Biology subjects

Hesselberg, T.

Publications and source records attributed to Hesselberg, T..

3 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↗

bioRxiv2025

The herpetofauna of Despotiko Island (Cyclades, Greece)

The Aegean islands are a known hotspot for herpetofauna and have been extensively studied in this area. However, there are still numerous islands that lack this research. This includes the uninhabited islet of Despotiko found in the Paros archipelago, Cyclades. It is known for its importance in archaeology, which in turn attracts tourism. However, there is not yet a complete understanding on the presence of herpetofauna there, with the last published records written in 1977. In an effort to address this, a combination of past ad-hoc sightings and visual surveys were carried out during summer 2024. These yielded two new records of reptile species, Eryx jaculus and Lacerta citrovittata. Furthermore, the enclosed archaeological site had greater reptile diversity and richness than outside the site. This highlights the potential importance of the archaeological site as a key reptile habitat. Our findings help to improve our understanding of reptilian diversity in the archipelago, providing avenues for further research into the potential interactions between archaeological sites and reptile diversity.

ecology↗

bioRxiv2023

Functional convergence underground? The scale-dependency of community assembly processes in European cave spiders

Understanding how species assemble into communities is a central tenet in ecology. One of the most elusive questions is the relative contribution of environmental filtering versus limiting similarity. Important advances in this area have been achieved by looking at communities through a functional lens (i.e., the traits they express), so as to derive principles valid across species pools. Yet, even using traits in lieu of taxonomy, the issue remains controversial because i) environmental filtering and limiting similarity often act simultaneously in shaping communities; and ii) their effect is scale-dependent. We exploited the experimental arena offered by caves, island-like natural laboratories characterized by largely constant environmental gradients and a limited diversity of species and interactions. Leveraging uniquely available data on distribution and traits for European cave spiders, we tested explicit hypotheses about variations in community assembly rules across ecological gradients and scales. We demonstrate that environmental filtering and limiting similarity shape cave communities acting on trait evolution in opposing directions. These effects are strongly scale dependent, varying along multiple environmental gradients. Conversely, the effect of geography on trait composition is weak, indicating that trait turnover in space happens primarily by substitution of species pursuing similar functions due to strong environmental filters. Our findings reconcile contrasted views about the relative importance of the two main mechanisms shaping patterns of biodiversity, and provide a conceptual foundation to account for scaling effects in the study of community assembly.

ecology↗