Biology subjects

Linke, D.

Publications and source records attributed to Linke, D..

9 recordsLinked to original sources

bioRxiv2026

Heated debate: Is the seasonal polyphenism of Araschnia levana (Lepidoptera: Nymphalidae) driven by thermoregulation?

The seasonal forms of the temperate butterfly Araschnia levana (Nymphalidae: Nymphalinae) differ in morphology (weight, wing area, and wing loading) and colouration. Spring individuals are predominantly orange with higher weight per wing area, (i.e. wing loading) while summer individuals are black with a white stripe and have lower wing loading. However, it remains unclear if and how these seasonal differences affect heating and cooling dynamics. We compared thermal responses of seasonal forms, focusing on the roles of morphology and colouration. Further, we assessed whether live butterflies heat and cool differently from dead individuals to detect the presence of active thermoregulation. Morphology and colouration influenced the thermal dynamics of the thorax and wings as expected from heat-transfer principles, but we found no evidence of active thermoregulation on the thorax. Based on aligned temperature curves, seasonal forms showed similar thermal dynamics. This similarity was driven by morphology and colouration, with larger wing area accelerating thermal change and higher body weight (or wing loading) reducing it, thereby masking underlying form-specific patterns. After accounting for significant morphological differences between forms, the thorax of spring individuals heated and cooled faster than that of summer ones. This trend suggests form-specific optimisation of thermal performance, likely as a response to temperate climates. Thermal responses differ between forms in ways not directly explained by the polyphenism itself, potentially reflecting a broader trait of multivoltine ectotherms to cope with seasonal temperature changes.

ecology↗

bioRxiv2025

Environmental Variation Promotes Convergent Evolution and Rapid Diversification of Wing Shape and Color in Skipper Butterflies

Predation is a key driver of speciation and phenotypic diversification, yet how antipredator traits evolve and persist over evolutionary time remains poorly understood. We generated target sequence capture and whole-genome sequencing data for the skipper butterfly subfamily Eudaminae (Hesperiidae) to test whether antipredator defenses, in interaction with environmental variation, promote diversification. We focus on two antipredation wing traits: hindwing tails, which deflect predator attacks, and blue-green coloration, which may enhance motion dazzle and be used as warning coloration. Applying phylogenomics, morphometrics, and comparative methods, we model trait evolution in relation to diel activity and geographic distribution and find that hindwing tails repeatedly evolved at least seven times and blue-green coloration at least fifteen times. Both traits are associated with elevated speciation rates, but evolutionary transitions toward tailless wings and non-iridescent coloration occurred more frequently than trait gains, indicating high evolutionary lability of these antipredator defenses. Trait loss, particularly pronounced in tropical diurnal species, may reflect trade-offs in flight performance, shifts in predation guilds, or the evolution of alternative defensive traits. Our findings highlight rampant convergent evolution of wing traits that are under strong predator-mediated selection. By identifying how antipredator defenses and environmental contexts influence phenotypic and species diversification, this study provides new insights into the ecological and evolutionary processes underlying insect diversity.

evolutionary biology↗

bioRxiv2025

Association of iridescence and tails with flight proxies suggests that predation drives convergence in skipper butterflies

1. Phenotypic evolution is shaped by phylogenetic, ecological and biomechanical constraints. Butterfly wings offer an ideal system to explore these constraints as their evolution is strongly influenced by natural and sexual selection affecting colour patterns and wing shape in relation to visual signalling and flight performance. 2. We focus on Eudamina skippers, butterflies with large-scale phenotypic convergences involving wing shape and colour pattern. Using a comprehensive morphometric dataset encompassing 176 species, we assess their morphological evolution in a phylogenetic framework. 3. We show that hindwing tails and dorsal iridescence, proposed to signal high escape ability, have repeatedly evolved in tropical species. Hindwing tails are associated with intermediate body size, low wing loading and a forewing shape that facilitates manoeuvrability; iridescence is more common in large species with significantly high wing loading and aspect ratio, indicating high flight speed and manoeuvrability. 4. The evolution of all tested morphometric traits is best described by Ornstein-Uhlenbeck models, indicating stabilising selection around fitness optima in Eudamina. Models testing for random drift or early burst dynamics were rejected in all cases. 5. We reveal a clear co-evolution between the fore- and hindwing shapes, despite both wings having different functional constraints. Hindwing tails have a significant recurrent effect on forewing shape in lineages evolving them independently, suggesting the existence of evolutionary trade-offs between flight performance and antipredator defences. 6. Our study shows that the convergent morphologies across Eudamina have likely arisen not by neutral evolution but by ecological selection influenced by biomechanical constraints.

evolutionary biology↗

bioRxiv2024

Quantifying the success of prey crypsis, aposematism and evasiveness in avoiding avian predators attack

Antipredator defences typically act at distinct stages of the predation sequence--encounter, identification, approach, and subjugation. However, their effectiveness has rarely been quantified and compared simultaneously in wild predator-prey systems. We conducted a study in Peru, where we installed aviaries at two localities and recorded the responses of wild avian predators to three types of antipredator defences--crypsis, aposematism, and evasiveness--expressed by three butterfly species. The study included both immature and adult birds from insectivorous species in forest and urban environments. We tested the theoretical expectations that cryptic butterflies (Nymphalidae: Euptychiina) were rarely detected, aposematic Heliconius (Nymphalidae: Heliconiinae) were often sighted but seldom attacked, and evasive Spicauda (Hesperiidae: Eudaminae) were frequently detected and attacked but evaded capture at higher rates. Despite these distinct defensive strategies, mortality rates among prey types were largely similar, but predator life stage strongly influenced defence effectiveness. Immature birds were more likely to attack Heliconius, possibly reflecting a lack of learned avoidance for aposematic signals. Additionally, predator family influenced predation patterns, with more skilled insectivores (e.g., Vireonidae) showing higher capture success against defended prey. These findings illuminate the evolutionary pressures that shape predator behaviour and prey defences in tropical ecosystems, where high predator diversity possibly maintains the coexistence of multiple defensive strategies. The observed similar mortality rates underscore the adaptive value of these defences, as they collectively distribute the total predation pressure across prey species.

ecology↗

bioRxiv2023

Reduced palatability, fast flight, and tails: Decoding the defence arsenal of Eudaminae skipper butterflies in a Neotropical locality

O_LIPrey often relies on multiple defences to avoid predators, such as difficulty of capture, attack deflection, or unpleasant taste. Eudaminae skipper butterflies rely on behavioural (fast flight) and mechanical defences (hindwing tails), but other defences like unpalatability (consumption deterrence), and the interaction among defences, have not been assessed. C_LIO_LIWe test the palatability of 12 abundant Eudaminae species from a Neotropical locality, using training and feeding experiments with domestic chicks. Further, we approximate the difficulty of capture explained by flight speed and quantified by wing loading. To test how multiple defences are associated and explained by body size and habitat preference, we perform phylogenetic Bayesian regression analyses. C_LIO_LIWe found a broad range of palatability in Eudaminae, within and among species. Palatability was negatively correlated with wing loading, indicating that butterflies with higher flight speed tend to have lower palatability. C_LIO_LIThe presence or absence of tails did not explain the level of butterfly palatability, showing that attack deflection and consumption deterrence are not mutually exclusive defences. Habitat preference (open or forested environments) did not explain the level of palatability in Eudaminae, but it seems that butterflies with high wing loading (fast flight) tended to occupy semi-closed (e.g., hilltops) or closed habitats (e.g., secondary forest). C_LIO_LIFinally, the level of unpalatability in Eudaminae is size dependent, larger butterflies are less palatable, perhaps due to their more likely detectability/preference by predators. Altogether, our findings shed light on the contexts favouring the prevalence of single vs. multiple defensive strategies in prey. C_LI

ecology↗

bioRxiv2023

Flight behaviour diverge more between seasonal forms than between species in Pieris butterflies

In flying animals, wing morphology is typically assumed to influence flight behaviours. Whether seasonal polymorphism behaviour might be associated with divergent fore wing shapes. Pieris individuals in the spring are small and have elongated fore wings, traits correlate with low fly speed and acceleration, and in butterfly morphology is linked to adaptive flight behaviour remains unresolved. Here we compare the flight behaviours and wing morphologies of the spring and summer forms of two closely related butterfly species, Pieris napi and P. rapae. We first quantify three-dimensional flight behaviour by reconstructing individual flight trajectories using stereoscopic high-speed videography in an experimental outdoor cage. We then measure wing size and shape, which are characteristics assumed to influence flight behaviours in butterflies. We show that seasonal, but not interspecific, differences in flight high flight curvature. Large summer individuals exhibit rounded fore wings, which correlate with high flight speed, acceleration, turning acceleration, and advance ratio. Our study provides quantitative evidence of different flight behaviours between seasonal forms of Pieris butterflies, and these differences were better predicted by body size and forewing shape, rather than other factors (e.g., species identity, ambient temperature). This points toward a possible adaptive role of seasonal morphology determining flight behaviours, although this needs to be thoroughly investigated to distinguish the effects of microhabitat (e.g., behavioural thermoregulation, resource distribution between seasons, such as nectar and larval food plants), predator and parasitoid pressure, and possible sexual behavioural differences.

animal behavior and cognition↗

bioRxiv2021

Streptococcus pyogenes forms serotype and local environment-dependent inter-species protein complexes

Streptococcus pyogenes is known to cause both mucosal and systemic infections in humans. In this study, we used a combination of quantitative and structural mass spectrometry techniques to determine the composition and structure of the interaction network formed between human plasma proteins and the surface of different S. pyogenes serotypes. Quantitative network analysis revealed that S. pyogenes form serotype-specific interaction networks that are highly dependent on the domain arrangement of the surface-attached M protein. Subsequent structural mass spectrometry analysis and computational modelling on one of the M proteins, M28 revealed that the network structure changes across different host microenvironments. We report that M28 binds secretory IgA via two separate binding sites with high affinity in saliva. During vascular leakage mimicked by increasing plasma concentrations in saliva, the binding of secretory IgA was replaced by binding of monomeric IgA and C4BP. This indicates that an upsurge of C4BP in the local microenvironment due to damage of the mucosal membrane drives binding of C4BP and monomeric IgA to M28. The results suggest that S. pyogenes has evolved to form microenvironment-dependent host-pathogen protein complexes to combat the human immune surveillance during both mucosal and systemic infections.

microbiology↗

bioRxiv2020

BamA and BamD are essential for the secretion of trimeric autotransporter adhesins

The BAM complex in Escherichia coli is composed of five proteins, BamA-E. BamA and BamD are essential for cell viability and are required for the assembly of {beta}-barrel outer membrane proteins. Consequently, BamA and BamD are indispensable for secretion via the classical autotransporter pathway (Type 5a secretion). In contrast, BamB, BamC and BamE are not required for the biogenesis of classical autotransporters. Recently, we demonstrated that TamA, a homologue of BamA, and its partner protein TamB, were required for efficient secretion of proteins via the classical autotransporter pathway. The trimeric autotransporters are a subset of the Type 5-secreted proteins. Unlike the classical autotransporters, they are composed of three identical polypeptide chains which must be assembled together to allow secretion of their cognate passenger domains. In contrast to the classical autotransporters, the role of the Bam and Tam complex components in the biogenesis of the trimeric autotransporters has not been investigated fully. Here, using the Salmonella enterica trimeric autotransporter SadA and the structurally similar YadA protein of Yersinia spp., we identify the importance of BamA and BamD in the biogenesis of the trimeric autotransporters and reveal that BamB, BamC, BamE, TamA and TamB are not required for secretion of functional passenger domain on the cell surface. ImportanceThe secretion of trimeric autotransporters (TAAs) has yet to be fully understood. Here we show that efficient secretion of TAAs requires the BamA and D proteins, but does not require BamB, C or E. In contrast to classical autotransporter secretion, neither trimeric autotransporter tested required TamA or B proteins to be functionally secreted.

microbiology↗

bioRxiv2019

Dynamic relocalization of the cytosolic type III secretion system components ensures specific protein secretion

Many bacterial pathogens use a type III secretion system (T3SS) to manipulate host cells. Protein secretion by the T3SS injectisome is activated upon contact to any host cell, and it has been unclear how premature secretion is prevented during infection. We found that in gastrointestinal pathogens, cytosolic injectisome components are temporarily released from the proximal interface of the injectisome at low external pH, preventing protein secretion in acidic environments, such as the stomach. In Yersinia enterocolitica, low external pH is detected in the periplasm and leads to a partial dissociation of the inner membrane injectisome component SctD, which in turn causes the dissociation of the cytosolic T3SS components. This effect is reversed upon restoration of neutral pH, allowing a fast activation of the T3SS at the native target regions within the host. These findings indicate that the cytosolic components form an adaptive regulatory interface, which regulates T3SS activity in response to environmental conditions.

microbiology↗