Biology subjects

Strona, G.

Publications and source records attributed to Strona, G..

9 recordsLinked to original sources

bioRxiv2026

Ubiquitous trophic niche partitioning drives species coexistence and biomass on coral reefs

Coral reefs support an extraordinary diversity and biomass of fishes. However, whether species coexist through fine-scale niche partitioning, and whether this impacts ecosystem functioning, remain unresolved. We combined DNA metabarcoding and stable isotope analysis to reconstruct a high-resolution food web and quantify the trophic niches of 2,060 reef fishes across 261 species. We observed extreme trophic partitioning: species pairs diverged by a median of 93% (DNA metabarcoding) and 86% (stable isotopes), consistently overlapping far less than expected by chance. Further, communities with greater trophic complementarity supported higher standing-stock biomass, particularly at high species richness. Our results confirm limiting similarity and trophic complementarity as the driving forces of coexistence and ecosystem functioning in the ocean's most diverse ecological community.

ecology↗

bioRxiv2026

Species richness and trait diversity show parallel island-biogeographic patterns across Australian islands

Island biogeography is the theoretical and empirically validated expectation that an islands biodiversity is ultimately limited by its size and isolation, with larger and less isolated (from mainland communities) islands supporting greater diversity. Island biogeography is generally applied to simple metrics of diversity such as species richness (number of different species); however, fewer studies have used traits to measure biodiversity. An organisms traits -- e.g., body mass, age at sexual maturity, trophic level -- can be used to measure biodiversity and understand how ecological communities function. We quantified species richness for birds, mammals, reptiles, and amphibians, and functional diversity for birds and mammals (for which sufficient trait data were available), and tested whether this diversity can be predicted using the theory of island biogeography. We identified 9,103 Australian islands, of which 1,661 had at least one (native and/or non-native) non-marine species present according to the Atlas of Living Australia. As expected, tetrapod species richness (S) increased with island area (A) (z = 0.299 {+/-} 0.012) following a typical power-law relationship (i.e., S = cAz, where z = 0.2-0.4), but was not predicted by distance from mainland -- consistent with the pattern observed on other recently (< 10,000 years) isolated continental islands. We found that trait richness increased at the same rate with island area as species richness for mammals, but for birds, trait richness increased more slowly than species richness. Trait turnover increased modestly with inter-island distance, whereas trait nestedness was unrelated to distance. Trait richness increased strongly with species richness in both birds and mammals, and island area and isolation explained no additional variation in functional richness after accounting for species richness. These results indicate that island geography influences functional diversity primarily through species accumulation, rather than through direct effects on occupied trait space. Overall, the trait space of smaller islands tended to be nested within that of larger, nearby islands; the main differences among similar-sized islands are due to turnover (change in species/trait combinations among assemblages), and the effects are more pronounced in mammals compared to birds. We also found evidence for an asymptotic relationship between trait and species turnover in both birds and mammals, suggesting close coupling between taxonomic and functional turnover, with some saturation of trait turnover at high species turnover. Large islands that are simultaneously more isolated might offer conservation advantages by reducing the influence of threatening processes on the mainland if distance limits access of people and invasive species.

ecology↗

bioRxiv2026

Warming amplifies short-term responses to disturbance in lake food webs

Ecological communities can exhibit transient amplification after disturbance even if asymptotically stable, yet how environmental change reshapes these short-term responses in real food webs remains unclear. We combined four decades of monthly plankton observations from nine Swiss lakes with a food-web model to quantify effects of warming and oligotrophication on two transient properties: reactivity (instantaneous sensitivity to small disturbances) and the time to peak response (tmax). Across lakes, community states lie in an asymptotically stable yet reactive regime. Warmer conditions consistently increased reactivity and lengthened tmax; after accounting for oligotrophication, a 1 {degrees}C rise in mean temperature corresponded to [~] 10% higher reactivity on average. Linking month-to-month variation in transient metrics to guild biomass showed that reactivity covaried strongly with consumer biomass, especially large herbivores, whereas tmax was most associated with predator biomass, a pattern consistent with metabolic-scaling predictions from thermal ecology. The central warming-reactivity association was preserved when we made the bioenergetic parameters themselves temperature-dependent through Boltzmann-Arrhenius scaling. Warming therefore systematically boosted transient sensitivity in these lake food webs via shifts in consumer and predator biomass. Author summaryEcological stability is often evaluated using long-term equilibrium properties that describe whether a community eventually returns toward its previous state after a disturbance, and how long this recovery takes. Yet a system that is stable in the long run can still undergo a strong short-term response before recovering. We asked whether environmental warming changes the magnitude and duration of these temporary responses in real ecosystems. We combined four decades of monthly plankton observations from nine Swiss lakes with a mathematical model describing interactions among major feeding groups. We found that warmer conditions were consistently associated with stronger responses to disturbance and with a longer delay before those responses reached their maximum. These patterns emerged despite the communities remining stable over the long term. Changes in the amount of biomass held by consumers and predators helped explain the observed responses, suggesting that warming alters stability through changes in food-web structure. Our findings show that long-term measures alone may overlook ecologically important short-term dynamics. Considering both eventual recovery and temporary amplification could therefore improve our understanding of how lakes and other ecosystems respond to ongoing climate change and increasingly frequent disturbances.

ecology↗

bioRxiv2026

Coral reef ecosystem functions in a human-dominated world

The metabolic processes sustaining coral reefs, from carbonate and primary production to secondary production, remain poorly integrated and rarely quantified simultaneously at global scales. This hampers our ability to predict global responses to accelerating human pressures and manage coral reef functioning. Using metabolic scaling and bioenergetic models applied to surveys from 1,100 reefs worldwide, we provide a global, standardized quantification of 14 ecosystem functions spanning benthic (corals and algae) and fish communities. Our analysis reveals a continuous functional spectrum of global coral reefs organized along four dominant axes: 1) primary production, 2) calcification and habitat structure, 3) secondary biomass production and consumption, and 4) biomass turnover. Functions mediated by fish and benthic communities show weak associations at the global scale rather than tight coupling. Climate stressors reduced calcification and local human impacts lowered secondary production. Yet these directional effects unfolded against a backdrop of substantial natural variability in reef functional configurations, such that heavily and minimally impacted reefs overlap substantially in the global functional space. Temporal analyses across three representative reef systems further revealed that functional trajectories following disturbance are context-dependent, with no universal pattern of recovery across locations. This continuous and context-dependent functional spectrum challenges the notion of universal functional benchmarks and supports locally tailored conservation strategies.

ecology↗

bioRxiv2026

We might not notice a 'mass' extinction

Enhanced AbstractO_ST_ABSBackgroundC_ST_ABSThere is overwhelming evidence that global change is having widespread, detrimental impacts on biodiversity. Population declines and local disappearances have been recorded with increasing frequency across all taxa, resulting in a steady rise in the number of threatened species. However, the number of documented extinctions remains counterintuitively low ([~] 1000 species across all kingdoms) compared to the sense of emergency pervading the scientific community. In isolation, that figure might fuel scepticism about the biodiversity crisis, but when put into context, it reveals that current extinction rates might be comparable to those that occurred during past mass extinction events estimated from the fossil record ([≥] 75% extinctions within < 2 million years). Although this is an important clue supporting the claim that we might now be witnessing a new ( sixth) mass extinction, it falls short of definitive proof. The claim bears such high importance that it requires exceptionally solid foundations. However, our main aim was not to ascertain whether current extinction rates qualify as a new mass extinction event in progress. Instead, we examined the intersection of potential future loss scenarios and species discovery rates to address the fundamental question of whether and when we will be able to confirm a mass extinction is under way. AdvancesOur extrapolations suggest that the timing for a mass extinction to materialise (2,604-34,808 years from now at 75% diversity loss) is consistent with past mass extinctions (e.g., 12,000-108,000 years estimated for the Permian-Triassic extinction to unfold) under modern extinction rates (loss of 0.004%-0.053% of global species richness per year). We identify the minimum necessary conditions in which we could confirm a mass extinction under the full range of assumptions related to total species diversity (ranging from < 1.8 million to 163.2 million animal species) and discovery rates (e.g., [~] 13,110 new animal species described per year as of 2026, with the number growing by [~]77 species per year), and the associated timeframe required. We show that there are many realistic future scenarios where we would fail to detect a mass extinction in progress. OutlookBased on available evidence, the rate of global biodiversity loss might already be consistent with the standard definition of a mass extinction. But even if true, current extinction rate estimates (20-8343 times background rates) would not necessarily imply a mass extinction is currently unfolding, because this claim can only be verified a posteriori. Our projections instead indicate that there is a high risk of not recognising a mass extinction as it unfolds -- 49% across all parametrisations we explored. Furthermore, the temporal scale required for a mass extinction to materialise is orders of magnitude longer than relevant policy and legislative horizons, a mismatch that might appear to absolve todays society of responsibility. In reality, the opposite is true -- underestimating the likelihood of already being on a trajectory toward a mass extinction could have catastrophic consequences for future generations and historical accountability. Future generations will be forced to confront a world they perceive as normal, unaware of how much better off humanity could have been.

ecology↗

bioRxiv2024

Trait-space disparity in fish communities spanning 380 million years from the Late Devonian to present

The diversity and distribution of species traits in an ecological community determine how it functions. While modern fish communities conse rve trait space across similar habitats, little is known about trait-space variation through deep time or across different habitats. We examined how fish trait diversity varies through space and time by comparing three Late Devonian fish communities -- a tropical reef (Gogo, Australia), a tropical estuary (Miguasha, Canada), and a temperate freshwater system (Canowindra, Australia) -- with six modern communities from diverse habitats. Trait-space metrics reflecting within-community diversity (functional richness) and species similarity (functional nearest-neighbour distance) indicated Late Devonian communities had scores similar to modern communities. However, they were less functionally rich than their closest modern analogues, and their species tended to be more functionally distinct from one another. Metrics describing location in trait space (centroid distances and hypervolume overlap) showed modern communities were similar to each other, Gogo and Miguasha were similar but distinct from modern communities, and Canowindra was distinct from all others. This pattern suggests period-associated differentiation and substantial heterogeneity among some Late Devonian communities. In addition to temporal changes, we found consistent differences associated with habitat type and climate zone. Reef and tropical communities were the most functionally rich, whereas functional nearest-neighbour scores were highest in estuarine and temperate communities. These results indicate fish community trait space varies with time, habitat and climate, suggesting (i) lability in fish trait space and (ii) that evolutionary history, environmental filtering, and stochasticity influence community assembly.

evolutionary biology↗

bioRxiv2022

Predicting predator-prey interactions in terrestrial endotherms using random forest

Species interactions play a fundamental role in ecosystems. However, few ecological communities have complete data describing such interactions, which is an obstacle to understanding how ecosystems function and respond to perturbations. Because it is often impractical to collect empirical data for all interactions in a community, various methods have been developed to infer interactions. Machine learning is increasingly being used for making interaction predictions, with random forest being one of the most frequently used of these methods. However, performance of random forest in inferring predator-prey interactions in terrestrial vertebrates and its sensitivity to training data quality remain untested. We examined predator-prey interactions in two diverse, primarily terrestrial vertebrate classes: birds and mammals. Combining data from a global interaction dataset and a specific community (Simpson Desert, Australia), we tested how well random forest predicted predator-prey interactions for mammals and birds using species ecomorphological and phylogenetic traits. We also tested how variation in training data quality--manipulated by removing records and switching interaction records to non-interactions--affected model performance. We found that random forest could predict predator-prey interactions for birds and mammals using ecomorphological or phylogenetic traits, correctly predicting up to 88% and 67% of interactions and non-interactions in the global and community-specific datasets, respectively. These predictions were accurate even when there were no records in the training data for focal species. In contrast, false non-interactions for focal predators in training data strongly degraded model performance. Our results demonstrate that random forest can identify predator-prey interactions for birds and mammals that have few or no interaction records. Furthermore, our study provides guidance on how to prepare training data to optimise machine-learning classifiers for predicting species interactions, which could help ecologists (i) address knowledge gaps and explore network-related questions in data-poor situations, and (ii) predict interactions for range-expanding species.

ecology↗

bioRxiv2020

Relative demographic susceptibility does not explain the extinction chronology of Sahul's megafauna

The causes of Sahuls megafauna extinctions remain uncertain, although multiple, interacting factors were likely responsible. To test hypotheses regarding plausible ecological mechanisms underlying these extinctions, we constructed the first stochastic, age-structured models for 13 extinct megafauna species from five functional/taxonomic groups, as well as 8 extant species within these groups for comparison. Perturbing specific demographic rates individually, we tested which species were more demographically susceptible to extinction, and then compared these relative sensitivities to the fossil-derived extinction chronology. Here we show that the macropodiformes were the most resilient to extinction, followed by carnivores, monotremes, vombatiform herbivores, and large birds. Five of the eight extant species were as or more susceptible than were the extinct species. There was no clear relationship between extinction susceptibility and the extinction chronology for any perturbation scenario, but body mass and generation length explained much of the variation in relative risk. Our models reveal that the actual mechanisms leading to extinction were unlikely related to variation in demographic susceptibility per se, but were driven instead by finer-scale variation in climate change and/or human prey choice and relative hunting success.

ecology↗

bioRxiv2020

Global gut content data synthesis and phylogeny delineate reef fish trophic guilds

The diversity of life on our planet has produced a remarkable variety of biological traits that characterize different species. Such traits are widely employed instead of taxonomy to increase our understanding of biodiversity and ecosystem functioning. However, for species trophic niches, one of the most critical aspects of organismal ecology, a paucity of empirical information has led to inconsistent definitions of trophic guilds based on expert opinion. Using coral reef fishes as a model, we show that experts often disagree on the assignment of trophic guilds for the same species. Even when broad categories are assigned, 60% of the evaluated trait schemes disagree on the attribution of trophic categories for at least 20% of the species. This disagreement greatly hampers comparability across studies. Here, we introduce a quantitative, unbiased, and fully reproducible framework to define species trophic guilds based on empirical data. First, we synthesize data from community-wide visual gut content analysis of tropical coral reef fishes, resulting in trophic information from 13,961 individuals belonging to 615 reef fish species across all ocean basins. We then use network analysis to cluster the resulting global bipartite food web into distinct trophic guilds, resulting in eight trophic guilds, and employ a Bayesian phylogenetic model to predict trophic guilds based on phylogeny and maximum body size. Our model achieved a misclassification error of 5%, indicating that our approach results in a quantitative and reproducible trophic categorization scheme, which can be updated as new information becomes available. Although our case study is for reef fishes, the most diverse vertebrate consumer group, our approach can be applied to other organismal groups to advance reproducibility in trait-based ecology. As such, our work provides an empirical and conceptual advancement for trait-based ecology and a viable approach to monitor ecosystem functioning in our changing world.

ecology↗