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.

Defining the Impact of Non-Native Species

Non-native species cause changes in the ecosystems to which they are introduced. These changes, or some of them, are usually termed impacts; they can be manifold and potentially damaging to ecosystems and biodiversity. However, the impacts of most non-native species are poorly understood, and a synthesis of available information is being hindered because authors often do not clearly define impact. We argue that explicitly defining the impact of non-native species will promote progress toward a better understanding of the implications of changes to biodiversity and ecosystems caused by non-native species; help disentangle which aspects of scientific debates about non-native species are due to disparate definitions and which represent true scientific discord; and improve communication between scientists from different research disciplines and between scientists, managers, and policy makers. For these reasons and based on examples from the literature, we devised seven key questions that fall into 4 categories: directionality, classification and measurement, ecological or socio-economic changes, and scale. These questions should help in formulating clear and practical definitions of impact to suit specific scientific, stakeholder, or legislative contexts.

Deep impact: in situ functional responses reveal context-dependent interactions between vertically migrating invasive and native mesopredators and shared prey

The ecological effects of invasive species depend on myriad environmental contexts, rendering understanding problematic. Functional responses provide a means to quantify resource use by consumers over short timescales and could therefore provide insight into how the effects of invasive species vary over space and time. Here, we use novel in situ microcosm experiments to track changes in the functional responses of two aquatic mesopredators, one native and the other an invader, as they undergo diel vertical migrations through a lake water column.
The Ponto–Caspian mysid, Hemimysis anomala, a known ecologically damaging invader, generally had higher a functional response towards cladoceran prey than did a native trophic analogue, Mysis salemaai. However, this differential was spatiotemporally dependent, being minimal during the day on the lake bottom, and increasing at night, particularly inshore.
Because the functional response of the native predator was spatiotemporally consistent, the above pattern was driven by changes in the invader functional response over the diel cycle. In particular, the functional response of H. anomala was significantly reduced on the lake bottom during the daytime relative to night, and predation was especially pronounced in shallow surface waters.
We demonstrate the context dependency of the effects of an invasive predator on prey populations and emphasise the utility of functional responses as tools to inform our understanding of predator–prey interactions. In situ manipulations integrate experimental rigour with field relevance and have the potential to reveal how impacts manifest over a range of spatiotemporal scales.

Predicting the predatory impacts of the “demon shrimp” Dikerogammarus haemobaphes, on native and previously introduced species

Biological invasions continue to exert pressure on ecosystems worldwide and we thus require methods that can help understand and predict the impacts of invasive species, on both native species and previously established invaders. Comparing laboratory derived functional responses among invasive and native predators has emerged as one such method, providing a robust proxy for field impacts. We used this method to examine the likely impacts of the Ponto–Caspian amphipod Dikerogammarus haemobaphes, known as the “demon shrimp”, a little investigated invader in European freshwaters that has recently established in the British Isles. We compared the functional responses on two prey species of D. haemobaphes with two other amphipod species: Dikerogammarus villosus, a congeneric invasive with well-documented impacts on macro-invertebrate communities and a native amphipod, Gammarus pulex. Prey species were native Chironomus sp. and the invasive Chelicorophium curvispinum, a tube-building amphipod also originating from the Ponto–Caspian region. D. villosus showed higher Type II functional responses towards both prey species than did D. haemobaphes and G. pulex, with the latter two predators exhibiting similar impacts on the native prey. However, D. haemobaphes had higher functional responses towards the invasive C. curvispinum than did G. pulex, both when prey individuals were tubeless and resident in their protective mud tubes. Thus, we demonstrate that functionally equivalent invasive congeners can show significantly different impacts on prey, regardless of shared evolutionary history. We also show that some predatory invaders can have impacts on native prey equivalent to native predator impacts, but that they can also exert significant impacts on previously introduced prey. We discuss the importance of invasion history and prey identity when attempting to understand and predict the impacts of new invaders.

When terror hits home: Identity Fused Americans who saw Boston bombing victims as “family” provided aid

When tragedy strikes a group, only some group members characteristically rush to the aid of the victims. What motivates the altruism of these exceptional individuals? Here, we provide one set of answers based on data collected before and shortly after the 15 April 2013, Boston Marathon bombings. The results of three studies indicated that Americans who were strongly “fused” with their country were especially inclined to provide various forms of support to the bombing victims. Moreover, the degree to which participants reported perceiving fellow Americans as psychological kin statistically mediated links between fusion and pro-group outcomes. Together, these findings shed new light on relationships between personal and group identity, cognitive representations of group members, and personally costly, pro-group actions.

Coexistence of congeneric native and invasive species: The case of the green algae Codium spp. in northwestern Spain

We examined the patterns of distribution and abundance, and reproductive traits (presence of gametophytes and size at time of reproduction) in the invasive Codium fragile ssp. fragile and the native C. tomentosum and C. vermilara on intertidal habitats of NW Spain at two dates. All three species coexist in the locations and habitats studied, although abundances were low. We found a greater proportion of C. fragile ssp. fragile towards the east of the Cantabrian coast and on upper levels on the shore, where conditions are more stressful. The proportion of thalli bearing gametangia in C. fragile ssp. fragile was greater than in the native species in all habitats. The presence of gametangia was size-dependent for all species, with the invasive species maturing at a smaller size, which combined with the previous features, might confer competitive advantages to this species over the native species. We also demonstrated that molecular analyses are necessary for the correct identification of C. fragile subspecies.

Harmful transgressions qua moral transgressions: A deflationary view

One important issue in moral psychology concerns the proper characterization of the folk understanding of the relationship between harmful transgressions and moral transgressions. Psychologist Elliot Turiel and associates have claimed with a broad range of supporting evidence that harmful transgressions are understood as transgressions that are authority independent and general in scope, which, according to them, characterizes these transgressions as moral transgressions. Recently, many researchers questioned the position advocated by the Turiel tradition with some new evidence. We entered this debate proposing an original, deflationary view in which perceptions of basic-rights violation and injustice are fundamental for the folk understanding of harmful transgressions as moral transgressions in Turiel’s sense. In this article, we elaborate and refine our deflationary view, while reviewing the debate, addressing various criticisms raised against our perspective, showing how our perspective explains the existent evidence, and suggesting new lines of inquiry.

Conduit artery structure and function in lowlanders and native highlanders: relationships with oxidative stress and role of sympathoexcitation

Research detailing the normal vascular adaptions to high altitude is minimal and often confounded by pathology (e.g. chronic mountain sickness) and methodological issues. We examined vascular function and structure in: (1) healthy lowlanders during acute hypoxia and prolonged (∼2 weeks) exposure to high altitude, and (2) high-altitude natives at 5050 m (highlanders). In 12 healthy lowlanders (aged 32 ± 7 years) and 12 highlanders (Sherpa; 33 ± 14 years) we assessed brachial endothelium-dependent flow-mediated dilatation (FMD), endothelium-independent dilatation (via glyceryl trinitrate; GTN), common carotid intima–media thickness (CIMT) and diameter (ultrasound), and arterial stiffness via pulse wave velocity (PWV; applanation tonometry). Cephalic venous biomarkers of free radical-mediated lipid peroxidation (lipid hydroperoxides, LOOH), nitrite (NO₂^–) and lipid soluble antioxidants were also obtained at rest. In lowlanders, measurements were performed at sea level (334 m) and between days 3–4 (acute high altitude) and 12–14 (chronic high altitude) following arrival to 5050 m. Highlanders were assessed once at 5050 m. Compared with sea level, acute high altitude reduced lowlanders’ FMD (7.9 ± 0.4 vs. 6.8 ± 0.4%; P = 0.004) and GTN-induced dilatation (16.6 ± 0.9 vs. 14.5 ± 0.8%; P = 0.006), and raised central PWV (6.0 ± 0.2vs. 6.6 ± 0.3 m s⁻¹; P = 0.001). These changes persisted at days 12–14, and after allometrically scaling FMD to adjust for altered baseline diameter. Compared to lowlanders at sea level and high altitude, highlanders had a lower carotid wall:lumen ratio (∼19%, P ≤ 0.04), attributable to a narrower CIMT and wider lumen. Although both LOOH and NO₂^– increased with high altitude in lowlanders, only LOOH correlated with the reduction in GTN-induced dilatation evident during acute (n = 11, r = −0.53) and chronic (n = 7, r = −0.69; P ≤ 0.01) exposure to 5050 m. In a follow-up, placebo-controlled experiment (n = 11 healthy lowlanders) conducted in a normobaric hypoxic chamber (inspired O₂ fraction () = 0.11; 6 h), a sustained reduction in FMD was evident within 1 h of hypoxic exposure when compared to normoxic baseline (5.7 ± 1.6 vs. 8.0 ±1.3%; P < 0.01); this decline in FMD was largely reversed following α₁-adrenoreceptor blockade. In conclusion, high-altitude exposure in lowlanders caused persistent impairment in vascular function, which was mediated partially via oxidative stress and sympathoexcitation. Although a lifetime of high-altitude exposure neither intensifies nor attenuates the impairments seen with short-term exposure, chronic high-altitude exposure appears to be associated with arterial remodelling.

High temperature thermal stability studies of ultrathin Al2O3 layers deposited on native oxide and sulphur passivated InGaAs surfaces

High resolution synchrotron radiation core level photoemission measurements have been used to undertake a comparative study of the high temperature stability of ultrathin Al2O3 layers deposited by atomic layer deposition (ALD) on both sulphur passivated and native oxide covered InGaAs. The residual interfacial oxides between sulphur passivated InGaAs and the ultrathin Al2O3 layer can be substantially removed at high temperature (up to 700 °C) without impacting on the InGaAs stoichiometry while significant loss of indium was recorded at this temperature on the native oxide InGaAs surface.

Genetic provenance and best practice woodland management: a case study in native alder (Alnus glutinosa)

In recent years, the native woodlands of Europe, including those of Britain and Ireland, have increasingly come under threat from a range of biotic and abiotic factors, and are therefore a conservation priority demanding careful management in order to realise their inherent ecological and cultural benefits. Because the distribution of genetic variation across populations and regions is increasingly considered an important component of woodland management, we carried out a population genetic analysis on black alder (Alnus glutinosa) across Northern Ireland in order to inform “best practice” strategies. Our findings suggest that populations harbour high levels of genetic diversity, with very little differentiation between populations. Significant F IS values were observed in over half of the populations analysed, however, which could reflect inbreeding as a result of the patchy occurrence of alder in Northern Ireland, with scattered, favourable damp habitats being largely isolated from each other by extensive tracts of farmland. Although there is no genetic evidence to support the broad-scale implementation of tree seed zones along the lines of those proposed for native woodlands in Great Britain, we suggest that the localised occurrence of rare chloroplast haplotypes should be taken into account on a case-by-case basis. This, coupled with the identification of populations containing high genetic diversity and that are broadly representative of the region as a whole, will provide a sound genetic basis for woodland management, both in alder and more generally for species that exhibit low levels of genetic differentiation.

Differential ecological impacts of an invader and a native under environmental change are revealed by comparative functional responses.

Predicting the ecological impacts of damaging invasive species under relevant environmental contexts is a major challenge, for which comparative functional responses (the relationship between resource availability and consumer uptake rate) have great potential. Here, the functional responses of Gammarus pulex, an ecologically damaging invader in freshwaters in Ireland and other islands, were compared with those of a native trophic equivalent Gammarus duebeni celticus. Experiments were conducted at two dissolved oxygen concentrations (80 and 50 % saturation), representative of anthropogenic water quality changes, using two larval prey, blackfly (Simuliidae spp.) and mayfly (Baetis rhodani). Overall, G. pulex had higher Type II functional responses and hence predatory impacts than G. d. celticus and the functional responses of both predators were reduced by lowered oxygen concentration. However, this reduction was of lower magnitude for the invader as compared to the native. Further, the invader functional response at low oxygen was comparable to that of the native at high oxygen. Attack rates of the two predators were similar, with low oxygen reducing these attack rates, but this effect occurred more strongly for blackfly than mayfly prey. Handling times were significantly lower for the invader compared with the native, and significantly higher at low oxygen, however, the effect of lowered oxygen on handling times was minimal for the invader and pronounced for the native. Maximum feeding rates were significantly greater for the invader compared with the native, and significantly reduced at low oxygen, with this effect again lesser for the invader as compared to the native. The greater functional responses of the invader corroborate with its impacts on recipient macroinvertebrate communities when it replaces the native. Further, our experiments predict that the impact of the invader will be less affected than the native under altered oxygen regimes driven by anthropogenic influences.