Loss of predation risk from apex predators can exacerbate marine tropicalization caused by extreme climatic events.

Extreme climatic events (ECEs) and predator removal represent some of the most widespread stressors to ecosystems. Though species interactions can alter ecological effects of climate change (and vice versa), it is less understood whether, when and how predator removal can interact with ECEs to exacerbate their effects. Understanding the circumstances under which such interactions might occur is critical because predator loss is widespread and ECEs can generate rapid phase shifts in ecosystems which can ultimately lead to tropicalization. Our goal was to determine whether loss of predation risk may be an important mechanism governing ecosystem responses to extreme events, and whether the effects of such events, such as tropicalization, can occur even when species range shifts do not. Specifically, our goal was to experimentally simulate the loss of an apex predator, the tiger shark Galeocerdo cuvier effects on a recently damaged seagrass ecosystem of Shark Bay, Australia by applying documented changes to risk-sensitive grazing of dugong Dugong dugon herbivores. Using a 16-month-field experiment established in recently disturbed seagrass meadows, we used previous estimates of risk-sensitive dugong foraging behaviour to simulate altered risk-sensitive foraging densities and strategies of dugongs consistent with apex predator loss, and tracked seagrass responses to the simulated grazing. Grazing treatments targeted and removed tropical seagrasses, which declined. However, like in other mixed-bed habitats where dugongs forage, treatments also incidentally accelerated temperate seagrass losses, revealing that herbivore behavioural changes in response to predator loss can exacerbate ECE and promote tropicalization, even without range expansions or introductions of novel species. Our results suggest that changes to herbivore behaviours triggered by loss of predation risk can undermine ecological resilience to ECEs, particularly where long-lived herbivores are abundant. By implication, ongoing losses of apex predators may combine with increasingly frequent ECEs to amplify climate change impacts across diverse ecosystems and large spatial scales.

The trophic role of a large marine predator, the tiger shark Galeocerdo cuvier.

Tiger sharks were sampled off the western (Ningaloo Reef, Shark Bay) and eastern (the Great Barrier Reef; GBR, Queensland and New South Wales; NSW) coastlines of Australia. Multiple tissues were collected from each shark to investigate the effects of location, size and sex of sharks on δ13C and δ15N stable isotopes among these locations. Isotopic composition of sharks sampled in reef and seagrass habitats (Shark Bay, GBR) reflected seagrass-based food-webs, whereas at Ningaloo Reef analysis revealed a dietary transition between pelagic and seagrass food-webs. In temperate habitats off southern Queensland and NSW coasts, shark diets relied on pelagic food-webs. Tiger sharks occupied roles at the top of food-webs at Shark Bay and on the GBR, but not at Ningaloo Reef or off the coast of NSW. Composition of δ13C in tissues was influenced by body size and sex of sharks, in addition to residency and diet stability. This variability in stable isotopic composition of tissues is likely to be a result of adaptive foraging strategies that allow these sharks to exploit multiple shelf and offshore habitats. The trophic role of tiger sharks is therefore both context- and habitat-dependent, consistent with a generalist, opportunistic diet at the population level.

Is a community still a community? Reviewing definitions of key terms in community ecology.

Community ecology is an inherently complicated field, confounded by the conflicting use of fundamental terms. Nearly two decades ago, Fauth et al. (1996) demonstrated that imprecise language led to the virtual synonymy of important terms and so attempted to clearly define four keywords in community ecology; "community," "assemblage," "guild," and "ensemble". We revisit Fauth et al.'s conclusion and discuss how the use of these terms has changed over time since their review. An updated analysis of term definition from a selection of popular ecological textbooks suggests that definitions have drifted away from those encountered pre-1996, and slightly disagreed with results from a survey of 100 ecology professionals (comprising of academic professors, nonacademic PhDs, graduate and undergraduate biology students). Results suggest that confusion about these terms is still widespread in ecology. We conclude with clear suggestions for definitions of each term to be adopted hereafter to provide greater cohesion among research groups.

Anterior thoracic foraminotomy through mini-thoracotomy for the treatment of giant thoracic disc herniations.

STUDY DESIGN: A retrospective review of a case series. OBJECTIVES: Giant thoracic disc herniations remain a surgical challenge and historically have been associated with significant complications. While neurological outcomes have improved with the abandonment of decompressive laminectomy, the attempt to minimize surgical complications and associated morbidities continues through less-invasive approaches. With the current study, we describe a surgical technique to treat giant thoracic disc herniations while minimizing approach-related morbidity. METHODS: Demographic and radiographic data; clinical outcome and perioperative complications were retrospectively analysed for patients with single-level giant thoracic disc herniations who underwent mini-thoracotomy and selective microsurgical anterior spinal cord decompression without instrumented fusion. RESULTS: Between 2007 and 2012, 7 consecutive patients with giant thoracic disc herniations were treated (average age of 53 years; range 45-66 years). The average canal encroachment was 73.2 % (range 40-92 %) with 5 grossly calcified discs of which 3 had transdural components. All patients had gradual myelopathic progression. The average Nurick grade was 3.5 (range 2-5). All patients were successfully treated with anterior microsurgical decompression without instrumentation. Uninstrumented fusion with rib graft was performed only in one patient with advanced degenerative changes. Average time of surgery was 337.8 min (range 220-450 min). The average length of hospital stay was 7.4 days (range 6-11 days). The average neurological status at follow-up (average 23.5 months; range 9-36 months) using the modified Nurick grading scale was 1.28. No vertebral collapse or loss of spinal alignment developed. There were no neurological complications. One patient developed an acute headache and diplopia, 10 days after surgery, following sneezing associated with a post-operative thoracic cerebrospinal fluid leakage requiring revision. Two patients suffered an approach-related complication in form of intercostal neuralgia; one was persistent. CONCLUSIONS: Anterior decompression using a mini-transthoracic approach provides sufficient exposure for microsurgical decompression of giant thoracic disc herniations without disrupting the stability of the spine. Microsurgical decompression without instrumentation does not appear to lead to vertebral collapse or spinal malalignment.

Rough neuro-fuzzy structures for classification with missing data.

This paper presents a new approach to fuzzy classification in the case of missing data. The rough fuzzy sets are incorporated into Mamdani-type neuro-fuzzy structures, and the rough neuro-fuzzy classifier is derived. Theorems that allow the determination of the structure of a rough neuro-fuzzy classifier are given. Several experiments illustrating the performance of the rough neuro-fuzzy classifier working in the case of missing features are described.