Biology subjects

De Wolf, K.

Publications and source records attributed to De Wolf, K..

5 recordsLinked to original sources

bioRxiv2026

Urbanization effects are trait-specific and city-dependent across a widespread spider's global range

Urban environments impose strong selective pressures through biotic and abiotic factors, driving changes in behavior, physiology, and morphology. Yet, responses vary across taxa and cities, and it remains unclear which traits respond consistently and what factors moderate this variation. We addressed these questions using the widespread European garden spider (Araneus diadematus) as a model, measuring size, color, and web-building traits along urban-rural transects in 22 cities across its distribution range. Using a meta-analytic framework, we assessed how city-specific characteristics influenced trait variation. Urbanization consistently reduced relative abdomen surface area, a proxy for body condition. Exploratory meta-regressions suggest that web-building response was predicted by temperature: compared to their non-urban surroundings, urban webs are larger in colder regions and smaller in warmer regions. In contrast, body size and abdomen brightness varied among cities without clear environmental predictors. These findings show that urbanization effects are trait- and context-dependent, likely influenced by local factors such as heat island intensity, microclimate, or prey availability. Linking within- and between-city variation will improve understanding of species phenotypic responses to urban environments.

ecology↗

bioRxiv2026

Morphological and thermoregulatory responses to urbanization in the European garden spider Araneus diadematus.

Urbanization creates novel environments that can drive phenotypic and behavioural responses, yet how multiple traits respond across spatial scales remains poorly understood. In particular, elevated ambient temperatures via the urban heat island effect may drive morphological and behavioural responses. We investigated body size, abdominal colouration, microhabitat use, behavioural thermoregulation and thermal offset relative to ambient air in the orb-weaving spider Araneus diadematus across rural-urban gradients in northern Belgium. Contrary to predictions from the temperature-size rule, body size increased with urbanization at large spatial scales, whereas size-corrected abdomen area--reflecting body condition and reproductive investment--declined with urbanization, with strongest support at local spatial scales. Abdominal colouration showed no response to urbanization despite evidence for both carotenoid-like pigments and melanin-associated structures. Nevertheless, body size and colouration covaried, with sites containing larger spiders tending to harbour darker individuals, whereas within sites larger individuals were slightly brighter than smaller conspecifics. Thermal responses showed little variation along the urbanization gradient. Retreats were consistently warmer than web hubs, and spiders maintained body temperatures above both their immediate microhabitat and ambient air. Only retreat-associated behavioural thermoregulation showed a weak decline with urbanization at local spatial scales. Our results reveal contrasting trait responses to urbanization across spatial scales and demonstrate that size-colour covariation can persist despite divergent responses of individual traits. These findings highlight the importance of considering multiple traits, their covariation and spatial scale to accurately understand and predict ecological responses of ectotherms to urban environments.

ecology↗

bioRxiv2024

Urban Cepaea nemoralis snails are less likely to have nematodes trapped within their shells

Urbanization is a major human-induced environmental change which can impact not only individual species, but also the way these species interact with each other. As a group, terrestrial molluscs interact frequently with a wide diversity of parasites, yet the way these interactions vary across space and in response to environmental pressures is poorly documented. In this study we leveraged a recently discovered defence mechanism, by which snails trap parasitic nematodes in their shells, to explore how snail-nematodes interactions may vary in response to city life. We examined shells from the generalist snail Cepaea nemoralis sampled in three urban areas in Belgium for trapped nematodes, and attempted to link this to urbanization and shell phenotypic traits. We found that even a small degree of urbanization led to large decreases in the rates of shell encapsulation, and that larger snails were more likely to contain trapped nematodes. However, we found no evidence that shell colour, which had been previously linked to immune function, was correlated to encapsulation rates. We discuss how between-population variation in encapsulation rates can result from urbanization-induced changes on the nematodes side, the snail side, or both, and suggest potential tests for future studies aiming to disentangle these mechanisms.

ecology↗

bioRxiv2023

Lack of abundant core virome in Culex mosquitoes from a temperate climate region despite a mosquito species-specific virome

In arthropod-associated microbial communities, insect-specific viruses (ISVs) are prevalent yet understudied due to limited infectivity outside their natural hosts. However, ISVs might play a crucial role in regulating mosquito populations and influencing arthropod-borne virus transmission. Some studies have indicated a core virome in mosquitoes consisting of mostly ISVs. Employing single mosquito metagenomics, we comprehensively profiled the virome of native and invasive mosquito species in Belgium. This approach allowed for accurate host species determination, prevalence assessment of viruses and Wolbachia, and the identification of novel viruses. Contrary to expectations, no abundant core virome was observed in Culex mosquitoes from Belgium. In that regard, we caution against rigidly defining mosquito core viromes and encourage nuanced interpretations of other studies. Nonetheless, our study identified 45 viruses of which 28 were novel, enriching our understanding of the mosquito virome and ISVs. We showed that the mosquito virome in this study is species-specific and less dependent on the location where mosquitoes from the same species reside. In addition, because Wolbachia has previously been observed to influence arbovirus transmission, we report the prevalence of Wolbachia in Belgian mosquitoes and the detection of several Wolbachia mobile genetic elements. The observed prevalence ranged from 83% to 92% in members from the Culex pipiens complex. ImportanceCulex pipiens mosquitoes are important vectors for arboviruses like West Nile virus and Usutu virus. Culex pipiens virome studies, and virome studies on mosquitoes from the Culex genus in general, are underrepresented in publications about the mosquito virome. To mitigate this, we sequenced the virome of 190 individual Culex and eight individual Aedes japonicus mosquitoes. We report the lack of a core virome in these mosquitoes from Belgium and caution the interpretation of other studies in this light. The discovery of new viruses in this study will aid our comprehension of ISVs and the mosquito virome in general in relation to mosquito physiology and mosquito population dynamics.

microbiology↗

bioRxiv2018

Evolution at two time frames: polymorphisms from an ancient singular divergence event fuel contemporary parallel evolution

When species occur in repeated ecologically distinct habitats across their range, adaptation may proceed surprisingly fast and result in parallel evolution. There is increasing evidence that such cases of rapid parallel evolution are fueled by standing genetic variation, but the origin of this genetic variation remains poorly understood. In Pogonus chalceus beetles, short- and long-winged ecotypes have diverged in response to contrasting hydrological regimes and can be repeatedly found along the Atlantic European coast. By analyzing genomic variation across the beetles distribution, we reveal that genomically widespread short-wing selected alleles evolved during a singular divergence event, estimated at ~0.19 Mya. The ancient and differentially selected alleles are currently polymorphic in all populations across the range, allowing for the fast evolution of one ecotype from a small number of random individuals, as low as 5 to 15, of the populations of the other ecotype. Our results suggest that cases of fast parallel ecological divergence might be the result of evolution at two different time frames: divergence in the past, followed by repeated selection on the divergently evolved alleles after admixture. We suggest that this mechanism may be common and potentially further driven by periods of geographic isolation imposed by large-scale environmental changes such as glacial cycles.

evolutionary biology↗