Neff, F., Chittaro, Y., Korner-Nievergelt, F., Litsios, G., Martínez-Núñez, C., Rey, E., & Knop, E. 2025. Contrasting 50-year trends of moth communities depending on elevation and species traits. Ecology Letters, 28, no. 8: e70195. https://doi.org/10.1111/ele.70195
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The Janzen-Connell Hypothesis posits that plant species diversity is maintained by a reduction in seedling survival near living conspecific trees relative to heterospecifics–known as negative conspecific density dependence (CDD). CDD facilitates coexistence if stronger than heterospecific density dependence (HDD). However, whether and how long CDD persists after trees die is unknown. In a three-year study across three forests, we monitored seedling survival near living and dead trees, both conspecific and heterospecific, across a seven-year chrono-sequence since tree death. CDD persisted for at least 5 years after tree death (‘legacy CDD’), and most species showed stronger CDD relative to HDD through time. We used our empirical findings to parametrize a theoretical community dynamics model. Our model suggests that both stabilising niche differences and fitness differences persist after tree death. While legacy CDD can facilitate coexistence, fitness differences often overwhelmed niche differences, making competitive exclusion the most likely outcome.
Dispersal syndromes based on traits assumed to be adaptations for specific dispersal mechanisms are routinely assigned to flowering plants. Using the colonisation record from a volcanic island formed in 1963, we assess whether dispersal syndromes predict which species establish on newly formed land. We evaluated the long-distance dispersal (LDD) syndromes of the 78 plant species using three European classification systems. Syndrome assignments were inconsistent between classifications (coinciding for ≤ 13% of species). Two systems showed no evidence that LDD syndromes conferred a colonisation advantage. The third classification suggested wind syndromes were favoured, but only assigned a minority of colonisers to LDD syndromes. ‘Unassisted’ species assumed to lack dispersal adaptations were dominant. However, empirical evidence supports endozoochory via aquatic birds for 62 colonisers. This suggests bird-dispersal is a major driver of colonisation for dry-fruited plants, and underscores the need for new approaches to plant dispersal that account for overlooked plant–animal interactions.
The cover image is based on the article Drying Spring Accelerates Transitions Toward Pyrogenic Vegetation in Eastern Boreal North America by Adam, Ahmed Ali et al., https://doi.org/10.1111/ele.70166
The Equilibrium Theory of Island Biogeography (ETIB) proposes that species richness on islands reflects a balance between extinctions and colonisations. However, ETIB assumes species neutrality, limiting predictions to species richness rather than types. Here, we integrate traits into equilibrium dynamics for 132 Australian islands' native floras sampled repeatedly over six decades. Our analysis shows that both species richness and community mean trait composition remain stable despite continuing turnover. We found evidence for traits being associated with both species' colonisation and extinction. Colonisations were faster for low-stature, small-seeded species, while extinctions were faster in species with low leaf mass per area and annual life history. Our results highlight that species equilibria on islands are maintained by species-specific turnover dynamics linked to traits. This trait dependence in colonisation and extinction helps explain how ecological communities assemble and why some species are more likely to occur on islands than others.
For nearly half a century, ecologists have sought to explain animal space use through characteristics of the environment (i.e., habitat). Recent evidence suggests animals also use memory of previous experiences to decide when and where to move. Yet, the relative influence of the two in explaining animal space use has not been resolved. Using six large ungulate species in the Rocky Mountains (USA), we evaluated the performance of a habitat selection model with 16 environmental variables and another with two variables representing previous use (i.e., memory). While memory outperformed the environment for two species and the environment outperformed memory for four species, the influence of memory and the environment was overall comparable. The environment best explained the space use of specialists, while memory best explained species with strong site fidelity. Our work challenges traditional habitat selection theory, showcasing that animals build their spatial preferences through experience just as much as merely responding to their environment.
The phenotypes of individuals within a population create a dynamic social environment that influences phenotypic selection and population growth. Fluctuations in the frequencies of these phenotypes can influence population mean fitness and the relative fitness of phenotypes, and thus impact both population dynamics and phenotypic evolution. Various theoretical frameworks have been used to study the impact of frequency dependence on ecological and evolutionary dynamics. However, their diversity and mathematical complexity have obscured the relationship between theoretical models and empirical work. To bridge this gap, we discuss the effects of frequency dependence on phenotypic selection and population growth from a statistical perspective. We classify frequency-dependent effects on fitness according to their additive, relative or multiplicative effects, and explore how their interaction with population density can affect the eco-evolutionary dynamics of continuous traits. We show how these different effects can be mapped onto the parameters of simple linear regression models and derive how their magnitude is expected to affect the population carrying capacity and equilibrium mean phenotype. We then use individual-based simulations to complement our analytical results and demonstrate that quantifying frequency-dependent effects on fitness is key for understanding how populations will respond to environmental change.
Agriculture is fundamentally dependent on biodiversity, yet unsustainable management practices increasingly threaten various organisms and ecosystem services. Confronting the global crisis of biodiversity loss requires a thorough understanding of the gaps, clusters and biases in existing knowledge across various management practices, spatial scales, and taxonomic groups. We undertook a comprehensive literature review, synthesising secondary data from 200 meta-analyses on agricultural management impacts on biodiversity in croplands. Our systematic map covers 1885 comparisons (mean effect sizes), from over 9000 primary studies. In the latter, seven high-income countries prevail (notably the USA, China and Brazil), with particular focus on fertiliser use, phytosanitary interventions and crop diversification. This emphasis on individual practices overshadows research at the farm and landscape levels. In secondary evidence, arthropods and microorganisms are most frequently studied, while annelids, vertebrates and plants are less represented. Evidence predominantly stems from averaged abundance data, revealing substantial gaps in studies on functional and phylogenetic diversity. Our findings highlight the need to analyse combinations of multiple practices to accurately reflect real-world farming contexts, and covering a wider range of taxa, biodiversity metrics and spatial levels, to enable evidence-based conservation strategies in agriculture. Given the uneven evidence on agricultural impacts, caution is required when applying meta-analytical findings to public policies and global assessments.
The island species–area relationship (ISAR) describes how larger islands support more species. ISARs of isolated oceanic archipelagos, assembled over millions of years, typically show positive relationships, steep slopes, and species richness equilibrium. However, it remains unclear how quickly such characteristics emerge. We compiled a dataset for fish communities of 79 postglacial peri-Alpine lakes and report an ISAR, formed de novo in less than 15,000 years, that partially mirrors older systems, but has an asymptotic shape. Immigration and speciation, the main ISAR drivers, are primarily associated with area and depth, respectively. Immigration increases with area, while speciation is promoted by greater depth, likely due to species depletion in the source pool and ecological constraints on speciation. This young ISAR has been reshaped by anthropogenic activities, with species introductions erasing its asymptotic shape. We demonstrate that ISARs can develop rapidly after insular habitat formation, offering insights into patterns of biodiversity assembly.
Ecological responses to climate extremes vary drastically in different spatiotemporal contexts. Here, we investigate how soil communities at high- and low-elevation sites respond to extreme heat events in different seasons (spring, summer and autumn). We simulated 1-week heat events based on site-specific climatic history in laboratory experiments using 360 field-collected soil cores and measured the resistance and recovery of two major groups of soil biota: Collembola and fungi. We found that Collembola communities from low elevations exhibited the lowest resistance to extreme heat in spring and summer, with full recovery occurring primarily in spring soils. Fungal communities remained generally stable, though pathogens increased their relative abundances following summer heat events. Network analysis revealed increased connectance of negative associations between Collembola and fungi in response to extreme heat. We provide experimental evidence for how heat events can restructure and destabilise ecological communities depending on spatiotemporal contexts like elevation and seasonality.
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