Ecomethodology for organoosmotrophs: Prokaryotic unicellular versus eukaryotic mycelial

Although they are very unlikely to play large direct roles in water-column microbial loops, eukaryotic mycelial decomposers (the mycelial true fungi, eumycotes, and zoosporic fungi, oomycotes) have the potential to be important secondary producers in decaying plant material in shallow aquatic systems. Their secondary productivity may lead to important exchanges of material with microbial loops: output of ascospores, conidia, zoosporic flagellates, leaked lysates, and particles of decayed plants containing mycelium; input of dissolved organics and inorganic nutrients. Development of methods for ecological study of the aquatic mycelial eukaryotic decomposers has not advanced as rapidly as that for the prokaryotes of microbial loops, probably because (1) there are fewer aquatic microbial ecologists with mycological training and inclination than with prokaryotic leanings; and (2) the mycelial decomposers are difficult to work with, because they produce their mycelial mass virtually entirely within opaque solid substrates. Direct microscopic methods have emerged as prime tools for the measurement of prokaryotic mass, whereas an index-chemical assay (ergosterol) is currently the most efficient way to measure the mass of eumycotes. For measuring productivity of prokaryotes of microbial loops, microbial ecologists may choose from several (>10) published and field-tested methods, involving direct microscopy or monitoring of radiotracers. Extensive reviews of distribution and dynamics of aquatic bacterial mass and productivity have appeared. For measuring productivity of eukaryotic mycelial decomposers, one has only two published methods from which to choose, a direct-microscopic and a radiotracer method, neither of which has had adequate field testing. We are, furthermore, much less well equipped to obtain mass and productivity information for the poorly known mycelial oomycotes than we are for the eumycotes. Application of productivity techniques and nucleic-acid technology, may within the next decade allow knowledge of ecology of aquatic eukaryotic mycelial decomposers to advance to levels approaching that for the prokaryotes of microbial loops.     

Release of dimethylsulfide from dimethylsulfoniopropionate by plant-associated salt marsh fungi

The range of types of microbes with dimethylsulfoniopropionate (DMSP) lyase capability (enzymatic release of dimethylsulfide [DMS] from DMSP) has recently been expanded from bacteria and eukaryotic algae to include fungi (a species of the genus Fusarium [M. K. Bacic and D. C. Yoch, Appl. Environ. Microbiol. 64:106-111, 1998]). Fungi (especially ascomycetes) are the predominant decomposers of shoots of smooth cordgrass, the principal grass of Atlantic salt marshes of the United States. Since the high rates of release of DMS from smooth cordgrass marshes have a temporal peak that coincides with peak shoot death, we hypothesized that cordgrass fungi were involved in this DMS release. We tested seven species of the known smooth cordgrass ascomycetes and discovered that six of them exhibited DMSP lyase activity. We also tested two species of ascomycetes from other DMSP-containing plants, and both were DMSP lyase competent. For comparison, we tested 11 species of ascomycetes and mitosporic fungi from halophytes that do not contain DMSP; of these 11, only 3 were positive for DMSP lyase. A third group tested, marine oomycotes (four species of the genera Halophytophthora and Pythium, mostly from mangroves), showed no DMSP lyase activity. Two of the strains of fungi found to be positive for DMSP lyase also exhibited uptake of DMS, an apparently rare combination of capabilities. In conclusion, a strong correlation exists between a fungal decomposer's ability to catabolize DMSP via the DMSP lyase pathway and the host plant's production of DMSP as a secondary product.     

Release of Dimethylsulfide from Dimethylsulfoniopropionate by Plant-Associated Salt Marsh Fungi

The range of types of microbes with dimethylsulfoniopropionate (DMSP) lyase capability (enzymatic release of dimethylsulfide [DMS] from DMSP) has recently been expanded from bacteria and eukaryotic algae to include fungi (a species of the genus Fusarium [M. K. Bacic and D. C. Yoch, Appl. Environ. Microbiol. 64:106–111, 1998]). Fungi (especially ascomycetes) are the predominant decomposers of shoots of smooth cordgrass, the principal grass of Atlantic salt marshes of the United States. Since the high rates of release of DMS from smooth cordgrass marshes have a temporal peak that coincides with peak shoot death, we hypothesized that cordgrass fungi were involved in this DMS release. We tested seven species of the known smooth cordgrass ascomycetes and discovered that six of them exhibited DMSP lyase activity. We also tested two species of ascomycetes from other DMSP-containing plants, and both were DMSP lyase competent. For comparison, we tested 11 species of ascomycetes and mitosporic fungi from halophytes that do not contain DMSP; of these 11, only 3 were positive for DMSP lyase. A third group tested, marine oomycotes (four species of the genera Halophytophthora and Pythium, mostly from mangroves), showed no DMSP lyase activity. Two of the strains of fungi found to be positive for DMSP lyase also exhibited uptake of DMS, an apparently rare combination of capabilities. In conclusion, a strong correlation exists between a fungal decomposer’s ability to catabolize DMSP via the DMSP lyase pathway and the host plant’s production of DMSP as a secondary product.     

Fungal importance extends beyond litter decomposition in experimental early‐successional streams

Fungi are important decomposers of leaf litter in streams and may have knock‐on effects on other microbes and carbon cycling. To elucidate such potential effects, we designed an experiment in outdoor experimental channels simulating sand‐bottom streams in an early‐successional state. We hypothesized that the presence of fungi would enhance overall microbial activity, accompanied by shifts in the microbial communities associated not only with leaf litter but also with sediments. Fifteen experimental channels received sterile sandy sediment, minimal amounts of leaf litter, and one of four inocula containing either (i) fungi and bacteria, or (ii) bacteria only, or (iii) no microorganisms, or (iv) killed microorganisms. Subsequently, we let water from an early‐successional catchment circulate through the channels for 5 weeks. Whole‐stream metabolism and microbial respiration associated with leaf litter were higher in the channels inoculated with fungi, reflecting higher fungal activity on leaves. Bacterial communities on leaves were also significantly affected. Similarly, increases in net primary production, sediment microbial respiration and chlorophyll a content on the sediment surface were greatest in the channels receiving a fungal inoculum. These results point to a major role of fungal communities in stream ecosystems beyond the well‐established direct involvement in leaf litter decomposition.     

Nitrogen availability affects saprotrophic basidiomycetes decomposing pine needles in a long term laboratory study

Fungi, especially basidiomycetous litter decomposers, are pivotal to the turnover of soil organic matter in forest soils. Many litter decomposing fungi have a well-developed capacity to translocate resources in their mycelia, a feature that may significantly affect carbon (C) and nitrogen (N) dynamics in decomposing litter. In an eight-month long laboratory study we investigated how the external availability of N affected the decomposition of Scots pine needles, fungal biomass production, N retention and N-mineralization by two litter decomposing fungi – Marasmius androsaceus and Mycena epipterygia. Glycine additions had a general, positive effect on fungal biomass production and increased accumulated needle mass loss after 8 months, suggesting that low N availability may limit fungal growth and activity in decomposing pine litter. Changes in the needle N pool reflected the dynamics of the fungal mycelium. During late decomposition stages, redistribution of mycelium and N out from the decomposed needles was observed for M. epipterygia, suggesting autophagous self degradation.     

Biodiversity amongst filamentous fungi

Diversities in fungi are manifold. Fungi themselves are heterogeneous and constitute at least three unrelated major taxa. Structural diversity reflects, in most cases, adaptive and functional strategies. Diversity in nucleic acids and chemical compounds is very high in several fungal taxa. Fungi play an essential role in the function of ecosystems. The diversity of plant parasites is extremely high and species-dependent associations exist. Saprobic fungi are most important in wood and litter decay and diverse taxa comprise the main decomposers in specific successional niches. Two dominating symbiotic systems have evolved convergently in various fungal groups, notably lichens and mycorrhizas, both remarkably diverse in their heterotrophic partners.     

Lentic and lotic habitats as templets for fungal communities: traits,adaptations, and their significance to litter decomposition within freshwater ecosystems

Decomposition of plant matter is a key ecosystem process and considerable research has examined plant litter decay processes in freshwater habitats. Fungi are common inhabitants of the decomposer microbial community and representatives of all major fungal phyla have been identified within freshwater systems. Development and application of quantitative methods over the last several decades have firmly established that fungi are central players in the decomposition of plant litter in freshwaters and are important mediators of energy and nutrient transfer to higher trophic levels. Despite the critical roles that fungi play in carbon and nutrient cycling in freshwater ecosystems, there are notable differences in the types and adaptations of fungal communities between lotic and lentic habitats. These differences can be explained by the wide range of hydrologic, physical, chemical and biological conditions within freshwater systems, all of which can influence the presence, type, and activity of fungal decomposers and their impact on litter decomposition. This paper seeks to provide a brief overview of the types, adaptations, and role of fungi within lotic and lentic freshwater ecosystems, with a particular emphasis on their importance to litter decomposition and the key environmental conditions that impact their growth and decay activities. This discussion will specifically focus on fungal dynamics occurring on plant litter in forested headwater streams and emergent freshwater marshes, since published data concerning their role in these systems is considerably more abundant in comparison to other freshwater habitats.     

Decomposition and Fungi of Needle Litter from Slow- and Fast-growing Norway Spruce (Picea abies) Clones

The fungal species involved in the decomposition of needle litter and their response to intraspecific genetic variation of trees are poorly known. First, we compared the needle decomposition and fungal decomposers underneath eight different Norway spruce clones in situ. This experiment revealed 60-70% loss of needle mass in two years. Although spruce clones differed considerably in growth (twofold height difference) and their needles differed in chemical composition, no significant difference was found for loss of needle mass under the spruce clones. Furthermore, the spruce clones did not affect the community structure of the fungal decomposers. Fungi inhabiting needle litter were identified by extracting ribosomal RNA (rRNA) and sequencing complementary DNA (cDNA) of internal trascribed spacer 1 (ITS1) region. The most frequent identifications were Lophodermium, Pezizales, Mycena, and Marasmius, suggesting that endophytic fungi were involved in the decomposition process. Second, we evaluated the potential of endophytes to decompose needle material in a microcosm experiment in which all other fungi than endophytes were excluded. Within 2 years, the endophytes had decomposed 35-45% of the needle mass. Sequences of Mollisia, Lophodermium, Lachnum, and Phialocephala were most frequently found in rRNA and rDNA extracted from the needles at the end of the microcosm experiment. The dominant needle endophyte in fresh, green needles was Lophodermium piceae, and this species was also found frequently in the needle material after 2 years of decay both in the field and laboratory experiments. Moreover, the relative abundance of Lophodermium-derived denaturing gradient gel electrophoresis (DGGE) bands correlated positively with the decomposition in the microcosm experiment. Hence, our results suggest a significant role of endophytic fungi, and particularly L. piceae, in the process of needle decomposition in boreal forests.     

Antagonism between Bacteria and Fungi on Decomposing Aquatic Plant Litter

Bacterial and fungal decomposers of aquatic plant litter may exhibit either synergistic or antagonistic interactions, which are likely to influence microbial growth as well as the decomposition of litter and, eventually, the carbon metabolism of aquatic systems. To elucidate such interactions, we inoculated decomposing Phragmites culms in microcosms with fungal isolates and with natural communities of bacteria and fungi in different combinations. The development of fungal and bacterial biomass and the carbon dynamics were studied during several months of degradation. The results show a bilateral antagonistic relationship between bacteria and fungi. After 3 months, fungal biomass accumulation was approximately 12 times higher in the absence than in the presence of bacteria. Bacterial biomass accumulation was about double in the absence of fungi compared to when fungi were present. Similar interactions developed between a natural assemblage of bacteria and five different fungal strains isolated from Phragmites litter (three identified hyphomycetes and two unidentified strains). Despite the great difference in biomass development between the treatments, the carbon metabolism was similar regardless of whether fungi and/or bacteria were present alone or in coexistence. We suggest that the antagonism between bacteria and fungi is an important controlling factor for microbial colonization and growth on aquatic plant litter.     

Black summer bushfires caused extensive damage to estuarine wetlands in New South Wales,Australia

There is now considerable evidence that, as the climate continues to warm, bushfires are becoming more common and severe, particularly in regions such as south-eastern Australia. The extraordinary Australian bushfires over the summer of 2019/2020 resulted in the burning of habitats such as highland peat swamps and intertidal estuarine wetlands over unprecedented spatial scales. Across New South Wales, these bushfires affected 183 ha of saltmarshes and 23 ha of mangroves in 19 estuaries. The percentage of fire-affected saltmarsh ranged from 51% to 81% in the worst impacted estuaries, although typically ≤15% of mapped saltmarsh was damaged. Just over 50% of mangroves were burnt in Wonboyn Lake (although this constituted <0.2 ha), whereas in all other estuaries, ≤5% of mangroves were burnt. At the state-wide scale, the likelihood of saltmarshes being affected by fire was unrelated to adjacent terrestrial vegetation; however, mangroves adjacent to burnt wet sclerophyll forest were more likely to burn than not. Burnt mangroves were almost exclusively associated with extreme or high severity fires in adjacent terrestrial vegetation, yet saltmarshes were also impacted in some cases by moderate or low-intensity fires. Many species of saltmarsh plants had re-sprouted or germinated after 6–24 months, but the extent of any recovery or changes in species composition were not quantified. The majority of fire-affected mangrove trees appeared to be dead 24 months after the fires, despite observations of epicormic growth on some trees after six months. Bushfire impacts to estuarine wetlands are likely to become more frequent and results from our work can help target hazard reduction burning that might be considered for minimising damage to mangroves. More work is required to better understand potential longer term impacts and the capacity for natural recovery of estuarine wetlands from bushfires.     

Effect of Inorganic Nutrients on Relative Contributions of Fungi and Bacteria to Carbon Flow from Submerged Decomposing Leaf Litter

The relative contributions of fungi and bacteria to carbon flow from submerged decaying plant litter at different levels of inorganic nutrients (N and P) were studied. We estimated leaf mass loss, fungal and bacterial biomass and production, and microbial respiration and constructed partial carbon budgets for red maple leaf disks precolonized in a stream and then incubated in laboratory microcosms at two levels of nutrients. Patterns of carbon flow for leaf disks colonized with the full microbial assemblage were compared with those colonized by bacteria but in which fungi were greatly reduced by placing leaf disks in colonization chambers sealed with membrane filters to exclude aquatic hyphomycete conidia but not bacterial cells. On leaves colonized by the full microbial assemblage, elevated nutrient concentrations stimulated fungi and bacteria to a similar degree. Peak fungal and bacterial biomass increased by factors of 3.9 and 4.0; cumulative production was 3.9 and 5.1 times higher in the high nutrient in comparison with the low nutrient treatment, respectively. Fungi dominated the total microbial biomass (98.4 to 99.8%) and cumulative production (97.3 and 96.5%), and the fungal yield coefficient exceeded that of bacteria by a factor of 36 and 27 in low- and high-nutrient treatments, respectively. Consequently, the dominant role of fungi in leaf decomposition did not change as a result of nutrient manipulation. Carbon budgets indicated that 8% of leaf carbon loss in the low-nutrient treatment and 17% in the high-nutrient treatment were channeled to microbial (essentially fungal) production. Nutrient enrichment had a positive effect on rate of leaf decomposition only in microcosms with full microbial assemblages. In treatments where fungal colonization was reduced, cumulative bacterial production did not change significantly at either nutrient level and leaf decomposition rate was negatively affected (high nutrients), suggesting that bacterial participation in carbon flow from decaying leaf litter is low regardless of the presence of fungi and nutrient availability. Moreover, 1.5 and 2.3 times higher yield coefficients of bacteria in the reduced fungal treatments at low and high nutrients, respectively (percentage of leaf carbon loss channeled to bacterial production), suggest that bacteria are subjected to strong competition with fungi for resources available in leaf litter.     

Ecology, disturbance and restoration of coastal saltmarsh in Australia: a review

It is clear that saltmarshes are a unique and important component of the coastal biosphere of Australia. Their contribution ranges from stabilisation of fine sediments and providing an excellent protective buffer between land and sea, to their diverse blend of terrestrial and marine fauna. Further, saltmarsh plants are highly specialised and adapted to fill a harsh niche allowing them to act in roles that other vegetation types cannot. Saltmarsh habitats are recognised for their importance to migratory waders under the Ramsar convention, but it is becoming increasingly evident that they are also important to a variety of commercially valuable fish and native mammal species. Activities that are detrimental to saltmarshes continue and need to be addressed in order to conserve remaining saltmarsh areas. In general, urbanisation of the catchment has lead to filling of saltmarshes, tidal restriction, use by recreational vehicles, grazing, trampling and increased sedimentation and nutrient runnoff allowing colonisation and invasion of mangroves. These disturbances have a number of ecological consequences ranging from weed infestation to complete changes in the species composition and ecology. Reversing the disturbance is not always simple and can require extensive groundwork to be successful. Rehabilitation of existing saltmarsh areas has been a successful means to enhance this habitat. In general, it requires relatively little effort to remove weeds and fence off areas to regenerate naturally. Saltmarsh areas have been shown to respond well to this type of manipulation. Restoration and creation require substantial effort and planning to ensure a successful outcome. However, given the right environmental combinations of elevation, tide and salinity, saltmarsh will establish and grow. To speed the process transplantation of saltmarsh plants can be considered either from donor sites or plants propagated in green houses.     

Does mixing litter of different qualities alter stream microbial diversity and functioning on individual litter species?

We examined effects of leaf litter quality and species mixing on microbial community diversity and litter processing in a forested headwater stream. Single- and mixed-species litter from dominant tree species ( Liriodendron tulipifera , Acer rubrum , Quercus prinus , Rhododendron maximum ) were incubated in a southern Appalachian headwater stream. Litter carbon-to-nitrogen ratios (C:N), mass loss, microbial respiration, and microbial community diversity were analyzed on individual litter species after incubation. Initial C:N varied widely among individual litter species, and these differences persisted throughout the 50-day incubation period. Litter C:N of the recalcitrant species R. maximum remained higher than that of all other litter species, and C:N of R. maximum and L. tulipifera increased when both species were present together in a mixture. Although mass loss of individual species was generally unaffected by mixing, microbial respiration was greater on A. rubrum and Q. prinus litter incubated with R. maximum compared to either species alone. Enhanced resource heterogeneity, which was experimentally achieved by litter mixing low- and higher-quality litter species, resulted in apparent shifts in microbial community diversity on individual litter species. Responses of bacterial and fungal community diversity to litter mixing varied among individual litter species. Our results suggest that changes in tree species composition in riparian forests and subsequent changes in litter resource heterogeneity could alter stream microbial community diversity and function. As bacteria and fungi are important decomposers of plant litter in aquatic ecosystems, resource-dependent changes in microbial communities could alter detrital processing dynamics in streams.     

Impacts of elevated temperature on the growth and functioning of decomposer fungi are influenced by grazing collembola

Elevated temperature has potential to influence the biological mechanisms regulating ecosystem–atmosphere carbon exchange. The relationship between warming and heterotrophic microbial respiration remains poorly understood, not least in terms of the differential sensitivity of microbial groups to temperature and the complexity of interactions with other biota. Cord‐forming basidiomycete fungi are dominant primary decomposers in temperate woodland. Decomposition rates are determined by the composition of the decomposer community, ecophysiological relationships between these fungi and abiotic variables and interactions with other organisms. Amongst the latter, a major determinant is the balance between mycelial growth and removal by soil invertebrate grazers, which can themselves be affected by elevated temperature. We investigated the impact of elevated temperature on fungal foraging and decomposition of beech (Fagus sylvatica) wood in soil microcosms to which the invertebrate grazers, Folsomia candida and Protophorura armata (Collembola), were added in factorial combinations with five basidiomycete fungi. Species‐specific impacts on mycelial development and function resulted from differential sensitivity of fungi to warming and grazing. Temperature impacts on collembola abundance were resource‐specific, causing increased grazing pressure by both species, but on different fungi. Grazing often counteracted warming‐induced stimulation of mycelial growth, but occasionally amplified the temperature effect, with implications for colonization rates of new resources. High grazing pressure did not prevent increased fungal‐mediated decomposition of colonized wood, as fungi utilized more resource‐derived energy to maintain explorative growth. Impacts of elevated temperature on decomposition are likely to depend on local composition of the fungal and invertebrate decomposer community.     

Environmental fungal diversity in the upwelling ecosystem off central Chile and potential contribution to enzymatic hydrolysis of macromolecules in coastal ecotones

Even though occurrence of fungi in several marine environments has been documented, their inclusion within the marine microbial loop is not fully recognized. A major constraint is whether fungi in coastal waters are truly marine or represent transient microorganisms transported from terrestrial environments. We approached this issue by analyzing ambient fungal composition and hydrolytic activity of culturable fungi along a nearshore-offshore gradient in the upwelling ecosystem off central Chile, a region of high marine productivity strongly influenced by river discharges. We detected different communities of fungi in nearshore and offshore waters, with near estuary strains hydrolyzing proteins and carbohydrates faster than those from offshore sites. We conclude that coastal waters off central Chile comprise distinct fungal communities representative of offshore and nearshore environments, and provide new evidence for fungi processing organic matter in coastal ecotones, opening a fresh perspective for disappearance of organics carried by rivers in the coastal ocean.     

Productivities of microbial decomposers during early stages of decomposition of leaves of a freshwater sedge

1. We examined standing-senescing, standing-dead and recently fallen leaf blades of Carex walteriana in fens of the Okefenokee Swamp to determine the nature of the microbial decomposers in the early stages of decomposition, measuring both standing crops and productivities ([³H]leucineprotein method for bacteria, [¹⁴C]acetateergosterol for fungi). 2. Fungal standing crops (ergosterol) became detectable at the mid-senescence stage (leaves about half yellow-brown) and rose to 14–31 mg living-fungal C g^?1 organic mass of the decaying system; bacterial standing crops (direct microscopy) were ± 0.2 mgC g^?1 until the fallen-leaf stage, when they rose to as high as 0.9 mgC g^?1. 3. Potential microbial specific growth rates were similar between fungi and bacteria, at about 0.03–0.06 day^?1, but potential production of fungal mass was 115–512 μgC g^?1 organic mass day^?1, compared with 0–22 μgC g^?1 day^?1 for bacteria. Rates of fungal production were about 6-fold lower on average than previously found for a saltmarsh grass, perhaps because much lower phosphorus concentratiofis in the freshwater fen limit fungal activity. 4. There was little change in lignocellulose (LC) percentage of decaying leaves, although net loss of organic mass at the fallen, broken stage was estimated to be 59%, suggesting that LC was lost at rates proportional to those for total organics during decay. Monomers of fungal-wall polymers (glucosamine and mannose) accumulated 2- to 4-fold during leaf decay. This may indicate that an increase found for proximate (acid-detergent) lignin could be at least partially due to accumulation of refractory fungal-wall material, including melanin. 5. A common sequence in decaying aquatic grasses is suggested: principally fungal alteration of LC during standing decay, followed by a trend toward bacterial decomposition of the LC after leaves fall and break into particles.     

Effects of grassland species on decomposition of litter and soil microbial communities

Decomposition of litter is greatly influenced not only by its chemical composition but also by activities of soil decomposers. By using leaf litter from 15 plant species collected from semi-natural and improved grasslands, we examined (1) how interspecific differences in the chemical composition of litter influence the abundance and composition of soil bacterial and fungal communities and (2) how such changes in microbial communities are related to the processes of decomposition. The litter from each species was incubated in soil of a standard composition for 60 days under controlled conditions. After incubation, the structure of bacterial and fungal communities in the soil was examined using phospholipid fatty-acid analysis and denaturing gradient gel electrophoresis. Species from improved grasslands had significantly higher rates of nitrogen mineralization and decomposition than those from semi-natural grasslands because the former were richer in nitrogen. Litter from improved grasslands was also richer in Gram-positive bacteria, whereas that from semi-natural grasslands was richer in actinomycetes and fungi. Nitrogen content of litter also influenced the composition of the fungal community. Changes in the composition of both bacterial and fungal communities were closely related to the rate of litter decomposition. These results suggest that plant species greatly influence litter decomposition not only through influencing the quality of substrate but also through changing the composition of soil microbial communities.     

Distribution and Diversity of Planktonic Fungi in the West Pacific Warm Pool

Fungi contribute substantially to biogeochemical cycles of terrestrial and marine habitats by decomposing matter and recycling nutrients. Yet, the diversity of their planktonic forms in the open ocean is poorly described. In this study, culture-independent and molecular approaches were applied to investigate fungal diversity and abundance derived from samples collected from a broad swath of the Pacific Warm Pool across major environmental gradients Our results revealed that planktonic fungi were molecularly diverse and their diversity patterns were related to major phytoplankton taxa and various nutrients including nitrate, nitrite, orthophosphate and silicic acid. Over 400 fungal phylotypes were recovered across this region and nearly half of them grouped into two major fungal lineages of Ascomycota and Basidiomycota, whose abundance varied among stations. These results suggest that planktonic fungi are a diverse and integral component of the marine microbial community and should be included in future marine microbial ecosystem models.     

The fungal dimension of biological invasions

Fungi represent an essential component of biodiversity, not only because of the large number of species, but also for their ecological, evolutionary and socio-economic significance. Yet, until recently, fungi received scant consideration in ecology, especially invasion ecology. Their under-representation is largely the result of a lack of scientific knowledge of fungal biodiversity and ecology. With the exception of pathogenic fungi, which cause emergent infectious diseases, the impact of fungal invasions is often difficult to quantify owing to limited baseline data on fungal communities. Here, we aim to raise awareness among mycologists and ecologists of the fungal dimension of invasions and of the need to intensify research in fungal ecology to address issues of future introductions.