Despite concerns about the richness of plant invaders on islands, and their likely effects on local systems, impacts of these species seem to be small. However, this may be due to an absence of information on impacts, including changing species occupancy and forecast occupancy, rather than lack of impact per se. Here we use the plant invaders on the sub-Antarctic Prince Edward Islands (PEIs) and spatially explicit modeling of presence-absence survey data to demonstrate that the geographic extent of many invasives is increasing and is forecast to lead to occupancy of >60% of the islands' surface area by 2060, with ongoing climate change. In keeping with theory, proximity to human activity, neighboring populations (i.e. propagule pressure) and residence time, along with more minor contributors such as elevation, explain >50% of the variation in the occupancy of each of the six main invasive species on the islands. Human disturbance and changing climates seem to have led to recent increases in the rate of range expansion. Our results suggest that impacts of island plant invaders may be more significant than previously estimated, largely owing to prior data deficiency. More specifically they also suggest that control plans for the PEI (and other Southern Ocean Islands, SOIS) should first target less widely distributed species, which are invasive elsewhere. They also indicate that for the other SOIS, and for Antarctica, surveillance and anticipatory control plans should be in place.

Abstract. The considerable threats of invasive rodents to island biodiversity are likely to be compounded by climate change. Forecasts for such interactions have been most pronounced for the Southern Ocean islands where ameliorating conditions are expected to decrease thermal and resource restrictions on rodents. Firm evidence for changing rodent populations in response to climate change, and demonstrations of associated impacts on the terrestrial environment, are nonetheless entirely absent for the region. Using data collected over three decades on sub-Antarctic Marion Island, we tested empirically whether mouse populations have changed through time and whether these changes can be associated significantly with changing abiotic conditions. Changes in invertebrate populations, which have previously been attributed to mouse predation, but with little explicit demographic analysis, were also examined to determine whether they can be associated with changing mouse populations. The total number of mice on the island at annual peak density increased by 430.0% between 1979-1980 and 2008-2011. This increase was due to an advanced breeding season, which was robustly related to the number of precipitation-free days during the non-breeding season. Mice directly reduced invertebrate densities, with biomass losses of up to two orders of magnitude in some habitats. Such invertebrate declines are expected to have significant consequences for ecosystem processes over the long term. Our results demonstrate that as climate change continues to create ameliorating conditions for invasive rodents on sub-Antarctic islands, the severity of their impacts will increase. They also emphasize the importance of rodent eradication for the restoration of invaded islands.

Metabolic rate is a fundamental characteristic of all organisms. It covaries most significantly with activity, body mass, seasonality, and temperature. Nonetheless, substantial additional variation in metabolic rate, especially either resting rate or basal rate, is associated with a range of factors including phylogenetic position, ecological distinctiveness, range position, and diet. Understanding this variation is a key goal of physiological ecology. The black-faced sheathbill is a phylogenetically distinct, highlatitude, island-endemic bird occurring exclusively on several archipelagos in the southern Indian Ocean. Here we examined the idea that the unique phylogenetic position and ecology of the black-faced sheathbill may lead to a basal metabolic rate (BMR) different from that predicted by its body mass. When compared with BMR data available for all birds and a subset of island species, it was clear that the BMR of the black-faced sheathbill on subantarctic Marion Island, estimated at 157C using indirect calorimetry (2.370 5 0.464 W, mean 5 SD; n p 22), for a group of birds with a mean mass of 459 5 64 g, is no different from that expected based on body mass. However, variation in BMR, associated with habitat use and diet, even when correcting for variation in mass, was found. Sheathbills foraging year-round in comparatively resource-rich king penguin colonies have a higher BMR (2.758 5 0.291 W, n p 12) than sheathbills that split their foraging between rockhopper penguin colonies and the intertidal zone (2.047 5 0.303 W, n p 10), which are poorer in resources. Because these populations coexist at relatively small spatial extents (the entire island is 290 km 2 ), other factors seem unlikely as causes of this variation.

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