Biology subjects

Witek, M.

Publications and source records attributed to Witek, M..

7 recordsLinked to original sources

bioRxiv2026

Isolation and introductions disrupt the homogeneity of Argentine ants in Europe.

The introduction of alien species into new habitats stands as a pressing economic and ecological challenge but it is also essential for unveiling evolutionary processes. The introduction of the Argentine ant (Linepithema humile) led to the spread of a single supercolony through different continents and thousands of kilometres like in Europe, from Northwest Spain to Greece. It was assumed that the high invasiveness of the species mainly relied on the lack of agonism among colonies, an effect derived from its introduction. However, recent studies suggest that local adaptations and evolutionary divergence could involve the disruption of the Argentine ant "empire" into a mosaic of competitive colonies. We investigated how isolation affects population divergence by comparing mainland and island populations in two distant regions colonized in Spain and in Greece with morphology, agonism, cuticular hydrocarbons, and genetic diversity of ant workers. Our results showed that all colonies sampled belonged to the most spread supercolony in Europe (main supercolony) except one sampled in Crete (Heraklion; Greece), which resulted to be a supercolony not registered in Europe. The Heraklian supercolony showed a different chemical and genetic profile and hostile agonism towards the other Greek colonies. Differences between islands and mainland colonies belonging to the main supercolony were higher in Galiza than in Greece. Surprisingly, the chemical profile of the Cretan colony belonging to the main supercolony showed more similarity with the Galizan colonies than with the Greek mainland, suggesting that L. humile may have been introduced into Greece through this island instead of the mainland. Our study suggests that local adaptations in Argentine ant colonies can trigger competition between colonies. Our data strongly support the existence of a candidate supercolony which highlights either ongoing introductions of L. humile in Europe or gaps in our understanding of its metapopulation dynamics.

evolutionary biology↗

bioRxiv2025

Ongoing coevolution between reintroduced Phengaris teleius butterflies and their Myrmica host ants

Coevolutionary interactions between parasites and hosts are key drivers of biological adaptation. In this study, we explore the evolutionary response of the social parasitic butterfly Phengaris teleius to its host ant, Myrmica scabrinodis, taking advantage of a unique opportunity: the reintroduction of the butterfly in the Netherlands thirty years ago. We compared the degree of host mimicry and behavioural performance of caterpillars between the reintroduced and the Polish source population. After about thirty generations, chemical and vibroacoustical signal profiles have diverged. Chemical mimicry remained limited during the pre-adoption phase for both groups; however, in the post-adoption phase, the source population showed significantly higher chemical similarity to their local hosts. In contrast, reintroduced pre-adoption caterpillars evolved vibroacoustic signals closely resembling local hosts, also resulting in a stronger response from their local host ants. This suggests that adoption is driven by acoustics and subsequently serves as a selective filter promoting post-entry chemical refinement. Behavioural data evince that despite the differences between the different communication channels, the combination of signals remains sufficient to ensure recognition and integration in both host-parasite systems. These results illustrate how social parasites involved in multisensory mimicry can rapidly recalibrate strategies to remain functional in new ecological contexts.

ecology↗

bioRxiv2025

Buzzed but not elated? Effect of ethanol on cognitive judgement bias in honeybees

Ethanol is a neuroactive compound known to alter cognition, behavior, and physiology in a diverse range of vertebrate and invertebrate animals. It is also naturally present in many environments and might exert ecology-shaping influence on various organisms, such as honeybees feeding on fermenting nectar. In this study, we tested whether exposure of honeybees to low ethanol concentrations (1%) induces pessimistic or optimistic cognitive judgment bias (CJB), an information processing pattern thought to be related to affective processes. Bees were trained in a classical olfactory conditioning paradigm and then presented with conditioned stimuli and ambiguous odor mixtures to assess changes in decision-making under uncertainty. We additionally measured locomotor performance and ethanol absorption via spectrophotometric analysis of hemolymph. Ethanol levels peaked rapidly and remained elevated throughout the testing period. Despite this, ethanol had no detectable effect on choices in the CJB assay or locomotor behavior. These findings suggest that acute exposure to low-dose ethanol does not induce affect-like changes in honeybees. Our study represents the first test of pharmacologically induced judgment bias in an invertebrate and contributes to understanding the resilience of insect cognition to natural neuroactive compounds. The results highlight the limits and potential of CJB paradigms for probing affect-like states across taxa and support the honeybee as a valuable model in comparative cognition and the behavioral ecology of neuroactive substance exposure.

animal behavior and cognition↗

bioRxiv2025

Complexity shapes uniqueness: Neuropil volumes and synaptic clusters shape behavioural plasticity under challenging environments in the invasive Argentine ants

Adaptation to new environments is key for organisms survival, but also for their invasiveness in their introduced areas. Behaviour is considered the fastest phenotype allowing adaptation, but its plasticity can involve costs as neural development. Although individuals investment in cognition was pointed out as unnecessary for colony behaviour in eusocial insects, recent studies are highlighting the behavioural dependence on neural traits in eusocial insects. The costs of producing behavioural and neural plastic offspring could exceed the investments of eusocial insects, in which one or certain reproductives must produce multiple offspring. Thus, we wanted to analyse the link between the neuroanatomy and the behavioural variability of Linepithema humile, an invasive species organised in supercolony units containing millions of individuals, to understand its adaptive mechanisms. We repeatedly tested same aged callow workers of L. humile in behavioural tests of increasing environmental complexity and analysed the volume of their brain functional areas (neuropils) and the synaptic clusters abundance in the mushroom body calices (information processing). Given the potential large cost of plasticity, we expected to find homogeneous interindividual neuronal structures and behavioural responses. Although L. humile is considered a monomorphic species, body size conditioned behavioural and neural traits and determined individuals efficiency in exploring simple environments. Contrary to our expectations, the increase in environmental complexity revealed the behavioural plasticity of Linepithema humile workers as well as its correlation with neuropil volumes and synaptic clusters. Our results highlight the relevance of the central complex and the mushroom bodies on exploration efficiency rather than optic and olfactory lobes. Behavioural plasticity under complex environments relied on the synaptic connections of the olfactory processing area (dense lip), while individuals with higher number of synaptic connections on the visual processing area (collar) explored complex environments less efficiently. Our results suggest that behavioural differences that correlate with morphological traits might promote adaptive mechanisms in simple environments, whereas neurologically based plastic behavior may be necessary to adapt in complex environments.

animal behavior and cognition↗

bioRxiv2024

Biotic challenges in the city: Dietary restrictions and body fat content of female sexuals in urban ant populations

Urban habitats represent an important challenge for many organisms. Besides the abiotic changes, urban habitats are also characterized by changes in the biotic conditions, such as a more uniform species composition and declining population sizes. For urban ants this can result in dietary shortages. In our study, we tested whether urban ant colonies might suffer from dietary restrictions by carrying out a common garden experiment in which ant colonies from urban and rural habitats were exposed to high carbohydrate, protein, and fat / protein diets. We also investigated the body fat content of individuals from both habitat types. Our findings suggest a lower availability of high-quality carbohydrates in urban areas. Additionally, while not statistically significant, rural colonies exhibited a tendency to consume greater quantities of proteins and fat compared to urban colonies. This trend was in line with a higher body fat content observed in female sexuals (gynes) from rural colonies. These results might indicate the outcome of an evolutionary feedback process in which ant colonies adapt to nutritional constraints in urban environments. They achieve this by minimizing the investment in gynes, which might require fewer reserves for survival during colony foundation due to reduced competition for nesting sites within urban green spaces.

ecology↗

bioRxiv2023

Dopamine dysregulation in Parkinson's disease flattens the pleasurable urge to move to musical rhythms

The pleasurable urge to move to music (PLUMM) elicits activity in motor and reward areas of the brain and is thought to be driven by predictive processes. Dopamine within motor and limbic cortico-striatal networks is implicated in the predictive processes underlying beat-based timing and music-induced pleasure, respectively. This suggests a central role of cortico-striatal dopamine in PLUMM. This study tested this hypothesis by comparing PLUMM in Parkinsons disease patients, healthy age-matched, and young controls. Participants listened to musical sequences with varying rhythmic and harmonic complexity (low, medium, high), and rated their experienced pleasure and urge to move to the rhythm. In line with previous results, healthy younger participants showed an inverted U-shaped relation between rhythmic complexity and ratings, with a preference for medium complexity rhythms, while age-matched controls showed a similar, but weaker, inverted U-shaped response. Conversely, PD patients showed a significantly flattened response for both the urge to move and pleasure. Crucially, this flattened response could not be attributed to differences in rhythm discrimination and did not reflect an overall decrease in ratings. Together, these results support the role of dopamine within cortico-striatal networks in the predictive processes that form the link between the perceptual processing of rhythmic patterns, and the affective and motor responses to rhythmic music.

neuroscience↗

bioRxiv2018

The sensation of groove is affected by the interaction of rhythmic and harmonic complexity

Groove is defined as the pleasurable desire to move to music. Research has shown that rhythmic complexity modulates the sensation of groove but how other musical features, such as harmony, influence groove is less clear. To address this, we asked people with a range of musical experience to rate stimuli that varied in both rhythmic and harmonic complexity. Rhythm showed an inverted U-shaped relationship with ratings of pleasure and wanting to move, whereas medium and low complexity chords were rated similarly. Pleasure mediated the effect of harmony on wanting to move and high complexity chords attenuated the effect of rhythm. While rhythmic complexity is the primary driver, harmony both modulates the effect of rhythm and makes a unique contribution via its effect on pleasure. These results may be accounted for by predictive processes based on rhythmic and harmonic expectancies that are known to contribute to musical pleasure or reward.

neuroscience↗