Marta Rueda

Research Highlight: Korejs, K., Hořák, D., Krystof, C., Sedlacek, O., Motombi, F., Ewome, F., Molua, L., Tache, J., Kamga, S., Christopher, J. & Riegert, J. (2026). Megafaunal engineering in the tropical rainforest: African forest elephants ( Loxodonta cyclotis ) reduce avian species richness but elevate functional diversity. Journal of Animal Ecology , https://doi.org/10.1111/1365‐2656.70369 . Elephants are major ecosystem engineers, but their effects on animal communities may be more complex than expected. A 4‐year study on Mount Cameroon found that grazing by African forest elephants ( Loxodonta cyclotis ) reduced avian species richness to levels comparable with those in forest degraded by human activity. Yet, unlike human‐driven degradation, elephant grazing did not promote the replacement of forest‐specialist birds by open‐habitat generalists. Instead, it shifted communities towards understorey and terrestrial invertivores at the cost of large frugivores. Despite lower species richness, elephant‐grazed forests showed higher functional diversity but lower functional redundancy than undisturbed forest, suggesting a change in community composition rather than simple ecological impoverishment. These findings show that the ecological signature of megaherbivore‐driven disturbance differs fundamentally from anthropogenic disturbance, and that species richness alone may not adequately capture the ecological role and conservation value of large herbivores.

Summary: Maintaining ecological stability is essential for sustaining ecosystem functions and the benefits they provide to society. Ecological theory predicts that plant diversity destabilizes local populations, yet empirical studies report variable effects. We hypothesize that this discrepancy arises at least in part from differences captured by different diversity (average vs cumulative richness, i.e. the mean annual richness vs the cumulative richness across years) and stability metrics (abundance‐unweighted vs weighted mean population stability). To test this, we analyzed data from > 8000 permanent vegetation plots across biomes on five continents. We found a negative (i.e. destabilizing) diversity–stability relationship when using abundance‐weighted rather than unweighted measures of population stability, which are more influenced by dominant species. Similarly, cumulative richness – capturing total species occurrence over time and long‐term turnover – reveals a stronger destabilizing effect compared to average annual richness. Our findings reveal that, when specific metrics of diversity and stability are considered, more species and potentially the associated increase in interspecific competition tend to destabilize populations across natural ecosystems world‐wide – particularly those of dominant species.

Life on Earth is a mosaic distributed across biogeographical regions. Their regional species pools have experienced distinct historical and eco-evolutionary pressures, leading to an expected context-dependent organization of biodiversity. Here we identify a general spatial organization within biogeographical regions of terrestrial and marine vertebrates, invertebrates and plants (more than 30,000 species). We detect seven types of areas in these biogeographical regions that reflect unique combinations of four fundamental aspects of biodiversity (species richness, range size, endemicity and biogeographical transitions). These areas form ordered layers from the core to the transition zones of the biogeographical regions, reflecting gradients in the biodiversity aspects, experiencing distinct environmental conditions, and exhibiting taxonomic dissimilarities due to nestedness. These findings suggest this ubiquitous organization is mainly driven by the action of two complementary environmental filters, one acting on species from regional hotspots and the other on species from permeable biogeographical boundaries. The influence of these regional filters extends across spatial scales and shapes global patterns of species richness. Regional biodiversity follows a universal core-to-transition organization governed by general forces operating across the tree of life and space.

Experimental evidence indicates that more diverse communities sustain higher levels of ecosystem functioning. Generally, bottom-up processes accounting for community selection and complementarity effects on biodiversity are used to explain biodiversity effects on ecosystem functioning. However, top-down macroecological processes can also influence the distribution of ecosystem functions across large environmental gradients and, importantly, biodiversity patterns. Here, we tested whether past climate instability, current climate, and climate-driven species abundance explain tree richness gradients, and therefore, determine the relationship between species richness and ecosystem functioning using 137,808 forest inventory plots across continental extents including forests of Canada, the US, and Mexico. Consistent with previous research, we found a positive monotonic relationship between species richness and biomass (measured as level stand basal area) across North American forests. However, structural equation models revealed that the indirect effect of past climate instability, current climate conditions, and climate-driven individuals’ abundance underlie species richness patterns and the positive covariation between species richness and biomass. The importance of top-down climatic processes varied from boreal to tropical regions, yet their significant effects were pervasive across all forest types, indicating that climate strongly modulates the strength of the relationships between species richness and basal area. Our results help to understand the assembly processes driving the ubiquitous positive monotonic relationship between species richness and basal area across continental extents. This knowledge, obtained from adopting a macroecological perspective, helps understanding biodiversity-functioning relationships, which are usually explained by mechanisms at the community level. Significance statement: More biodiverse communities sustain higher levels of ecosystem functions (BEF hypothesis). The role of biotic interactions among trees within ecological communities determining BEF has been widely studied, but it is not well known how past climatic variability, current climate, and species abundance determine BEF. Using 137,808 forest inventory plots across North American forests located in Canada, the US, and Mexico, we document a positive relationship between tree species richness and stand basal area. Detailed analysis revealed that the positive BEF relationship is underlined by a strong and indirect effect of past and current climate. Our results highlight the importance of top-down climate processes operating at macroecological scales to understand biodiversity-functioning relationships.

Ecologists have long documented that the world's biota is spatially organised in regions with boundaries shaped by processes acting on geological and evolutionary timescales. Although growing evidence suggests that historical human impact has been key in how biodiversity is currently assembled, its role as a driver of the geographical organisation of biodiversity remains unclear. Using non‐volant terrestrial mammals we set up a bioregionalization procedure focused on two datasets, one describing the current ranges of terrestrial mammals, and another describing their potential natural ranges in absence of historic anthropogenic land use. We then quantified the relative importance of anthropogenic land use (5000 and 2000 years ago, and present time) to predict the current and natural biogeographical regions across the Earth. In general, past and present human land use were important predictors of current bioregions but did not largely contribute to predict natural bioregions. Past anthropogenic land use seems to have left an imprint on the taxonomic differentiation of some of the largest biogeographical realms, whereas land use at present stands out as a driver of the taxonomic differences between medium‐sized subregions, i.e. within and among continents. Our findings suggest that anthropogenic actions during the last millennia have had a far‐reaching effect on the spatial organisation of the Earth's non‐volant mammals.

Ecological theory posits that temporal stability patterns in plant populations are associated with differences in species' ecological strategies. However, empirical evidence is lacking about which traits, or trade-offs, underlie species stability, especially across different biomes. We compiled a worldwide collection of long-term permanent vegetation records (greater than 7000 plots from 78 datasets) from a large range of habitats which we combined with existing trait databases. We tested whether the observed inter-annual variability in species abundance (coefficient of variation) was related to multiple individual traits. We found that populations with greater leaf dry matter content and seed mass were more stable over time. Despite the variability explained by these traits being low, their effect was consistent across different datasets. Other traits played a significant, albeit weaker, role in species stability, and the inclusion of multi-variate axes or phylogeny did not substantially modify nor improve predictions. These results provide empirical evidence and highlight the relevance of specific ecological trade-offs, i.e. in different resource-use and dispersal strategies, for plant populations stability across multiple biomes. Further research is, however, necessary to integrate and evaluate the role of other specific traits, often not available in databases, and intraspecific trait variability in modulating species stability.

Summary: Ecological theory posits that temporal stability patterns in plant populations are associated with differences in species’ ecological strategies. However, empirical evidence is lacking about which traits, or trade-offs, underlie species stability, specially across different ecosystems. To address this, we compiled a global collection of long-term permanent vegetation records (>7000 plots from 78 datasets) from a wide range of habitats and combined this with existing trait databases. We tested whether the observed inter-annual variability in species abundance (coefficient of variation) was related to multiple individual traits and multivariate axes of trait variations (PCoA axes). We found that species with greater leaf dry matter content and seed mass were consistently more stable over time (lower variability in species abundance) although other leaf traits played a significant role as well, albeit weaker. Using multivariate axes did not improve predictions by specific traits. Our results confirm existing theory, providing compelling empirical evidence on the importance of specific traits, which point at ecological trade-offs in different resource use and dispersal strategies, on the stability of plant populations worldwide.

Analysing temporal patterns in plant communities is extremely important to quantify the extent and the consequences of ecological changes, especially considering the current biodiversity crisis. Long‐term data collected through the regular sampling of permanent plots represent the most accurate resource to study ecological succession, analyse the stability of a community over time and understand the mechanisms driving vegetation change. We hereby present the LOng‐Term Vegetation Sampling (LOTVS) initiative, a global collection of vegetation time‐series derived from the regular monitoring of plant species in permanent plots. With 79 data sets from five continents and 7,789 vegetation time‐series monitored for at least 6 years and mostly on an annual basis, LOTVS possibly represents the largest collection of temporally fine‐grained vegetation time‐series derived from permanent plots and made accessible to the research community. As such, it has an outstanding potential to support innovative research in the fields of vegetation science, plant ecology and temporal ecology.

Analysing temporal patterns in plant communities is extremely important to quantify the extent and the consequences of ecological changes, especially considering the current biodiversity crisis. Long-term data collected through the regular sampling of permanent plots represent the most accurate resource to study ecological succession, analyse the stability of a community over time and understand the mechanisms driving vegetation change. We hereby present the LOng-Term Vegetation Sampling (LOTVS) initiative, a global collection of vegetation time-series derived from the regular monitoring of vascular plants in permanent plots. With 79 datasets from five continents and 7789 vegetation time-series monitored for at least six years and mostly on an annual basis, LOTVS possibly represents the largest collection of temporally fine-grained vegetation time-series derived from permanent plots and made accessible to the research community. As such, it has an outstanding potential to support innovative research in the fields of vegetation science, plant ecology and temporal ecology.