Bird's nest ferns as model systems and conservation tools

We are in a race against time to understand the response of natural systems to climate change and anthropogenic disturbances, such as large scale land conversion for oil palm expansion. However, it is incredibly difficult to quantify multi-trophic biodiversity-ecosystem function (BEF) relationships because natural ecosystems are complex. Nowhere is this challenge more apparent than in the primary tropical rainforests of Borneo where biodiversity reaches its highest concentration. The bird’s nest fern (Asplenium spp.) is an elegant solution to the problem of studying complex tropical rainforest because the ferns are natural microcosms. The ferns themselves, are keystone species in rainforest canopies, and studies have shown that they are hotspots for invertebrate biodiversity and functional processes such as decomposition in the rainforest canopy. Bird’s nest ferns are therefore the ideal natural model system, for testing ecological theory, investigating BEF relationships, and performing manipulation experiments to predict the effects of future disturbance. This thesis begins by defining the soil properties that allow bird’s nest ferns to regulate their internal microclimate in both rainforest and oil palm plantations. Quantifying the extent to which the ferns buffered extreme climate variation in these habitats, revealed why they are such important thermal refuges in both rainforest and oil palm. By defining the ferns’ soil properties, I was also able to determine the significant functional role of bird’s nest ferns in above ground water storage and natural flood mitigation. Because the ferns are model systems, so too are the animals they support. I used cockroaches collected from bird’s nest ferns in Borneo and the Eden Project to demonstrate the relationship between the oxygen isotopic composition (δ18O) of insect chitin and climate. By revealing that δ18O in chitin is independent of phylogeny, but entirely a reflection of climate and the way in which the physiological or behavioural traits of a species lead it to interact with its’ habitat, I paved the way for studies of δ18O in chitin to quantify species vulnerability or resilience to habitat disturbance and climate change. While cockroaches provided the ideal model animal for quantifying δ18O, centipedes were the ideal group for studying the role of predators in the bird’s nest ferns. This thesis presents the first study of centipedes in the forest canopy, and the first study of predators in bird’s nest ferns. It demonstrated that predation may be more important than competition, in structuring communities in forest canopies and that predators themselves behave in unexpected ways when it comes to using the ferns as a resource. My final chapter showed that the ferns can be used as conservation tools, to improve connectivity and facilitate the dispersal of animals through oil palm plantations. By transplanting ferns, and their faunal inhabitants, from rainforest to oil palm, I was able to increase biodiversity in plantations. Essentially priming the oil palm landscape with a boost of native biodiversity. This demonstrated that conservation practices in oil palm plantations can work to improve biodiversity, and indeed this is a critical component of the industry’s sustainability agenda. In revealing the importance of bird’s nest ferns as umbrella species for biodiversity and ecosystem function, I have paved the way for using these ubiquitous epiphytes as a novel tool for conserving biodiversity and improving sustainability within the oil palm landscape

Partial information decomposition as a unified approach to the specification of neural goal functions

In many neural systems anatomical motifs are present repeatedly, but despite their structural similarity they can serve very different tasks. A prime example for such a motif is the canonical microcircuit of six-layered neo-cortex, which is repeated across cortical areas, and is involved in a number of different tasks (e.g. sensory, cognitive, or motor tasks). This observation has spawned interest in finding a common underlying principle, a ‘goal function’, of information processing implemented in this structure. By definition such a goal function, if universal, cannot be cast in processing-domain specific language (e.g. ‘edge filtering’, ‘working memory’). Thus, to formulate such a principle, we have to use a domain-independent framework. Information theory offers such a framework. However, while the classical framework of information theory focuses on the relation between one input and one output (Shannon’s mutual information), we argue that neural information processing crucially depends on the combination of multiple inputs to create the output of a processor. To account for this, we use a very recent extension of Shannon Information theory, called partial information decomposition (PID). PID allows to quantify the information that several inputs provide individually (unique information), redundantly (shared information) or only jointly (synergistic information) about the output. First, we review the framework of PID. Then we apply it to reevaluate and analyze several earlier proposals of information theoretic neural goal functions (predictive coding, infomax and coherent infomax, efficient coding). We find that PID allows to compare these goal functions in a common framework, and also provides a versatile approach to design new goal functions from first principles. Building on this, we design and analyze a novel goal function, called ‘coding with synergy’, which builds on combining external input and prior knowledge in a synergistic manner. We suggest that this novel goal function may be highly useful in neural information processing

Terrane boundary reactivation, barriers to lateral fault propagation and reactivated fabrics - Rifting across the Median Batholith Zone, Great South Basin, New Zealand

Prominent pre‐existing structural heterogeneities within the lithosphere may localise or partition deformation during tectonic events. The NE‐trending Great South Basin, offshore New Zealand, formed perpendicular to a series of underlying crustal terranes, including the dominantly granitic Median Batholith Zone, which along with the boundaries between individual terranes, exert a strong control on rift physiography and kinematics. We find that the crustal‐to‐lithospheric scale southern terrane boundary of the Median Batholith Zone is associated with a crustal‐scale shear zone that was reactivated during Late Cretaceous extension between Zealandia and Australia. This reactivated terrane boundary is oriented at a high‐angle to the faults defining the Great South Basin. We identify a large granitic laccolith along the southern margin of the Median Batholith, expressed as sub‐horizontal packages of reflectivity and acoustically transparent areas on seismic reflection data. The presence of this strong granitic body inhibits the lateral south‐westward propagation of NE‐trending faults, which segment into a series of splays that rotate to align along the margin as they approach. Further, we also identify two E‐W and NE‐SW oriented basement fabrics, likely corresponding to prominent foliations, which are exploited by small‐scale faults across the basin. We show that different mechanisms of structural inheritance are able to operate simultaneously, and somewhat independently, within rift systems at different scales of observation. The presence of structural heterogeneities across all scales need to be incorporated into our understanding of the structural evolution of complex rift systems

Genetic variation in tropical Meloidogyne spp. as shown by RAPDs

La technique des RAPD a été utilisée pour évaluer la variabilité intra- et inter-spécifique chez des lignées de #Meloidogyne tropicaux. La reproductibilité de la technique a été évaluée ; pour chaque couple "amorce - ADN testé", l'ADN des différentes lignées de #Meloidogyne testées n'est pas en cause pour expliquer les différences de reproductibilité ; ce sont les amorces qui en sont responsables, certaines se révélant meilleures que d'autres en terme de reproductibilité des résultats et donc de fiabilité. #M. arenaria montre la variabilité intraspécifique la plus importante ; quelques amorces seulement suffisent à distinguer les espèces bien que les données produites par certaines d'entre elles révèlent plus de similitude entre certaines lignées de #M. arenaria et de #M. javanica qu'au sein même du groupe de lignées de #M. arenaria. Trois lignées virulentes de #M. arenaria peuvent être distinguées tant des autres lignées, non virulentes, de #M. arenaria que des autres lignées de #M. javanica, #M. incognita, #M. mayaguensis et #M. hapla. La comparaison des données obtenues sur le même jeu de lignées par RFLP et RAPD révèle des valeurs équivalentes en terme de différence interspécifique mais la technique des RAPD met en évidence une variation plus importante au niveau intraspécifique. (Résumé d'auteur

Sedimentary and structural evolution of a relict subglacial to subaerial drainage system and its hydrogeological implications: an example from Anglesey, north Wales, UK

Subglacial drainage systems exert a major control on basal-sliding rates and glacier dynamics. However, comparatively few studies have examined the sedimentary record of subglacial drainage. This is due to the paucity of modern analogues, the limited recognition and preservation of upper flow regime deposits within the geological record, and the difficulty of distinguishing subglacial meltwater deposits from other meltwater sediments (e.g. glacier outburst flood deposits). Within this study, the sedimentological and structural evolution of a subglacial to subaerial (ice-marginal/proglacial) drainage system is examined. Particular emphasis is placed upon the genetic development and preservation of upper flow regime bedforms and specifically recognising them within a subglacial meltwater context. Facies are attributed to subglacial meltwater activity and record sedimentation within a confined, but progressively enlargening, subglacial channel system produced under dune to upper flow regime conditions. Bedforms include rare large-scale sinusoidal bedding with syn-depositional deformation produced by current-induced traction and shearing within the channel margins. Subglacial sedimentation culminated with the abrupt change to a more ephemeral drainage regime indicating channel-abandonment or a seasonal drainage regime. Retreat of the ice margin, led to the establishment of subaerial drainage with phases of sheet-flow punctuated by channel incision and anastomosing channel development under diurnal, ablation-related, seasonal discharge. The presence of extensive hydrofracture networks demonstrate that proglacial groundwater-levels fluctuated markedly and this may have influenced later overriding of the site by an ice stream

Dietary non-starch polysaccharides influenced natural food web and fish production in semi-intensive pond culture of Nile tilapia

Dietary non-starch polysaccharides (NSP) changes the nutrient digestibility and faecal characteristics in fish. This study assessed the effect of the type of dietary NSPs on fish production and the contribution of natural food to the total fish production in semi-intensively managed tilapia ponds. Twelve ponds, each divided into three equally-sized compartments, were assigned to test the effect of the type of dietary NSPs (i.e. “PecHem-Diet”, a diet with easily fermentable NSP, vs “LigCel-Diet”, a diet with slowly fermentable NSP). Fish were restrictively fed, based on the crude protein content of the feed. Three feeding levels (“no = 0”, “low = 9 g.kg-0.8.d−1” and “high= 18 g.kg-0.8.d-1”) nested in pond were analysed in a split plot design. Initial fish biomass was 3084 g.compartment−1 and the experiment lasted 56 days. With the “LigCel-Diet” biomass gain was higher (2599 vs 2192 g.compartment−1) and feed conversion ratio (FCR) was lower (1.4 vs 1.9; P 13C and δ15N from the stable isotope analysis revealed that N gain in fish originated from both feed and natural food of the pond. Natural food abundance in the pond increased over time for both diets. Chlorophyll-a was higher in the pond fed with “LigCel-Diet”. Fish gut content and calculated N gain indicated an enhanced contribution of natural food to fish growth in ponds fed with “LigCel-Diet”. In conclusion, the type of dietary NSP determines tilapia productivity in semi-intensive managed ponds by altering food web productivity.</p

Electromagnetic interactions for the two-body spectator equations

This paper presents a new non-associative algebra which is used to (i) show how the spectator (or Gross) two-body equations and electromagnetic currents can be formally derived from the Bethe-Salpeter equation and currents if both are treated to all orders, (ii) obtain explicit expressions for the Gross two-body electromagnetic currents valid to any order, and (iii) prove that the currents so derived are exactly gauge invariant when truncated consistently to any finite order. In addition to presenting these new results, this work complements and extends previous treatments based largely on the analysis of sums of Feynman diagrams.Comment: 44 pages, 14 figure

Evidence that stimulation of gluconeogenesis by fatty acid is mediated through thermodynamic mechanisms

AbstractWe have studied the stimulatory effects of palmitate on the rate of glucose synthesis from lactate in isolated hepatocytes. Control of the metabolic flow was achieved by modulating the activity of enolase using graded concentrations of fluoride. Unexpectedly, palmitate stimulated gluconeogenesis even when enolase was rate-limiting. This stimulation was also observed when the activities of phosphoenolpyruvate carboxykinase and aspartate aminotransferase were modulated using graded concentrations of quinolinate and aminooxyacetate, respectively. Linear force-flow relationships were found between the rate of gluconeogenesis and indicators of cellular energy status (i.e. mitochondrial membrane and redox potentials and cellular phosphorylation potential). These findings suggest that the fatty acid stimulation of glucose synthesis is in part mediated through thermodynamic mechanisms

Bounded and unitary elements in pro-C^*-algebras

A pro-C^*-algebra is a (projective) limit of C^*-algebras in the category of topological *-algebras. From the perspective of non-commutative geometry, pro-C^*-algebras can be seen as non-commutative k-spaces. An element of a pro-C^*-algebra is bounded if there is a uniform bound for the norm of its images under any continuous *-homomorphism into a C^*-algebra. The *-subalgebra consisting of the bounded elements turns out to be a C^*-algebra. In this paper, we investigate pro-C^*-algebras from a categorical point of view. We study the functor (-)_b that assigns to a pro-C^*-algebra the C^*-algebra of its bounded elements, which is the dual of the Stone-\v{C}ech-compactification. We show that (-)_b is a coreflector, and it preserves exact sequences. A generalization of the Gelfand-duality for commutative unital pro-C^*-algebras is also presented.Comment: v2 (accepted