Evolution of sociality

Species have to navigate both the physical and social environment in order to survive and attain fitness benefits. Yet, in a changing environment, it may be difficult for species to adjust. Disturbances or perturbations may differentially affect a population’s ability to cope with this change, i.e., resilience. Biological systems, such as ecosystems and social systems, are often resilient. Thus, although individual components have disappeared, the system is able to recover. But how species can cope with the change is not clear. I am interested in getting a better understanding of social evolution and in identifying the mechanisms for species to cope with changing social environments.

An examination of the role played by key individuals in driving social instability in a cooperative small mammal

In group-living species, social structure and organization is present and important for the group to function. Yet, these may change over time. The role group members play in their social group is imperative to studying the extent to which groups are resilient and how the presence of key individuals could impact social instability and group dynamics. This research will identify key individuals and how they impact social stability and the extent to which groups are resilient to change in the small semifossorial degu, Octodon degus. This study will provide insight into a better understanding of social structure but will also identify the mechanisms for species to cope with changing environments.

This work is funded by FONDECYT postdoctorado 2022 and is in collaboration with Dr. Luis Ebensperger at the Pontificia Universidad Católica de Chile and Dr. Loren Hayes at the University of Tennessee at Chattanooga.

Effect of perturbations on individual- and group-level social dominance in monk parakeets

Social structures are dynamic over time due to changes in group membership or in relationship strengths, but the direction and magnitude of social changes are difficult to predict. In the Hobson lab, I studied how individual-level and group-level social dominance are affected by social change. We performed social manipulation experiments where we removed and subsequently reintroduced differently-ranked birds within captive monk parakeet social groups. We found that none of the removed birds could retake their previous rank position but that top-ranked focal birds showed a greater rank loss than middle/low-ranked birds (van der Marel et al. 2022a). Also, the group adjusted their group-level consensus as to where direct their aggression (social dominance patterns) differently dependent on the rank of the perturbed focal birds. The group bullied the reintroduced top-ranked focal bird, whereas the group directed their aggression randomly below themselves toward middle/low-ranked birds (van der Marel et al. 2022b). These results show that social history matters in monk parakeets, where birds pay attention to the social standing of their group members and respond accordingly to perturbations. Predicting the effect of perturbation events, and consequently, the identification of network resilience, may allow us to prevent future instability from emerging and reduce potential costs upon system collapses.

This work was carried out while I was a postdoc in Dr. Elizabeth Hobson’s lab at the University of Cincinnati. For some parakeet drama, check out UC grad student Claire O’Connell’s twitter thread about our 2022 field season.

Life history traits, social organisation and the drivers of sociality in invasive Barbary ground squirrel

Many social groups are formed by natal philopatry with the environment constraining levels of sociality. For example, diurnal rodents living in harsh environments can be social to avoid the costs of predation. I used the non-endemic population of the Barbary ground squirrel (Atlantoxerus getulus) on the arid island of Fuerteventura, Spain, as my study system to explore this idea. Barbary ground squirrels show potential for rapid population growth with a generation time of approximately one year, which may have contributed to their success to occupy their non-endemic range. They are social, as both males and females interact throughout the day, but they show sexual segregation of sleeping burrows (van der Marel et al. 2020). The constraints of living as a diurnal species in an arid environment and predation pressure are possible selective pressures explaining sociality in the non-endemic Barbary ground squirrel (van der Marel et al. 2019, 2021). This work advances our understanding of sociality in African ground squirrels, but also provides valuable insight into population growth and corresponding success of an introduced species, as non-endemic species provide a unique framework to study evolution of sociality and population biology over a relatively short timeframe.

This work was in collaboration with Dr. Jane Waterman at the University of Manitoba and Dr. Marta Lopez-Darias at IPNA-CSIC, Island Ecology and Evolutionary Research Group.

Individual behavioural variation

Individual differences in behaviour that are consistent across time or context, or personality, can have implications for an individual’s life. I studied personality in relation to 1) phenotypic plasticity in a migratory shorebird, red knots, 2) home range movements in female Columbian ground squirrels, 3) survival in Barbary ground squirrels, and 4) assortment and reproductive success in degus (in revision).