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| INTRODUC TI ONTo quantify the influence of competition on species presence, absence and abundance, ecologists need to be able to identify the species that will win and the species that will lose in competition over the long term (i.e. over multiple generations). The ecological literature on competition is vast, covering decades of empirical research, many reviews of both empirical methods (Brooker , 1992;Schoener, 1983), and the development of over 50 different metrics of competitive ability based on measurements of individual performance (Weigelt & Jolliffe, 2003). Despite the tremendous research attention, however, the question of how to identify the ultimate winners and losers in competition from empirical studies remains unclear (Trinder, Brooker, & Robinson, 2013). For example, the most recent comprehensive review of interspecific competition between plants (Aschehoug et al., 2016) concludes that the hundreds of studies that have examined the impacts of interspecific competition on the performance of individual plants "…have told us little about how such competitive effects ramify to populations." This observation matches messagesfrom influential reviews of empirical studies from previous decades Abstract 1. Understanding the role of competition in structuring communities requires that we quantify competitive ability in a way that permits us to predict the outcome of competition over the long term. Given such a clear goal for a process that has been the focus of ecological research for decades, there is surprisingly little consensus on how to measure competitive ability, with up to 50 different metrics currently proposed.2. Using competitive population dynamics as a foundation, we define competitive ability-the ability of one species to exclude another-using quantitative theoretical models of population dynamics to isolate the key parameters that are known to predict competitive outcomes.3. Based on the definition of competitive ability we identify the empirical requirements and describe straightforward methods for quantifying competitive ability in future empirical studies. In doing so, our analysis also allows us to identify why many existing approaches to studying competition are unsuitable for quantifying competitive ability. Synthesis.Competitive ability is precisely defined starting from models of competitive population dynamics. Quantifying competitive ability in a theoretically justified manner is straightforward using experimental designs readily applied to studies of competition in the laboratory and field. K E Y W O R D S competitive ability, competitive dominance, competitive effect, competition model, competitive response, interspecific competition, population dynamics, response surface | 1903 Journal of Ecology HART eT Al.

Ongoing climate change is thought to disrupt trophic relationships, with consequences for complex interspecific interactions, yet the effects of climate change on species interactions are poorly understood, and such effects have not been documented at a global scale. Using a single database of 38,191 nests from 237 populations, we found that shorebirds have experienced a worldwide increase in nest predation over the past 70 years. Historically, there existed a latitudinal gradient in nest predation, with the highest rates in the tropics; however, this pattern has been recently reversed in the Northern Hemisphere, most notably in the Arctic. This increased nest predation is consistent with climate-induced shifts in predator-prey relationships.

Highlights d More than 1,000 data-deficient amphibians are threatened with extinction d Almost 500 species are endangered or critically endangered d Threatened species are located mainly in South America and Southeast Asia d Urgent conservation actions are needed to avert the loss of data-deficient species

Intense selection by pesticides and antibiotics has resulted in a global epidemic of evolved resistance. In agriculture and medicine, using mixtures of compounds from different classes is widely accepted as optimal resistance management. However, this strategy may promote the evolution of more generalist resistance mechanisms. Here we test this hypothesis at a national scale in an economically important agricultural weed: blackgrass (Alopecurus myosuroides), for which herbicide resistance is a major economic issue. Our results reveal that greater use of herbicide mixtures is associated with lower levels of specialist resistance mechanisms, but higher levels of a generalist mechanism implicated in enhanced metabolism of herbicides with diverse modes of action. Our results indicate a potential evolutionary trade-off in resistance management, whereby attempts to reduce selection for specialist resistance traits may promote the evolution of generalist resistance. We contend that where specialist and generalist resistance mechanisms co-occur, similar trade-offs will be evident, calling into question the ubiquity of resistance management based on mixtures and combination therapies.