Biology subjects

Sulc, M.

Publications and source records attributed to Sulc, M..

7 recordsLinked to original sources

bioRxiv2025

Conspecific brood parasitism in the barn swallow (Hirundo rustica)

Conspecific brood parasitism (CBP) has been reported in many altricial avian species, yet its prevalence and underlying behavioural mechanisms remain poorly understood. We studied CBP in the barn swallow (Hirundo rustica), a species in which conspecific brood parasitism has been reported. We conducted parentage analysis on 1945 barn swallow broods involving 7816 offspring. Samples were collected over 12 breeding seasons at 5 colonies/populations. Contrary to expectations, we identified only six cases of CBP (0.3 % of broods). By identifying all individuals involved, i.e. the parasitic females, the female hosts and the males that fathered the parasitic eggs, we determined these cases of CBP resulted most likely from either a failed nest take-over (three times), the disappearance of a female partner or a disruption caused by researchers while only one case could be interpreted as a result of females mixed reproductive tactic. Based on a review of the literature on CBP in seven other Hirundinidae, we conclude that the only reliable evidence for CBP comes from cliff swallows (Petrochelidon pyrrhonata). Studies on other species either failed to identify the parasitic females or do not present sufficient evidence supporting the occurrence of CBP. Several studies relied on the appearance of two eggs in a nest within 24 hours to conclude that CBP occurred. However, based on the parentage analysis, we show that CBP only occurred in one out of 11 such cases in our barn swallow data. Our findings highlight that CBP is rare in our barn swallow populations, and have been likely overestimated in other studies. We emphasize the importance of frequent nest checks and rigorous genetic validation in CBP research. Overall, our results challenge existing assumptions about the prevalence of CBP and provide insights into the behavioural mechanisms that lead to CBP, with ecological and evolutionary implications.

ecology↗

bioRxiv2025

Recent breeding experience improves egg ejection behaviour

Recognizing ones own eggs is crucial for birds, especially for hosts of brood parasites that must identify and reject different-looking parasitic eggs. While birds seem to possess a template image of their eggs, whether it is innate or learnt remains unclear. We addressed this question by experimentally inserting either artificial mimetic eggs (ME) or non-mimetic eggs (NME) into the nests of barn swallows (Hirundo rustica) during pre-laying stage. Our individually marked population allowed a unique comparison between naive first-time breeders and experienced females, as well as females with old (from a previous season) and recent (from the previous breeding attempt within the same season) experience allowing to investigate the role of memory. We found that both naive and experienced females ejected ME and NME at similar rates, indicating that the template image is neither innate nor learnt and does not play a primary role in egg recognition. Instead, our findings suggest that awareness of own egg-laying is the crucial mechanism at play, and may facilitate nest sanitation behaviour. Finally, we provide the first evidence that this mechanism improves with recent breeding experience. Future studies should investigate the role of non-visual factors that may modulate nest sanitation, such as endocrine regulation.

animal behavior and cognition↗

bioRxiv2024

Machine learning outcompetes human assessment in identifying eggs of a conspecific brood parasite

Avian brood parasitism provides an exceptional system for studying coevolution. While conspecific brood parasitism (CBP) is more common than interspecific parasitism, it is less studied due to the challenge of detecting parasitic eggs, which closely resemble those of the host. Although molecular genotyping can accurately detect CBP, its high cost has led researchers to explore egg appearance as a more accessible alternative. Barn swallows (Hirundo rustica) are considered conspecific brood parasites, but identifying parasitic eggs has traditionally relied on human visual assessment. Here, we used UV-visible photographs of non-parasitized barn swallow clutches and simulated parasitism to compare the accuracy of human assessment with automated methods. In two games, participants and models identified parasitic eggs from six or two options. While humans performed better than chance (72% and 87% accuracy), they still made significant errors. In contrast, the automated supervised model was far more reliable, achieving 95% and 97% accuracy. We think that the model outperformed humans due to its ability to analyse a broader range of visual information, including UV reflectance, which humans cannot perceive. We recommend using supervised models over human assessment for identifying conspecific parasitic eggs and highlight their potential to advance research on evolution of egg colouration.

zoology↗

bioRxiv2024

Secondary metabolites and their impact on symbiotic interactions in the ambrosia fungus Geosmithia eupagioceri

Ambrosia fungi colonize freshly dead trees, sequester nutrients, and serve as nutritional source for ambrosia beetles in exchange for dispersal. A key aspect of this symbiosis is the ability of fungi to colonize and dominate the wood around the beetle tunnels, forming a monospecific nutritional mycelium in the beetle gallery. Hypotheses for these dynamics include active beetle management, fungal inoculation priority, and the funguss chemical ecology facilitating resource capture and competition. The ecological role of allelochemicals produced by ambrosia fungi is unknown, although they may suppress microbes while being harmless to beetles, which has potential medical or food technology applications. This study presents a comprehensive analysis of secondary metabolites from the ambrosia fungus Geosmithia eupagioceri (Ascomycota: Hypocreales). Eight extracellular compounds were identified in vitro: 5-hydroxymethyl-2-furancarboxylic acid, 4-hydroxybenzoic acid, 2,3-dihydroxybenzoic acid, 3,4-dihydroxybenzoic acid, 4-hydroxyphenylacetic acid (4-HPA), 4-HPA methyl ester, tyrosol, and thymine. Most compounds show cross-taxon activity, suppressing the growth of bacteria, fungi, a nematode, and a mite. We have shown that often overlooked chemically simple compounds may have activities leading to increased fitness of beetle hosts, including previously unconsidered activity against mites and nematodes. For the first time, we point out that these compounds also have the previously unconsidered potential to modulate the physiology of their producer (by inducing symbiotic morphology by quorum sensing mechanisms), the beetle host and associated microbes through synergism. Furthermore, we have shown that the ambrosia fungi have biotechnological potential in the search for growth suppressors of microorganisms and invertebrates, not toxic to humans. IMPORTANCEBark and ambrosia beetles and their microbial symbionts play crucial roles in forest ecosystems by aiding in the decomposition of dead trees, nutrient cycling, and habitat creation. However, they can cause extensive damage to both natural and planted forests by killing trees. Our study has led to a fundamental shift in the understanding of interactions between beetle symbiotic fungi and the environment, mediated by secondary metabolites. Newly, we show that these substances can not only be antimicrobial but also suppress the growth of mites, nematodes, but also can modulate the physiology of the producer fungus and potentially the host beetle and associated microbes. Our study, although conducted on a relatively artificial system with the need for validation on other lineages of ambrosia fungi, suggests entirely new research directions in the understanding of bark beetle holobiont and ambrosia beetles.

microbiology↗

bioRxiv2020

Automatic identification of bird females using egg phenotype

O_LIIdentification of individuals greatly contributes to understanding animal ecology and evolution, and in many cases can only be achieved using expensive and invasive techniques. Advances in computing technology offer alternative cost-effective techniques which are less invasive and can discriminate between individuals based on visual and/or acoustic cues. Here, we employ human assessment and an automatic analytical approach to predict the identity of common cuckoo (Cuculus canorus) females based on the appearance of their eggs. The cuckoos secretive brood parasitic strategy makes studying its life history very challenging. Eggs were analysed using calibrated digital photography for quantifying spotting pattern, size and shape, and spectrometry for measuring colour. Cuckoo females were identified from genetic sampling of their nestlings, allowing us to determine the accuracy of human and automatic female assignment. Finally, we used a novel same-different approach that uses both genetic and phenotypic information to assign eggs that were not genetically analysed. C_LIO_LIOur results supported the constant egg-type hypothesis, showing that individual cuckoo females lay eggs with a relatively constant appearance and that eggs laid by different females differ more than eggs laid by the same female. The accuracy of unsupervised hierarchical clustering was comparable to assessments of experienced human observers. Supervised random forest analysis showed better results, with higher cluster accuracy. Same-different analysis was able to assign 22 of 87 unidentified cuckoo eggs to seven already known females. C_LIO_LIOur study showed that egg appearance on its own is not sufficient for identification of individual cuckoo females. We therefore advocate genetic analysis to be used for this purpose. However, supervised analytical methods reliably assigned a relatively high number of eggs without genetic data to their mothers which can be used in conjunction with genetic testing as a cost-effective method for increasing sample sizes for eggs where genetic samples could not be obtained. C_LI

ecology↗

bioRxiv2020

Fast and furious: host aggression modulates behaviour of brood parasites

Avian brood parasites pose a serious threat for hosts, substantially reducing their fitness which selects for the evolution of host defences. A classic example of a host frontline defence is mobbing which frequently includes contact attacking of brood parasites. Here, we investigated how the nest defence of a very aggressive great reed warbler (Acrocephalus arundinaceus) host influences the speed of egg-laying and egg-removing behaviour of its brood parasite - the common cuckoo (Cuculus canorus). We video-recorded 168 brood parasitic events at 102 active host nests and found that cuckoos avoided host mobbing in only 62% of cases. If hosts spotted the cuckoo at their nests, they almost always attacked it (in 91 of 104 cases), however, such attacks only rarely and temporarily prevented cuckoos from parasitizing (11 additional cases). When attacked, cuckoos parasitized host nests significantly faster and left them immediately. However, when not attacked, cuckoos frequently stayed at or near the nest suggesting that host aggression, rather than the risk of being spotted, influences the speed of brood parasitism in this species. Further, we found that cuckoos performed egg-removing behaviour in all parasitic events without regard to host aggression. As a result, cuckoos removed at least one egg during all brood parasitism events except those when an egg slipped from their beaks and fell back into the nest (in 9 of 73 cases). This indicates that egg-removing behaviour is not costly for the common cuckoo and is an essential part of its parasitism strategy, widening understanding of this currently unexplained behaviour.

ecology↗

bioRxiv2019

Gliotoxin, identified from a screen of fungal metabolites, disrupts 7SK snRNP, releases P-TEFb and reverses HIV-1 latency

A leading pharmacological strategy towards HIV cure requires "shock" or activation of HIV gene expression in latently infected cells with Latency Reversal Agents (LRAs) followed by their subsequent clearance. In a screen for novel LRAs we used fungal secondary metabolites (extrolites) as a source of bio-active molecules. Using orthogonal mass spectrometry (MS) coupled to latency reversal bioassays, we identified gliotoxin (GTX) as a novel LRA. GTX significantly induced HIV-1 gene expression in latent ex vivo infected primary cells and in CD4+ T cells from all aviremic HIV-1+ participants. RNA sequencing identified 7SK RNA, the scaffold of the P-TEFb inhibitory 7SK snRNP complex to be significantly reduced upon GTX treatment of independent donor CD4+T cells. GTX disrupted 7SK snRNP, releasing active P-TEFb, which then phosphorylated RNA Pol II CTD, inducing HIV transcription. Our data highlight the power of combining a medium throughput bioassay, mycology and orthogonal mass spectrometry to identify novel potentially therapeutic compounds.

molecular biology↗