Edge effects in patchy seagrass landscapes : the role of predation in determining fish distribution

Predation is often described as an underlying mechanism to explain edge effects. We assessed the importance of predation in determining edge effects in seagrass using two approaches: a video survey to sample predators at small scales across seagrass edges, and a tethering experiment to determine if predation was an underlying mechanism causing edge effects. Underwater videos were placed at four positions: middle of seagrass patches; edge of seagrass; sand immediately adjacent to seagrass and sand distant from seagrass. Fish abundances and the time fish spent in view were measured. The main predatory fish (Australian salmon, Arripis spp.) spent more time over adjacent sand than other positions, while potential prey species (King George whiting, Sillaginodes punctata (Cuvier), recruits) were more common in the middle of seagrass patches. Other species, including the smooth toadfish, Tetractenos glaber (Freminville), and King George whiting adults, spent more time over sand adjacent to seagrass than distant sand, which may be related to feeding opportunities. King George whiting recruits and pipefish (Stigmatopora spp.) were tethered at each of the four positions. More whiting recruits were preyed upon at outer than inner seagrass patches, and survival time was greater in the middle of shallow seagrass patches than other positions. Relatively few pipefish were preyed upon, but of those that were, survival time was lower over sand adjacent to seagrass than at the seagrass edge or middle. Video footage revealed that salmon were the dominant predators of both tethered King George whiting recruits and pipefish. The distribution of predators and associated rate of predation can explain edge effects for some species (King George whiting) but other mechanisms, or combinations of mechanisms, are determining edge effects for other species (pipefish).

Research mentoring on the edge : early career researchers and academic fringe-dwelling

Discourses of research leadership define not only what quality research leadership can and should be, but also identify those who speak and act with authority. Similarly, these discourses construct particular professional identities and idealised ‘ways of being’. They provide possibilities for research leaders as well as those categorised as 'Early Career Researchers' (ECRs) to create alternative identities and representations of themselves. This study reports the views of 32 academics across 16 Australian universities in four States about research mentoring and leadership for ECRs. The primary interest was to explore how research leadership is conceptualised, implemented and negotiated in the disciplinary fields of business, nursing and education. Whilst a number of ECRs viewed formal research mentoring as taking a ‘tick the box’ approach that they believed of limited value, a number of research leaders had different views. Most senior research leaders viewed the systemic provision of assistance their universities offered in a positive light. The dissonance in views centred on the subject positioning of academics in research. The dissatisfaction expressed by ECRs, a number of whom positioned themselves as fringe-dwellers ‘on the edge’ of their institutional research culture, raises questions about research sustainability and succession planning in Australian tertiary
institutions.

Co-evolution path model : how enterprises as complex systems survive on the edge of chaos

In this theoretical paper, we introduce and describe a model, and demonstrate its origins from the disciplines of Enterprise Architecture, cybernetics and systems theory. We use cybernetic thinking to develop a ‘Co-evolution Path Model’ that describes how enterprises as complex systems co-evolve with their complex environments. The model re-interprets Stafford Beer’s Viable System Model, and also uses the theorem of the ‘good regulator’ of Conant and Ashby, exemplifying how various complexity management theories could be synthesised into a cybernetic theory of Enterprise Architecture, using concepts from the generalisation of EA frameworks.

Identity on the edge: The impact of risk, compliance and performativity on VET practitioner identity.

 German Sociologist, Ulrich Beck’s seminal political analysis of risk, Risk Society: Towards a New Modernity, in 1992 posited the concept of ‘risk’ that has become privatised, objectified and a matter for individual concern. This study examines how the management of ‘risk’ is achieved through individual scrutiny, audit and review and the impact these practices have on changing VET practitioner identity. Preliminary PhD interviews with VET practitioners, using grounded theory methodology, identified the symbiotic nature of risk management and generation within the current diverse and challenging VET environment. Resistance or acquiescence to compliance practices and the performative VET environment have significant implications for VET practitioners’ identity construction.

Gradient edge map features for frontal face recognition under extreme illumination changes

Our aim in this paper is to robustly match frontal faces in the presence of extreme illumination changes, using only a single training image per person and a single probe image. In the illumination conditions we consider, which include those with the dominant light source placed behind and to the side of the user, directly above and pointing downwards or indeed below and pointing upwards, this is a most challenging problem. The presence of sharp cast shadows, large poorly illuminated regions of the face, quantum and quantization noise and other nuisance effects, makes it difficult to extract a sufficiently discriminative yet robust representation. We introduce a representation which is based on image gradient directions near robust edges which correspond to characteristic facial features. Robust edges are extracted using a cascade of processing steps, each of which seeks to harness further discriminative information or normalize for a particular source of extra-personal appearance variability. The proposed representation was evaluated on the extremely difficult YaleB data set. Unlike most of the previous work we include all available illuminations, perform training using a single image per person and match these also to a single probe image. In this challenging evaluation setup, the proposed gradient edge map achieved 0.8% error rate, demonstrating a nearly perfect receiver-operator characteristic curve behaviour. This is by far the best performance achieved in this setup reported in the literature, the best performing methods previously proposed attaining error rates of approximately 6–7%.

Finding the edge : online persona creation by fringe artists

Self-presentation through the creation of profiles and pages on digitally networked spaces is becoming ever more ubiquitous. In order to develop greater depth of understanding of the place of social media in our self-identification practice, my dissertation investigates the experiences of online persona creation by eight artists. Drawing on sociological and cultural studies approaches to understanding identity as performance, I tie current artists’ presentational and representational practices to historically grounded, socio-culturally constructed discourses of ‘artistness’. Through this connection, I argue that the creation of online persona has not radically changed notions of what it means to be an artist, or how artistness is represented and understood by audiences of fans or followers, but rather that digital technology has allowed for renegotiation of the boundaries of artistness that still draws from historical understandings of the role and persona of the artist. This shifting of boundaries, allowing for more inclusivity within the art world, is demonstrated by my focus on ‘fringe’ artists: those whose creative practice places them outside of the traditional art world and its existing structures of representation, distribution and consumption. The eight fringe artists who participated in this study are drawn from street art, performance poetry, craftivism and tattoo.

Interpretative Phenomenological Analysis drives the methodological focus on the experiences of the artists. Rather than a consideration of behaviour and habit, or what the artists do, this phenomenological approach allowed me to instead focus on what it is like for the artists to create persona, what drives particular types of representational practices. Using unstructured interviews, and online listening as an extension of participant observation, the artists’ narratives of experience are expressed through transcript extracts and screenshots: both are necessary to fully explore the nature of online persona creation.

My analysis of the artists experiences has demonstrated that there are three somewhat distinct registers of performance with which an artist’s persona can engage: the professional register, where one demonstrates ones proficiency, experience, popularity, and professionalism; the personal register, where one connects with
wider social and political interests and activities; and the intimate register, where one allows the audience in to one’s private world. These three registers occupy the same performance space, but are implicitly or explicitly for different segments of the digitally networked audience of fans, followers, friends and family. The complexity of the performance and reception of these registers is influenced by the shared nature of the performance space – where previously different roles would be performed for different audiences without reference to one another, the networked nature of online social media influences decisions of how much, and when, to share with whom.

Interpreted here using themes of strategy|happenstance, specialisation|diversification, visibility|self-protection,
self|others and work|play, the professional, personal and intimate registers of performance enable us to see the consideration and care with which each participant creates their artists persona. The experiences of performing the self in these three registers, as presented here, provides an insight into the complexities involved in creating online persona, while also demonstrating that this type of presentation of self is, in itself, no different from the types of role play and performance of self that has arguably always occurred in our physical world. Despite focusing on the role and performance of artistness, this dissertation speaks to the creation and performance of online persona more broadly. 

Living on the edge: how philopatry maintains adaptive potential.

Without genetic variation, species cannot cope with changing environments, and evolution does not proceed. In endangered species, adaptive potential may be eroded by decreased population sizes and processes that further reduce gene flow such as philopatry and local adaptations. Here, we focused on the philopatric and endangered loggerhead sea turtle (Caretta caretta) nesting in Cape Verde as a model system to investigate the link between adaptive potential and philopatry. We produced a dataset of three complementary genomic regions to investigate female philopatric behaviour (mitochondrial DNA), male-mediated gene flow (microsatellites) and adaptive potential (major histocompatibility complex, MHC). Results revealed genetically distinct nesting colonies, indicating remarkably small-scale philopatric behaviour of females. Furthermore, these colonies also harboured local pools of MHC alleles, especially at the margins of the population's distribution, which are therefore important reserves of additional diversity for the population. Meanwhile, directional male-mediated gene flow from the margins of distribution sustains the adaptive potential for the entire rookery. We therefore present the first evidence for a positive association between philopatry and locally adapted genomic regions. Contrary to expectation, we propose that philopatry conserves a high adaptive potential at the margins of a distribution, while asymmetric gene flow maintains genetic connectivity with the rest of the population.

An experimental investigation of edge strain and bow in roll forming a V-section

V-sections were roll formed from two grades of steel, and the strain on the top and bottom of the strip near the edge was measured using electrical resistance strain gauges. The channels were bent to a radius of 2 and 15 mm along the centerline. The steel strips were of mild and dual phase steel of yield strength 367 MPa and 597 MPa respectively. The longitudinal bow was measured using a 3-dimensional scanning system. The strain measurements were analysed to determine bending and mid-surface strains at the edge during forming. The peak longitudinal edge strain increased with material yield strength for both profile radii. For the 15 mm radius, the bow was larger in the dual phase steel than in the mild steel. For the 2 mm profile radius, the bow was smaller compared with the 15 mm profile radius and it was similar for both steels. It was observed that the difference between the peak longitudinal edge strain and yield strength to Youngs modulus ratio of the material is an important factor in determining longitudinal bow.

Edge patterns in aquatic invertebrates explained by predictive models

Predictive frameworks for understanding and describing how animals respond to habitat fragmentation, particularly across edges, have been largely restricted to terrestrial systems. Abundances of zooplankton and meiofauna were measured across seagrasssand edges and the patterns compared with predictive models of edge effects. Artificial seagrass patches were placed on bare sand, and zooplankton and meiofauna were sampled with tube traps at five positions (from patch edges: 12, 60 and 130 cm into seagrass; and 12 and 60 cm onto sand). Position effects consisted of the following three general patterns: (1) increases in abundance around the seagrasssand edge (total abundance and cumaceans); (2) declining abundance from seagrass onto sand (calanoid copepods, harpacticoid copepods and amphipods); and (3) increasing abundance from seagrass onto sand (crustacean nauplii and bivalve larvae). The first two patterns are consistent with resource-distribution models, either as higher resources at the confluence of adjacent habitats or supplementation of resources from high-quality to low-quality habitat. The third pattern is consistent with reductions in zooplankton abundance as a consequence of predation or attenuation of currents by seagrass. The results show that predictive models of edge effects can apply to aquatic animals and that edges are important in structuring zooplankton and meiofauna assemblages in seagrass. © 2010 CSIRO.