Trichostomopsis aaronis (Lor.) Agnew & Townsend new to the U.S.S.R.

Abstract

Occurrence of Ptilidium pulcherrimum in transects and spore dispersal from a single colony have been studied in a coastal spruce forest in northern Sweden. The main substrate type was rotting wood with 75% of all occurrences. Annual spore production was 68,500 spores/m² forest, 640,000 spores/m² substrate and 44,000,000 spores/m² colony. Almost 50% of the spores were deposited within 2.5 m of the colony. Annual spore deposition between colonies was estimated to be between 24,000–39,000 and deposition on the main substrate, decaying logs, was about 340–600 spores/m² forest. P. pulcherrimum showed a clumped distribution pattern up to about a 15 m neighbourhood distance. This pattern could not be explained by a similar clumping of the substrate. Instead a limitation by distance in establishment due to a deficit of spores is assumed.     

Basidiospore dispersal in the old-growth forest fungus Phlebia centrifuga (Basidiomycetes)

Dispersal of the old‐growth forest hngus Phlebia centrifuga was studied under natural conditions in an old‐growth forest stand in south Sweden using spore trapping with single spore mycelia as bait. Sampling was done not only in the forest but also 500 and 1000 m outside it. Within 100 m of the basidomata source, spore dispersal was very efficient, and it was estimated that 385 spores settled per m² during 24 h. The minimum total number of spores calculated to have fallen within the 100 m circle was 1.21 × 70⁷. The spore fall decreased significantly with distance from the basidiomata. Almost all of the mycelia were dikaryotised at lm distance, compared with less than half at 10 and 100 m. Dikaryotisation was observed in a small but significant number of mycelia at 500 and 1000 m. Mating success between different single spore mycelia differed significantly and we speculate that effective population size may be affected by mating choice in this species. What factors restrict this species to old‐growth forests? In the light of the dikaryotisation observed at 1000 m from the source, it seems unlikely that this fungus is restricted by spore dispersal distance, which implies good prospects for its successful establishment in restored habitats, i.e. first‐generation forests with much coarse woody debris.     

Long-Distance Wind-Dispersal of Spores in a Fungal Plant Pathogen: Estimation of Anisotropic Dispersal Kernels from an Extensive Field Experiment

Given its biological significance, determining the dispersal kernel (i.e., the distribution of dispersal distances) of spore-producing pathogens is essential. Here, we report two field experiments designed to measure disease gradients caused by sexually- and asexually-produced spores of the wind-dispersed banana plant fungus Mycosphaerella fijiensis. Gradients were measured during a single generation and over 272 traps installed up to 1000 m along eight directions radiating from a traceable source of inoculum composed of fungicide-resistant strains. We adjusted several kernels differing in the shape of their tail and tested for two types of anisotropy. Contrasting dispersal kernels were observed between the two types of spores. For sexual spores (ascospores), we characterized both a steep gradient in the first few metres in all directions and rare long-distance dispersal (LDD) events up to 1000 m from the source in two directions. A heavy-tailed kernel best fitted the disease gradient. Although ascospores distributed evenly in all directions, average dispersal distance was greater in two different directions without obvious correlation with wind patterns. For asexual spores (conidia), few dispersal events occurred outside of the source plot. A gradient up to 12.5 m from the source was observed in one direction only. Accordingly, a thin-tailed kernel best fitted the disease gradient, and anisotropy in both density and distance was correlated with averaged daily wind gust. We discuss the validity of our results as well as their implications in terms of disease diffusion and management strategy.     

The Fate of the Missing Spores - Patterns of Realized Dispersal beyond the Closest Vicinity of a Sporulating Moss

It is well-known that many species with small diaspores can disperse far during extended temporal scales (many years). However, studies on short temporal scales usually only cover short distances (in, e.g., bryophytes up to 15 m). By using a novel experimental design, studying the realized dispersal, we extend this range by almost two orders of magnitude. We recorded establishment of the fast-growing moss Discelium nudum on introduced suitable substrates, placed around a translocated, sporulating mother colony. Around 2,000 pots with acidic clay were placed at different distances between 5 m and 600 m, in four directions, on a raised bog, with increased pot numbers with distance. The experiment was set up in April-May and the realized dispersal (number of colonized pots) was recorded in September. Close to the mother colony (up to 10 m), the mean colonization rates (ratio of colonized pots) exceeded 50%. At distances between 10 and 50 m colonization dropped sharply, but beyond 50 m the mean colonization rates stabilized and hardly changed (1-3%). The estimated density of spores causing establishments at the further distances (2-6 spores/m(2)) was realistic when compared to the estimated spore output from the central colonies. Our study supports calculations from earlier studies, limited to short distances, that a majority of the spores disperse beyond the nearest vicinity of a source. The even colonization pattern at further distances raises interesting questions about under what conditions spores are transported and deposited. However, it is clear that regular establishment is likely at the km-scale for this and many other species with similar spore output and dispersal mechanism.     

Abundance and viability of fungal spores along a forestry gradient – responses to habitat loss and isolation?

Regional variation in spore deposition and viability was studied for two fungi, Fomitopsis rosea (Alb. & Schwein.: Fr.) P. Karst. and Phlebia centrifuga P. Karst., both confined to old‐growth spruce forests in the boreal zone. Seven regions in Sweden were studied along a north‐south transect in which the historical impact from forestry increases and the amount old forests decreases towards the south. The two southernmost regions were located outside the distribution border of the species. Spore deposition was measured species specifically as heterokaryotisation of homokaryotic mycelia growing on wood discs. There was a significant decline in spore deposition towards the south for both species. F. rosea deposited an average amount of 111 spores m^?2 24 h^?1 in the northernmost region compared to less than 1 spore in the four southernmost regions. The corresponding values for P. centrifuga were 27 spores m^?2 24 h^?1 in the north compared to less than 2 spores in the 4 southernmost regions. No deposition was found south of the distribution borders. The viability of spores from local populations within each region was measured as germination success on nutrient media. Individual fruiting bodies from large populations in the north generally produced spores with higher germinability than fruiting bodies from geographically isolated populations in the central and southern regions. However, there was a high variation among the southern populations. Our data suggest that some populations in mid‐ and south Sweden may suffer from negative genetic effects, possibly associated with fragmentation and loss of habitat. Thus, the combination of low spore deposition and low germinability of spores may be a threat to the long‐term persistence of F. rosea and P. centrifuga in southern Sweden. Several other species may experience the same situation, especially when considering the severe decline of dead wood in Swedish forests.     

Testing a mechanistic dispersal model against a dispersal experiment with a wind‐dispersed moss

Wind is the main dispersal agent for a wide array of species and for these species the environmental conditions under which diaspores are released can potentially modify the dispersal kernel substantially. Little is known about how bryophytes regulate spore release, but conditions affecting peristome movements and vibration of the seta may be important. We modelled airborne spore dispersal of the bryophyte species Discelium nudum (spore diameter 25 μm), in four different release scenarios, using a Lagrangian stochastic dispersion model and meteorological data. We tested the model predictions against experimental data on colonization success at five distances (5, 10, 30, 50 and 100 m) and eight directions from a translocated point source during seven two‐day periods. The model predictions were generally successful in describing the observed colonization patterns, especially beyond 10 m. In the laboratory we established spore release thresholds; horizontal wind speed sd > 0.25 m s^?1 induced the seta to vibrate and in relative humidity < 75% the peristome was open. Our dispersal model predicts that the proportion of spores dispersing beyond 100 m is almost twice as large if the spores are released under turbulent conditions than under more stable conditions. However, including release thresholds improved the fit of the model to the colonization data only minimally, with roughly the same amount of variation explained by the most constrained scenario (assuming both vibration of the seta and an open peristome) and the scenario assuming random release. Model predictions under realised experimental conditions suggest that we had a low statistical power to rank the release scenarios due to the lack of measurements of the absolute rate of spore release. Our results hint at the importance of release conditions, but also highlight the challenges in dispersal experiments intended for validating mechanistic dispersal models.     

EXCHANGES OF INFORMATION,ENERGY & MATERIALS IN SYMBIOSES

We investigated patterns of spore dispersal in the giant kelp Macrocystis pyrifera by collecting 80 independent measurements of spore dispersal from isolated individuals and isolated groups of individuals over a two‐year period. Our results indicate that giant kelp spores routinely disperse both short (i.e. a couple meters) and long (i.e. hundreds to thousands of meters) distances depending on the oceanographic conditions. One consequence of spore dispersal over short distances is self‐fertilization (i.e., fertilization between male and female gametophytes derived from the same sporophyte). Field experiments designed to test the effects of self‐fertilization on lifetime fitness in Macrocystis revealed significant inbreeding depression. Birth rates in self‐fertilized populations were ca. 50% of those produced from outcrossing, which lead to significant differences in cohort size that persisted up through the adult stage. In contrast to outcrossed populations, very few individuals produced from selfing became reproductively mature, and those that did were significantly less fecund than outcrossed individuals. By contrast, long‐range dispersal of spores leads to increased rates of outcrossing. However, long‐range dispersal is typically accompanied by massive dilution of spores, leading to low densities of spore settlement. Sparse spore settlement decreases the overall chance of fertilization in the microscopic gametophyte generation thereby reducing the potential for colonization of the macroscopic sporophyte stage. Large population size of adult sporophytes coupled with the synchronous release of spores in response to environmental cues can help offset the effects of spore dilution and extend the distances over which giant kelp is able to colonize.     

Dispersal of Septoria nodorum Pycnidiospores by Simulated Raindrops in Still Air

Simulated raindrops, diameter c. 3 or 4 mm, fell 13 m down a raintower onto suspensions of Septoria nodorum pycnidiospores, depth 0.5 mm, or infected straw pieces. Splash droplets were collected on pieces of fixed photographic film. It was estimated that one drop generated c. 300 spore carrying splash droplets, containing c. 6000 spores, from a concentrated spore suspension (6.5 × 10⁵ spores/ml) and c. 25 spore-carrying droplets, containing c. 30 spores, from infected straw pieces (11 × 10⁶ spores/g dry wt). When the target was a spore suspension in water without surfactant, most spore-carrying droplets were in the 200—400 μm size category and most spores were carried in droplets with diameter >1000 μm. When surfactant was added to spore suspensions, most spore-carrying droplets were in the 0–200 μm category and most spores were carried in droplets with diameter 200–400 μm and none in droplets >1000 μm. Regression analyses showed a significant (p < 0.001) relationship between square root (number of spores per droplet) and droplet diameter; the slope of the regression line was greatest when surfactant was added to the spore suspensions. The distribution of splash droplets with distance travelled from the target was better fitted by an exponential model than by power law or Gaussian models. The distributions of spore-carrying droplets and spores with distance were fitted better by an exponential model than by a power law model. Thus regressions of log, (number collected) against distance were all significant (p < 0.01); the slopes of the regression lines were steepest when surfactant was added to the spore suspension. At a distance of 10 cm from target spore suspensions most splash droplets and spore-carrying droplets were collected at height 10–20 cm, with none above 40 cm; at a distance of 20 cm there were most at heights 0–10 cm and 40–50 cm.     

Dispersal of single‐ and double‐brood populations of the European earwig,Forficula auricularia: a mark‐recapture experiment

Quantitative information on dispersal of insects should be taken into consideration for making efficient pest management decisions. Such information was not available for the European earwig, Forficula auricularia L. (Dermaptera: Forficulidae), an important biocontrol agent in fruit orchards. A mark‐recapture experiment was carried out in Belgian orchards, where marked earwigs were released at a single point and recaptured after 1 month. Dispersal from this release point was analysed using an analytical formula of a simple diffusion model with disappearance (e.g., as a result of death) derived by Turchin & Thoeny (1993; Quantifying dispersal of southern pine beetles with mark‐recapture experiments and a diffusion model. Ecological Applications 3: 187) . The cumulative number of recaptured earwigs as a function of the distance of release was used to fit the model and estimate parameters. A derived expression, in terms of these parameters, was used to estimate the frequency distribution of the population, as the radius of a circle enclosing various proportions of the earwigs’ dispersal distances. In Belgium, populations of the European earwig can have two life‐history strategies, single‐ (SBP) and double‐brood populations (DBP). Therefore, mark‐recapture experiments were carried out on both population types. We fitted data from SBP (n = 10) and DBP (n = 16) successfully in both the diffusion model and in an exponential curve. Because of the biological relevance, estimates of the diffusion model were used for calculating the frequency distributions. Males and females dispersed the same distances. No differences were found between orchards with different spatial structures (apple and pear). According to literature data, mobility of earwigs is very low compared with other arthropods, which has consequences for the efficiency of biocontrol interventions, like mass releases of earwigs or the use of hedgerows for the establishment of healthy (source) populations. Quantitative results revealed that earwigs of SBP dispersed four times further than earwigs of double‐brood populations. For instance, 95% of the population remained within a radius of 28.6 m in SBP and 7.54 m in DBP.     

Dispersal of Septoria nodorum Pycnidiospores by Simulated Rain and Wind

The influence of wind on the splash dispersal of Septoria nodorum pycnidiospores was studied in a raintower/wind tunnel complex with single drops or simulated rain falling on spore suspensions or infected stubble with windspeeds of 1.5 to 4 m/sec. When single drops fell on spore suspensions (depth 0.5 mm, concentration 7.8 × 10⁵ spores/ml) most of the spore-carrying droplets collected on fixed photographic film between 0–4 m downwind (windspeed 3 m/sec) were >200 μm in diameter. However, most spores were carried in droplets with diameter > 1000 μm, 70 % of which carried more than 100 spores. When simulated rain fell on infected stubble most of the spore-carrying droplets collected beyond 1 m downwind (windspeeds 1.4 and 4 m/sec) were <200 μm in diameter and none were >600 μm; most of these droplets carried only one spore. The distribution of splash droplets (with diameter >100 μm) deposited on chromatography paper showed a maximum at 40–50 cm upwind of the target but many more droplets were deposited 20–30 cm downwind, when single drops fell on a spore suspension (concentration 1.2 × 10⁵ spores/ ml) containing fluorescein dye with a windspeed of 2 m/sec; droplets were collected up to 3 m downwind but not more than 70 cm upwind. With a windspeed of 3 m/sec, numbers of sporecarrying droplets and spores collected on film decreased with increasing distance downwind; most were collected within 2 m of the target but some were found up to 4 m. When simulated rain fell on infected stubble, increasing the windspeed from 1.5 to 4 m/sec greatly increased the number of spores deposited more than 1 m downwind. At 1.5 m/sec none were collected beyond 2 m downwind, whereas at 4 m/sec some were collected at 4 m. A few air-borne S. nodorum spores were collected by suction samplers at a height of 40 cm at distances up to 10 m downwind of a target spore suspension on which simulated rain fell.     

Fine-scale spatial genetic structure of a liverwort (<Emphasis Type="Italic">Barbilophozia attenuata</Emphasis>) within a network of ant trails

Fine-scale spatial genetic structure (SGS) of the liverwort, Barbilophozia attenuata, occupying an area characterized by a network of ant trails, was investigated using microsatellite markers. This is the first study investigating SGS in a liverwort. Significant genetic differentiation was detected among colonies along and outside ant trails, and the SGS pattern varied depending on the spatial scale. At short distances, kinship coefficients were significantly positive up to about eight meters, after which they approached zero and turned negative, while at distances greater than 25 m the values were about zero. Thus, nearby individuals are more closely related than expected, at mid-distances less related, and at great distances genotypes show a random distribution. We suggest that the reproductive mode strongly affects SGS in B. attenuata. Asexual propagation by relatively large gemmae allows more effective establishment than sexual reproduction by small-sized spores, and causes an aggregation of similar genotypes, although the inbreeding effect cannot be ruled out. In environments with small-scale disturbances, e.g., ant trails, gemmae are favoured over spores at establishment. Also, the diaspore bank of the forest floor can be activated by disturbances, which may affect SGS. At mid-distances, the isolation by distance effect, presumably related to comparatively ineffective gemma dispersal, is visible, while at greater distances, the role of spores as effective means of dispersal is evident. The Sp statistic values, which quantify the strength of SGS, indicate that outsider colonies possess less SGS than do plant colonies along ant trails, which relates to the more frequent spore production of outsider colonies. Moreover, dispersal from fallen logs or stumps may be more effective than dispersal from ground-level colonies along ant trails. Apparently, ants do not have much role as dispersal vectors, nor do the physical structures of ant trails as dispersal corridors, although they provide open areas for colonization.     

Dispersal of Monochamus galloprovincialis (Col.: Cerambycidae) as recorded by mark–release–recapture using pheromone traps

The spread of the pine wood nematode (PWN), Bursaphelenchus xylophylus (Nematoda; Aphelenchoididae), the causal agent of the pine wilt disease, is greatly constrained to the dispersal of its vectors, long‐horned beetles of the Monochamus genus. Disease spread at global and regional scales has been mainly caused by human‐mediated transport, yet at a local scale, the short‐ and long‐distance dispersal behaviour of the beetles determine colonization dynamics. Three mark–release–recapture experiments using commercial traps and lures allowed the parameterization of the dispersal kernel under two landscape fragmentation scenarios for the only known European PWN vector, Monochamus galloprovincialis. The respective release of 171 and 353 laboratory‐reared beetles in continuous pine stands in 2009 and 2010 resulted in 36% and 28% recapture rates, yet, at a fragmented landscape in 2011, only 2% of the released 473 individuals could be recaptured. Recaptures occurred as soon as 7–14 days after their release, in agreement with the requirement of sexual maturation to respond to the pheromone–kairomone attractants. Data from the first two experiments were fitted to one mechanical and two empirical dispersal models, from which the distance dispersal kernels could be computed. Derived estimated radii enclosing 50% and 99% of dispersing M. galloprovincialis under continuous pine stands ranged between 250–532 m and 2344–3495 m depending on the replicate and choice of model. Forecasted recaptures in 2011 resulted in a moderate underestimation of long‐distance dispersal, probably influenced by the high degree of habitat fragmentation. In addition, trapping parameters such as the effective sampling area (0.57–0.76 ha) or the seasonal sampling range (426–645 m) could be derived. Observed results, derived dispersal kernels and trapping parameters provide valuable information for the integrated pest management of PWD. Furthermore, estimated dispersal distances indicate that ongoing clear‐cut measures for eradication in the European Union are likely ineffective in stopping the vectors dispersal.     

Spore rain in relation to regional sources and beyond

While patterns of spore dispersal from single sources at short distances are fairly well known, information about ‘spore rain’ from numerous sources and at larger spatial scales is generally lacking. In this study, I sampled spore rain using a novel method consisting of 0.25–0.5 m² cotton cloth traps at nine sites in the boreo‐nemoral vegetation zone in eastern Sweden during two seasons, using Sphagnum spores as a model. Traps were located in various landscapes (mainland, islands). Additional trapping was done in an arctic area (Svalbard) without spore production. Spore densities were tested against distance from the nearest source and area of sources (open peatlands) within different radii around each site (5, 10, 20, 50, 100, 200, 300, 400 km). The cloth method appeared reliable when accounting for precipitation losses, retaining approximately 20–60% of the spores under the recorded amounts of precipitation. Estimated spore densities ranged from 6 million m^?2 and season within a large area source, via regional deposition of 50 000–240 000 spores m^?2, down to 1000 m^?2 at Svalbard. Spore rain for all sites was strongly related to distance from the nearest source, but when excluding samples taken within a source peatland, the amount of sources within 200 km was most important. Spores were larger at isolated island sites, indicating that a higher proportion originated from distant, humid areas. Immense amounts of Sphagnum spores are dispersed across regional distances annually in boreal areas, explaining the success of the genus to colonise nutrient poor wetlands. The detectable deposition at Svalbard indicates that about 1% of the regional spore rain has a trans‐ or intercontinental origin. The regional spore rain, originating from numerous sources in the landscape, is probably valid for most organisms with small diaspores and provides a useful insight in ecology, habitat restoration and conservation planning.     

143 Coalescense During Early Recruitment of Mazzaella Laminarioides

Coalescence in seaweeds is known to occur in the laboratory among young and older sporelings and in the field between neighboring conspecific clumps. However, because spores and germlings are difficult to study in the field, it is as yet unknown at which stage of population development coalescence is most important. Since many seaweeds disperse aggregated propagules, often with a sticky mucilagous envelope around the spores, aggregated recruitment and coalescence might be more important at early stages of population establishment than among fully grown, well established clumps. Using recruitment plates maintained during several experimental times in the field, we are evaluating the above idea with mid‐intertidal populations of Mazzaella laminarioides. During high fertility seasons, close to 45% of the spores settling within or at close (<1 m) distances of the bed exhibited aggregated recruitment, forming groups of 2 to 150+spores. The probability of aggregated recruitments is a function of dispersal distance and spore density. The number of sporelings produced is a function of spore density and coalescence. Highest after‐recruitment mortality (first 15 days) occurs among solitary recruits, followed by sporelings conformed by small number of spores (2–4). Approximately 50% of the spores recruited, isolated or in group, coalesce within these 15 days, gradually forming massive sporelings with increasingly larger basal areas. Thus, after recruitment, sporelings may disappear (die), survive or coalesce. These three alternatives are integrated in a new demographic model for coalescing seaweeds (supported by grant FONDECYT 1020855).     

Beetles provide directed dispersal of viable spores of a keystone wood decay fungus

Wood decay fungi are considered to be dispersed by wind, but dispersal by animals may also be important, and more so in managed forests where dead wood is scarce. We investigated whether beetles could disperse spores of the keystone species Fomitopsis pinicola. Beetles were collected on sporocarps and newly felled spruce logs, a favourable habitat for spore deposition. Viable spores (and successful germination) of F. pinicola were detected by dikaryotization of monokaryotic bait mycelium from beetle samples. Viable spores were on the exoskeleton and in the faeces of all beetles collected from sporulating sporocarps. On fresh spruce logs, nine beetle species transported viable spores, of which several bore into the bark. Our results demonstrate that beetles can provide directed dispersal of wood decay fungi. Potentially, it could contribute to a higher persistence of some species in fragmented forests where spore deposition by wind on dead wood is less likely.     

95% of basidiospores fall within 1 m of the cap: a field-and modeling-based study

Plant establishment patterns suggest that ectomycorrhizal fungal (EMF) inoculant is not found ubiquitously. The role of animal vectors dispersing viable EMF spores is well documented. Here we investigate the role of wind in basidiospore dispersal for six EMF species, Inocybe lacera, Laccaria laccata, Lactarius rufus, Suillus brevipes, Suillus tomentosus and Thelephora americana. Basidiospores adhered to microscope slides placed on three 60 cm transects radiating from sporocarps. Morphological characteristics of species as well as average basidiospore volume were recorded. Number of basidiospores was quantified at specific distances to produce actual dispersal gradients. We found a negative exponential decay model using characteristics for each species fit the field data well. The 95% modeled downwind dispersal distance of basidiospores was calculated for each species. The 95% modeled downwind dispersal distance increased with increasing cap height and decreasing basidiospore volume for the species sampled, with 95% of basidiospores predicted to fall within 58 cm of the cap. Differences in anatomical characteristics of EMF species influence how far basidiospores are dispersed by wind. We discuss the role of wind dispersal leading to patterns of EMF establishment during primary succession.     

Modeling mycorrhizal fungi dispersal by the mycophagous swamp wallaby (Wallabia bicolor)

Despite the importance of mammal‐fungal interactions, tools to estimate the mammal‐assisted dispersal distances of fungi are lacking. Many mammals actively consume fungal fruiting bodies, the spores of which remain viable after passage through their digestive tract. Many of these fungi form symbiotic relationships with trees and provide an array of other key ecosystem functions. We present a flexible, general model to predict the distance a mycophagous mammal would disperse fungal spores. We modeled the probability of spore dispersal by combining animal movement data from GPS telemetry with data on spore gut‐retention time. We test this model using an exemplar generalist mycophagist, the swamp wallaby (Wallabia bicolor). We show that swamp wallabies disperse fungal spores hundreds of meters—and occasionally up to 1,265 m—from the point of consumption, distances that are ecologically significant for many mycorrhizal fungi. In addition to highlighting the ecological importance of swamp wallabies as dispersers of mycorrhizal fungi in eastern Australia, our simple modeling approach provides a novel and effective way of empirically describing spore dispersal by a mycophagous animal. This approach is applicable to the study of other animal‐fungi interactions in other ecosystems.     

Dispersal potential of spores and asexual propagules in the epixylic hepatic Anastrophyllum hellerianum

Dispersal ability is of great importance for plants, which commonly occupy spatially and temporally limited substrate patches. Mixed reproductive strategies with abundant diaspore production are favoured in a heterogeneous landscape to ensure successful colonisation at different distances. In bryophytes, long-distance dispersal has been thought to take place primarily by spores, while asexual propagules are important in local dispersal and in the maintenance of colonies. In the present study, we investigated the dispersal potential of two equally sized propagules, sexually formed spores and asexually produced gemmae in the dioecious, epixylic hepatic, Anastrophyllum hellerianum, which inhabits spatially and temporally limited substrate patches. We trapped propagules at different distances (0–10 m) and directions from the source colonies in two experiments: one in a natural habitat within a forest and another involving an artificial set-up in an open habitat. Spore dispersal showed only slight distance dependence both in the open and the forest habitats, presumably as a consequence of wind affecting the dispersal pattern. Gemma dispersal was more strongly distance-dependent in the open habitat than in the forest sites. Considerably more gemmae were deposited during rainy than dry periods, possibly because of the effect of rain drops on gemma release. However, weather conditions had no effect on the dispersal patterns of spores or gemmae. In A. hellerianum, the combination of occasional spore production and practically continuous, massive gemma production facilitates dispersal both on local scale and over long distances. Unlike previously assumed, not only spores but also the asexual propagules may contribute to long-distance dispersal, thus allowing considerable gene flow at the landscape level.     

Sedimentation velocity of myxomycete spores

Sedimentation velocities were measured for seven myxomycete species and one fungus. Values for these first measurements for Myxomycetes were fitted with the formula of Stoke’s law for the terminal velocity of small spherical bodies in air. The obtained correlation coefficient of R=0.939 indicates that sedimentation velocities of myxomycete spores follow Stoke’s law well. With spore density as a parameter, the fit estimated a mean density of 0.74 g/cm³ for air-dried spores. The importance of the stalked spore case as well as the spore diameter for dispersal abilities of Myxomycetes is discussed.