Genetic population structure and neighbourhood population size estimates of the caddisfly Plectrocnemia conspersa

1. We used both genetic and ecological methods to evaluate the role of history and the scale of colonisation in structuring populations of the caddisfly Plectrocnemia conspersa. There was no genetic differentiation between sites up to 20 km apart, despite population sizes suggesting that genetic drift could create substantial variation at this scale. 2. Genetic differentiation between populations separated by more than 20 km was greater than expected given the contrasting short‐range trend, and implied a neighbourhood population size that is implausibly small. Therefore, the evolutionary processes that affect the short‐range trend do not explain differentiation over greater distances. 3. At small scales (<20 km), relatively short flights by winged adults spread over a number of generations could account for the spread of genes. For instance, dispersing individuals could found small (often temporary) populations, which may then grow and exchange genes with larger and more permanent local populations, amplifying the effects of the initial gene flow. 4. Over larger scales (20–500 km), substantial gaps between regions containing suitable habitat patches could reduce the number of colonisation events. Genetic patterns at this scale may date from the time they were last colonised. Previous ecological studies have rarely examined the dynamics of aquatic insect populations over these larger geographical scales, yet these processes may be central to their persistence and spread.     

Ecological correlates of local extinction and colonisation in the British ladybird beetles (Coleoptera: Coccinellidae)

Five main drivers of population declines have been identified: climate change, habitat degradation, invasive alien species (IAS), overexploitation and pollution. Each of these drivers interacts with the others, and also with the intrinsic traits of individual species, to determine species’ distribution and range dynamics. We explored the relative importance of life-history and resource-use traits, climate, habitat, and the IAS Harmonia axyridis in driving local extinction and colonisation dynamics across 25 ladybird species (Coleoptera: Coccinellidae).Species were classified as continually present, continually absent, extinct, or colonising in each of 4,642 1-km² grid squares. The spatial distribution of local extinction and colonisation events (in the grid squares) across all species’ ranges were related to ecological traits, overlap with H. axyridis, climate, and habitat factors within generalised linear models (GLMs). GLMs were also used to relate species’ traits, range characteristics, and niche overlap with H. axyridis to extinction and colonisation rates summarised at the species level. Bayesian model averaging was used to account for model uncertainty, and produce reduced sets of models which were well-supported by data. Species with a high degree of niche overlap with H. axyridis suffered higher extinction rates in both analyses, while at the spatial scale extinctions were more likely and colonisations less likely in areas with a high proportion of urban land cover. In the spatial analysis, polymorphic species with large range sizes were more likely to colonise and less likely to go extinct, and sunny grid squares were more likely to be colonised. Large, multivoltine species and rainy grid squares were less likely to colonise or be colonised. In conclusion for ladybirds, extinction and colonisation dynamics are influenced by several factors. The only factor that both increased the local extinction likelihood and reduced colonisation likelihood was urban land cover, while ecological overlap with H. axyridis greatly increased extinction rates. Continued spread of H. axyridis is likely to adversely affect native species and urban areas may be particularly vulnerable.     

Competition between Invasive and Indigenous Species: Impact of Spatial Pattern and Developmental Stage

Elodea canadensis (indigenous) and Elodea nuttallii (invasive) were grown in experimental tanks in monocultures and mixtures in two spatial patterns (aggregated or mixed) and two developmental stages (small or large plants of E. canadensis, and small plants of E. nuttallii). Competitive interactions between the two species were assessed by monitoring the area colonised by each species, the number of rootings and biomass after 10 weeks. In monocultures the growth of E. canadensis was significantly lower than that of E. nuttallii. In mixtures the number of rootings and biomass of E. canadensis were always significantly less than those of E. nuttallii. The tank surface area colonised by E. canadensis was always significantly less than that occupied by E. nuttallii, but it was higher in the aggregated treatment, where the colonisation of E. nuttallii was lower. Therefore both spatial pattern and developmental stage of an indigenous species (E. canadensis) may influence the outcome of competition with potential invaders (E. nuttallii).     

Colonisation pattern of nonpathogenic Fusarium oxysporum, a potential biological control agent, in roots and rhizomes of tissue cultured Musa plantlets

Under laboratory conditions, nonpathogenic, endophytic Fusarium oxysporum inflicts high mortality among banana weevils and nematodes. Following inoculation into banana (Musa spp.) tissue cultured plants, successful colonisation is necessary for efficient biological control of these pests. The pattern of root and rhizome colonisation by two nonpathogenic Ugandan F. oxysporum strains (V2w2 and III4w1) in cv. Nabusa (AAA‐EA) was investigated using light microscopy. Percentage of colonisation in the rhizomes (93%) was higher than in the roots (56%), but hyphal density in the roots (0.30 mm^?2) was higher than in the rhizomes (0.21 mm^?2). The root bases were better colonised (76%) than root midsections (53%) or tips (39%). Both the strains colonised the roots and the rhizomes, with numerous hyphae infecting the hypodermis but fewer infecting the cortex. Colonisation of vascular tissues was not recorded. Despite the presence of hyphae in intercellular and intracellular spaces of the roots and the rhizomes, normal cell structure was observed. Our report provides the first in situ observation and quantification of endophyte colonisation in banana. The study demonstrated the ability of F. oxysporum strains V2w2 and III4w1 to penetrate intact host tissues and recolonise the host internally upon inoculation, an important step for their suitability as biological control agents.     

Field experiments on the spread of black currant reversion virus and its gall mite vector (Phytoptus ribis Nal.)

In two experiments the spread of reversion virus from a row of systemi-cally infected black currant bushes heavily infested by the gall mite vector (Phytoptus ribis Nal.) was predominantly in the direction of the winds prevailing during the dispersal period. On each side of the sources there was a curvilinear decrease of galled buds and of virus infection as distance increased. In another experiment a central source of mites and virus was surrounded by concentric hexagons comprising alternate rows of healthy and virus-infected bushes. At leaf-fall, galls were forty times more numerous on virus-infected than on healthy bushes; plants in the sector downwind developed the most galls and those upwind the least. On both healthy and virus-infected bushes in each sector, the incidence of galls decreased with increasing distance from the source. The gradients of infestation were steeper on healthy than on virus-infected bushes, especially in sectors upwind from the source. In some sectors the infestation gradients were distorted because many of the virus-infected bushes were so heavily infested that most of the buds became galled. The spread of virus to initially healthy plants decreased from 100 to 75% near the source, to zero at the periphery. More bushes became infected downwind from the source than upwind. In each experiment more bushes developed galls than later produced symptoms of virus infection, the incidence of which was positively correlated with the number of galls recorded the previous winter.     

Organic enrichment of sediments reduces arbuscular mycorrhizal fungi in oligotrophic lake plants

1. Arbuscular mycorrhizal fungi (AMF) commonly colonise isoetid species inhabiting oxygenated sediments in oligotrophic lakes but are usually absent in other submerged plants. We hypothesised that organic enrichment of oligotrophic lake sediments reduces AMF colonisation and hyphal growth because of sediment O₂ depletion and low carbon supply from stressed host plants. 2. We added organic matter to sediments inhabited by isoetids and measured pore‐water chemistry (dissolved O₂, inorganic carbon, Fe²⁺ and ), colonisation intensity of roots and hyphal density after 135 days of exposure. 3. Addition of organic matter reduced AMF colonisation of roots of both Lobelia dortmanna and Littorella uniflora, and high additions stressed the plants. Even small additions of organic matter almost stopped AMF colonisation of initially un‐colonised L. uniflora, though without reducing plant growth. Mean hyphal density in sediments was high (6 and 15 m cm^?3) and comparable with that in terrestrial soils (2–40 m cm^?3). Hyphal density was low in the upper 1 cm of isoetid sediments, high in the main root zone between 1 and 8 cm and positively related to root density. Hyphal surface area exceeded root surface area by 1.7–3.2 times. 4. We conclude that AMF efficiently colonise isoetids in oligotrophic sediments and form extensive hyphal networks. Small additions of organic matter to sediments induce sediment anoxia and reduce AMF colonisation of roots but cause no apparent plant stress. High organic addition induces night‐time anoxia in both the sediment and the plant tissue. Tissue anoxia reduces root growth and AMF colonisation, probably because of restricted translocation of nutrient ions and organic solutes between roots and leaves. Isoetids should rely on AMF for P uptake on nutrient‐poor mineral sediments but are capable of growing without AMF on organic sediments.     

The effect of spatial scale on interactions between two weevils and their food plant

The effect of spatial scale on the interactions between the weevils Gymnetron pascuorum Gyll. and Mecinus pyraster Herbst and their host plant, ribwort plantain Plantago lanceolata L., was studied. Both weevils developed in plantain seedheads but occupied different niches within the seedhead. Seedheads were sampled annually from 162 plants at each of two experimental sites consisting of a series of habitat patches of two distinct sizes. Data were analysed from three site-years. Our results suggest that the density of available seedheads varied among years and this had a direct effect on abundance. M. pyraster, which develops in the stem within the seedhead, was more sensitive to changes in seedhead density than was G. pascuorum, which develops within the seeds themselves. The presence of a hedgerow along one side of the experimental site affected the pattern of colonisation of newly-created habitat patches by G. pascuorum but not by M. pyraster. Changes in spatial scale did not affect the variability of seedhead and insect densities. G. pascuorum had an aggregated distribution at all the spatial scales considered, but the distribution of M. pyraster was very scale dependent. The distributions of the two weevil species were positively associated amongst infested plants but not amongst infested seedheads. Behavioural and ecological factors that could explain the results of the data analyses are discussed.     

The influence of host plant genotype on variation in population densities of the gorse thrips,Sericothrips staphylinus (Thysanoptera: Thripidae), and its consideration in relation to release strategies

Large variations in population densities of Sericothrips staphylinus were observed between gorse bushes at a field site in an earlier Tasmanian study. A replicated potted plant experiment was conducted to assess whether genetic variation between gorse bushes could affect densities of S. staphylinus. There were significant differences in the number of S. staphylinus recovered from the individual bushes sampled within sites and individual bushes across all sites. This provides evidence that genetic variation between gorse bushes is at least partly responsible for the observed variability in field populations. The result validates the current release strategy used for the field establishment of S. staphylinus in south-eastern Australia. This strategy involves making multiple small releases (ca. 250 adults per bush per site) instead of a small number of large releases (ca. 1000 per bush per site), thereby reducing variation in numbers due to genetic affects. Genetic variation between individual plants of the same species and associated effects on herbivore densities should be considered when devising release strategies for biological control agents.     

Searching at different spatial scales: the foraging behaviour of the aphid parasitoid Aphidius rosae in rose bushes

The searching patterns of the aphid parasitoid Aphidius rosae were analysed at three different spatial scales: leaves, shoots and bushes. Parasitoid females searched aphid-infested leaves and shoots intensively and remained on average more than twice as long on infested than on uninfested shoots. Patch times and oviposition numbers per shoot were highly variable both between females and for different shoot visits within females. However, at the shoot and bush level low oviposition numbers were generally found. The time spent on different behavioural patterns (searching, resting, feeding, host handling) changed significantly during subsequent shoot visits of individual females but oviposition success was not influenced by this change. Parasitoids searched individual leaves and shoots mainly by walking, while moving between shoots occurred exclusively by flight. The travel time between shoots (i.e. flight time) accounted for less than 1% of the residence time in a bush. At the bush level foraging was characterized by a high ability to localize infested shoots and consequently little time was wasted in searching on uninfested shoots. The pattern of resource exploitation of individual females was consistent with the distribution of A. rosae larvae in field samples taken from individual rose bushes.     

Experiments on competitiveness of three endomycorrhizal fungi

Summary This paper examines competition between three VA endophytes places respectively as “inoculant” fungus in an inner compartment (300 ml) below the germinating seed, and as “indigenous” fungus in an outer compartment (900 ml). Previously prepared infested soil was used as source of the endophytes. Inner and outer compartment roots were harvested separately and percentage infection determined for each fungus, using diagnostic anatomical features of each fungus. Changes in colonisation patterns were followed up to 4 and 5 months. Treatments with non-infested soil in the outer compartment were used to compare infectivity and spread of the different endophytes. All three endophytes were able to invade soil already colonised by either of the other two, butGlomus fasciculatum (E₃) was more invasive thanGlomus tenue. This pattern appeared to be related to rates of spread of the fungi in the non-infested soil. The pattern was not affected by host, clover or sorghum, or by position, immediately below the seed or in the outer compartment. It seemed that the endophyte in the inner compartment had overriding and persistent effects on plant growth, unrelated to its dominance pattern or share of overall root infection at the later harvests.     

Mycorrhiza modulates aboveground tri‐trophic interactions to the fitness benefit of its host plant

1. Arbuscular mycorrhiza (AM), the association of AM fungi and plant roots, may alter morphological and physiological attributes of aboveground plant parts and thereby influence plant‐associated organisms such as herbivores and their natural enemies, predators and parasitoids. 2. The interactions between AM and the players of aboveground tri‐trophic systems have mainly been considered in isolation from each other. The effects of AM on aboveground herbivore–carnivore population dynamics and the consequences to plant fitness are unknown. 3. We explored AM‐induced compensatory mechanisms for AM‐promoted proliferation of the herbivorous spider mite, Tetranychus urticae Koch, on whole bean plants, Phaseolus vulgaris L. Vegetative and reproductive plant growth, AM fungal colonisation levels, and mite densities were assessed on spider mite‐infested plants colonised or not by the AM fungus Glomus mosseae Nicol. & Gerd, and harbouring the natural enemy of the spider mites, the predatory mite Phytoseiulus persimilis Anthias‐Henriot or not. 4. AM symbiosis modulated the aboveground tri‐trophic system to the fitness benefit of the plant. AM‐increased plant productivity outweighed the fitness decrease due to AM‐promoted herbivory: at similar vegetative growth, mycorrhizal plants produced more seeds than non‐mycorrhizal plants. 5. AM‐increased spider mite population levels were compensated for by enhanced population growth of the predators and increased plant tolerance to herbivory. 6. AM‐enhanced predator performance looped back to the AM fungus and stabilised its root colonisation levels, providing the first experimental evidence of a mutually beneficial interaction between AM and an aboveground third trophic level natural enemy.     

Impact of defoliation intensities on plant biomass,nutrient uptake and arbuscular mycorrhizal symbiosis in Lotus tenuis growing in a saline‐sodic soil

The impact of different defoliation intensities on the ability of Lotus tenuis plants to regrowth, mobilise nutrients and to associate with native AM fungi and Rhizobium in a saline‐sodic soil was investigated. After 70 days, plants were subjected to 0, 25, 50, 75 and 100% defoliation and shoot regrowth was assessed at the end of subsequent 35 days. Compared to non‐defoliated plants, low or moderate defoliation up to 75% did not affect shoot regrowth. However, 100% treatment affected shoot regrowth and the clipped plants were not able to compensate the growth attained by non‐defoliated plants. Root growth was more affected by defoliation than shoot growth. P and N concentrations in shoots and roots increased with increasing defoliation while Na⁺ concentration in shoots of non‐defoliated and moderately defoliated plants was similar. Non‐defoliated and moderately defoliated plants prevented increases of Na⁺ concentration in shoots through both reducing Na⁺ uptake and Na⁺ transport to shoots by accumulating Na⁺ in roots. At high defoliation, the salinity tolerance mechanism is altered and Na⁺ concentration in shoots was higher than in roots. Reduction in the photosynthetic capacity induced by defoliation neither changed the root length colonised by AM fungi nor arbuscular colonisation but decreased the vesicular colonisation. Spore density did not change, but hyphal density and Rhizobium nodules increased with defoliation. The strategy of the AM symbiont consists in investing most of the C resources to preferentially retain arbuscular colonisation as well as inoculum density in the soil.     

Plant growth, nutrient acquisition and mycorrhizal symbioses of a waterlogging tolerant legume (Lotus glaber Mill.) in a saline-sodic soil

Seedlings of Lotus glaberMill., were grown in a native saline-sodic soil in a greenhouse for 50 days and then subjected to waterlogging for an additional period of 40 days. The effect of soil waterlogging was evaluated by measuring plant growth allocation, mineral nutrition and soil chemical properties. Rhizobiumnodules and mycorrhizal colonisation in L. glaberroots were measured before and after waterlogging. Compared to control plants, waterlogged plants had decreased root/shoot ratio, lower number of stems per plant, lower specific root length and less allocation of P and N to roots. Waterlogged plants showed increased N and P concentrations in plant tissues, larger root crown diameter and longer internodes. Available N and P and organic P, pH and amorphous iron increased in waterlogged soil, but total N, EC and exchangeable sodium were not changed. Soil waterlogging decreased root length colonised by arbuscular mycorrhizal (AM) fungi, arbuscular colonisation and number of entry points per unit of root length colonised. Waterlogging also increased vesicle colonisation and Rhizobium nodules on roots. AM fungal spore density was lower at the end of the experiment in non-waterlogged soil but was not reduced under waterlogging. The results indicate that L. glaber can grow, become nodulated by Rhizobium and colonised by mycorrhizas under waterlogged condition. The responses of L. glaber may be related its ability to form aerenchyma.     

Relationships between soil heavy metal concentration and mycorrhizal colonisation in<Emphasis Type="Italic"> Thymus polytrichus</Emphasis> in northern England

A study was conducted to establish whether the wild thyme [Thymus polytrichus A. Kerner ex Borbás ssp. britannicus (Ronn.) Kerguelen (Lamiaceae)] growing in the metal-contaminated soils along the River South Tyne, United Kingdom, is colonised by arbuscular mycorrhizal (AM) fungi, and whether the degree of colonisation increases (perhaps suggesting increasing mycorrhizal dependence) or decreases (indicating possible inhibition of AM growth) with increasing degree of soil contamination. Seasonal changes in AM colonisation were also assessed. The AM fungal communities colonising T. polytrichus were also investigated, using the polymerase chain reaction with restriction fragment length polymorphism and sequencing of fungal DNA to establish whether AM species richness varied between sites, and whether fungal ecotypes specific to sites with different amounts of metal contamination could be identified. All plants examined were heavily colonised by AM fungi, and mean percentage root length colonised did not increase significantly with increasing soil metal contamination. However, AM vesicle abundance (percentage of mycorrhizal root length containing vesicles) at the most contaminated site was significantly greater than at the other sites. No significant seasonal variation in degree of colonisation or vesicle abundance was found. Glomus was the predominant AM genus detected at all sites. The number of AM genotypes colonising T. polytrichus roots was similar at all sites but, although some were common to all sites, certain strains appeared to be specific to either the most- or the least-contaminated site. This variation in species may account for the difference in vesicle abundance between sites. The consistently heavy AM colonisation of T. polytrichus found suggests that these fungi are not inhibited by soil heavy metals at these sites, and that the host derives some benefit from its AM symbiont.     

Effect of root exudates of mycorrhizal tomato plants on microconidia germination of Fusarium oxysporum f. sp. lycopersici

The effect of root exudates from mycorrhizal and non-mycorrhizal tomato plants on microconidia germination of the tomato pathogen Fusarium oxysporum f. sp. lycopersici was tested. Microconidia germination was enhanced in the presence of root exudates from mycorrhizal tomato plants. Tomato plants were colonised by the arbuscular mycorrhizal fungus Glomus fasciculatum, indicating that alterations of the exudation pattern depended on the degree of root AM colonisation. Testing the exudates from plants with a high and a low P level revealed that the alterations of the root exudates from mycorrhizal plants, resulting in a changed effect on microconidia germination, are not due to an improved P status of mycorrhizal plants.     

Patterns of endemism of the eastern North American cave fauna

Aim Over 250 species of obligate terrestrial cave‐dwelling animals (troglobionts) are known from single caves in the eastern United States. We investigate their geographical distribution, especially in relation to other troglobionts. We relate these patterns to taxonomic group, opportunities for dispersal and geographical location. Location Caves of the United States east of the Mississippi River. Methods We associated over 3000 records of more than 450 troglobiotic species and subspecies with hexagons of 1000, 5000 and 10,000 km² in size. We calculated Moran's I, black–white joins and cubic regression of endemics on non‐endemics at all three spatial scales. For 5000 km² hexagons, we modelled the spatial autocorrelation of the residuals of the cubic regression of endemics on non‐endemics. Results Differences among orders in percentage single‐cave endemism were not significant, except for Pseudoscorpionida, which was higher (69%) than any other order. At all three scales, Moran's I and black–white joins were significant, indicating a clumped distribution of both single‐cave endemics and other troglobionts. Spatial patterns were similar at all three scales and Moran's I was highest at 5000 km². The cubic fit of endemics to non‐endemics was consistently better, with less systematic error or residuals, than were linear or quadratic models. Residuals showed a significant geographical pattern with excess endemics in more southerly locations. Main conclusions There was both a non‐spatial and spatial component to the pattern of single‐cave endemism. The non‐spatial component was the association of high levels of single‐cave endemism with areas of high diversity of non‐endemics. It may be that both are high because of high secondary productivity. Spatially, single‐cave endemism is high in central rather than peripheral areas and in the southern part of the range. It is not higher in areas of more dissected limestone, which would reduce migration rates; if anything endemism is lower. Regional spatial effects are important, indicating that cave communities cannot be understood (or protected) in isolation.     

Spatial patterns on the sagebrush steppe/Western juniper ecotone

Analysis of the spatial patterns of woody plants is important to better understand the ecological processes that govern the worldwide expansion of woody plants across semi-arid ecosystems. Second-order characteristics of a marked spatial point pattern of western juniper (Juniperus occidentalis subsp. occidentalis) were analyzed using Ripley’s K-functions and the pair-correlation function g. The marked point process of crown diameters was produced via two-dimensional wavelet analysis of a fine scale aerial photograph at the woodland-steppe ecotone in the Reynolds Creek watershed in the Owyhee Mountains, southwestern Idaho. Colonization of J. occidentalis stems from mature juniper trees growing in rocky, fire resistant areas. Although these areas introduce components of natural heterogeneity within the landscape, the selected study area is situated within a single soil type, and we modeled the expansion of juniper plants into previously juniper-free sagebrush steppe as a homogeneous point process with constant intensity. Through this research we have identified two statistically significant spatial scales characteristic of J. occidentalis on the woodland/steppe ecotone: (1) We observed inhibition between J. occidentalis plants at distances <15 m, resulting in a regular pattern, rather than clumped or random. This short-distance inhibition can be attributed to competition for water and other resources. Recruitment of young J. occidentalis occurs significantly more often in a direction away from older plants, maximizing the utilization of water and light resources, and perpetuating the spread of the species into previously juniper-free shrub-steppe. (2) J. occidentalis on the ecotone exhibits significant clustering within a 30–60 m radius. Bivariate point pattern analyses provide evidence that, within a distance of 50–70 m, there is a spatial dependence in tree size such that medium trees are more likely than small trees to be close to large trees. We attribute these phenomena to the fact that juniper seeds are commonly dispersed by berry-eating birds with small territories (0.3–1 ha). Beyond a distance of 50–70 m, juniper plants are randomly distributed, suggesting that additional long-range seed dispersal processes are at work. We further acknowledge the importance of including a reference to spatial scale when formulating hypotheses in statistical analysis of spatio-temporal point patterns.     

Local adaptation in the monocarpic perennial Carlina vulgaris at different spatial scales across Europe

Spatial variation in environmental conditions can lead to local adaptation of plant populations, particularly if gene flow among populations is low. Many studies have investigated adaptation to contrasting environmental conditions, but little is known about the spatial scale of adaptive evolution. We studied population differentiation and local adaptation at two spatial scales in the monocarpic grassland perennial Carlina vulgaris. We reciprocally transplanted seedlings among five European regions (northwestern Czech Republic, central Germany, Luxembourg, southern Sweden and northwestern Switzerland) and among populations of different sizes within three of the regions. We recorded survival, growth and reproduction over three growing periods. At the regional scale, several performance traits and the individual fitness of C. vulgaris were highest if the plants were grown in their home region and they decreased with increasing transplant distance. The effects are likely due to climatic differences that increased with the geographical distance between regions. At the local scale, there were significant interactions between the effects of the population of origin and the transplant site, but these were not due to an enhanced performance of plants at their home site and they were not related to the geographical or environmental distance between the site of origin and the transplant site. The size of the population of origin did not influence the strength of local adaptation. The results of our study suggest that C. vulgaris consists of regionally adapted genotypes, and that distance is a good predictor of the extent of adaptive differentiation at large scales ( > 200 km) but not at small scales. We conclude that patterns of local adaptation should be taken into account for the efficient preservation of genetic resources, when assessing the status of a plant species and during conservation planning.Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible for authorized users.     

Sebacinales are associates of the leafy liverwort Lophozia excisa in the southern maritime Antarctic

The leafy liverwort Lophozia excisa, which is colonised by basidiomycete fungi in other biomes and which evidence suggests may be colonised by mycorrhizal fungi in Antarctica, was sampled from Léonie Island in the southern maritime Antarctic (67°36′ S, 68°21′ W). Microscopic examination of plants indicated that fungal hyphae colonised 78% of the rhizoids of the liverwort, apparently by entering the tips of rhizoids prior to growing into their bases, where they formed hyphal coils. Extensive colonisation of stem medullary cells by hyphae was also observed. DNA was extracted from surface-sterilised liverwort tissues and sequenced following nested PCR, using the primer set ITS1F/TW14, followed by a second round of amplification using the ITSSeb3/TW13 primer set. Neighbour-joining analyses showed that the sequences obtained nested in Sebacinales clade B as a 100% supported sister group to Sebacinales sequences from the leafy liverworts Lophozia sudetica, L. incisa and Calypogeia muelleriana sampled from Europe. Direct PCR using the fungal specific primer set ITS1F/ITS4 similarly identified fungi belonging to Sebacinales clade B as the principal colonists of L. excisa tissues. These observations indicate the presence of a second mycothallus in Antarctica and support the previous suggestion that the Sebacinales has a wide geographical distribution.