Gjoni, V., F. Altermatt, A. Garnier, et al. 2025. “Biodiversity Modulates the Cross-Community Scaling Relationship in Changing Environments.” Ecology Letters 28, no. 9: e70208. https://doi.org/10.1111/ele.70208.
In the author affiliations, for the corresponding author Vojsava Gjoni, the third and current affiliation “Institute for Marine Biological Resources and Biotechnology, National Research Council (CNR), Mazara del Vallo, Italy,” is missing.
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Trophic interactions can strongly influence metacommunity dynamics and patterns of biodiversity in spatially heterogeneous environments. Theory predicts that herbivory facilitates plant species coexistence at small scales by reducing extinctions and promoting colonisations but reduces diversity at larger scales by promoting dominance of herbivore-resistant species. We examined how mammalian herbivory interacts with habitat size and connectivity to affect plant diversity in a unique, naturally fragmented grassland metacommunity system located in Southern Finland. We found that herbivory increased plant diversity across scales of measurement. In addition, herbivory reversed the diversity–area relationship such that there was a positive diversity–area relationship in grazed grasslands, but a negative relationship in ungrazed grasslands. Connectivity exhibited a unimodal relationship with diversity but did not interact with herbivory. Our empirical results demonstrate that herbivores can promote plant coexistence across scales and highlight the interplay between habitat area and trophic interactions in facilitating plant biodiversity in grassland metacommunities.
Landscape-scale ecological restoration is a key strategy for halting and reversing biodiversity decline. However, ensuring the long-term sustainability of restoration efforts requires guiding the recovery of complex ecological systems with many interdependent species at a landscape scale. Due to these challenges, our understanding of recovery trajectories remains limited. Using metacommunity models and experiments, we explore how the spatial configuration of communities and food-web complexity jointly influence species recovery at different spatial scales. We find that the number and spatial placement of communities affect the colonisation of empty habitat patches, but do not influence population recovery in patches where communities are introduced. Food-web complexity reduces the recovery of lower trophic levels. However, this negative effect may be partially mitigated at higher levels of food-web complexity. Our results demonstrate that the joint consideration of spatial configuration and species interactions could enhance the effectiveness of restoration actions.
Debates over whether and how populations are regulated have recently shifted away from detecting and instead towards quantifying the strength of density dependence and its variation among systems. Yet, the degree of variation in density-dependent mortality and the factors driving this variation remain poorly understood. Here, we conducted a meta-analysis of 38 reef fish species across 56 studies, which yielded 147 estimates of intraspecific density-dependent mortality, primarily during early or small life stages. The magnitude of density-dependent mortality (the increase in the per capita mortality rate due to one fish per unit area of habitat) was surprisingly inconsistent both within and among species. Several factors emerged as drivers of variation. Predators amplified the negative effects of density, and density-dependent mortality was greater for species that typically colonize at low densities or achieve larger maximum sizes. However, even within a single species, the strength of density-dependent mortality varied dramatically—often by several orders of magnitude—and sometimes changed sign. This heterogeneity likely reflects multiple processes acting together, including environmental context (e.g., predator density or refuge availability), traits of the focal organism (e.g., size) and methodological differences (e.g., study design) among studies. Our results underscore the need for future efforts to quantify and report ancillary variables and strive to identify how much these factors contribute to population regulation.
Climate change-amplified extreme weather events are reshaping ecological communities globally. On coral reefs, heatwaves typically disrupt the obligate coral–algal symbiosis, with symbiont identity a prime determinant of coral resilience to these thermal extremes. Yet, whether heatwaves have long-term effects on coral symbioses remains unclear due to a lack of longitudinal symbiont data. Here, we report on a decadal coral symbiont survey (2013–2023), spanning the most prolonged tropical marine heatwave on record (2015–2016) and its aftermath. Concomitant with mass coral mortality, we document wholesale transformation of the symbiont assemblages in two coral species, the legacy of which was persistent for 7 years post heatwave. We also found evidence suggestive of a symbiont's local extinction, of local human disturbance impeding symbiont recovery, and of new coral recruits hosting symbiont assemblages distinct from survivors. Our study demonstrates heatwaves can have long-lasting impacts on symbioses raising concern for coral resilience to future heatwaves.
Understanding temporal variability and synchrony across biological hierarchical levels (from species to metacommunities) and ecosystems, and their underlying drivers, remains a fundamental ecological question. However, most studies are performed within an ecosystem, overlooking the complexity structuring natural high-level metacommunities across ecosystems. By applying theoretical frameworks of metacommunity variability with phytoplankton datasets across a pond–stream–lake continuum, we show that (i) temporal variability decreases from species to metacommunities, while synchrony exhibits complex hierarchical patterns and varies depending on spatial scales; (ii) temporal variability and synchrony are lower in streams than in ponds or the lake, and spatiotemporal community–environment relationships are stronger in the lake than in the ponds or streams. These patterns are strongly related to environmental fluctuations, dispersal and species diversity. Our study advances the theoretical and empirical understanding of how complex biological hierarchies and freshwater networks influence biotic variability and synchrony, providing valuable insights for aquatic biodiversity conservation.
Microbial communities are fundamental to host health, yet their assembly dynamics under environmental change remain poorly understood. We analysed individual-level host-microbe networks in the non-native wild black rats (Rattus rattus) across a land-use gradient in Madagascar. By applying a moving prevalence threshold, we distinguished between core and non-core microbes and compared the assembly drivers shaping their network structures. Non-core microbes formed fragmented, modular networks shaped mainly by heterogeneous selection, reflecting environmental filtering. In contrast, core microbes exhibited stable, less modular networks driven primarily by stochastic ecological drift. These distinct assembly processes persisted across thresholds, highlighting fundamental differences in microbial structuring. Land-use change significantly influenced the modular structure of non-core microbes but had minimal effects on core microbes, demonstrating the differential sensitivity of microbial groups to environmental variation. This study advances our understanding of host–microbe interactions and provides a framework for assessing microbiome assembly under anthropogenic change.
Predator-induced changes in prey traits can cascade through ecosystems to impact biogeochemical cycling and community structure. Whether these effects persist, amplify or diminish across prey generations remains uncertain. We tested for predator transgenerational effects using a 3-year common garden experiment in a terrestrial old-field ecosystem. Predator exposure was manipulated across two generations of four grasshopper herbivore prey populations, with measurements of ecosystem processes made alongside measurements of prey trait responses. We found predators had larger effects on plant community biomass, plant diversity and soil carbon accumulation in the second generation of predator exposure than in the first generation. Paired with trait data on the grasshoppers, we found this amplification of ecosystem effects corresponded with heightened antipredator behaviours in the second generation. Our results show that transgenerational behavioural plasticity can magnify predator-driven ecosystem impacts across generations, linking eco-evolutionary processes with ecosystem dynamics.
Exploitative interactions, such as predator–prey and host–parasite interactions, are ubiquitous in microbial communities. These interactions shape community density and composition, imposing strong selection on members to evolve countermeasures reducing the negative impacts of exploitation. Exploitative coevolution is often studied between species pairs in isolation, which may overestimate the strength and relevance of pairwise coevolution. Here we studied how community context influences coevolution between Pseudomonas fluorescens (exploited) and Variovorax sp. (exploiter). We evolved these species in pairwise coculture and embedded within a five-species community to investigate evolved changes in pairwise interactions. We found evidence for asymmetrical coevolution: Variovorax evolved more rapidly than Pseudomonas, leading to increased exploitation through time, while Pseudomonas evolved increased tolerance to Variovorax with a time lag. The pairwise coevolutionary dynamics were not affected by the presence of other community members. Understanding how coevolutionary patterns change with increasing community complexity can have important implications for community persistence and function.
Carryover effects broadly influence adult performance and population persistence. Although variation in developmental environments can have contrasting effects on survival and reproduction, current predictive models of vulnerability to environmental change typically ignore simultaneous changes in both fitness components. We tested how developmental temperatures shape survival and multiple aspects of reproduction in a plant-living insect (Enchenopa binotata treehoppers) and used population dynamic models to examine the cumulative impact of these complex effects on population growth. We show that elevated developmental temperatures increase adult fertility, offsetting reduced juvenile survival and potentially forestalling population declines following global warming. Moreover, pairing mates from different developmental temperatures exacerbated morphological mismatches between sexes, reducing mating success and sperm transfer. Our findings thereby provide novel evidence that thermal carryover effects can generate assortative mating and selection on adult reproductive morphology, in addition to shaping the relative importance of survival and reproduction for persistence in warming climates.
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