Habitat augmentation drives secondary invasion: an experimental approach to determine the mechanism of invasion success

The entry of secondary invaders into, or their expansion within, native communities is contingent on the changes wrought by other (primary) invaders. When primary invaders have altered more than one property of the recipient community, standard descriptive and modeling approaches only provide a best guess of the mechanism permitting the secondary invasion. In rainforest on Christmas Island, we conducted a manipulative field experiment to determine the mechanism of invasion success for a community of land snails dominated by non-native species. The invasion of rainforest by the yellow crazy ant (Anoplolepis gracilipes) has facilitated these land snails, either by creating enemy-free space and/or increased habitat and resources (in the form of leaf litter) through the removal of the native omnivorous-detritivorous red land crab (Gecarcoidea natalis). We manipulated predator densities (high and low) and leaf litter (high and low) in replicated blocks of four treatment combinations at two sites. Over the course of one wet season (five months), we found that plots with high leaf litter biomass contained significantly more snails than those with low biomass, regardless of whether those plots had high or low predation pressure, at both the site where land crabs have always been abundant, and at the site where they have been absent for many years prior to the experiment. Each site was dominated by small snail species (<2 mm length), and through handling size and predation experiments we demonstrated that red crabs tend not to handle and eat snails of that size. These results suggest that secondary invasion by this community of non-native land snails is facilitated most strongly by habitat and resource augmentation, an indirect consequence of red land crab removal, and that the creation of enemy-free space is not important. By using a full-factorial experimental approach, we have confidently determined—rather than inferred—the mechanism by which primary invaders indirectly facilitate a community of secondary invaders

Neural Likelihood Approximation for Integer Valued Time Series Data

Stochastic processes defined on integer valued state spaces are popular within the physical and biological sciences. These models are necessary for capturing the dynamics of small systems where the individual nature of the populations cannot be ignored and stochastic effects are important. The inference of the parameters of such models, from time series data, is difficult due to intractability of the likelihood; current methods, based on simulations of the underlying model, can be so computationally expensive as to be prohibitive. In this paper we construct a neural likelihood approximation for integer valued time series data using causal convolutions, which allows us to evaluate the likelihood of the whole time series in parallel. We demonstrate our method by performing inference on a number of ecological and epidemiological models, showing that we can accurately approximate the true posterior while achieving significant computational speed ups in situations where current methods struggle

How practitioners integrate decision triggers with existing metrics in conservation monitoring

Decision triggers are defined thresholds in the status of monitored variables that indicate when to undertake management, and avoid undesirable ecosystem change. Decision triggers are frequently recommended to conservation practitioners as a tool to facilitate evidence-based management practices, but there has been limited attention paid to how practitioners are integrating decision triggers into existing monitoring programs. We sought to understand whether conservation practitioners’ use of decision triggers was influenced by the type of variables in their monitoring programs. We investigated this question using a practitioner-focused workshop involving a structured discussion and review of eight monitoring programs. Among our case studies, direct measures of biodiversity (e.g. native species) were more commonly monitored, but less likely to be linked to decision triggers (10% with triggers) than measures being used as surrogates (54% with triggers) for program objectives. This was because decision triggers were associated with management of threatening processes, which were often monitored as a surrogate for a biodiversity asset of interest. By contrast, direct measures of biodiversity were more commonly associated with informal decision processes that led to activities such as management reviews or external consultation. Workshop participants were in favor of including more formalized decision triggers in their programs, but were limited by incomplete ecological knowledge, lack of appropriately skilled staff, funding constraints, and/or uncertainty regarding intervention effectiveness. We recommend that practitioners consider including decision triggers for discussion activities (such as external consultation) in their programs as more than just early warning points for future interventions, particularly for direct measures. Decision triggers for discussions should be recognized as a critical feature of monitoring programs where information and operational limitations inhibit the use of decision triggers for interventions. © 2018 Elsevier Ltd. **Please note that there are multiple authors for this article therefore only the name of the first 5 including Federation University Australia affiliate “Philip Barton” is provided in this record*

Surrogacy in invasion research and management: inferring “impact” from “invasiveness”

Biological invasions are widely accepted drivers of biodiversity decline, yet the ecological impacts of invaders in many contexts remain largely unmeasured. Consequently, other measures of a species invasion (e.g. local abundance) are regularly used as surrogates (or ‘proxies’) to infer impact on recipient ecosystems. The use of surrogates for impact represents an implicit application of ecological surrogacy in invasion science, but without the evaluation and validation of surrogate-target relationships that characterizes surrogate use in other fields. While there are practical reasons for this, there also are risks associated with not testing the accuracy, stability and certainty of surrogate-impact relationships that need to be acknowledged. Recognizing the role of surrogacy in invasion science offers previously unappreciated solutions for increasing the quantitative rigor of invasive species impact assessments that inform management decisions.ARC Laureate Fellowshi

The use and utility of surrogates in biodiversity monitoring programmes

**Please note that there are multiple authors for this article therefore only the name of the first 5 including Federation University Australia affiliate “Philip Barton” is provided in this record*

Higher-taxon and functional group responses of ant and bird assemblages to livestock grazing : a test of an explicit surrogate concept

Biodiversity monitoring programs are routinely established to quantify changes in biotic communities in response to land management. Surrogacy is implicitly used in many such monitoring programs whereby the measurement of a component of biodiversity is used to infer responses of broader biodiversity. Yet rarely is this surrogacy validated by demonstrating that measured variables and the target variable of interest have matching responses to management treatments. Here we examined the responses of higher-taxon and functional groupings of ants and birds (our surrogate variables) two years after the implementation of experimental livestock grazing treatments, and compared these with the responses of total ant and bird species richness (our target variables) to the same treatments. We found significant and strong correlations between surrogate and target variables, but this did not predict corresponding similar response to treatments. For ants, we found that the genus Monomorium had a negative response to the grazing exclusion treatment, but there was no matching response of species richness, and so no surrogacy was identified. For birds, total species richness had a weak positive response to spring/summer grazing exclusion, and the abundance of honeyeaters (Meliphagidae) showed a similar positive response, suggesting surrogacy. Our study highlights that correlations among variables do not necessarily lead to surrogacy, and indeed that different sub-components of biotic assemblages can respond in ways that contrast with overall species richness. Careful assessment of the matched responses of surrogate and target variables to management can provide a simple and robust way to critically assess biodiversity surrogacy. © 2018 Elsevier Ltd. **Please note that there are multiple authors for this article therefore only the name of the first 5 including Federation University Australia affiliate “Philip Barton” is provided in this record*

The importance of Travelling Stock Reserves for maintaining high-quality threatened temperate woodlands

Travelling Stock Reserves are thought to represent some of the highest-quality and least degraded remnants of threatened temperate woodland in south-eastern Australia. These public reserves have not had the same high levels of grazing pressure and other disturbances as woodland remnants on private land. Thus, Travelling Stock Reserves are expected to be important for the protection of biodiversity in heavily cleared and modified landscapes. We tested the hypothesis that land tenure had significant effects on the quality of woodlands by comparing vegetation structural attributes between Travelling Stock Reserves and remnant vegetation used for primary production purposes. Vegetation attributes were monitored in 155 permanent plots over five years in remnant temperate woodland sites in the Riverina bioregion of New South Wales. Overall, Travelling Stock Reserves supported higher native plant species richness and were characterized by higher ground cover of native shrubs and less cover of exotic plant species when compared to agricultural production areas. We found land tenure had significant effects on some vegetation attributes demonstrated to be important for threatened fauna. We attribute these results to Travelling Stock Reserves having a history of lower grazing pressure compared to remnants managed for agricultural production. Our study provides empirical evidence to support the high conservation value of Travelling Stock Reserves in formerly woodland-dominated, but now extensively cleared, agricultural landscapes

Using ecological niche theory to avoid uninformative biodiversity surrogates

Surrogates and indicators of biodiversity are used to infer the state and dynamics of species populations and ecosystems, as well as to inform conservation and management actions. Despite their widespread use, few studies have examined how ecological theory can guide the selection or surrogates and indicators, and thus reduce the likelihood of failure or cost of validation. We argue that ecological niche theory and knowledge of the extent to which particular limiting factors (e.g. physiological tolerances, limits to growth rates, or competitive exclusion) affect species distributions, abundance and coexistence could inform the choice of potential surrogates. Focusing on the environmental characteristics that define species niches makes it possible to identify situations where surrogates are likely to be ineffective, such as when there is no mechanistic basis for a candidate surrogate to be related to a biodiversity target. We describe two case studies where different candidate surrogate variables are shown to have contrasting potential as indicators of sustainable farming. Variables not mechanistically linked to the driver of change or responsive over appropriate timeframes or spatial scales are suggested a priori to be uninformative. The niche concept provides a framework for exploring ecological relationships that can inform the selection or exclusion of potential biodiversity surrogates. We think that this new approach to integrating ecological theory and application could lead to improved effectiveness of biodiversity monitoring and conservation.DBL was funded by an ARC Laureate Fellowship (LF120100108). MRW was supported in part by a grant from the US National Science Foundation (DEB-1546686)

Effects of antiplatelet therapy on stroke risk by brain imaging features of intracerebral haemorrhage and cerebral small vessel diseases: subgroup analyses of the RESTART randomised, open-label trial

Background Findings from the RESTART trial suggest that starting antiplatelet therapy might reduce the risk of recurrent symptomatic intracerebral haemorrhage compared with avoiding antiplatelet therapy. Brain imaging features of intracerebral haemorrhage and cerebral small vessel diseases (such as cerebral microbleeds) are associated with greater risks of recurrent intracerebral haemorrhage. We did subgroup analyses of the RESTART trial to explore whether these brain imaging features modify the effects of antiplatelet therapy

Effects of antiplatelet therapy after stroke due to intracerebral haemorrhage (RESTART): a randomised, open-label trial

Background: Antiplatelet therapy reduces the risk of major vascular events for people with occlusive vascular disease, although it might increase the risk of intracranial haemorrhage. Patients surviving the commonest subtype of intracranial haemorrhage, intracerebral haemorrhage, are at risk of both haemorrhagic and occlusive vascular events, but whether antiplatelet therapy can be used safely is unclear. We aimed to estimate the relative and absolute effects of antiplatelet therapy on recurrent intracerebral haemorrhage and whether this risk might exceed any reduction of occlusive vascular events. Methods: The REstart or STop Antithrombotics Randomised Trial (RESTART) was a prospective, randomised, open-label, blinded endpoint, parallel-group trial at 122 hospitals in the UK. We recruited adults (≥18 years) who were taking antithrombotic (antiplatelet or anticoagulant) therapy for the prevention of occlusive vascular disease when they developed intracerebral haemorrhage, discontinued antithrombotic therapy, and survived for 24 h. Computerised randomisation incorporating minimisation allocated participants (1:1) to start or avoid antiplatelet therapy. We followed participants for the primary outcome (recurrent symptomatic intracerebral haemorrhage) for up to 5 years. We analysed data from all randomised participants using Cox proportional hazards regression, adjusted for minimisation covariates. This trial is registered with ISRCTN (number ISRCTN71907627). Findings: Between May 22, 2013, and May 31, 2018, 537 participants were recruited a median of 76 days (IQR 29–146) after intracerebral haemorrhage onset: 268 were assigned to start and 269 (one withdrew) to avoid antiplatelet therapy. Participants were followed for a median of 2·0 years (IQR [1·0– 3·0]; completeness 99·3%). 12 (4%) of 268 participants allocated to antiplatelet therapy had recurrence of intracerebral haemorrhage compared with 23 (9%) of 268 participants allocated to avoid antiplatelet therapy (adjusted hazard ratio 0·51 [95% CI 0·25–1·03]; p=0·060). 18 (7%) participants allocated to antiplatelet therapy experienced major haemorrhagic events compared with 25 (9%) participants allocated to avoid antiplatelet therapy (0·71 [0·39–1·30]; p=0·27), and 39 [15%] participants allocated to antiplatelet therapy had major occlusive vascular events compared with 38 [14%] allocated to avoid antiplatelet therapy (1·02 [0·65–1·60]; p=0·92). Interpretation: These results exclude all but a very modest increase in the risk of recurrent intracerebral haemorrhage with antiplatelet therapy for patients on antithrombotic therapy for the prevention of occlusive vascular disease when they developed intracerebral haemorrhage. The risk of recurrent intracerebral haemorrhage is probably too small to exceed the established benefits of antiplatelet therapy for secondary prevention