Species introduction represents one of the most serious threats for biodiversity. The realized climatic niche of an invasive species can be used to predict its potential distribution in new areas, providing a basis for screening procedures in the compilation of black and white lists to prevent new introductions. We tested this assertion by modeling the realized climatic niche of the Eastern grey squirrel Sciurus carolinensis. Maxent was used to develop three models: one considering only records from the native range (NRM), a second including records from native and invasive range (NIRM), a third calibrated with invasive occurrences and projected in the native range (RCM). Niche conservatism was tested considering both a niche equivalency and a niche similarity test. NRM failed to predict suitable parts of the currently invaded range in Europe, while RCM underestimated the suitability in the native range. NIRM accurately predicted both the native and invasive range. The niche equivalency hypothesis was rejected due to a significant difference between the grey squirrel’s niche in native and invasive ranges. The niche similarity test yielded no significant results. Our analyses support the hypothesis of a shift in the species’ climatic niche in the area of introductions. Species Distribution Models (SDMs) appear to be a useful tool in the compilation of black lists, allowing identifying areas vulnerable to invasions. We advise caution in the use of SDMs based only on the native range of a species for the compilation of white lists for other geographic areas, due to the significant risk of underestimating its potential invasive range.

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Summary1. There is increasing evidence that disease-mediated invasions are widespread across a range of vertebrate, invertebrate and plant systems. We therefore need a better understanding of the role of disease in managing conservation threats due to introduced and invasive species. 2. Here, we develop a general theoretical model framework to assess the impact of diseasemediated invasion on the viability of conserving native species through refuges taking into account explicit spatial and stochastic processes. 3. The model techniques are applied to the well-documented red and grey squirrel conservation system in the UK as a case study. 4. By combining general and specific modelling approaches, we are able to make management predictions while also gaining an understanding of the processes that underlie population outcomes leading to more robust conservation practice. 5. Model results indicate that in the absence of control of the invading species,

The Eurasian Red Squirrel (Sciurus vulgaris) is under threat from the invasive North American eastern Grey Squirrel (Sciurus carolinensis) with 80% of the remaining red squirrel populations in the British Isles found in Scotland. In this study we develop a spatially explicit mathematical model of the red and grey squirrel system and use it to assess the population viability of red squirrels across Scotland. In particular, we aim to identify existing forests – natural strongholds for red squirrels – that can successfully support red squirrels under UK Forestry Standard management and protect them from potential disease-mediated competition from grey squirrels. Our model results indicate that if current levels of grey squirrel control, which restrict or reduce the distribution of grey squirrels, are continued then there will be large expanses of forests in northern Scotland that support viable red squirrel populations. Model results that represent (hypothetical) scenarios where grey squirrel control no longer occurred indicated that grey squirrel range expansion and the process of red squirrel replacement would be slow. Model results for an assumed worst-case scenario where grey squirrels have expanded to all regions in Scotland identified forest regions – denoted natural strongholds – that could currently support red squirrels under UK Forestry Standard management practice. The results will be used to inform forest management policy and support a strategic review of red squirrel management by land management agencies and other stakeholders.

A temporal refuge from predation can change the outcome of prey species competition. Supplement to "A temporal refuge from predation can change the outcome of prey species competition" Derivation of Analytic Results Two-Species Competition Model with Constant Predator DensityWe outline a model to represent the dynamics of two competing prey species that are subject to predation. The model is based on the classical Lotka-Volterra framework for competing species.The model represents the densities of prey species X 1 and X 2 at time t as follows: