Ecological impacts of an invasive predator explained and predicted by comparative functional responses

Forecasting the ecological impacts of invasive species is a major challenge that has seen little progress, yet the development of robust predictive approaches is essential as new invasion threats continue to emerge. A common feature of ecologically damaging invaders is their ability to rapidly exploit and deplete resources. We thus hypothesized that the 'functional response' (the relationship between resource density and consumption rate) of such invasive species might be of consistently greater magnitude than those of taxonomically and/or trophically similar native species. Here, we derived functional responses of the predatory Ponto-Caspian freshwater 'bloody red' shrimp, Hemimysis anomala, a recent and ecologically damaging invader in Europe and N. America, in comparison to the local native analogues Mysis salemaai and Mysis diluviana in Ireland and Canada, respectively. This was conducted in a novel set of experiments involving multiple prey species in each geographic location and a prey species that occurs in both regions. The predatory functional responses of the invader were generally higher than those of the comparator native species and this difference was consistent across invaded regions. Moreover, those prey species characterized by the strongest and potentially de-stabilizing Type II functional responses in our laboratory experiments were the same prey species found to be most impacted by H. anomala in the field. The impact potential of H. anomala was further indicated when it exhibited similar or higher attack rates, consistently lower prey handling times and higher maximum feeding rates compared to those of the two Mysis species, formerly known as 'Mysis relicta', which itself has an extensive history of foodweb disruption in lakes to which it has been introduced. Comparative functional responses thus merit further exploration as a methodology for predicting severe community-level impacts of current and future invasive species and could be entered into risk assessment protocols.

Assessment Method for a Power Analysis to Identify Differentially Expressed Pathways

Gene expression data can provide a very rich source of information for elucidating the biological function on the pathway level if the experimental design considers the needs of the statistical analysis methods. The purpose of this paper is to provide a comparative analysis of statistical methods for detecting the differentially expression of pathways (DEP). In contrast to many other studies conducted so far, we use three novel simulation types, producing a more realistic correlation structure than previous simulation methods. This includes also the generation of surrogate data from two large-scale microarray experiments from prostate cancer and ALL. As a result from our comprehensive analysis of 41,004 parameter configurations, we find that each method should only be applied if certain conditions of the data from a pathway are met. Further, we provide method-specific estimates for the optimal sample size for microarray experiments aiming to identify DEP in order to avoid an underpowered design. Our study highlights the sensitivity of the studied methods on the parameters of the system. © 2012 Tripahti and Emmert-Streib.

Has habitat heterogeneity promoted phenotypic and ecological sub-structuring among a Coregonus lavaretus population in a large Scottish lake?

Differences in stable-isotope values, morphology and ecology in whitefish Coregonus lavaretus were investigated between the three basins of Loch Lomond. The results are discussed with reference to a genetic investigation to elucidate any substructuring or spawning site fidelity. Foraging fidelity between basins of Loch Lomond was indicated by delta 13C and delta 15N values of C. lavaretus muscle tissue. There was, however, no evidence of the existence of sympatric morphs in the C. lavaretus population. A previous report of two C. lavaretus 'species' in Loch Lomond probably reflects natural variation between individuals within a single mixed population.

Lux-biosensor assessment of pH effects on microbial sorption and toxicity of chlorophenols

Lux-marked bacterial biosensors and a commercial toxicity testing bacterial strain (Microtox) were exposed to 2,4-dichlorophenol (DCP) and the light output response measured. Increasing DCP concentrations caused a decrease in light output in all three biosensors with an order of sensitivity (in terms of luminescence decrease over the DCP concentration range) of Pseudomonas fluorescens <Escherichia coli <Microtox. Adsorption of DCP to E. coli was measured using uniformly ring labelled [14C]DCP and found to be very rapid. The effect of pH on toxicity and adsorption was also investigated. Low pH values increased the amount of DCP adsorbed to the cell and increased the toxicity of DCP.

Parallel and nonparallel ecological, morphological and genetic divergence in lake-stream stickleback from a single catchment

Parallel phenotypic evolution in similar environments has been well studied in evolutionary biology; however, comparatively little is known about the influence of determinism and historical contingency on the nature, extent and generality of this divergence. Taking advantage of a novel system containing multiple lake-stream stickleback populations, we examined the extent of ecological, morphological and genetic divergence between three-spined stickleback present in parapatric environments. Consistent with other lake-stream studies, we found a shift towards a deeper body and shorter gill rakers in stream fish. Morphological shifts were concurrent with changes in diet, indicated by both stable isotope and stomach contents analysis. Performing a multivariate test for shared and unique components of evolutionary response to the distance gradient from the lake, we found a strong signature of parallel adaptation. Nonparallel divergence was also present, attributable mainly to differences between river locations. We additionally found evidence of genetic substructuring across five lake-stream transitions, indicating that some level of reproductive isolation occurs between populations in these habitats. Strong correlations between pairwise measures of morphological, ecological and genetic distance between lake and stream populations supports the hypothesis that divergent natural selection between habitats drives adaptive divergence and reproductive isolation. Lake-stream stickleback divergence in Lough Neagh provides evidence for the deterministic role of selection and supports the hypothesis that parallel selection in similar environments may initiate parallel speciation.

The biology of habitat dominance; can microbes behave as weeds?

Competition between microbial species is a product of, yet can lead to a reduction in, the microbial diversity of specific habitats. Microbial habitats can resemble ecological battlefields where microbial cells struggle to dominate and/or annihilate each other and we explore the hypothesis that (like plant weeds) some microbes are genetically hard-wired to behave in a vigorous and ecologically aggressive manner. These 'microbial weeds' are able to dominate the communities that develop in fertile but uncolonized - or at least partially vacant - habitats via traits enabling them to out-grow competitors; robust tolerances to habitat-relevant stress parameters and highly efficient energy-generation systems; avoidance of or resistance to viral infection, predation and grazers; potent antimicrobial systems; and exceptional abilities to sequester and store resources. In addition, those associated with nutritionally complex habitats are extraordinarily versatile in their utilization of diverse substrates. Weed species typically deploy multiple types of antimicrobial including toxins; volatile organic compounds that act as either hydrophobic or highly chaotropic stressors; biosurfactants; organic acids; and moderately chaotropic solutes that are produced in bulk quantities (e.g. acetone, ethanol). Whereas ability to dominate communities is habitat-specific we suggest that some microbial species are archetypal weeds including generalists such as: Pichia anomala, Acinetobacter spp. and Pseudomonas putida; specialists such as Dunaliella salina, Saccharomyces cerevisiae, Lactobacillus spp. and other lactic acid bacteria; freshwater autotrophs Gonyostomum semen and Microcystis aeruginosa; obligate anaerobes such as Clostridium acetobutylicum; facultative pathogens such as Rhodotorula mucilaginosa, Pantoea ananatis and Pseudomonas aeruginosa; and other extremotolerant and extremophilic microbes such as Aspergillus spp., Salinibacter ruber and Haloquadratum walsbyi. Some microbes, such as Escherichia coli, Mycobacterium smegmatis and Pseudoxylaria spp., exhibit characteristics of both weed and non-weed species. We propose that the concept of nonweeds represents a 'dustbin' group that includes species such as Synodropsis spp., Polypaecilum pisce, Metschnikowia orientalis, Salmonella spp., and Caulobacter crescentus. We show that microbial weeds are conceptually distinct from plant weeds, microbial copiotrophs, r-strategists, and other ecophysiological groups of microorganism. Microbial weed species are unlikely to emerge from stationary-phase or other types of closed communities; it is open habitats that select for weed phenotypes. Specific characteristics that are common to diverse types of open habitat are identified, and implications of weed biology and open-habitat ecology are discussed in the context of further studies needed in the fields of environmental and applied microbiology.

Ecological and societal benefits of jellyfish blooms

Jellyfish are often considered as stressors on marine ecosystems or as indicators of highly perturbed systems. Far less attention is given to the potential of such species to provide beneficial ecosystem services in their own right. In an attempt to redress this imbalance we take the liberty of portraying jellyfish in a positive light and suggest that the story is not entirely one of doom and gloom. More specifically, we outline how gelatinous marine species contribute to the four categories of ecosystem services (regulating, supporting, provisioning and cultural) defined by the Millennium Ecosystem Assessment. This discussion ranges from the role of jellyfish in carbon capture and advection to the deep ocean through to the creation of micro habitat for developing fishes and the advancement of citizen science programmes. Attention is paid also to incorporation of gelatinous species into fisheries or ecosystem level models and the mechanisms by which we can improve the transfer of information between jellyfish researchers and the wider non-specialist community.

Empirical assessment of non-invasive population genetics in bats:Comparison of DNA quality from faecal and tissue samples

Non-invasive population genetics has become a valuable tool in ecology and conservation biology, allowing genetic studies of wild populations without the need to catch, handle or even observe the study subjects directly. We address some of the concerns regarding the limitations of using non-invasive samples by comparing the quality of population genetic information gained through DNA extracted from faecal samples and biopsy samples of two elusive bat species, Myotis mystacinus and Myotis nattereri. We demonstrate that DNA extracted from faeces and tissue samples gives comparable results for frequency based population genetic analyses, despite the occurrence of genotyping errors when using faecal DNA. We conclude that non-invasive genetic sampling for population genetic analysis in bats is viable, and although more labour-intensive and expensive, it is an alternative to tissue sampling, which is particularly pertinent when specimens are rare, endangered or difficult to capture. © 2012 Museum and Institute of Zoology PAS.

Predicting the ecological impacts of a new freshwater invader:Functional responses and prey selectivity of the 'killer shrimp', Dikerogammarus villosus, compared to the native Gammarus pulex

The ability to predict the likely ecological impacts of invasive species in fresh waters is a pressing research requirement. Whilst comparisons of species traits and considerations of invasion history have some efficacy in this respect, we require robust methods that can compare the effects of native and invasive species. Here, we utilise comparative functional responses and prey selectivity experiments to understand and predict the ecological impact of an invader as compared to a native. We compared the predatory functional responses of an emerging invasive species in Europe, the 'killer shrimp', Dikerogammarus villosus, and an analogous native species, Gammarus pulex, towards three representative prey species: Asellus aquaticus, Daphnia magna and Chironomus sp. Furthermore, as ecological impact may be greater for invasive species with more indiscriminate feeding habits, we compared the selectivity for the three prey types between the invasive and native species. In both the presence and absence of experimental habitats, large D. villosus, and those matched for body size with G. pulex, generally showed higher (Type II) functional responses than G. pulex, with the invasive species exhibiting higher maximum feeding rates. Further, D. villosus exhibited significantly more indiscriminate prey selection compared with G. pulex, a trait that became more evident as the invader increased in size. Differences in functional responses and prey selectivity were prey species specific, with higher to lower predicted impacts in the order A. aquaticus, D. magna and Chironomus sp. This is in accord with the impact of this invasive species on macroinvertebrates in the field. We thus provide understanding of the known ecological impact of D. villosus and discuss the utility of the phenomenological use of comparative functional responses and resource use as a tool through which the potential ecological impacts of invasive species may be identified. © 2013 John Wiley & Sons Ltd.

Relative Biological Effectiveness Variation Along Monoenergetic and Modulated Bragg Peaks of a 62-MeV Therapeutic Proton Beam: A Preclinical Assessment

iological optimization of proton therapy critically depends on detailed evaluation of relative biological effectiveness (RBE) variations along the Bragg curve. The clinically accepted RBE value of 1.1 is an oversimplification, which disregards the steep rise of linear energy transfer (LET) at the distal end of the spread-out Bragg peak. We observed significant cell killing RBE variations dependent on beam modulation, intrinsic radiosensitivity, and LET in agreement with the LEM predicted values, indicating dose-averaged LET as a suitable parameter for biological effectiveness. Data have also been used to validate a RBE parameterized model.

Invading and expanding: range dynamics and ecological consequences of the greater white-toothed shrew (Crocidura russula) invasion in Ireland

Establishing how invasive species impact upon pre-existing species is a fundamental question in ecology and conservation biology. The greater white-toothed shrew (Crocidura russula) is an invasive species in Ireland that was first recorded in 2007 and which, according to initial data, may be limiting the abundance/distribution of the pygmy shrew (Sorex minutus), previously Ireland’s only shrew species. Because of these concerns, we undertook an intensive live-trapping survey (and used other data from live-trapping, sightings and bird of prey pellets/nest inspections collected between 2006 and 2013) to model the distribution and expansion of C. russula in Ireland and its impacts on Ireland’s small mammal community. The main distribution range of C. russula was found to be approximately 7,600 km2 in 2013, with established outlier populations suggesting that the species is dispersing with human assistance within the island. The species is expanding rapidly for a small mammal, with a radial expansion rate of 5.5 km/yr overall (2008–2013), and independent estimates from live-trapping in 2012–2013 showing rates of 2.4–14.1 km/yr, 0.5–7.1 km/yr and 0–5.6 km/yr depending on the landscape features present. S. minutus is negatively associated with C. russula. S. minutus is completely absent at sites where C. russula is established and is only present at sites at the edge of and beyond the invasion range of C. russula. The speed of this invasion and the homogenous nature of the Irish landscape may mean that S. minutus has not had sufficient time to adapt to the sudden appearance of C. russula. This may mean the continued decline/disappearance of S. minutus as C. russula spreads throughout the island.

Genetic assessment of parentage in the caridean rock shrimp Rhynchocinetes typus based on microsatellite markers

Over the past decade, the common rock shrimp, Rhynchocinetes typus H. Milne Edwards, 1837, has been the focus of extensive investigations on mating behaviour. The species is now perceived as a model system for the study of reproductive strategies and sexual conflict in crustaceans displaying external fertilization. Using molecular markers, the current study assesses whether social mating behaviour in common rock shrimp translates into true genetic parentage. In a large mesocosm tank with >200 individuals of both sexes, the analysis of 15 families (22 eggs per female) for three informative microsatellites unambiguously confirmed multiple paternity in 11 instances (73%) involving, in each case, two to four males. Where more than one male was identified siring a particular brood, reproductive skew was apparent towards a single individual. Results suggest that multiple paternity in this species results from subordinate male coercive behaviour, female solicitation of multiple male matings or a combination of both.

Assessment of lux-marked Pseudomonas fluorescens for reporting on organic carbon compounds

Carbon-flow from plant roots to the rhizosphere provides a major source of nutrients for the soil microbial population. However, quantification of carbon-flow is problematic due to its complex composition. This study investigated the potential of lux-marked Pseudomonas fluorescens to discriminate between forms of carbon present in the rhizosphere by measuring the light response to a range of carbon compounds. Results indicate that bioluminescence of short-term carbon-starved P. fluorescens is dependent upon the source and concentration of carbon. This system, therefore, has the potential to both quantify and qualify organic acids present in rhizodeposits.