Breeding habitat selection in an obligate beach bird: a test of the food resource hypothesis

The food resource hypothesis of breeding habitat selection in beach-nesting birds suggests that birds breed at sites with more prey to meet the increased energetic requirements associated with breeding. We compare prey resources using pitfall traps and core samples at breeding sites and absence sites of the eastern population of hooded plover, Thinornis rubricollis rubricollis, which, in this part of its range, is a threatened obligate beach bird. Breeding sites had higher abundances, equivalent species richness, and different assemblages of invertebrate prey compared with absence sites. Assemblages at breeding sites were characterised by more isopods, and fewer beetles of the family Phycosecidae. Breeding habitat selection by plovers appears to be associated with selection for sites with more food, and any process that degrades food resources at a site (e.g. kelp harvesting or marine pollution events) may reduce the likelihood of occupancy of that site by breeding birds.

Increased premotor cortex activation in high functioning autism during action observation

The mirror neuron (MN) hypothesis of autism has received considerable attention, but to date has produced inconsistent findings. Using functional MRI, participants with high functioning autism or Asperger's syndrome were compared to typically developing individuals (n=12 in each group). Participants passively observed hand gestures that included waving, pointing, and grasping. Concerning the MN network, both groups activated similar regions including prefrontal, inferior parietal and superior temporal regions, with the autism group demonstrating significantly greater activation in the dorsal premotor cortex. Concerning other regions, participants with autism demonstrated increased activity in the anterior cingulate and medial frontal gyrus, and reduced activation in calcarine, cuneus, and middle temporal gyrus. These results suggest that during observation of hand gestures, frontal cortex activation is affected in autism, which we suggest may be linked to abnormal functioning of the MN system.

Life history influences how fire affects genetic diversity in two lizard species

'Fire mosaics' are often maintained in landscapes to promote successional diversity in vegetation with little understanding of how this will affect ecological processes in animal populations such as dispersal, social organization and re-establishment. To investigate these processes, we conducted a replicated, spatiotemporal landscape genetics study of two Australian woodland lizard species [Amphibolurus norrisi (Agamidae) and Ctenotus atlas (Scincidae)]. Agamids have a more complex social and territory structure than skinks, so fire might have a greater impact on their population structure and thus genetic diversity. Genetic diversity increased with time since fire in C. atlas and decreased with time since fire in A. norrisi. For C. atlas, this might reflect its increasing population size after fire, but we could not detect increased gene flow that would reduce the loss of genetic diversity through genetic drift. Using landscape resistance analyses, we found no evidence that postfire habitat succession or topography affected gene flow in either species and we were unable to distinguish between survival and immigration as modes of postfire re-establishment. In A. norrisi, we detected female-biased dispersal, likely reflecting its territorial social structure and polygynous mating system. The increased genetic diversity in A. norrisi in recently burnt habitat might reflect a temporary disruption of its territoriality and increased male dispersal, a hypothesis that was supported with a simulation experiment. Our results suggest that the effects of disturbance on genetic diversity will be stronger for species with territorial social organization.

Clinical MRSA isolates from skin and soft tissue infections show increased in vitro production of phenol soluble modulins

BACKGROUND: Phenol-soluble modulins (PSMs) are amphipathic, pro-inflammatory proteins secreted by most Staphylococcus aureus isolates. This study tested the hypothesis that in vitro PSM production levels are associated with specific clinical phenotypes. METHODS: 177 methicillin-resistant S. aureus (MRSA) isolates from infective endocarditis (IE), skin and soft tissue infection (SSTI), and hospital-acquired/ventilator-associated pneumonia (HAP) were matched by geographic origin, then genotyped using spa-typing. In vitro PSM production was measured by high performance liquid chromatography/mass spectrometry. Statistical analysis was performed using Chi-squared or Kruskal-Wallis tests as appropriate. RESULTS: Spa type 1 was significantly more common in SSTI isolates (62.7% SSTI; 1.7% IE; 16.9% HAP; p < 0.0001) while HAP and IE isolates were more commonly spa type 2 (0% SSTI; 37.3% IE; 40.7% HAP; p < 0.0001). USA300 isolates produced the highest levels of PSMs in vitro. SSTI isolates produced significantly higher quantities of PSMα1-4, PSMβ1, and δ-toxin than other isolates (p < 0.001). These findings persisted when USA300 isolates were excluded from analysis. CONCLUSIONS: Increased in vitro production of PSMs is associated with an SSTI clinical source. This significant association persisted after exclusion of USA300 genotype isolates from analysis, suggesting that PSMs play a particularly important role in the pathogenesis of SSTI as compared to other infection types.

Niacin skin sensitivity is increased in adolescents at ultra-high risk for psychosis

BACKGROUND: Most studies provide evidence that the skin flush response to nicotinic acid (niacin) stimulation is impaired in schizophrenia. However, only little is known about niacin sensitivity in the ultra-high risk (UHR) phase of psychotic disorders.

METHODS: We compared visual ratings of niacin sensitivity between adolescents at UHR for psychosis according to the one year transition outcome (UHR-T n = 11; UHR-NT n = 55) with healthy controls (HC n = 25) and first episode schizophrenia patients (FEP n = 25) treated with atypical antipsychotics.

RESULTS: Contrary to our hypothesis niacin sensitivity of the entire UHR group was not attenuated, but significantly increased compared to the HC group, whereas no difference could be found between the UHR-T and UHR-NT groups. As expected, niacin sensitivity of FEP was attenuated compared to HC group. In UHR individuals niacin sensitivity was inversely correlated with omega-6 and -9 fatty acids (FA), but positively correlated with phospholipase A2 (inPLA2) activity, a marker of membrane lipid repair/remodelling.

CONCLUSIONS: Increased niacin sensitivity in UHR states likely indicates an impaired balance of eicosanoids and omega-6/-9 FA at a membrane level. Our findings suggest that the emergence of psychosis is associated with an increased mobilisation of eicosanoids prior to the transition to psychosis possibly reflecting a "pro-inflammatory state", whereas thereafter eicosanoid mobilisation seems to be attenuated. Potential treatment implications for the UHR state should be further investigated.

The dynamic regeneration niche of a forest following a rare disturbance event

Aim: Knowledge of how climate and fire regimes affect regeneration in foundation species is critical to the conservation of entire ecosystems. Different stages of regeneration often require different ecological conditions, but dynamic constraints on regeneration are poorly known for species that regenerate only after infrequent wildfires. Focussing on a long-lived, foundation tree species (Eucalyptus regnans), we tested the hypothesis that the relative importance of fire regime variables (fire severity and time since previous fire) and environmental gradients on post-fire regeneration would shift as seedlings developed. Location: South-eastern Australia. Methods: Following a large (> 59,000 ha) summer wildfire in 2009, we sampled 131 sites (61 burnt) annually for four years (2009-2012), representing the range of environmental conditions in which E. regnans occurs. We analysed the effect of fire severity, time since fire and environmental variables on early regeneration processes critical for post-fire species distributions: seedling establishment, seedling density and growth through different height stages (10 cm, 25 cm, 50 cm and 200 cm). Results: The regeneration niche of E. regnans was defined by different factors at different stages of development. Initially, seedlings established prolifically on burnt sites, regardless of severity. Three years into the regeneration process, high-severity fire became the dominant driver of seedling persistence and growth over 25 cm. Growth over 50 cm was dependent on environmental conditions relating to elevation and precipitation. Main conclusions: Our results describe how fire occurrence, fire severity and environmental gradients affected seedling establishment, persistence and growth. The dynamic constraints on regeneration likely reflect temporal changes in the biotic and abiotic environment and variation in resource requirements during the early post-fire years. Our findings will enable more accurate forecasts of species distributions to assist forest conservation in the face of global changes in climate and fire regimes.

Personality and innate immune defenses in a wild bird: evidence for the pace-of-life hypothesis

We tested the two main evolutionary hypotheses for an association between immunity and personality. The risk-of-parasitism hypothesis predicts that more proactive (bold, exploratory, risk-taking) individuals have more vigorous immune defenses because of increased risk of parasite exposure. In contrast, the pace-of-life hypothesis argues that proactive behavioral styles are associated with shorter lifespans and reduced investment in immune function. Mechanistically, associations between immunity and personality can arise because personality differences are often associated with differences in condition and stress responsiveness, both of which are intricately linked with immunity. Here we investigate the association between personality (measured as proactive exploration of a novel environment) and three indices of innate immune function (the non-specific first line of defense against parasites) in wild superb fairy-wrens Malurus cyaneus. We also quantified body condition, hemoparasites (none detected), chronic stress (heterophil:lymphocyte ratio) and circulating corticosterone levels at the end of the behavioral test (CORT, in a subset of birds). We found that fast explorers had lower titers of natural antibodies. This result is consistent with the pace-of-life hypothesis, and with the previously documented higher mortality of fast explorers in this species. There was no interactive effect of exploration score and duration in captivity on immune indices. This suggests that personality-related differences in stress responsiveness did not underlie differences in immunity, even though behavioral style did modulate the effect of captivity on CORT. Taken together these results suggest reduced constitutive investment in innate immune function in more proactive individuals.

The effects of an invasive seaweed on native communities vary along a gradient of land-based human impacts

The difficulty in teasing apart the effects of biological invasions from those of otheranthropogenic perturbations has hampered our understanding of the mechanismsunderpinning the global biodiversity crisis. The recent elaboration of global-scalemaps of cumulative human impacts provides a unique opportunity to assess howthe impact of invaders varies among areas exposed to different anthropogenicactivities. A recent meta-analysis has shown that the effects of invasive seaweeds onnative biota tend to be more negative in relatively pristine than in human-impactedenvironments. Here, we tested this hypothesis through the experimental removalof the invasive green seaweed, Caulerpa cylindracea, from rocky reefs across theMediterranean Sea. More specifically, we assessed which out of land-based andsea-based cumulative impact scores was a better predictor of the direction andmagnitude of the effects of this seaweed on extant and recovering native assemblages.Approximately 15 months after the start of the experiment, the removal ofC. cylindracea from extant assemblages enhanced the cover of canopy-formingmacroalgae at relatively pristine sites. This did not, however, result in major changesin total cover or species richness of native assemblages. Preventing C. cylindraceare-invasion of cleared plots at pristine sites promoted the recovery of canopyformingand encrusting macroalgae and hampered that of algal turfs, ultimatelyresulting in increased species richness. These effects weakened progressively withincreasing levels of land-based human impacts and, indeed, shifted in sign at theupper end of the gradient investigated. Thus, at sites exposed to intense disturbancefrom land-based human activities, the removal of C. cylindracea fostered the coverof algal turfs and decreased that of encrusting algae, with no net effect on speciesrichness. Our results suggests that competition from C. cylindracea is an importantdeterminant of benthic assemblage diversity in pristine environments, but less so inspecies-poor assemblages found at sites exposed to intense disturbance from landbasedhuman activities, where either adverse physical factors or lack of propagulesmay constrain the number of potential native colonizers. Implementing measures toreduce the establishment and spread of C. cylindracea in areas little impacted byland-based human activities should be considered a priority for preserving thebiodiversity of Mediterranean shallow rocky reefs.

Reptile responses to fire and the risk of post-disturbance sampling bias

Altered fire regimes are a driver of biodiversity decline. To plan effective management, we need to know how species are influenced by fire and to develop theory describing fire responses. Animal responses to fire are usually measured using methods that rely on animal activity, but animal activity may vary with time since fire, potentially biasing results. Using a novel approach for detecting bias in the pit-fall trap method, we found that leaf-litter dependent reptiles were more active up to 6 weeks after fire, giving a misleading impression of abundance. This effect was not discovered when modelling detectability with zero-inflated binomial models. Two species without detection bias showed early-successional responses to time since fire, consistent with a habitat-accommodation succession model. However, a habitat specialist did not have the predicted low abundance after fire due to increased post-fire movement and non-linear recovery of a key habitat component. Interactions between fire and other processes therefore must be better understood to predict reptile responses to changing fire-regimes. We conclude that there is substantial bias when trapping reptiles after fire, with species that are otherwise hard to detect appearing to be abundant. Studies that use a survey method based on animal activity such as bird calls or animal movements, likely face a similar risk of bias when comparing recently-disturbed with control sites.