Ecology Letters最新文献

We utilized a long-term study of Weddell seals to compute lifetime reproductive success (LRS) distributions using a theoretical approach and an empirical approach. These comparisons are often difficult to achieve among natural populations but are important for disentangling sources of variation in lifetime measures. We performed three independent analyses: the first compared LRS and age-at-death distributions among populations living under different environmental conditions, the second focused on populations differing in individual heterogeneity (i.e., high or low reproductive strategy), and the third compared a theoretical LRS distribution with an empirical LRS distribution. Iceberg conditions increased the probability of LRS = 0 while individual heterogeneity had little influence on LRS distributions. Age-at-death distributions were also highly skewed and only early life mortality was affected by environmental condition. Our theoretical LRS distribution was strikingly similar to the empirical distribution estimated from females experiencing natural intrinsic trait variability and extrinsic environmental variability. We also examine inequality measures which show that females must be ‘lucky’ to survive past maturity and of those who do, only 74% breed. These findings contribute to ongoing research that reveals how diversity in lifetime outcomes is largely governed by chance alone.

Animal movement and habitat selection underpin important ecological phenomena, from individual behaviour to population-level distributions. Despite navigating three-dimensional space, animals' movement is typically measured and analysed on a two-dimensional plane, which limits our understanding of species that swim or fly. Therefore, we propose a step selection function (SSF) capable of quantifying animal movement and habitat selection in three dimensions. We formulate a very general family of three-dimensional correlated random walks, aimed at capturing unique features of three-dimensional data. Using Antarctic petrel data, we illustrate how these SSFs can be used to assess selection for vertically-stratified habitat, account for barriers (e.g., the ground or ocean surface), and model attraction to any number of directional targets. Our modelling framework provides a solid foundation for three-dimensional analyses, which will be crucial to answer ecological questions that would otherwise be ignored in two dimensions.

Higher-order interactions (HOIs) are widely predicted to promote coexistence, yet the underlying ecological mechanisms behind this effect remain largely unexplored in natural communities. Here, we integrate natural history and theory to show how HOIs can restructure competitive networks and influence coexistence. With over 2 years of data on a tropical ant community, we estimate pairwise competitive interactions and demonstrate that, in isolation, they fail to recreate observed community dynamics. We find that inclusion of an HOI, imposed by a parasitoid of the dominant species, can theoretically reorganize competitive networks to mirror the dynamics of the empirical system. We demonstrate how temporal variation in HOIs forces the community between dominance regimes and that the interregnum between regimes is riddled with competitive intransitivities that promote coexistence. This work provides an empirical example of the ecological mechanisms behind the coexistence-promoting effects of HOIs and suggests that HOIs and intransitivity, which are typically treated separately, can be mechanistically linked through the rewiring of species interactions.

The evolutionary imbalance hypothesis predicts that species from ecologically stable regions of high genetic potential and intense competition are more likely to be invasive, while regions with the opposite characteristics are more likely to be invasible. Relative phylogenetic diversity (PD) of species' indigenous ranges could indicate evolutionary imbalance and help identify high-risk invaders and vulnerable communities. We tested this with three seed addition experiments where 166 species of varying origins were sown into disturbed and undisturbed grassland plots. Species with high relative indigenous-PD had high colonisation and first-year survival regardless of disturbance, whereas species with low relative indigenous-PD only colonised disturbed communities and at a lower rate. Species' indigenous-PD did not appear to affect second-year survival. Although long-term outcomes are unknown, evidence suggests that species with high relative indigenous-PD pose a high invasion risk, even to intact communities. Regional PD could help indicate species invasiveness and community invasibility, informing biosecurity.

Niche overlap (NO) is a cornerstone of coexistence theory, summarising the strength of competitive coupling among species. Yet NO collapses distinct mechanisms into a single value and may miss key dynamical features. We quantify this limitation by examining temporal correlations in species abundances, a key out-of-equilibrium observable in microbial ecology. Using a MacArthur-type consumer-resource model, we show that communities with identical NO can display opposite dynamical patterns. Within the resource-mediated fluctuation regime studied here, a yield-depletion mismatch (YDM)—the difference between depletion and yield dissimilarities—consistently predicts the sign and magnitude of abundance correlations across analytical approximations, stochastic simulations, and a reanalysis of microbial time series. In contrast, growth-rate correlations are governed by NO. More broadly, our results show that dynamical observables can depend on mechanistic details beyond those summarised by niche overlap.

Biological communities follow a remarkably consistent negative relationship between individual mass (M) and abundance (N), represented by a power law (N ~ M^λ). The parameter λ denotes the rate of decline in relative abundance from small to large individuals and serves as a proxy for energy transfer efficiency in food webs. Although warming is expected to affect λ, its influence remains uncertain, possibly due to interactions with resource supply. Using ~670,000 individual body sizes from stream food webs, we tested how temperature and resources shape λ. Temperature effects depended on resource supply (gross primary production [GPP] and organic matter standing stock [OM]) but contradicted expectations that λ becomes more negative with warming. At medium and high resources, λ becomes less negative under warming while no change occurred at low resources. Variation in OM, not GPP, drove these patterns, highlighting the role of external energy inputs and challenging the idea that large organisms are rarer at higher temperatures.

When and how much plants grow under environmental constraints are fundamental questions in biology and increasingly important for predicting biomass production and carbon sequestration under climate change. While temperature and water availability directly regulate plant growth, the timing and rate of growth are also shaped by internal developmental programming, though this is rarely considered in predictions of tree growth responses to future climates. Here, we revisit a concept central to this internal programming—(in)determinacy. Focusing on woody plants, we define it as the extent to which annual shoot growth is deployed from preformed organs versus produced de novo during the current season. We argue that this trait is best understood as a continuum and that it can help explain contrasting growth responses in a changing climate. More determinate species concentrate growth within a narrow seasonal window, which may reduce exposure to late-season stress but also limit their ability to exploit longer growing seasons. More indeterminate species retain greater flexibility to extend or resume growth when conditions remain favourable, which may be advantageous under climate change, but this same flexibility may also increase exposure to frost, drought and incomplete tissue maturation. Because primary shoot growth also shapes canopy development and is linked to other growth processes, variation in (in)determinacy could help explain broader differences in whole-plant performance, carbon gain and species responses to climate change.