Research

Current Projects

Together with Jan Oettler, I lead CoRe (Cardiocondyla obscurior Research), an international collaborative effort to establish one ant as a model for the many questions about social life. My focus within CoRe and beyond lies in the study of ant development, plasticity and symbiosis, with recent projects summarized below. For an overview of all CoRE projects and collaborators, see https://cardiocondyla.org.

Social traits of developing ants

Ants develop in complex social environments where they interact with both adult nest members and other developing individuals. However, developing ants are often perceived as powerless and their social role within societies remains poorly understood. In Formica wood ants, larvae actively influence their own survival by engaging in egg cannibalism (Schultner et al. 2013), a prime example of selfish offspring behavior. Whether a larva engages in cannibalism depends on its own sex as well as its genetic relatedness to the egg (Schultner et al. 2014), which suggests that larvae are able to assess variation in their social environment. Indeed, variation in social environment influences the expression of sensory genes in larvae, including odorant receptors (Morandin et al. 2018, Pulliainen et al. 2022). By adjusting egg consumption behaviour to social environment, larvae may even be able to help defend the nest against social parasites (Pulliainen et al. 2019). These are just some of the cool things developing ants can do (for another example, see Pegnier et al. 2019) and there are many more ways that brood influence social processes in insect colonies (reviewed in Schultner et al. 2017, Schultner & Pulliainen 2020). By taking an approach focused on brood, we aim to shine new light on social evolution.

Caste determination and differentiation in ants

Individuals that share the same genes can follow different developmental pathways so that as adults, they differ in morphology, physiology and behaviour. Much of this variation is due to phenotypic plasticity, which allows organisms to express a range of phenotypes in response to variation in their intrinsic and extrinsic environment. Using the model ant Cardiocondyla obscurior, a species with two female castes (queens & workers) and two male morphs (winged & wingless males), we study the basis of differential caste and morph development. So far, we’ve found that that sex differentiation pathways have been co-opted to regulate differential caste and morph development (Klein et al. 2016). We also discovered that queens and workers can be distinguished across the entire course of development by caste-specific crystalline deposits visible in embryos and larvae, pointing towards maternal caste determination in this species (Schultner et al. 2023). Using this unique trait, we are now investigating caste-specific development and gene expression in embryos and attempting to identify potential maternal determinants of caste. 

Ants and their symbionts in a changing world

Understanding how organisms cope with environmental change is one of the most important challenges facing biologists. Predicting the effects of extreme environmental conditions is not straightforward because, in addition to genotype and abiotic factors, organisms are influenced by a multitude of biotic interactions, including those with their competitors, predators and microbial symbionts - who themselves are exposed to changing environmental conditions. The cosmopolitan ant Cardiocondyla obscurior is infected with two main endosymbionts: Candidatus Westeberhardia cardiocondylae (Klein et al. 2015) and Wolbachia (Ün et al. 2021). Populations from Brazil and Japan carry distinct Wolbachia strains, which differ in their infection titres and ability to manipulate host reproduction by inducing cytoplasmic incompatibility (Ün et al. 2021), as well as in their sensitivity to environmental stress (Ün et al. 2022). Currently we are focusing on understanding the functional relationship between the ant, its symbionts and the environment, with particular focus on the effects of stressors such as chemical pollution (Leponiemi et al. 2022) and extreme temperatures. We do this using a holobiome approach incorporating genomic, morphological, and behavioral data.