Mareike Kortmann

Amid widespread biodiversity loss and alarming rates of tropical deforestation, the potential of secondary forest succession in restoring β‐diversity is still widely unexplored. To investigate β‐diversity along naturally recovering forests, we collected the functionally diverse group of tiger moths (Erebidae: Arctiinae) with light traps in the Ecuadorian Chocó. Our plots ranged from active small‐scale agricultural lands over natural regrowth stages (1–38 years) to old‐growth forests. Along this gradient of increasing forest complexity, fundamental ecological theory predicts a rise in taxonomic (TBD), functional (FBD) and phylogenetic β‐diversity (PBD). We also predicted an increase in body size, insect mimicry and aposematism, as well as a decrease of brightness and wing loading in assemblages along the gradient. To test these predictions, we calculated sample coverage‐standardized TBD, FBD and PBD along Hill numbers. Community‐weighted means (CWM) and standardized effect sizes of mean functional (ses.MFD) as well as phylogenetic distances (ses.MPD) were calculated to quantify functional and phylogenetic differences among species and communities. TBD and FBD showed non‐linear responses with peaks in late recovery forests, with the effect restricted to rare species in FBD but evident for both rare and common species in TBD. In contrast, PBD declined linearly along the gradient only for rare species. While body size and aposematism responded as predicted, communities significantly decreased in mimicry and increased in wing loading along the gradient, contrary to our expectations. The decreasing ses.MFD along the gradient suggests increasing habitat filtering towards old‐growth forests. Our study indicates that secondary forests can recover functional traits relatively quickly, while old‐growth forests retain more stable and specialized communities, highlighting their continued importance for conservation.

Insects make up the majority of all animal species, with 70% occurring in the tropics ¹ , yet the impacts of warming on tropical insects remain highly uncertain ² . This stems from sparse, taxonomically biased data on thermal tolerance of tropical insects and an incomplete understanding of the underlying physiological mechanisms ³ . Here we compared environmental temperatures with field-measured upper and lower thermal tolerance limits of around 2,300 insect species along Afrotropical and Neotropical elevational gradients and identified genomic signatures of thermal tolerance across the insect tree of life. We show that thermal tolerances do not proportionally track environmental temperatures but approach an asymptote in tropical lowlands. Insects at high elevations utilize plasticity to cope with rising temperatures, whereas lowland species have limited plastic abilities. Heat tolerance showed strong differences among insect orders and families, reflected in the thermal stability of proteins, suggesting that variation in thermal tolerance is founded in the fundamental protein architecture. Up to 52% of future surface temperatures and 38% of air temperatures in the Amazonian lowlands can cause heat mortality in half of the studied community. Our data suggest a limited capacity of insects in the Earth’s most biodiverse regions to buffer future warming.

Conserving the remaining primary forests and restoring forests on former agricultural lands are two key strategies to conserve biodiversity in the tropics. Natural regrowth of forest following the abandonment of agricultural land use is one way of forest restoration and thus, it is important to understand how biodiversity shifts with ongoing recovery and whether communities become more similar over time to those in old‐growth forests. We studied patterns of taxonomic, functional and phylogenetic diversity as well as community composition of Saturniidae, as one of the most conspicuous and well‐studied families of moths. Our study covered a forest recovery gradient from active agriculture via early and advanced stages of regrowth to old‐growth rainforests in the lowland Chocó region of Ecuador. Saturniidae diversity patterns did not follow the hypothesized increase from agriculture to old‐growth forest, but instead, the highest taxonomic and functional diversity was found in early regrowth, and the highest phylogenetic diversity in active agriculture. Diversity differences along the forest recovery gradient were overall weak and occurred mainly when focusing on common and dominant species, but community composition showed a gradual turnover with the strongest differences between old‐growth forest and active agriculture. Our results show that diverse Saturniidae communities are found in naturally recovering tropical forests. But although Saturniidae have been recommended as indicator species due to their well‐documented taxonomy, our results suggest that they are not well suited as indicators of forest recovery. Nevertheless, due to their striking appearance, Saturniidae could serve as flagship species for the conservation of tropical forests.

Homogenisation caused by intensive land-use is one of the drivers of global biodiversity decline. However, the contribution of land-use intensity to insect diversity loss is still largely untested. Therefore, we compare the rate of species homogenisation of ~12.000 arthropod species (using Barcode Index Numbers) from 450 families, using distance-decay relationships. We study communities along an increasing local land-use intensity gradient from forests to managed grasslands, to arable lands and to settlements situated within near-natural, agricultural, and urban regional landscapes. Our approach for incidence data under consideration of incomplete samples identifies that grasslands harbour the most homogenous communities after taking frequency and species traits into account. In contrast, the most modified land-use types, settlements, and arable lands do not differ from forests, and showed the most heterogeneous communities between locations. Large- and low-mobility species communities are the most heterogeneous in space, but patterns are dependent on local land-use. Regional landscapes modify the community response to local land-use types: near-natural landscapes reduce homogenisation, while agricultural landscapes increase homogenisation. Based on our findings we recommend enhanced conservation efforts particularly in managed grasslands to reverse homogenisation, while settlements and arable lands could be considered more in arthropod community heterogenisation.

Macroclimate is a key driver of biodiversity, but habitat conditions can modulate the local microclimate by amplifying or buffering macroclimatic temperatures. The interplay between microclimatic modulation and macroclimatic temperature is crucial for shaping local biodiversity in a warming world, but remains poorly understood across life forms. We examined how macroclimate and microclimatic modulation jointly shape alpha diversity across eight taxonomic groups. We surveyed multi‐taxon biodiversity along gradients of macroclimate (elevation) and microclimatic modulation (habitat structure), focusing on soil bacteria, soil fungi, understory plants, ground‐dwelling arthropods, moths, flying insects, bats, and birds. We hypothesized that alpha diversity would increase with temperature at both macro‐ and microclimatic scales, with the strongest effects for immobile and ectothermic taxa, and that microclimatic effects would be more pronounced in thermally constrained (cold) macroclimates. Contrary to our expectations, micro‐ and macroclimatic effects were weakest for soil bacteria, soil fungi, and vascular plants, which responded more strongly to edaphic factors. Alpha diversity increased with macroclimatic temperature for arthropods, but not for the other groups. Effects of microclimatic amplification varied across taxa, with positive effects for flying insects and bats, but negative effects for soil bacteria and fungi. Interactive effects of microclimatic modulation and macroclimatic temperature on understory plants, ground‐dwelling arthropods, moths, and birds indicated that microclimate influenced diversity differently in warm versus cold macroclimates. However, we found both stronger (ground‐dwelling arthropods and moths) and weaker (understory plants and birds) positive effects of microclimatic amplification under cold compared to warm macroclimates. Our findings demonstrate that effects of microclimatic modulation on biodiversity depend on macroclimatic context and differ between taxa, and thus, both have to be considered when predicting climate‐change impacts on biodiversity. Conservation planning should account for potentially changing effects of microclimatic modulation under climate warming that might affect the role of climatic microrefugia within the landscape.

When biodiversity–stability relationships are assessed from temporal patterns of species (or species assemblages) biomass or other key variables, ecological stability is commonly quantified as the inverse of the coefficient of variation ( CV ) or its square. However, just as biodiversity cannot be fully characterized by a single value, the complexity of temporal stability/invariability cannot be completely captured by one metric, especially since CV is disproportionally sensitive to large data values. Ecologists now recognize that species diversity can be fully characterized by a continuum of Hill-number-based measures parametrized by a diversity order q ≥0, which determines the sensitivity of the measure to species abundance. Building on the intuitive concept that temporal stability can be quantified by the closeness between the data vector and the ideally maximally stable vector, we propose a continuum of information-based measures of temporal stability/invariability parameterized by an order q >0. This continuous parameter q determines the sensitivity of the measure to the magnitude of biomass or other ecosystem functions. By varying q , researchers can differentially weight small, medium, or large values in a time series, thereby disentangling their respective contributions to stability. Our framework unifies and generalizes classical measures: the case q =1 links to Shannon entropy, reflecting MacArthur’s 1955 stability concept; q =2 connects to the conventional CV -based measure. Unlike these traditional metrics, our approach explicitly accounts for the number of data values (i.e., time points), adjusting for time-series-length effects to enable fair and meaningful comparisons across datasets of varying lengths. We extend the framework to hierarchical structures by developing additive and multiplicative decompositions of stability in a metacommunity (or metapopulation) into alpha and beta components. The beta component can be further used to obtain measures that quantify (a)synchrony among communities (or populations). For q =2, the resulting (a)synchrony measure provides a mathematically rigorous, CV -based metric. The proposed measures are illustrated using 22-year biomass time series data from the Jena Experiment in Germany. We developed the R package iSTAY (information-based stability measures) and online tools for computation and visualization. Our measures are adaptable to other functions beyond biomass and are applicable in both temporal and spatial contexts. Open Research Statement: The original biomass data of the Jena Experiment, covering the years 2003 to 2023, can be retrieved from https://jexis.idiv.de/ddm/Data/ShowData/624 , while the 2024 data are available at https://jexis.idiv.de/ddm/Data/ShowData/695 . These datasets, along with the R code used in this study, are currently accessible on Github at https://github.com/AnneChao/MS_iSTAY for review purposes and will be archived on Zenodo upon journal acceptance.

Properly managing forests requires tools that offer up-to-date information on forest dynamics.

In recent years, climate change has caused an unprecedented wave of tree mortality across Europe, reshaping forest canopy cover and deadwood structures. Nevertheless, the effects of tree mortality on species‐rich groups, such as insects are still unclear, mainly because few replicated disturbance experiments exist and most studies focus on small taxonomic subsets of the species‐rich class of insects, both of which prevent generalization. To disentangle the effects of canopy cover and deadwood on total above‐ground insect diversity collected with Malaise traps, we experimentally applied different disturbance treatments in 11 commercial forests throughout Germany. We quantified taxonomic (TD) and phylogenetic diversity (PD) among 22,889 operational taxonomic units from 362 insect families along Hill numbers (q = 0, 1, 2) using metabarcoding, and standardized diversities by sample coverage as an objective measure of sample completeness. Our results showed a systematically lower sample coverage in canopy gaps compared with closed canopy forests, highlighting that the true diversity in open forest habitats is underestimated in bulk samples if sample coverage is not considered. Controlled for sample coverage, TD increased by up to 47% in canopy gaps with deadwood, compared with controls under closed canopy and without deadwood. The increase in TD was accompanied by a similar increase in PD only in rare species (q = 0), underlining the gain in evolutionary diverse communities of rare species, but redundancy in dominant species (q = 2). Synthesis and applications. Our experiment provides strong evidence for the importance of clustered tree mortality for comprehensive insect diversity in temperate forests and highlights the potential of forest management to enhance insect diversity in homogeneous commercial forests, particularly through the creation of canopy gaps and the retention of deadwood. Both mimic natural dynamics and can support rare species along with the ecosystem functions they may provide.

Identifying key drivers of insect diversity decline in the Anthropocene remains a major challenge in biodiversity research. Metabarcoding has rapidly gained popularity for species identification, yet the lack of abundance data complicates accurate diversity metrics like sample coverage-standardized species richness. Additionally, the vast number of taxa lacks a unified phylogeny or trait database. We introduce a new workflow for metabarcoding insect data that constructs a phylogenetic tree for most insect families, standardizes sample coverage and assesses both taxonomic and phylogenetic diversity along the Hill series. Applying this workflow to Central Europe, we analysed insect diversity from 400 families across a land-use gradient. Our results show that land-use intensity significantly affects sample coverage, highlighting the necessity of biodiversity standardization. Taxonomic diversity declined by 27–44% and phylogenetic diversity by 13–29% across 39 000 operational taxonomic units, with diversity decreasing from forests to agricultural areas. When focusing on rare species communities exhibited greater phylogenetic diversity loss than taxonomic diversity, whereas dominant species experienced smaller phylogenetic losses but more pronounced declines in taxonomic diversity. Our findings underscore the detrimental effects of agriculture on insect taxa and reveal a dramatic loss of phylogenetic diversity among rare species with potential consequences for ecosystem stability.