SummaryMechanistic models can help resolve controversy over the responses of mast seeding plants to future environmental change.We evaluate drivers of mast seeding by: developing and validating a new mechanistic resource-based model of mast seeding using four 40-yr Chionochloa (snow tussock) datasets; and comparing the performance of competing empirically-based statistical models, that aim to approximate the mechanisms underlying mast seeding, in explaining simulated and observed data.Our mechanistic model explained 90-99% of the variation in Chionochloa flowering, with higher rates of stored resource mobilisation and lower probability of climatic induction of flowering occurring at lower fertility sites. Inter-annual variation in floral induction and the degree to which seeding is resource-limited explained shifts in the relative performance of different empirical models fitted to data simulated from the mechanistic model. Empirical models explicitly capturing the interaction between the floral induction cue and internal resource state underlying the resource-limited induction mechanism had > 8.79 the statistical support of alternatives when fitted to Chionochloa datasets.We find support for resource-limited floral induction with multiple empirical models consistent with this same mechanism. As both resource acquisition and flowering cues are climate sensitive, we expect climate change to impact upon patterns of mast seeding.
A lthough islands cover only ~5% of the global land area, they support ~20% of terrestrial plant and vertebrate species (Courchamp et al. 2014). Insular species are particularly vulnerable to extinction; one-third of critically endangered species and nearly two-thirds of recent extinctions consisted of species endemic to islands (Tershy et al. 2015), and these declines may have impacts on Indigenous peoples (Lyver et al. 2019). Several interacting factors contribute to this vulnerability, including invasions by non-native species and habitat loss (Simberloff et al. 2013). Island ecosystems are particularly susceptible to multiple climate-change factors, including rising sea level and loss of suitable climatic conditions (Courchamp et al. 2014), but conservation and restoration efforts rarely account for such interacting drivers of change (Parmesan et al. 2013). Understanding the effects of climate change on island ecosystems necessitates knowing how climate interacts with other ecologically influential processes (eg habitat loss, land transformation, invasive species). Here, we use the example of New Zealand to highlight interactions between changing climate and other threats to biodiversity, and stress the need to collect and maintain long-term datasets to improve strategies to mitigate climate-change effects. Lessons learned from New Zealand are relevant to islands (and potentially continental systems) elsewhere (Simberloff 2019), particularly with respect to the indirect and interactive effects of climate-change impacts. Although we focus on land-based ecosystems, we note that warming seas and ocean acidification are affecting marine systems in New Zealand's territorial waters, as well as elsewhere. Finally, we emphasize the need to work with Indigenous communities to improve the effectiveness of mitigation and adaptation approaches. New Zealand (also known by the Indigenous name Aotearoa) consists of three main islands, along with hundreds of smaller islands in rivers, lakes, and harbors, as well
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Birds living in alpine environments are becoming increasingly impacted by human‐induced threats. We investigated the impacts of introduced mammalian predators on an endangered alpine species, the New Zealand Rockwren Xenicus gilviventris, and assessed whether predator control improved its breeding success. Nest monitoring revealed that the primary cause of nest failure was predation by invasive mammals, primarily Stoats Mustela erminea and House Mice Mus musculus. Daily survival rates (DSR) decreased with nest age, and nests were at their most vulnerable to predators just prior to fledging. DSR, egg‐hatching and fledgling rates were all improved by predator trapping, demonstrating the significant impacts that even low numbers of invasive predators can have on sensitive alpine and upland species.
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