PD Dr. Stefan Jarau
My research interests deal with different aspects of the evolution, ecology, and behavioral physiology of social bees, with a strong emphasis on tropical and temperate zone corbiculate bees from the Apidae family. The current model organisms of our studies comprise a variety of stingless bee species (Meliponini), the western honey bee, Apis mellifera (Apini), and the buff-tailed bumble bee, Bombus terrestris (Bombini).
(For further reading see below picture gallery.)
Social insects play a prominent role in almost all terrestrial ecosystems. Some species are also of great economical importance, either as beneficial organisms (e.g., pollinators) or pest insects (e.g., invasive fire ants). The evolutionary success and the ecological importance of social insects are underlined by their huge biodiversity and biomass. Ever since Aristotle (and likely even before) mankind was wondering about social insects. Despite huge scientific efforts to understand their miraculous lives, many details about social insects remain to be elucidated.
The main purpose of my research is to better understand the evolution of social life strategies within the group of bees. For that purpose we study proximate mechanisms of key life aspects, which are indispensable for a (eu)social colony organization, in comparative studies including a variety of species with the aim to reach insights into their ultimate reasons.
In recent years I also got interested in the detrimental effects of anthropogenic changes in the environment on the behavior and survival of bees.
Specific lines of research
Foraging behavior, recruitment communication, and diversity of stingless bees
The species rich group of stingless bees, which live in tropical and subtropical regions around the globe, show a fascinating behavioral diversity in foraging strategies and recruitment mechanisms. We study recruitment communication in species that do not communicate the precise location of resources to their nestmates (e.g., Melipona spp.), as well as in species that often lead large numbers of recruited nestmates to a particular feeding site by means of chemical markings deposited from a forager’s labial glands at and near that food source (e.g., species within the genera Trigona, Scaptotrigona, Geotrigona). We analyze the composition of chemical recruitment signals in stingless bees and investigate the role of learning in recruitment communication in these insects.
We are also interested in how different foraging strategies and communication mechanisms of sympatrically occurring stingless bee species may contribute to resource partitioning and competitor avoidance. In that sense, we study how biotic interactions and adaptations to specific abiotic conditions may have led to the evolution of the behavioral diversity observed in stingless bee foraging.
Evolution of trophogenic caste determination in social bees
Reproductive division of labor with cooperative brood care – one of the main characteristics of eusocial insects – is based on the development of two physiologically (and more or less morphologically) distinct female castes, queens and workers. A key to caste development lies in the regulation of growth and development in the larval stages by colony internal factors, which can be a modification of the larval food, or changes in the feeding behavior of the adult nurse workers. The nutrition of a larva is subsequently translated into endocrine signals (juvenile hormone and ecdysteroid titers) that finally control the caste specific developmental patterns. The actual stimuli that initially elicit the specific developmental pathway leading to either of the two alternative phenotypes remain largely unknown. In addition, the questions regarding how caste determining nutritional factors are perceived and processed remain elusive.
A central question in understanding the evolution of caste differences in social insects is how incidental differences in larval nutrition were finally channeled effectively into the development of alternative phenotypes. The first step towards answering this question is the identification of the respective caste determining factor(s) from the provision of larvae. We currently investigate caste determining factors from the larval food of stingless bees (Melipona beecheii and Plebeia remota) and bumble bees (Bombus terrestris). In particular, we identify compounds from cephalic glands of adult bees that feed the larvae and test the effects of identified potential caste determining components on the development of bee larvae in experimental colonies that receive extra amounts of these compounds. Future studies will include honey bees, as well as analyses of larval food from solitary bee species in order to look for potential evolutionary origins for chemical molecules that act as caste determinating compounds in social bees.
Impact of pesticides on learning, orientation, and communication in honey bees
The populations of many insect species are in constant decline. A variety of reasons, many of which are of anthropogenic origin, may account for this alarming observation. Among these reasons is the widespread use of agrochemicals in modern farming practices. Currently we study potential detrimental effects of pesticides, such as compounds known as neonicotinoids, on learning and memory abilities, orientation behavior, and communication in honey bees. We plan to expand our research to other native temperate zone bees (both solitary and social ones), as well as to tropical eusocial stingless bees.