

The terrestrial arthropods of Sør Rondane in eastern Dronning Maud Land,Antarctica, with biogeographical notes

Five species of terrestrial arthropods have been found in Sør Rondane inland nunataks of eastern Dronning Maud Land, Antarctica, so far almost a biologically unexplored region. These arthropods comprised one collembolan and four mite species (one oribatid mite and three prostigmatic mite). Their occurrence was restricted to the nunataks in the central and western parts of the region. The same was also observed for the visible vegetation, such as algae and mosses, near nesting-bird colonies. The maximum reorded population density was 859 arthropods/100 ml soil at the nest of snow petrel at Tanngarden, in the northwestern part of the region. The arthropod fauna of Sør Rondane is very similar to that of central Dronning Maud Land, particularly in Gjelsvikfjella and Mühlich-Hofmannfjella. The fauna is, however, different from that of the eastern region, e.g. at Syowa Station and Enderby Land. Different species of collembolans and oribatid mites occur at locations separated by the Lüitzow-Holm Bay and Shirase Glaciers, whereas prostigmatic mites do not show such a difference.     

Food web assembly in isolated habitats: A study from recently emerged nunataks,Iceland

Allochthonous arthropods can sustain a local food web on seemingly barren land, but are nevertheless often neglected in studies of community assembly. In the present study, we investigated primary food web assembly on nunataks (ice-free areas) in a retreating glacier in Iceland. Nunataks enable studies that take into account both the temporal factor of the assembly and the influx of allochthonous organisms. Arthropods were collected on sites of different age on five nunataks younger than 70 years, as well as the youngest parts of one old nunatak. The youngest sites had no vegetation and were dominated by detritivores and predators along with allochthonous arthropods. The arthropod biomass, that was considered established, increased with vegetation cover and site age but also differed among nunataks. To investigate whether or not the assembly of arthropods was consistent with the predictions of assembly rules, we tested whether, (1) the proportion of each trophic level changed non-randomly, (2) predator–prey ratio remained constant, and (3) larger species replaced smaller ones. We could only verify that proportions of trophic levels changed non-randomly. As assembly rules only apply for established organisms, it is possible that difficulties in determining whether e.g. generalist predators were established or not may affect the outcome of analyses of assembly rules. It is thus important to be aware that unintentional inclusion of allochthonous arthropods in models of community assembly may affect whether or not the community can be explained and predicted by assembly rules.     

Species diversity and random distribution of microfauna in extremely isolated habitable patches on Antarctic nunataks

Populations of metazoan microfauna (nematodes, rotifers and tardigrades) are patchily distributed on mountain outcrops penetrating the ice sheet (nunataks) in continental Antarctica. The abundance and fauna composition of microscopic animals vary greatly also among samples from similar types of habitats. Occurrence of similar seemingly habitable sites without microfauna and sites with various combinations of animal taxa indicates that stochastic colonization processes as well as local environmental factors and historical factors influence faunal composition in a specific habitable patch. The abundance of nematodes, rotifers and tardigrades in various combinations of co-occurrence was analyzed. One objective was to investigate if biotic interactions structuring these simple communities could be observed. The 368 samples analysed originate from three kinds of habitats, viz. mosses, ornithogenic soils and fellfield soils, obtained from 14 nunataks in Dronning Maud Land, East Antarctica. It is suggested that high population densities of any of the three animal groups, when they were found alone and lower densities, when they coexisted with other taxa could indicate the presence of competition or predation. However, the great variability in microfauna densities for similar habitable patches made it difficult to find significant differences among population densities in samples with varying complexity.     

Islands in the ice: detecting past vegetation on Greenlandic nunataks using historical records and sedimentary ancient DNA meta-barcoding

Nunataks are isolated bedrocks protruding through ice sheets. They vary in age, but represent island environments in 'oceans' of ice through which organism dispersals and replacements can be studied over time. The J.A.D. Jensen's Nunataks at the southern Greenland ice sheet are the most isolated nunataks on the northern hemisphere - some 30 km from the nearest biological source. They constitute around 2 km(2) of ice-free land that was established in the early Holocene. We have investigated the changes in plant composition at these nunataks using both the results of surveys of the flora over the last 130 years and through reconstruction of the vegetation from the end of the Holocene Thermal Maximum (5528 ± 75 cal year BP) using meta-barcoding of plant DNA recovered from the nunatak sediments (sedaDNA). Our results show that several of the plant species detected with sedaDNA are described from earlier vegetation surveys on the nunataks (in 1878, 1967 and 2009). In 1967, a much higher biodiversity was detected than from any other of the studied periods. While this may be related to differences in sampling efforts for the oldest period, it is not the case when comparing the 1967 and 2009 levels where the botanical survey was exhaustive. As no animals and humans are found on the nunataks, this change in diversity over a period of just 42 years must relate to environmental changes probably being climate-driven. This suggests that even the flora of fairly small and isolated ice-free areas reacts quickly to a changing climate.     

Echiniscus corrugicaudatus (Heterotardigrada; Echiniscidae) a new species from Ellsworth Land, Antarctica

Echiniscus corrugicaudatus sp. nov., (Heterotardigrada; Echiniscidae) was found in the limited vegetation from the inland nunataks of Ellsworth Land, West Antarctica. The tardigrade fauna of this a rarely explored region shows limited overlap with the fauna from the maritime or coastal continental Antarctic. This species is placed within the Echiniscus “arctomys-group” based on the characteristic of, “a lack of body appendages other than cirrus A”. It has less well-defined edges to the dorsal plates than other species within the group and distinct ridges on the caudal plate. Males were found in the population indicating gonochoristic reproduction, and a large number of juveniles suggesting an over-wintering strategy of eggs or a biennial population over-wintering as adults/sub-adults and eggs.     

Glacial refugia,recolonization patterns and diversification forces in Alpine‐endemic Megabunus harvestmen

The Pleistocene climatic fluctuations had a huge impact on all life forms, and various hypotheses regarding the survival of organisms during glacial periods have been postulated. In the European Alps, evidence has been found in support of refugia outside the ice shield (massifs de refuge) acting as sources for postglacial recolonization of inner‐Alpine areas. In contrast, evidence for survival on nunataks, ice‐free areas above the glacier, remains scarce. Here, we combine multivariate genetic analyses with ecological niche models (ENMs) through multiple timescales to elucidate the history of Alpine Megabunus harvestmen throughout the ice ages, a genus that comprises eight high‐altitude endemics. ENMs suggest two types of refugia throughout the last glacial maximum, inner‐Alpine survival on nunataks for four species and peripheral refugia for further four species. In some geographic regions, the patterns of genetic variation are consistent with long‐distance dispersal out of massifs de refuge, repeatedly coupled with geographic parthenogenesis. In other regions, long‐term persistence in nunataks may dominate the patterns of genetic divergence. Overall, our results suggest that glacial cycles contributed to allopatric diversification in Alpine Megabunus, both within and at the margins of the ice shield. These findings exemplify the power of ENM projections coupled with genetic analyses to identify hypotheses about the position and the number of glacial refugia and thus to evaluate the role of Pleistocene glaciations in driving species‐specific responses of recolonization or persistence that may have contributed to observed patterns of biodiversity.     

A re-appraisal of nunatak survival in arctic-alpine phylogeography

A long standing and at times fervid debate in biogeography revolves around the question whether arctic and high alpine organisms survived Pleistocene ice ages on small island-like areas protruding above the ice-sheet, socalled nunataks, or whether they did so in peripheral nonglaciated refugial areas. A common picture emerging from a plethora of molecular phylogeographic studies in the last decade is that both in the Arctic and in temperate mountain ranges such as the European Alps nunatak survival needs to be only rarely invoked to explain observed genetic patterns (for a rare example see Stehlik et al. 2002). As two studies in this issue show, depreciation of the nunatak hypothesis is, however, not warranted. In this issue of Molecular Ecology Westergaard et al. (2011) investigate genetic patterns of two arctic-alpine plant species distributed on both sides of the Atlantic exclusively in areas that were mostly covered by ice-sheets during Pleistocene glacial advances. In both species, amplified fragment length polymorphism (AFLP) data identified divergent and partly genetically diverse groups east and west of the Atlantic. This suggests, for the first time in Arctic plants, in situ survival on nunataks. In an entirely different geographic setting and on a different geographic scale, Lohse et al. (2011, this issue) study the colonization of high alpine areas in the Orobian Alps, situated within and adjacent to a prominent peripheral refugial area (massif de refuge) in the Southern Alps of northern Italy, by dispersal-limited carabid ground beetles. Using explicit hypothesis testing and inference of ancestral locations in a Bayesian framework, stepwise colonization from two separate southern refugia is found to shape the genetic pattern of these beetles, but at the northern edge, populations survived at least parts of the last glaciation in situ on nunataks.     

Peracarid composition,diversity and species richness in the area of the Northeast Water polynya,East Greenland (Crustacea,Malacostraca)

During the ARK XI-2 expedition with RV Polarstern in September/October 1995, a transect of epibenthic sledge (EBS) samples was taken in the area of the Northeast Water Polynya off the Greenland coast, from the shelf down into the deep sea. A total of 85,304 specimens of Peracarida were collected at seven stations. These individuals comprised 45 families, 103 genera and 180 species. With regard to abundance, Cumacea occurred with highest numbers, 31,269, followed by Isopoda, Amphipoda, Mysidacea and Tanaidacea. Species richness was highest in Amphipoda with 94 species, followed by Isopoda with 43 species, Cumacea with 20 species, Tanaidacea with 15 and Mysidacea with 8 species. Species richness was highest at the shallowest station 37-016 and lowest at the deepest station 37-021, whereas the opposite pattern was found for abundance. Diversity and eveness were highest at the southernmost station and lowest at the deepest station. Amphipoda occurred more frequently at the shallower stations, while Cumacea were very frequent at the deepest station. Numbers of species were lowest for Cumacea at the deepest station, while Amphipoda and Isopoda generally occurred with high species richness at all stations. On the basis of the species composition stations were compared.     

湖南会同5个亚热带树种的细根构型及功能特征分析

细根(直径2mm)具有复杂的分枝系统,不同树种间的细根在空间分布、形态和大小上有较大差异,研究不同树种的细根构型及不同根序的养分特征,对认识不同树种的细根形态和化学成分的变异格局,及其对树种地下生态位分离(niche segregation)、共存和森林生态系统功能过程的影响有着重要意义。在湖南会同林区选择青冈(Cyclobalanopsis glauca)、枫香(Liquidanbar formosana)、拟赤杨(Alniphyllum fortunei)、杉木(Cunninghamia lanceolata)、马尾松(Pinus massoniana)等5个亚热带树种,用挖掘法采集完整的细根根系,按照Pregitzer细根分级方法对细根分级,用Win-RHIZO根系测定系统对细根构型的参数进行测定,同时测定各级根系的C、N含量,以探讨各树种各级细根的功能特征,揭示不同树种细根构型与养分策略之间的关系。结果表明:5个亚热带树种细根1级根比根长、比表面积最高,直径最细;3级根比根长、比表面积最低,直径最粗。不同树种之间细根形态特征和构型也表现出差异性:枫香的1级根序比根长最大,为31.45m·g-1,杉木的最小,为16.34m·g-1,枫香和杉木之间差异显著。马尾松的1、2级根序的比表面积最大,杉木的1级根序的比表面积最小,青冈2级根序的比表面积最小,3级根序比表面积杉木最大,青冈最小。不同树种之间的细根直径差异达到极显著水平,各根序的平均直径以杉木的最大,拟赤杨的最小。5个树种细根根尖密度大小顺序为马尾松青冈枫香杉木拟赤杨,各树种细根分叉数以拟赤杨和马尾松的较高,杉木最低。除杉木和枫香外,5个树种细根C含量均呈现出随着根序上升而增加的趋势,C/N比也随根序的上升而增加,而细根N含量呈现出随着根序上升而明显下降的趋势。细根平均C含量以杉木的最高,拟赤杨的最低,马尾松、青冈与枫香之间的差异不显著。细根平均N含量以拟赤杨的最高,马尾松的最低。C/N比以马尾松的最高,拟赤杨的最低。5个树种中,马尾松的外生菌根有很强的拓展能力,因此能显著地增强植物根系的养分、水分吸收能力,即使在贫瘠和干旱的土壤环境中,也能有效地利用有限的养分和水分,促进个体生长。而杉木细根吸收养分和水分的效率及能力最小。     

Community analysis of sublittoral Harpacticoida (Copepoda,Crustacea) in the western Baltic Sea

This study compares two stations each sampled at the Øresund (Denmark) and the German coast (western Baltic Sea), with respect to sublittoral Harpacticoida. The associations were found to differ considerably in diversity, species numbers, evenness and also in the species composition. At the two northern stations, mainly polyhaline species were found and they showed the highest species and individual numbers as well as the most even species distribution. At the two southern stations, mainly pleiomesohaline species were found and they were dominated by one species that was very resistant to eutrophication, so that they showed an uneven species distribution, but also had lower individual numbers and thus lower diversity. Some samples at the German coast were found to have an extremely low harpacticoid number, which was attributed to the severe oxygen deficiency that occurred in autumn 2002 in the western Baltic Sea. This can also be considered to be the main reason for the low species diversity of the southern stations.     

Cold tolerance in Tardigrada from Dronning Maud Land,Antarctica

Survival at low temperatures was studied in three species of Tardigrada from Müihlig-Hofmannfjella, Dronning Maud Land, Antarctica. Both hydrated and dehydrated specimens of Echiniscus jenningsi, Macrobiotus furciger and Diphascon chilenense had high survival rates following exposure to -22°C for ca. 600 days, and dehydrated specimens following 3040 days at this temperature. In hydrated E. jenningsi, mortality increased with the duration of exposure from 7 to 150 days at -80°C, while mortalities of the two other species did not change. Hydrated specimens of all species were rapidly killed at -180°C, but all species exhibited good survivorship in the dehydrated state after 14 days at -180°C. In conclusion, hydrated tardigrades are able to survive extended periods at low temperatures, and dehydrated specimens are even better adapted to survive overwintering on Antarctic nunataks.     

Pleistocene survival on central Alpine nunataks: genetic evidence from the jumping bristletail Machilis pallida

Mechanisms of survival during the Pleistocene glaciation periods have been studied for more than a century. Until now, molecular studies that confirmed animal survival on Alpine nunataks, that is, ice‐free summits surrounded by glaciers, were restricted to peripheral areas. Here, we search for molecular signatures of inner‐Alpine survival of the narrow endemic and putatively parthenogenetic Alpine jumping bristletail Machilis pallida combining mitochondrial and AFLP data from its three known populations. The mitochondrial data indicate survival on both peripheral and central nunataks, the latter suggesting that refugia in the centre of the Alpine main ridge were more widespread than previously recognized. Incongruences between mitochondrial and AFLP patterns suggest a complex evolutionary history of the species and may be explained via parallel fixation of parthenogenesis of different origins during the last glacial maximum. We suggest that the inferred parthenogenesis may have been essential for central nunatak survival, but may pose a serious threat for M. pallida in consideration of the present climatic changes.     

Southern Ocean deep-sea isopod species richness (Crustacea, Malacostraca): influences of depth, latitude and longitude

We examined deep-sea epibenthic sledge isopod data from the Atlantic sector of the Southern Ocean (SO) (depth range=742–5,191 m). Samples were taken during the expeditions EASIZ II (ANT XV-3) in 1998 and ANDEEP I and II (ANT XIX3/4) in 2002. A total of 471 isopod species were recorded from 28 sites. The species richness of the epibenthic sledge samples was highly variable (6–82 species). Species richness was highest at site 131-3 in 3,053 m depth in the north-eastern Weddell Sea. The highest numbers of species were sampled in the middle depth range and lower species richness was found in the shallower and deeper parts of the study area. Depth is suggested to explain isopod species richness better than both latitude and longitude. Between 58°S and 65°S, the number of species ranged from 9 to 82 (mean=35.9). Further south in the Weddell Sea, between 73°S and 74°S, species richness was lower and the number of species ranged from 6 to 35 (mean=19.2). With regard to longitude, the highest species richness (up to 82 species) was found between 50°W and 60°W in the area of the South Shetland Islands and around the Antarctic Peninsula, while numbers did not exceed 50 species in the eastern Weddell Sea. The haul length, ranging from 807 to 6,464 m, was positively correlated with depth; however, there was no linear relationship between haul length and species richness. We therefore suggest that depth was the most important factor explaining isopod species richness. However, only 28 sites were visited and the statistical power is thus limited. Sampling in the deep sea is expensive and time consuming and as yet this is the best isopod data set available from the Atlantic sector of the SO. Future expeditions are therefore important to better explain the current patterns of benthic diversity in Antarctica.     

青岛崂山的重寄生菌白粉寄生孢及其寄主多样性

2005－2007年从青岛崂山的16科30属35种植物上采集了143份白粉菌样品,经形态鉴定分属于7属22种。其中40份样品中检测到白粉寄生孢Ampelomyces quisqualis,其寄主植物属于8科14属15种,其寄主真菌属于7属10种白粉菌。统计分析发现,多孢穆氏节丝壳上白粉寄生孢的发生率和重寄生强度均为最高;群落组成分析发现,棕丝单囊壳为白粉寄生孢寄主真菌中的优势种,其重要值为89.22%;菊科为白粉寄生孢寄主植物中的优势科,其重要值为97.85%。     

A survey of metal concentrations in higher plants, mosses, and lichens collected on King George Island in 1988

Antarctica is considered to be one of the least polluted regions on earth, and therefore, it is important to survey and control the level of contamination. Antarctic vegetation is very sparse and is essentially restricted to seashore oases and nunataks. Therefore, any data concerning metal levels in plants and lichens are of crucial value for this area. Our first goal was to determine metal concentrations in two higher plants and the most dominant species of mosses and lichens collected in 1988. We then compared the results of our survey with recent studies employing similar methodology. In our study, Cr, Cu, Fe, Ni, Pb, V, and Zn concentrations in mosses, C. quitensis and D. antarctica were also higher than typical values for mosses and vascular plants from unpolluted areas indicating anthropogenic influence. Mosses were determined to be better bioindicators of metals than lichens. Hg concentrations in mosses were significantly higher than those in shoots of C. quitensis and D. antarctica. Increases in Cr, Pb, and V concentrations over time were observed in moss when concentrations from samples collected in 1988 were compared with more recent data from other studies. Our results for King George Island may apply at least to all the maritime Antarctic where climate and plant communities are similar.     

Concordant genetic breaks, identified by combining clustering and tessellation methods, in two co-distributed alpine plant species

Natural genetic breaks may indicate limitations to gene flow or the presence of contact zones of previously isolated populations. Molecular evidence suggests that genetic breaks have aggregated in distinct geographical areas. We propose a new application of well-established statistical methods for analysing multilocus genetic data to identify intraspecific genetic breaks. The methodological approach combines Bayesian clustering with a spatially explicit maximum-difference algorithm to visualize and quantify breaks between clusters. We used amplified fragment length polymorphism data of two co-distributed, silicicolous alpine plant species, Geum montanum and Geum reptans , exhaustively sampled on a consistent, regular grid over their entire range of the European Alps and the Carpathians. We found a distinct and highly similar allocation of genetic breaks in both species. The pattern of breaks did not conform to scenarios of glacial refugial survival, alternatively in peripheral refugia or on nunataks, as expected because of the species' ecologies (late-successional low alpine vs. early-successional high alpine). Our findings rather substantiated the postulate of a general pattern of genetic breaks in alpine plants and corresponded well with biogeographical regions formerly described. Our approach could serve as a tool not only for landscape genetics and comparative phylogeography, but also for floristics or faunistics to compare biogeographic with phylogeographic breaks.