Variable direct and indirect effects of a habitat-modifying invasive species on mortality of native fauna

Habitat-modifying invasive species can influence rates of predation on native prey either directly by providing protective structure or indirectly by modifying traits of prey species responding to the habitat. The alga Caulerpa taxifolia is one of the most successful invasive species of shallow-water marine systems globally, often provisioning habitat in areas previously lacking in vegetated structure. We experimentally evaluated the direct effect of Caulerpa to provide refuge for the native clam Anadara trapezia and how this balances with its influence on two trait-mediated indirect interactions that may increase Anadara\u27s susceptibility to predators. Specifically, Caulerpa\u27s alteration of physical and chemical properties of the surrounding water and sediment deteriorate Anadara\u27s condition and predator resistance properties and also cause Anadara, though normally buried, to project from beneath the sediment, exposing it to predators. Our results show that Anadara are somewhat (but not consistently) protected from predators by living among Caulerpa. Shallow burial depth did not counteract this protective effect. However at times of year when predator activity diminishes and conducive environmental conditions develop, negative effects of Caulerpa habitat such as hypoxia and lowered flow may dominate. Under such situations, poor clam condition accentuates Anadara\u27s susceptibility to mortality. Ultimately, a slight and inconsistent positive effect of Caulerpa to protect Anadara from predators is exceeded by the strong negative effect of Caulerpa on clam mortality, which is heightened by clams\u27 weakened condition produced by chronic exposure to Caulerpa. Our results show that invasive habitat-modifying species can affect mortality of native species not simply through obvious positive direct effects of their protective structure, but indirectly through contrasting negative modification of the traits of prey species responding to the habitat

Invasive ecosystem engineer selects for different phenotypes of an associated native species

Invasive habitat-forming ecosystem engineers modify the abiotic environment and thus represent a major perturbation to many ecosystems. Because native species often persist in these invaded habitats but have no shared history with the ecosystem engineer, the engineer may impose novel selective pressure on native species. In this study, we used a phenotypic selection framework to determine whether an invasive habitat-forming ecosystem engineer (the seaweed Caulerpa taxifolia) selects for different phenotypes of a common cooccurring native species (the bivalve Anadara trapezia). Compared to unvegetated habitat, Caulerpa habitat has lower water flow, lower dissolved oxygen, and sediments are more silty and anoxic. We determined the performance consequences of variation in key functional traits that may be affected by these abiotic changes (shell morphology, gill mass, and palp mass) for Anadara transplanted into Caulerpa and unvegetated habitat. Both linear and nonlinear performance gradients in Anadara differed between habitats, and these gradients were stronger in Caulerpa compared to unvegetated sediment. Moreover, in Caulerpa alternate phenotypes performed well, and these phenotypes were different from the dominant phenotype in unvegetated sediment. By demonstrating that phenotype-performance gradients differ between habitats, we have highlighted a role for Caulerpa as an agent of selection on native species

Asexual propagation of Asparagopsis armata gametophytes: fragmentation, regrowth and attachment mechanisms for sea-based cultivation

The red algal genus Asparagopsis produces secondary metabolites that when fed to ruminants reduce methane production by up to 98%. However, cultivation methods for Asparagopsis are nascent and fundamental information on reproduction, which is essential for large-scale cultivation, is lacking. In this study we examined asexual propagation in Asparagopsis armata, the regrowth of fragments and mechanisms of attachment to assess the potential for fragments to be used in sea-based cultivation. Asparagopsis armata gametophytes grow specialised structures, barbs, that hook fragments onto substrata. Surveys revealed barbs were abundant occurring at ~ 1 barb every 3–4 cm on gametophyte branches. Barbs did not regrow, but fronds did, either when attached to a barb or on their own. In contrast, fronds doubled in size with most developing barbs within 4 weeks. Barbs were, however, critical for the reattachment of fragments: barbs attached to substrata at four times the rate of frond fragments without barbs and they also attached in higher proportions to mussel rope than polypropylene rope, and two types of net. Utilising fragmentation for the propagation of A. armata gametophytes in sea-based cultivation requires that fragments can attach to a substratum and regrow once attached. We have shown that A. armata fragments in Tasmania require barbs for attachment and frond tissue for growth, which has implications for cultivation. Optimising fragmentation, attachment and out-planting methods are important future steps in establishing fragmentation as a method for sea-based cultivation in A. armata

Gold substrate-induced single-mode lasing of GaN nanowires

We demonstrate a method for mode-selection by coupling a GaN nanowire laser to an underlying gold substrate. Multimode lasing of GaN nanowires is converted to single-mode behavior following placement onto a gold film. A mode-dependent loss is generated by the absorbing substrate to suppress multiple transverse-mode operation with a concomitant increase in lasing threshold of only ∼13%. This method provides greater flexibility in realizing practical single-mode nanowire lasers and offers insight into the design of metal-contacted nanoscale optoelectronics

Differences in soft-sediment macrobenthic assemblages invaded by Caulerpa taxifolia compared to uninvaded habitats

Caulerpa taxifolia is a habitat-forming green alga that has invaded several temperate regions worldwide. Although C. taxifolia covers large areas of soft-sediment habitat, little is known about its effects on soft-sediment invertebrate assemblages. We compared soft-sediment macroinvertebrate assemblages in 2 estuaries in southeastern Australia invaded by C. taxifolia to examine 2 main predictions: (1) areas covered with C. taxifolia will have different assemblages compared to unvegetated sediment because infauna are inhibited but epifauna are facilitated, and (2) areas with C. taxifolia will have different assemblages compared to those with native seagrasses (Halophila ovalis and Zostera capricorni) because infauna are inhibited but epifauna are not. Multidimensional scaling and ANOSIM showed differences in invertebrate assemblages between all habitats. In C. taxifolia, infauna were less abundant and epifauna were more abundant compared to unvegetated sediment. However, when compared to native seagrasses, epifauna in C. taxifolia were more abundant than in H. ovalis in one estuary but less abundant than in Z. capricorni in another estuary, while infauna in C. taxifolia were less abundant than in both seagrass species. The consistently low infaunal abundance in C. taxifolia, irrespective of infaunal feeding mode, suggests C. taxifolia impacts infauna generally. Examination of environmental factors potentially responsible for the low abundance of infauna indicated that differences in redox potential (and associated chemical changes) may explain patterns in abundance of infauna among habitats. Our findings indicate that invasion by C. taxifolia causes important changes to soft-sediment macroinvertebrate assemblages and suggest that infauna may be particularly vulnerable to invasion because of changes to sediment chemistry

Field evaluation of six Gros Michel banana accessions (Musa spp., AAA group) for agronomic performance, resistance to Fusarium wilt race 1 and yellow Sigatoka

Three Gros Michel mutants (‘IBP 5-B’, ‘IBP 5–61’ and ‘IBP 12’) from the Cuban Instituto de Biotecnología de las Plantas, two semi-dwarf Gros Michel varieties (‘Highgate’ and ‘Cocos’) and a Thai accession (‘Hom Thong Mokho’) were evaluated in Australia over a five year period. They were screened for their resistance to Fusarium wilt Race 1 (FocR1) caused by the pathogen Fusarium oxysporum f.sp. cubense, as well as resistance to yellow Sigatoka (Pseudocercospora musae Zimm [teleomorph Mycosphaerella musicola Leach]). They were also grown for a plant and ratoon crop in the tropics (17°S) and a plant crop in the subtropics (28°S) with no disease pressure to record their agronomic characteristics. They were compared with Australian industry standards, ‘Williams’ (AAA, Cavendish subgroup) and ‘Lady Finger’ (AAB, Pome subgroup). In the subtropics the Gros Michel mutants and semi-dwarf accessions were sensitive to cold and very susceptible to FocR1 and yellow Sigatoka while their agronomic performance in the tropics was good, with ‘Highgate’ having the best bunch weight on a shorter, more manageable plant. Of the six accessions evaluated, ‘Hom Thong Mokho’ showed the highest level of resistance to FocR1 although it had poor cold tolerance, as did the other Gros Michel selections, and consequently had low productivity compared to ‘Williams’ and even ‘Lady Finger’. However in the warmer, more humid tropics ‘Hom Thong Mokho's performance was much better and it was less susceptible to yellow Sigatoka than the other Gros Michel selections. Subsequent genetic analysis by Christelová et al. (2011) has revealed that although ‘Hom Thong Mokho’ is marketed as a Gros Michel variety in Asia, it is closer to the Rio subgroup (AAA) of dessert bananas

Understanding Unauthorized Access using Fine-Grained Human-Computer Interaction Data

Unauthorized Data Access (UDA) by an internal employee is a major threat to an organization. Regardless of whether the individuals engaged in UDA with malicious intent or not, real-time identification of UDA events and anomalous behaviors is extremely difficult. For example, various artificial intelligence methods for detecting insider threat UDA have become readily available; while useful, such methods rely on post hoc analysis of the past (e.g., unsupervised learning algorithms on access logs). This research-in-progress note reports on if the analysis of Human-Computer Interaction (HCI) behaviors, which have been empirically validated in various studies to reveal hidden cognitive state, can be utilized as a method to detect UDAs. To examine this, an experimental design was required that would grant the subjects an opportunity to engage in UDA events while tracking the HCI behaviors in an unobtrusive manner. Background, experimental design, study execution, preliminary results, and future research plans are presented

Exoplanet Catalogues

One of the most exciting developments in the field of exoplanets has been the progression from 'stamp-collecting' to demography, from discovery to characterisation, from exoplanets to comparative exoplanetology. There is an exhilaration when a prediction is confirmed, a trend is observed, or a new population appears. This transition has been driven by the rise in the sheer number of known exoplanets, which has been rising exponentially for two decades (Mamajek 2016). However, the careful collection, scrutiny and organisation of these exoplanets is necessary for drawing robust, scientific conclusions that are sensitive to the biases and caveats that have gone into their discovery. The purpose of this chapter is to discuss and demonstrate important considerations to keep in mind when examining or constructing a catalogue of exoplanets. First, we introduce the value of exoplanetary catalogues. There are a handful of large, online databases that aggregate the available exoplanet literature and render it digestible and navigable - an ever more complex task with the growing number and diversity of exoplanet discoveries. We compare and contrast three of the most up-to-date general catalogues, including the data and tools that are available. We then describe exoplanet catalogues that were constructed to address specific science questions or exoplanet discovery space. Although we do not attempt to list or summarise all the published lists of exoplanets in the literature in this chapter, we explore the case study of the NASA Kepler mission planet catalogues in some detail. Finally, we lay out some of the best practices to adopt when constructing or utilising an exoplanet catalogue.Comment: 14 pages, 6 figures. Invited review chapter, to appear in "Handbook of Exoplanets", edited by H.J. Deeg and J.A. Belmonte, section editor N. Batalh

Optical and ultraviolet spectroscopic analysis of SN 2011fe at late times

We present optical spectra of the nearby Type Ia supernova SN 2011fe at 100, 205, 311, 349, and 578 days post-maximum light, as well as an ultraviolet spectrum obtained with Hubble Space Telescope at 360 days post-maximum light. We compare these observations with synthetic spectra produced with the radiative transfer code PHOENIX. The day +100 spectrum can be well fit with models which neglect collisional and radiative data for forbidden lines. Curiously, including this data and recomputing the fit yields a quite similar spectrum, but with different combinations of lines forming some of the stronger features. At day +205 and later epochs, forbidden lines dominate much of the optical spectrum formation; however, our results indicate that recombination, not collisional excitation, is the most influential physical process driving spectrum formation at these late times. Consequently, our synthetic optical and UV spectra at all epochs presented here are formed almost exclusively through recombination-driven fluorescence. Furthermore, our models suggest that the ultraviolet spectrum even as late as day +360 is optically thick and consists of permitted lines from several iron-peak species. These results indicate that the transition to the "nebular" phase in Type Ia supernovae is complex and highly wavelength-dependent.Comment: 22 pages, 21 figuress, 1 table, submitted to MNRA