Biology subjects

Knop, E.

Publications and source records attributed to Knop, E..

6 recordsLinked to original sources

bioRxiv2026

The diel structure and robustness of plant-pollinator networks are driven by the shifting influences of plant traits

O_LISpecies interactions are increasingly recognised as temporally dynamic. For plant-pollinator networks, evidence shows that interactions vary not only seasonally but also over the diel cycle. However, we still know little about what determines their diel structure, whether this structure is important for robustness to species loss, and which plant traits are associated with the roles plants play in this structure. These gaps are fundamental, because knowing what shapes networks over the diel cycle is required to predict the effects of global change drivers, such as light pollution, that may shift the timing of interactions. C_LIO_LIUsing 22 plant-pollinator networks sampled over morning, afternoon, and night, we addressed these gaps by applying a multilayer framework to characterise their diel structure, link it to robustness, and test which plant traits are associated with plant roles across diel periods (participation, versatility) and within them (centrality). C_LIO_LIDiel structure was non-random: interactions were segregated among diel periods yet integrated through plants visited across the diel cycle. Networks were more robust to simulated species loss when interactions were on average more evenly distributed across periods and when plants were more strongly interconnected among periods, although this benefit diminished when both properties were high simultaneously. The association between plant traits and their roles shifted with the temporal scale. Across diel periods, structural traits were the stronger predictors: taller plants were visited more evenly across the diel cycle (higher participation), whereas shorter plants shared pollinators with plants from multiple periods (higher versatility), potentially mediating indirect effects among them. Within diel periods, floral visual cues became more influential, with achromatic contrast the most consistent predictor: at night, plants with brighter flowers were well visited within the period, sharing pollinators with other plants of that period (higher centrality). C_LIO_LIThese findings identify diel structure as a functional axis of network organisation and indicate that plant-pollinator networks are assembled hierarchically: structural traits set a baseline across the diel cycle, whereas light conditions determine which traits matter within periods, ultimately defining distinct temporal pathways vulnerable to global change. C_LI

ecology↗

bioRxiv2025

Butterflies Are Shrinking: Evidence from the Past Century

Climate change has had strong impacts on biodiversity, including well-documented shifts in the distributions and phenology of species. Reductions in body size represent a third pervasive biological response; it has garnered significantly less attention despite great ecological relevance. Theoretical frameworks-the temperature-size rule, Bergmanns rule, and Jamess rule-predict that warmer temperatures are associated with smaller body sizes in ectotherms. In contrast, empirical evidence concerning this pattern is mixed across both taxa and environments. In the present study, we applied computer vision techniques to historical data from two large butterfly museum collections, totaling 593 species across 10 terrestrial biomes over more than a century, in order to investigate long-term trends in butterfly body size. We measured forewing length through both manual image analyses and automated computer vision algorithms proxying body size and analyzed trends by using generalized additive models in order to consider a temporal, biome-specific pattern assessment. We have tested two hypotheses: that butterfly body size (1) declines over time, in conjunction with increasing ambient temperatures, in agreement with the temperature-size rule, and (2) its variation is more marked in warm, dry biomes. Results indicate a significant overall reduction in the body size of butterflies during the last century and that this reduction is indeed more pronounced in those biomes facing higher rises in temperature. These findings constitute large-scale evidence in support of the temperature-size rule and indicate a potential ecological impact of climate change on butterfly populations.

ecology↗

bioRxiv2025

Butterfly body size shrinkage: the impact of ecological traits across varied environments

Because of its close ties to numerous ecological and life history characteristics, body size is regarded as one of an organisms most important characteristics and is frequently considered a significant indicator of fitness. According to recent studies, ectotherms in particular, may see a reduction in body size with rising temperatures. How life history and ecological traits influence, however, shifts in butterfly body size in response to environmental changes, particularly focusing on the effects of temperature and land use is poorly studied. Using Generalized Additive Models (GAM), we analyzed forewing length data alongside various life history (phenology, overwintering developmental stage, voltinism, diet breadth, gender) and ecological traits (mobility, thermal tolerance) as well as environmental parameters for a period that lasts 110 years. Smaller body sizes were linked to early-season emergence and increasing forest cover, while larger sizes were linked to longer flight durations and later seasonal appearance. Males exhibited a pronounced decline in body size while females showed an opposite trend, suggesting sex-specific vulnerabilities to climate change. This research highlights the complex interplay between climate change, habitat fragmentation, and butterfly morphology, emphasizing the need for further investigation into sexual size dimorphism as anthropogenic influences continue to reshape butterfly populations.

ecology↗

bioRxiv2025

Climate-Driven Reshuffling of Butterfly Communities: Body Size Declines and Community Homogenization in a Rapidly Warming Switzerland

Climate change has been reshaping natural communities by driving species to change their ranges in response to warming temperatures. In Switzerland, the rate of warming since 1950 has approached nearly double the global average, making these impacts important for community composition and ecosystem function. Using the Community Weighted Length Index (CWLI) as the body size estimator, previously extracted by museum specimens, we studied two decades of butterfly community data that have been inventoried by the Biodiversity Monitoring Switzerland program. We checked for deviations from the expectation of random trends in the CWLI using null models. We modeled the long-term patterns at each site and the overall long-term patterns through linear regression and mixed-effects models alongside the model of the relationship between wing length, elevation, and abundance. CWLI of Swiss butterfly assemblages dropped by 5.2% over two decades, suggesting that warmer temperatures are differentially affecting large-bodied species. While CWLI trends were significantly declining at most sites (73%), a subset of sites (27%) showed trends of increasing CWLI, sometimes associated with cooler microclimates either in forests or at higher elevation. Our results further indicate a progressive homogenization of butterfly communities, marked by smoother CWLI slopes and reduced CWLI range over time. These results underline complex relations of climate-driven range shifts with body-size dynamics and community restructuring, emphasizing the importance of understanding the processes to mitigate biodiversity loss in thermally sensitive ecosystems.

ecology↗

bioRxiv2023

Do nocturnal pollinators carry a more conspecific pollen load than diurnal ones?

Plant-pollinator interactions are key for the reproduction of wild plants and for food security. However, the role nocturnal pollinators play in wild plant communities is not yet clear. Specifically, it has rarely been studied whether nocturnal pollinators are comparable to diurnal ones in the pollination services they deliver in plant communities. We tested whether nocturnal pollinators have the potential to provide higher pollination services than diurnal ones by carrying a more conspecific pollen load. We compared pollen loads carried by nocturnal and diurnal pollinators captured over 24-hour cycles in co-flowering plant communities in European ruderal meadows. Pollen load was less diverse at night, and the proportion of conspecific pollen carried by nocturnal pollinators was similar to or higher than that of diurnal ones. Thus, nocturnal pollinators do not only carry pollen but can remove and deposit conspecific pollen with a comparable or even superior performance to diurnal ones. Therefore, nocturnal pollinators can be more efficient pollination vectors than diurnal ones, which might compensate their lower pollen load.

ecology↗

bioRxiv2021

Matthew effect: common species become more common and rare ones become more rare in response to artificial light at night

Artificial light at night (ALAN) has been and still is rapidly spreading, and has become an important component of global change. Although numerous studies have tested its potential biological and ecological impacts on animals, fewer have tested its impacts on plants, and very few studies have tested whether it affects alien and native plants differently. Furthermore, common plant species, and particularly common alien species, are often found to benefit more from additional resources than rare native and rare alien species. Whether this is also the case with regard to increasing light due to ALAN is still unknown. Here, we tested how ALAN affects the performance of common and rare alien and native plants directly and indirectly via flying insects. We grew five common alien, six rare alien, five common native and four rare native plant species under four combinations of two ALAN (no ALAN vs ALAN) and two insect-exclusion (no exclusion vs exclusion) treatments, and compared their biomass production. We found that common plant species, irrespective of whether they are alien or native, produced significantly more biomass than rare species, particularly under ALAN. Furthermore, alien species tended to show a slightly stronger positive response to ALAN than native species (marginally significant origin x ALAN interaction, p = 0.079). Our study shows that common plant species benefited more from ALAN than rare ones. This might lead to shifts in plant diversity and vegetation composition, further propelling global biodiversity decline, when ALAN becomes more widespread. In addition, the slightly more positive response of alien species indicates that ALAN might increase the risk of alien plant invasions.

ecology↗