Social evolution in Ceratina bees: a comparative approach

Project Information

Ceratina

Grant agreement ID: 893244

DOI

10.3030/893244

Project closed

EC signature date 5 March 2020

Start date 1 November 2020

End date 31 October 2023

Funded under

• EXCELLENT SCIENCE - Marie Skłodowska-Curie Actions

Total cost

€ 233 434,56

EU contribution

€ 233 434,56

Coordinated by

MARTIN-LUTHER-UNIVERSITAT HALLE-WITTENBERG
Germany

Periodic Reporting for period 2 - Ceratina (Social evolution in Ceratina bees: a comparative approach)

Reporting period: 2022-11-01 to 2023-10-31

Summary of the context and overall objectives of the project

Social insects have commonly high abundances and an impressive role in ecosystems. For example, ants are key predators in many ecosystems and bees provide important pollination services. Moreover, social insects have always fascinated biologists by the complexity of their behaviour, division of labour and interactions between colony members. Behaviour of workers, which resign to own reproduction but help increase reproduction of queen is a challenge for evolutionary theories since Darwin and therefore the evolution of social behaviour is one of the key topics of evolutionary biology.
The most impressive are large societies, however, for studying the origin of sociality insects forming small societies and optimally facultative social species are better, where it is possible to compare different strategies between solitary and social strategies within one population. Ceratina bees are excellent model taxa for studying the origin of social behaviour and also the evolution of different types of parental behaviour. This genus have worldwide distribution and there are almost 400 species in the world. Traditionally they were considered as solitary, but there is growing evidence that most species are facultatively social with the ability of forming two female nests. Moreover, in several species not only females but also males in nest duration phase of provisioning brood cells can be present and parental care is generally very diverse.
The goal of this project is to perform a comparative analysis of behaviour of multiple species of Ceratina bees and infer evolution of social and parental behaviour from this analysis. The first step for this is to perform high resolution molecular phylogeny (based on ultraconservative elements), which is a prerequisite for the interpretation of evolution. The next goal is to collect natural history data about Ceratina nests, from which it is possible to infer social and parental strategies of the studied species. The last goal is to study within nest relatedness between colony members of facultative social species. Relatedness is supposed to be a key parameter influencing the origin of cooperation between individuals of the same species. The combination of all three goals together can uncover the evolution of sociality in Ceratina bees.
This project is mainly basic research, which is important mainly for better understanding nature, especially the evolution of cooperative behaviour. However, knowledge about Ceratina bees can be important for human society also in multiple ways. Firstly, there exist some parallels between animal and human behaviour and especially bees are similar behaviourally to humans more than many other organisms, e.g. by forming family-like structures. Behaviour of animals can do some mirror to human behaviour and therefore studying animal behaviour can be also beneficial for understanding ourselves. Moreover, results of this research can also have a positive impact on nature conservation. For effectively protecting species, knowledge about natural history is very helpful. Therefore, collecting natural history data about Ceratina species can help with their effective conservation.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

During my project, I worked firstly in molecular phylogeny and historical biogeography of the genus. I used ultraconservative elements (UCE) as markers for phylogeny. I have already sequences of about 1900 loci of ultraconservative elements for more than 150 Ceratina species. This allows to perform high resolution phylogeny which contains all main lineages of Ceratina bees. Preliminary results show that the origin of Ceratina bees is probably in Africa with several colonizations of Indomalayan and Palearctic region, but only one colonization of the American continent. Also, monophyly of most of traditionally recognized subgenera is confirmed, with exception of Ceratina s.s. which is truly multiple independent lineages.
I gathered a large dataset of nesting biology of Ceratina bees – this dataset contains information about more than 16500 nests with information about the number of adults and offspring, from which we infer the social and parental strategy of species. I have relevant data (more than 40 nests per species) for 29 Ceratina species. These data confirm that most species are facultatively social, even in temperate regions, where it was supposed that solitary behaviour is prevailing. Moreover, males can be present in the nest. However, it seems that the role of males is different in different species – in some species, like C. nigrolabiata males are partners of the female and hope for mating with her. In other species, like C. chalybea, males are usually the sons of the female and maybe stay in the nest for obtaining food from their mother.
The third topic of my project is within nest relatedness of Ceratina bees. Relatedness is a key factor influencing benefits of sociality because for related individuals it is more often beneficial to supress their own reproduction in favour of other individuals. This feature is important for understand the origin of social behaviour. I studied several species of palearctic subgenus Euceratina where social nesting is present. There is variability in relatedness between females in all species – females can be full sister, mother and daughter(s) or unrelated females. However, only one female in the nest reproduces, other females have no direct fitness regardless of relatedness to adult female. Single mating prevails in all facultative social species, although mating of female with multiple males is also possible.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

uring the last period, I nearly completed the molecular phylogeny and continued to collect data on natural history and relatedness. Natural history information was gathered during field expeditions to tropical regions (Bangladesh and Guatemala) and Mediterranean locations (Greece, and Portugal). The obtained data included characteristics such as the proportion of social nests, biparental nests, the number of brood cells, and maternal protection strategies. The collected natural history data were analyzed, revealing key factors influencing the evolution of sociality in Ceratina bees. The connection between natural history data, relatedness, and their interpretation in light of phylogeny will soon lead to the identification of crucial factors. Although only a portion of the project results has been published so far, the gathered data will contribute to approximately eight more scientific publications.
While my research primarily focuses on fundamental aspects, it has indirect implications for efficient species conservation, emphasizing the importance of understanding their natural history. Educational activities undertaken during the project aimed to foster a stronger connection to and understanding of nature, contributing to its protection. Furthermore, the intricate behavior of Ceratina bees presents parallels to human societal behavior, adding depth to the study's broader implications.

Nesting cycle of Ceratina nees

Social nest of Ceratina cypriaca