Heteroplasmy due to chloroplast paternal leakage: another insight into <Emphasis Type="Italic">Phragmites</Emphasis> haplotypic diversity in North America

Chloroplasts contain several copies of their DNA, and intra-individual haplotypic variation (heteroplasmy) is common in plants, but unexplored in the cosmopolitan genus Phragmites. The aims of this study were to assess if heteroplasmy due to paternal leakage of the chloroplast occurs in Phragmites and which new insights into the evolutionary history of Phragmites australis in North America can be identified from the heteroplasmic variation. Eight non-native P. australis haplotypes occur in North America and can interbreed with P. australis ssp. americanus and P. australis var. berlandieri, creating opportunities for biparental inheritance of distinctive haplotypes. The polymorphism in the trnT-trnL sequence length revealed seventeen cases of heteroplasmy worldwide, in contact zones of distantly related haplotypes and in known hybrid populations, nine of which occurred in North America. In America, the cloned sequences, combined with nuclear markers, identified recombined haplotypes between native P. australis ssp. americanus and invasive P. australis haplotype M, and between the species P. mauritianus and P. australis, due to chloroplast paternal leakage. The occurrence of heteroplasmy and recombined haplotypes suggest a local origin for some of the rare non-native haplotypes occurring in North America, and plastid leakage events in the evolutionary histories of P. australis ssp. americanus and P. australis var. berlandieri.     

The Impacts of Above- and Belowground Plant Input on Soil Microbiota: Invasive <Emphasis Type="Italic">Spartina alterniflora</Emphasis> Versus Native <Emphasis Type="Italic">Phragmites australis</Emphasis>

Invasive plants affect soil food webs through various resource inputs including shoot litter, root litter and living root input. The net impact of invasive plants on soil biota has been recognized; however, the relative contributions of different resource input pathways have not been quantified. Through a 2 × 2 × 2 factorial field experiment, a pair of invasive and native plant species (Spartina alterniflora vs. Phragmites australis) was compared to determine the relative impacts of their living roots or shoots and root litter on soil microbial and nematode communities. Living root identity affected bacteria-to-fungi PLFA ratios, abundance of total nematodes, plant-feeding nematodes and omnivorous nematodes. Specifically, the plant-feeding nematodes were 627% less abundant when living roots of invasive S. alterniflora were present than those of native P. australis. Likewise, shoot and root biomass (within soil at 0–10 cm depth) of S. alterniflora was, respectively, 300 and 100% greater than those of P. australis. These findings support the enemy release hypothesis of plant invasion. Root litter identity affected other components of soil microbiota (that is, bacterial-feeding nematodes), which were 34% more abundant in the presence of root litter of P. australis than S. alterniflora. Overall, more variation associated with nematode community structure and function was explained by differences in living roots than root or shoot litter for this pair of plant species sharing a common habitat but contrasting invasion degrees. We conclude that belowground resource input is an important mechanism used by invasive plants to affect ecosystem structure and function.     

Native ecosystem engineer facilitates recruitment of invasive crab and native invertebrates

Native ecosystem engineers that add physical structure to ecosystems can facilitate invasive species. In this study we determined the effects of the native tube-forming serpulid worm, Galeolaria caespitose on the recruitment of the invasive New Zealand porcelain crab, Petrolisthes elongatus, and whether invasive crab recruitment was related to the recruitment of native species. P. elongatus is abundant beneath intertidal rocks around Tasmania, southern Australia, and the underside of these rocks is usually covered with a calcareous matrix formed by the serpulid. We used an experimental approach to investigate whether rocks, serpulids on the underside of rocks and adult P. elongatus influenced the recruitment P. elongatus and native communities. P. elongatus and native invertebrates only recruited in the presence of rocks indicating the importance of rock as primary recruitment habitat. Moreover, the presence of serpulids on the underside of rocks significantly increased the recruitment of P. elongatus and native invertebrates compared to rocks without serpulids. Rocks with higher densities of adult P. elongatus at the end of the experiment also had higher densities of P. elongatus recruits. The density of P. elongatus recruits did not influence native species richness and abundance although there was some evidence that high P. elongatus recruitment was correlated with shifts in native community structure. We have shown that a native ecosystem engineer facilitates recruitment of an invasive crab but this does not appear to influence the recruitment of native species.     

<Emphasis Type="Italic">Phragmites</Emphasis><Emphasis Type="Italic">australis</Emphasis> as a model organism for studying plant invasions

The cosmopolitan reed grass Phragmites australis (Poaceae) is an intensively studied species globally with a substantial focus in the last two decades on its invasive populations. Here we argue that P. australis meets the criteria to serve as a model organism for studying plant invasions. First, as a dominant species in globally important wetland habitats, it has generated significant pre-existing research, demonstrating a high potential for funding. Second, this plant is easy to grow and use in experiments. Third, it grows abundantly in a wide range of ecological systems and plant communities, allowing a broad range of research questions to be addressed. We formalize the designation of P. australis as a model organism for plant invasions in order to encourage and standardize collaborative research on multiple spatial scales that will help to integrate studies on the ecology and evolution of P. australis invasive populations, their response to global environmental change, and implications for biological security. Such an integrative framework can serve as guidance for studying invasive plant species at the population level and global spatial scale.     

Performance of two alpine plant species along environmental gradients in an alpine meadow ecosystem in central Tibet

Understanding how biotic interactions and abiotic conditions affect plant performance is important for predicting changes in ecosystem function and services in variable environments. We tested how performances of Astragalus rigidulus and Potentilla fruticosa change along gradients of biotic interactions (represented by plant species richness, abundance of the dominant plant species Kobresia pygmaea, and herbivory intensity) and abiotic conditions (represented by elevation, aspect, and slope steepness) across a semi-arid landscape in central Tibet. Redundancy analyses showed that the biotic variables explained 30 and 39 % of the variation in overall performance of A. rigidulus (P = 0.03) and P. fruticosa (P = 0.01), respectively. Abiotic variables did not contribute significantly to variation among A. rigidulus populations. Plant size decreased with species richness in both species and was larger on south- rather than north-facing slopes. Reproductive effort for both species was significantly negatively related to the abundance of K. pygmaea and both species had larger reproductive effort on south- rather than north- and west-facing slopes. The proportion of biomass allocated to sexual reproduction in P. fruticosa was negatively correlated with K. pygmaea abundance and herbivory intensity. The population density of P. fruticosa was positively related to elevation, species richness, and K. pygmaea abundance. We conclude that plant performance at a local scale was more strongly related to biotic than abiotic conditions, but different components of plant performance responded differently to predictor variables and the responses were species-specific. These findings have important implications for rangeland management under changing environmental conditions.     

Local and regional disturbances associated with the invasion of Chesapeake Bay marshes by the common reed <Emphasis Type="Italic">Phragmites australis</Emphasis>

The invasion of wetlands by Phragmites australis is a conservation concern across North America. We used the invasion of Chesapeake Bay wetlands by P. australis as a model system to examine the effects of regional and local stressors on plant invasions. We summarized digital maps of the distributions of P. australis and of potential stressors (especially human land use and shoreline armoring) at two spatial scales: for 72 subestuaries of the bay and their local watersheds and for thousands of 500 m shoreline segments. We developed statistical models that use the stressor variables to predict P. australis prevalence (% of shoreline occupied) in subestuaries and its presence or absence in 500 m segments of shoreline. The prevalence of agriculture was the strongest and most consistent predictor of P. australis presence and abundance in Chesapeake Bay, because P. australis can exploit the resulting elevated nutrient levels to enhance its establishment, growth, and seed production. Phragmites australis was also positively associated with riprapped shoreline, probably because it creates disturbances that provide colonization opportunities. The P. australis invasion was less severe in areas with greater forested land cover and natural shorelines. Surprisingly, invasion was low in highly developed watersheds and highest along shorelines with intermediate levels of residential land use, possibly indicating that highly disturbed systems are uninhabitable even to invasive species. Management strategies that reduce nutrient pollution, preserve natural shorelines, and limit nearshore disturbance of soils and vegetation may enhance the resilience of shorelines to invasion.     

Comparison of trophic function between the globally invasive crayfishes <Emphasis Type="Italic">Pacifastacus leniusculus</Emphasis> and <Emphasis Type="Italic">Procambarus clarkii</Emphasis>

Impacts of invasive species may manifest most strongly if these organisms are highly distinct functionally from the native species they often replace. Yet, should we expect functional differences between native and invasive species of generalist organisms like freshwater crayfish? Some existing evidence has pointed to native and invasive crayfish species as ecologically equivalent. We contribute to this literature by comparing the trophic niches of the globally invasive crayfishes Pacifastacus leniusculus and Procambarus clarkii, by applying carbon and nitrogen stable isotope analyses to replicated allopatric (alone) and sympatric (together) lake populations in western Washington State, USA, where P. clarkii has been recently introduced and P. leniusculus is presumed native. Our study corrected for potential inherent differences in lake food webs as a consequence of lake abiotic or biotic characteristics using random effects in linear mixed effects models. We found that although overall trophic niche size or area of these species was not significantly different, P. leniusculus was significantly higher in trophic position than P. clarkii when also accounting for the effects of body size, sex, and lakes as random effects. This pattern of increased trophic position of P. leniusculus over P. clarkii was conserved over time in one sympatric lake for which we had data over multiple years. Cumulatively, our findings point to trophic differences between the globally cosmopolitan crayfishes P. leniusculus and P. clarkii, particularly when accounting for the ways that ecosystem context can affect food web structure of communities and the trophic resources available to these consumers.     

Early <Emphasis Type="Italic">Acacia</Emphasis> invasion in a sandy ecosystem enables shading mediated by soil,leaf nitrogen and facilitation

Australian species of the genus Acacia are amongst the most invasive trees. As nitrogen fixers, they are able to invade oligotrophic ecosystems and alter ecosystem functioning to their benefit. We aimed to answer three questions: How does early Acacia invasion influence nitrogen and light in a sandy savanna? How does early Acacia invasion impact biodiversity? Does early invasion alter ecosystem functioning towards the dominance of Acacia? We analyzed (using generalized linear mixed models and richness estimators) paired plots focused on plants of Acacia mangium (Fabaceae) and plants of Marcetia taxifolia (Melastomataceae) by taking hemispherical photos and sampling plants, leaves and soil for measurements of light, richness, leaf nitrogen, leaf δ15N, soil nitrogen and soil coarse sand. The results suggest that early Acacia invasion alters the control of soil and of leaf nitrogen and increases shading, enabling a much wider range of light variation. The δ15N results suggest that the nitrogen taken up by Acacia is transferred to neighboring plants and influences the light environment, suggesting facilitation. The enrichment of plant species observed during early Acacia invasion is consistent with the wider range of light variation, but the forecasted leaf nitrogen conditions during the established phase of Acacia invasion might cause loss of light-demanding species because of increased shading. If early Acacia invasion turns into an established phase with highly increased shading, Acacia seedlings might be favored and ecosystem functioning might change towards its dominance.     

Interactions between the grass shrimp <Emphasis Type="Italic">Palaemonetes pugio</Emphasis> and the salt marsh grasses <Emphasis Type="Italic">Phragmites australis</Emphasis> and <Emphasis Type="Italic">Spartina alterniflora</Emphasis>

The grass shrimp Palaemonetes pugio, a species common to Spartina alterniflora-dominated marshes, may be sensitive to the invasion of the common reed Phragmites australis in northeastern US salt marshes. We examined two questions: (1) Do grass shrimp have a preference for the native plant over the non-native plant? (2) Are grass shrimp more effective foragers on P. australis? We tested the first hypothesis by comparing the amount of time shrimp spend in physical contact with the plant types over a 1-h period. Shrimp were observed under different arrangements of vegetation to control for differences in conspicuous structural features. Additionally, the amount of time shrimp spent foraging on S. alterniflora and P. australis shoots was compared to determine if shrimp graze more often on S. alterniflora. Shrimp spent significantly more time in contact with S. alterniflora only when plant types were grouped at opposite ends of aquaria, but did not exhibit a foraging preference for this plant type. To address our second question, we investigated the effects of shrimp foraging on stem epifauna, an assemblage of semi-aquatic invertebrates associated with macrophyte shoots. Previous research showed that P. australis supports a lower density of stem-dwelling epifauna relative to S. alterniflora. We hypothesized that the primary grazer of this community, P. pugio, can forage on P. australis stems more effectively due to structural differences between the two plants, causing the lower abundance of epifauna through top-down effects. We exposed individual shoots inhabited by epifauna to shrimp and compared faunal densities on exposed shoots to densities on control shoots after 18 h. The reduction of epifauna by predation was proportional on the two plant types. Therefore, top-down effects can be ruled out as an explanation for the patchy distribution of epifauna observed in P. australis–S. alterniflora marshes.     

Crustacean metamorphosis: an omics perspective

We quantified the independent impacts of flooding salinity, flooding depth, and flooding frequency on the native species, Phragmites australis and Scirpus mariqueter, and on the invasive species Spartina alterniflora in the Yangtze River Estuary, China. Total biomass of all three species decreased significantly with increasing salinity, but S. alterniflora was less severely affected than P. australis and S. mariqueter. Elevated flooding depth significantly decreased their live aboveground biomass of P. australis and S. mariqueter, while S. alterniflora still had high live aboveground biomass and total biomass even at the highest flooding depth. These findings indicated that S. alterniflora was more tolerant to experimental conditions than the two native species, and an unavoidable suggestion is the expansion of this non-native species in relation to the native counterparts in future scenarios of increased sea-level and saltwater intrusion. Even so, environmental stresses might lead to significant decreases in total biomass and live aboveground biomass of all three species, which would potentially weaken their ability to trap sediments and accumulate organic matter. However, the relatively high belowground-to-aboveground biomass ratio indicated phenotypic plasticity in response to stressful environmental conditions, which suggest that marsh species can adapt to sea-level rise and maintain marsh elevation.     

Microsatellite DNA analysis of spatial and temporal population structuring of <Emphasis Type="Italic">Phragmites australis</Emphasis> along the Hudson River Estuary

Phragmites australis is a perennial grass that has invaded wetlands of the northeastern United States over the past century. The Hudson River Estuary and surrounding watersheds are no exception in that populations of P. australis have spread dramatically along its shores and tributaries in the past 40 years. Recent studies have shown that genetically variable populations of P. australis can spread by seed dispersal in addition to clonal mechanisms. It is important to characterize the genetic variation of Hudson River populations as part of a management strategy for this species to determine the mechanisms by which its spreads and colonizes new habitats, particularly those with frequent anthropogenic disturbances. The goals of this study were to quantify levels of genetic variation and structuring in Hudson River populations of P. australis using microsatellite DNA analysis. A total of 354 culms of P. australis were collected from nine locations ranging from Albany, New York to Staten Island, New York in the summers of 2004 (N = 174) and 2011 (N = 180). Microsatellite data from eight loci indicated that the Hudson River Estuary has some of the highest levels of genetic variation of all U. S. Atlantic Coast regions containing P. australis. Gene diversity (Hs) across all loci in the 2004 collection was 0.45 (±0.02) and that of the 2011 collection was 0.47 (±0.07). Patches within sample sites were rarely monoclonal and had multiple genetic phenotypes. Moran’s Identity tests indicated that individuals within a patch were closely related, whereas little genetic relatedness was evident among individuals from sample sites >1 km apart. Spatial structuring was also not evident in autospatial correlation and principle coordinate analyses. These findings suggest that genetic diversity is maintained within stands by sexual reproduction and that seeds are important in dispersal of P. australis across the Hudson River Estuary. Ample habitats are available for establishment of new Phragmites stands due to high levels of anthropogenic disturbance from populations living along the Estuary. Wildlife managers should focus on monitoring habitats that provide seedbed for Phragmites and promote land use practices that prevent soil disturbance and establishment of new stands.     

Heat and hypoxia give a global invader, <Emphasis Type="Italic">Gambusia holbrooki,</Emphasis> the edge over a threatened endemic fish on Australian floodplains

Deciphering the mechanisms by which climate change interacts with invasive species to affect biodiversity is a major challenge of global change biology. We conducted experiments to determine whether the global invader, Gambusia holbrooki, was more resistant to high water temperature (heat) and low dissolved oxygen (hypoxia) than a threatened native fish, Nannoperca australis. Metabolic experiments conducted at 25 and 29 °C showed that G. holbrooki had at least four times the capacity for metabolic depression during hypoxia than N. australis. An increase in environmental temperature from 25 to 29 °C had no significant impact on the critical oxygen tension, P _crit, of G. holbrooki, but significantly and strongly increased P _crit of N. australis. Gambusia holbrooki also had a lower Q ₁₀ of standard metabolic rate than N. australis. Our results indicate that G. holbrooki have physiological traits conferring greater resistance to hypoxia than N. australis, and as temperature increases, the resistance of N. australis to hypoxia was more eroded than that of G. holbrooki. Intensive monitoring of the temperature and dissolved oxygen dynamics of wetlands showed that contemporary heat waves are already causing conditions that might give G. holbrooki the edge over N. australis on Australian floodplains. Our study adds weight to recent anecdotal reports of drought and heat waves causing localised extinction of N. australis, but the proliferation of G. holbrooki.     

Temporal and spatial impact of <Emphasis Type="Italic">Spartina alterniflora</Emphasis> invasion on methanogens community in Chongming Island,China

Methane production by methanogens in wetland is recognized as a significant contributor to global warming. Spartina alterniflora (S. alterniflora), which is an invasion plant in China’s wetland, was reported to have enormous effects on methane production. But studies on shifts in the methanogen community in response to S. alterniflora invasion at temporal and spatial scales in the initial invasion years are rare. Sediments derived from the invasive species S. alterniflora and the native species Phragmites australis (P. australis) in pairwise sites and an invasion chronosequence patch (4 years) were analyzed to investigate the abundance and community structure of methanogens using quantitative real-time PCR (qPCR) and Denaturing gradient gel electrophoresis (DGGE) cloning of the methyl-coenzyme M reductase A (mcrA) gene. For the pairwise sites, the abundance of methanogens in S. alterniflora soils was lower than that of P. australis soils. For the chronosequence patch, the abundance and diversity of methanogens was highest in the soil subjected to two years invasion, in which we detected some rare groups including Methanocellales and Methanococcales. These results indicated a priming effect at the initial invasion stages of S. alterniflora for microorganisms in the soil, which was also supported by the diverse root exudates. The shifts of methanogen communities after S. alterniflora invasion were due to changes in pH, salinity and sulfate. The results indicate that root exudates from S. alterniflora have a priming effect on methanogens in the initial years after invasion, and the predominate methylotrophic groups (Methanosarcinales) may adapt to the availability of diverse substrates and reflects the potential for high methane production after invasion by S. alterniflora.     

The necromass of the <Emphasis Type="Italic">Posidonia oceanica</Emphasis> seagrass meadow: fate,role, ecosystem services and vulnerability

Posidonia oceanica is a seagrass endemic to the Mediterranean Sea. Most of the primary production of the P. oceanica meadow is not directly consumed by herbivores and plays a role as dead rhizomes and roots, dead leaves and drift epibionts (hereafter necromass). The fate of this necromass is (i) sequestration within the matte, (ii) consumption by detritus-feeders within the meadow, (iii) export towards other marine ecosystems, where it constitutes a source for food webs, (iv) export towards beaches, where it constitutes banquettes, reduces the impact of waves and contributes to the beach ecosystem, and (v) export towards the terrestrial dune ecosystem. These five stocks can exchange necromass. The ecosystem services of the P. oceanica necromass are pivotal. For example, the role of P. oceanica banquettes is fundamental in protecting beaches from erosion, and the carbon sequestration within the matte contributes to the mitigation of emissions of CO₂. Human impact on each of these stocks can affect the other stocks and their ecosystem services. The removal of banquettes from beaches can have a dramatic negative impact on P. oceanica ecosystem services, including the sustaining of beaches. The erosion of matte due to trawling and anchoring can remobilize the sequestrated carbon stock.     

Nitrogen addition drives convergence of leaf litter decomposition rates between <Emphasis Type="Italic">Flaveria bidentis</Emphasis> and native plant

Evidence is growing that invasive species can change decomposition rates and associated nutrient cycling within an ecosystem by changing the quality of the litter entering a system. However, the relative contribution of their distinct litter types to carbon turnover is less understood, especially in the context of enhanced N deposition. The objective of this study was to investigate the whole-plant responses of an invasive plant Flaveria bidentis in litter decay to simulated N eutrophication. A 1-year study was conducted to assess if N enhancement influenced decomposition and nutrient dynamics of litters from foliage, fine roots and twigs of F. bidentis compared to co-occurring native species Setaria viridis. N fertilization significantly decreased the decomposition rate of the foliage of the invasive F. bidentis by more than 25% relative to the water control, but had relatively minor effects on decomposition of its twigs and fine root litter or leaf litter from the native species. Collectively, decomposition rates of foliar litters of the invasive and native species become convergent over time in the presence of N addition. Moreover, net N loss was predominately influenced by litter species, followed by the litter type, while N addition had little effect on net N loss. Our study showed that the variation in litter decomposition was much greater between litter types of the invasive F. bidentis than between different plant species under the N addition and that the litter of invasive species with higher inherent decomposability did not always decompose more rapidly than the litter of native species in response to predicted N deposition enhancement.     

Resolving neutral and deterministic contributions to genomic structure in <Emphasis Type="Italic">Syntrichia ruralis</Emphasis> (Bryophyta,Pottiaceae) informs propagule sourcing for dryland restoration

Syntrichia ruralis is a cosmopolitan moss that occupies steep environmental gradients. In arid to semi-arid regions of the world it is a key component of biological soil crusts, which are fundamental to healthy dryland ecosystem processes. As such, S. ruralis has attracted the attention of conservationists seeking to restore degraded biological soil crust communities and their associated vascular flora. Here, we generate genomic data for S. ruralis populations that span climatic gradients across the Colorado Plateau of the southwestern USA to investigate the contributions of neutral and deterministic processes to the partitioning of genomic structure. Although S. ruralis appears to be highly dispersible, geographic proximity significantly predicts genomic similarity. In addition, even when taking into account apparently high migration rates among populations and spatial autocorrelation of allele frequencies, some genomic variation is explained by environmental gradients correlated with elevation and latitude. Consequently, efforts to restore dryland ecosystems by establishing S. ruralis as a foundation should include strategies to ensure that propagule sources of this moss are environmentally stratified and targeted to the current/future climates of restoration sites.     

Local distribution of native and invasive earthworms and effects on a native salamander

North America is home to both native and invasive earthworms acting as ecosystem engineers as they build burrows that can serve as habitat for other species or otherwise alter soil structure, affecting nutrient cycling and other ecosystem processes. Here I determine where and what earthworm species commonly occur in my study area, and compare effects of native and invasive earthworms on the common woodland salamander, Plethodon cinereus, in field surveys and laboratory experiments. The native earthworm Eisenoides carolinensis was the most common earthworm, followed by two invasive species Dendrobaena octaedra and Octolasion tyrtaeum. The presence of O. tyrtaeum was associated with a narrower O-horizon (i.e., organic layer in the soil). Using structural equation modeling to explore direct and indirect pathways of these three most common earthworm species on salamanders, I found O. tyrtaeum occurrence was negatively correlated with nighttime salamander counts, a proxy for total salamander numbers, mediated by negative effects on O-horizon depth and microinvertebrate numbers. In the laboratory, O. tyrtaeum and D. octaedra consumed more leaf litter per gram of earthworm per day than the native E. carolinensis. However, salamanders consumed earthworms and used burrows of all native and invasive species of earthworms similarly. The potential for negative indirect effects of the invasive earthworm O. tyrtaeum on P. cinereus was demonstrated both in the field and laboratory, highlighting that seemingly small differences between native and invasive ecosystem engineers have the potential to significantly alter the effects of these closely related native and invasive organisms.     

Variability in the response of amphipods and macroinvertebrate assemblage structure to prolonged drought in forested upland streams

With climate change set to increase the frequency and severity of drought in many parts of the world, there is a need to better understand the effects of drying on stream ecosystems. We investigated the long-term effects of drought on two amphipod taxa Paramoera fontana (Pontogeneiidae) and Austrogammarus australis (Paramelitidae) and macroinvertebrate assemblage structure through an analysis of 13 years of data collected from four forested stream reaches (Victoria, Australia). Abundances of A. australis and P. fontana in the lower reach of Lyrebird Creek declined to zero following surficial streambed drying. Similar declines in abundances were not observed in Sassafras Creek or the two headwater springs, which continued to flow throughout the drought. P. fontana was detected again in the lower reach of Lyrebird Creek 12 months after the final cease-to-flow, however A. australis remained undetected 5 years later, despite an upstream source population within 2 km. Both the entire and shredder macroinvertebrate assemblage structure in Sassafras Creek and the lower reach of Lyrebird Creek shifted significantly pre- and post-surficial streambed drying in the lower reach of Lyrebird Creek. Despite signs of recovery following a return to more average flows, assemblage composition remained considerably different. The substantial differences in the recovery of the two species indicates varying resistance and resilience traits. The failure of A. australis to recolonize after 5 years indicates an absence of any significant resistance or resilience traits. In contrast, the rapid re-colonization of P. fontana may indicate poor resistance traits, but strong resilience traits. The sensitivity of A. australis to cease-to-flow events points to the need to carefully manage water extraction to protect this threatened species. The effective management of macroinvertebrate assemblages in the face of drought requires a clear understanding of their response to drying, the conservation of refugia and the minimization of additional stressors which reduce ecosystem resilience.     

A New record of four <Emphasis Type="Italic">Penicillium</Emphasis> species isolated from <Emphasis Type="Italic">Agarum clathratum</Emphasis> in Korea

Agarum clathratum, brown algae, play important ecological roles in marine ecosystem, but can cause secondary environment pollution when they pile up on the beach. In order to resolve the environment problem by A. clathratum, we focus to isolate and identify Penicillium because many species are well known to produce extracellular enzymes. A total of 32 Penicillium strains were isolated from A. clathratum samples that collected from 13 sites along the mid-east coast of Korea in summer. They were identified based on morphological characters and phylogenetic analysis using β-tubulin DNA sequences as well as a combined dataset of β-tubulin and calmodulin. A total of 32 strains were isolated and they were identified to 13 Penicillium species. The commonly isolated species were Penicillium citrinum, P. roseomaculatum, and Penicillium sp. Among 13 Penicillium species, four species – P. bilaiae, P. cremeogriseum, P. madriti, and P. roseomaculatum – have not been previously recorded in Korea. For these four new species records to Korea, we provide morphological characteristics of each strain.