Ecology Letters最新文献

Root exudates act as key energy and signalling carriers linking roots with rhizosphere microbes, yet how their quantity and quality mediate root-microbe coordination remains unclear. Here, we measured fine root exudation rates and chemical composition, functional traits, and soil microbial communities across 13 coexisting subtropical tree species. Root exudation release rates and composition tightly aligned with the conservative-acquisitive root economics spectrum, bridging strategic synergy between roots and their microbial partners. Acquisitive roots with higher nitrogen concentrations released exudates at higher rates and greater chemodiversity, supporting more diverse microbial communities enriched in fast-growing copiotrophs and saprotrophic fungi, but with reduced symbiotic fungal abundance, whereas conservative roots with higher tissue density showed the opposite pattern. These results highlight root exudate, especially its chemical composition, as a key trait shaping the root-microbe functional continuum, providing novel insights into mechanisms of belowground functional integrations which affect species coexistence and ecosystem functioning under environmental change.

In theory, biased adult sex ratios combined with high population densities in physically coercive mating systems could trigger an extinction vortex, regardless of external factors such as predation or habitat loss. However, this has never been documented in the wild. In an exceptionally dense island population of Hermann's tortoises in Lake Prespa in North Macedonia, sexually coercive males dramatically overnumber females, inflict severe copulatory injuries and put them at risk of fatal falls from the island plateau's sheer rock faces. Harassed females are emaciated, reproduce less frequently, produce smaller clutches and have lower annual survival rates compared to females from a neighbouring mainland population. Sixteen years of capture-recapture data reveal an ongoing extinction event and predict that the last island female will die in 2083. Paradoxically, while high population density might suggest prosperity, it can trigger population collapse under highly skewed adult sex ratio in a coercive mating system.

Turnover in species composition often lags behind the pace of climate change, resulting in mismatches between climate and communities. However, the impact of these community-climate disequilibria on ecosystem functions is rarely considered, and current methods for measuring disequilibria assume that species ranges were, until recently, in equilibrium with climate. Here, we develop a simple theoretical model to address both of these problems by linking community-climate disequilibrium with ecosystem functioning. We show how disequilibrium can impair functioning in the near-term even when climate change is expected to enhance functioning in the long-term. Responses are most likely to change over time in communities where turnover is slow, the impact of disequilibrium counteracts the direct effects of climate on ecosystem function, and pre-existing disequilibrium is large. These findings emphasise the importance of precise and unbiased estimates of community-climate disequilibria for improving ecological forecasts. By fitting our model to time series of both climate and ecosystem function from a metacommunity simulation, we show the potential for community-climate disequilibrium to be inferred without direct knowledge about species' distributions or climatic tolerances. We end by outlining a research agenda to apply dynamic disequilibrium concepts and test novel hypotheses across diverse ecosystems.

While climate adaptation is typically quantified across broad gradients, the potential for adaptation to the same environmental variables at small scales is rarely tested. If local-scale environmental heterogeneity can generate patterns of adaptation similar to broad gradients, then we currently underestimate adaptive capacity to global change. We quantified population variation in climate tolerance traits and their plasticity for five populations of Drosophila melanogaster from a 3000-km latitudinal gradient, which we contrasted with eight local populations from an environmentally heterogeneous 600 × 300 km area. Population variation in stress tolerance at the local scale was comparable to that across latitude. Consistent with local adaptation, populations from warmer and drier environments showed greater heat and desiccation tolerance and populations from more predictable environments showed greater plasticity. Climate adaptation at smaller geographic scales can therefore be comparable to adaptation across broad geographic scales. However, patterns of adaptation often changed across geography, which makes predicting responses to global change challenging.

Understanding responses of ecological communities to shocks that displace species abundances is of paramount importance given the increasing frequency of extreme climatic events. However, current theory on responses to such pulse perturbations focuses on equilibrium points and we lack a unified framework that accommodates other common, but more complicated, population fluctuations such as transients and cycles. Here we introduce this framework by deriving metrics that quantify the minimum, typical and maximum amplification of perturbed abundances for nonequilibrium population dynamics. By simulating models under several nonequilibrium scenarios, we demonstrate that these metrics accurately characterise the full range of amplification of perturbed abundances in the short and long terms. Notably, we show that perturbation amplification depends strongly on community state in the short term, but this state dependency vanishes in the long term. We illustrate how our framework can provide insights about models and data for communities that are not at equilibrium.

When populations suffer reduced fitness in novel environments, genotypes that better adjust their phenotype to cope with environmental change can aid persistence by reducing the severity of fitness declines. However, we know little about how plastic changes in phenotype allow different genotypes to track environmental variation across ecological gradients, particularly as environments become novel. We transplanted clones of 19 genotypes of a Sicilian daisy, Senecio chrysanthemifolius, at four elevations on Mt. Etna. We assessed fitness within native and novel elevations, and quantified leaf plasticity across and within elevations. Genotypes with higher fitness at novel elevations showed lower variance in fitness, lower plasticity across elevations, but higher plasticity within elevations compared to those with higher fitness in the native range. Our results suggest there are genotypes hidden in populations whose plasticity better tracks novel environmental variation at multiple ecological scales. Such genotypes will be crucial for population persistence under rapid environmental change.