A biotrophic fungal infection of the great burnet Sanguisorba officinalis indirectly affects caterpillar performance of the endangered scarce large blue butterfly Phengaris teleius

Interactions between ecological communities of herbivores and microbes are commonly mediated by a shared plant. A tripartite interaction between a pathogenic fungus-host plant-herbivorous insect is an example of such mutual influences. In such a system a fungal pathogen commonly has a negative influence on the morphology and biochemistry of the host plant, with consequences for insect herbivore performance. Here we studied whether the biotrophic fbngus Podosphaera ferruginea, attacking the great burnet Sanguisorba officinalis, affects caterpillar performance of the endangered scarce large blue butterfly Phengaris teleius. Our results showed that the pathogenic ftmgus affected the number and size of inflorescences produced by food-plants and, more importantly, had in direct, plant-mediated effects on the abun dance, body mass and immune response of caterpillars. Specifically, we found the relationship between caterpillar abundance and variability in inflorescence size on a plant to be positive among healthy food-plants, and negative among infected food-plants. Caterpillars that fed on healthy food-plants were smaller than those that fed on infected food-plants in one studied season, while there was no such difference in the other season. We observed the relationship between caterpillar immune response and the proportion of infected great burnets within a habitat patch to be positive when caterpillars fed on healthy food-plants, and negative when caterpillars fed on infected food-plants. Our results suggest that this biotrophic fungal infection of the great burnet may impose a significant indirect influence on P. teleius caterpillar performance with potential consequences for the population dynamics and structure of this endangered butterfly.

Sexual dichromatism,size dimorphism,and microscale anatomy of white wing stripe in blue tits

Achromatic patches are a common element of plumage patterns in many bird species and there is growing body of evidence that in many avian taxa they can play a signaling role in mate choice.Although the blue tit Cyanistes caeruleus is a well-established model species in the studies on coloration,its white wing patch has never been examined in the context of sex-specific trait expression.In this exploratory study,we examined sexual size dimorphism and dichromatism of greater covert’s dots creating white wing patch and analyzed its correlations with current body condition and crown coloration—a trait with established role in sexual selection.Further,we qualitatively analyzed microstructural barb morphology underlying covert’s coloration.We found significant sexual dimorphism in the dot size independent of covert size and sexual dichromatism in both white dot and blue outer covert’s vane spectral characteristics.Internal structure of covert barbs within the white dot was similar to the one found in barbs from the blue part that is,with a medullary area consisting of dead keratinocytes containing channel-typeß-keratin spongy nanostructure and centrally located air cavities.However,it lacked melanosomes which was the main observed difference.Importantly,UV chroma of covert’s blue vane was positively correlated with crown UV chroma and current condition(the latter only in males),which should be a premise for further research on the signal function of the wing stripe.