IS: Who are you and what do you do?

KH: Katja Hogendoorn, bee researcher at the school of Agriculture, Food and Wine of the University of Adelaide. At the moment, I lead a project that investigates revegetation strategies for crop pollinators.

IS: How did you end up researching social insects?

KH: I love solving puzzles and have always been fascinated by animal behaviour. As a lonely four year old, I spent many days observing the effects of manipulations of ant foraging trails. In Utrecht, where I studied, the choice in ethology was between primates and social insects. Insects seemed relatively easy study objects and the evolution of the worker caste was one of the more intriguing puzzles.

IS: What is your favourite social insect and why?

KH: There isn’t one, but there is a family: the Xylocopidae. The variation in social behaviour within this family is phenomenal- everything from solitary to primitively eusocial and there is even a species with an allometric worker caste. Together with the Halictidae, the Xylocopidae offer the best opportunities for studying the evolution of sociality.

IS: What is the best moment/discovery in your research so far? What made it so memorable?

KH: I’m not one to look back – my best is still to come. I thrive on new insights, which do not necessarily get published. So I’m happiest when, through thinking, I can make sense of something that I earlier didn’t understand. The best moments were when I finally understood the factors that shape mating strategies, the drivers in the evolution of buzz pollinated plants and the morphology of Australian flowers. At the moment I am grappling with the evolution of diet width and male sleeping clusters in bees.

IS: If teaching is part of your work, what courses do you teach? Has your work on social insects helped to shape your teaching?

KH: I supervise postgrads, but I don’t teach.

IS: What is the last book you read? Would you recommend it? Why or why not?

KH: The ‘Noise of Time’, by Julian Barnes, whom I consider one of the best living authors. He writes beautiful prose and combines humour with sensitivity.

IS: Did any one book have a major influence in shaping your career? What was the book and how did it affect you?

KH: Two books: ‘Onder proffessoren’ by Willem Frederik Hermans, and ‘Brazzaville Beach’ by William Boyd. Though neither are very good books, both satirise the pettiness, jealousy and power games that occur in the academic world, which I loathe. The books improved my ability to place that kind of behaviour and therefore allowed me to better savour the wonderful sides of working in academia.

IS: Outside of science, what are your favourite activities, hobbies or sports?

KH: Reading a very wide range of books, growing and cooking food.

IS: How do you keep going when things get tough?

KH: Prioritise and relativise. Not everything is important – some things are allowed to fall by the wayside. Then knuckle down and get at least the most important things done one at a time.

IS: If you were to go live on an uninhabited island and could only bring three things, what would you bring? Why?

KH: A large box of matches, a knife and a boat. I’d need to eat, make tools and leave the island.

IS: Who do you think has had the greatest influence on your science career?

KH: Three people: My dad. I couldn’t compete with his knowledge of art and languages, so I turned towards science instead. My PhD supervisor Hayo Velthuis. He was very encouraging during my first forays in honey bee kin recognition and encouraged me to publish my results. He also introduced me to the IUSSI. Attending IUSSI conferences has been a major influence in the early stages of my career. My partner, Remko Leijs. Exploring life’s puzzles together remains great fun.

IS: What advice would you give to a young person hoping to be a social insect researcher in the future?

KH: Try to design intelligent, elegant experiments that can give answers to interesting questions. Publish early in your career.

 

 

A blog post highlighting the article by R. Gloag, K. Tan, Y. Wang, W. Song, W. Luo, G. Buchman, M. Beekman, B. P. Oldroyd in Insectes Sociaux

Written by Ros Gloag

Some social insects have proved to be adept invaders. Assisted by the international trade of the modern world, these species have spread far beyond the ocean and mountain barriers that once determined their distributions. In some cases, these range expansions have brought previously isolated sister species back into contact. What happens when such species try to mate?

We were interested in this question of interspecific mating in the case of two honey bees: the Western honey bee Apis mellifera and the Eastern honey (or hive) bee, Apis cerana. These species diverged from a common ancestor at least 6 million years ago, with A. mellifera native to Europe and Africa and A. cerana native to Asia and India. Western honey bees have of course since been transported, in association with agriculture, to every human-inhabited continent on earth. Eastern honey bees meanwhile, have been quietly expanding their range too in recent decades, invading both Papua New Guinea and Australia. Thus what were allopatric (or separate) ranges for millions of years have suddenly become partially sympatric.

The possible outcomes of A. mellifera and A. cerana mating are varied. It may produce high-fitness hybrids, low-fitness hybrids or no viable offspring at all. In the case of honey bees, there is also a more unusual possibility; interspecific mating might cause queens to produce some female diploid offspring asexually via a process called thelytokous parthenogenesis. Thelytoky is not uncommon in Hymenoptera, though the mechanisms controlling it vary between species. In honey bees, it appears to have some genetic basis, but its unclear whether environmental factors – such as interspecific mating – also play a role in determining its incidence. Honey bee queens mate with twenty or more males during a short period early in their lives and store the sperm, so it is unlikely that naturally-mated queens will have mated exclusively with the wrong species. As such, any peculiar effects of interspecific mating could be easily obscured in populations where the two species co-occur.

We decided to perform an experiment to reveal the effects of interspecific mating on the offspring of A. mellifera and A. cerana. We performed reciprocal crosses via artificial insemination (inseminating queens of each species with the sperm of the other species) in China. Artificial insemination is a fairly standard beekeeping procedure for A. mellifera, but a much trickier business for the relatively diminutive A. cerana. Enough inseminated queens survived the procedure though to confirm that theytoky is not a consistent outcome of these matings. We detected only the odd few thelytokous eggs, from both queens and laying workers. Rather, our results confirmed that interspecific mating has fitness costs for both species: cross-inseminated A. mellifera queens produced only males or inviable hybrid females, while cross-inseminated A. cerana queens produced either males only or no eggs at all. Interestingly, A. cerana workers sometimes rebelled against their “wrongly-mated” queen and took control of reproduction themselves by laying unfertilized male-destined eggs.

Of course, understanding what happens if species mate is different to knowing whether they do mate. A previous study confirmed that A. mellifera will sometimes mate naturally with A. cerana males, but whether the reciprocal pairing ever occurs is unknown. We checked the sperm-storage organs of 17 A. cerana queens collected from Australia’s invasive population and failed to detect A. mellifera semen, despite the fact that we have observed A. mellifera males hanging about in areas where Australian A. cerana queens mate. Possibly A. cerana queens simply cannot survive interspecific matings with their larger sister species, which would be a particularly brutal and conclusive form of reproductive interference because its effects could not be diluted by multiple mating.

Wherever interspecific mating does occur between Western and Eastern honey bees, we can expect that natural selection will eventually intervene. After all, there are other honey bee species in the world that naturally coexist without incident, generally by having species-specific mating times and locations. A. mellifera and A. cerana are recent bedfellows, but given that interspecific mating in their case appears to have no redeeming features, selection should act to favour those queens and drones that succeed in keeping sex strictly within the species.

A blog post highlighting the article by M. J. Ferreira-Caliman, J. S. Galaschi-Teixeira and F. S. do Nascimento in Insectes Sociaux

Written by Maria Juliana Ferreira-Caliman

A few species of stingless bees have fooled human observers. The queen, often seen on brood combs and exhibiting active egg laying, ceases her posture and hides herself between the food pots during an event known as reproductive diapause. Diapause is considered an adaptation that allows the queen (and colony’s) survival in adverse environmental conditions. This event is mostly common in temperate zones, but it also occurs in the tropics as an adaptive response to diminishing resources in the cold and dry season.

Reproductive diapause is common among queens in the stingless bee genus Plebeia, occurring as an obligatory condition in some species. Reports on the occurrence of reproductive diapause in other stingless bee genera in Brazil are scarce. In our study, we described for the first time the occurrence of reproductive diapause in Melipona marginata in Southeast region of Brazil, comparing this event with events observed in South Brazil by Borges and Blochtein (2006) in Melipona obscurior, a closely related species. In the study described here, we compared the photoperiod and temperature in both localities to understand the factors that trigger the reproductive diapause in eusocial bees. In addition, we compared the queen’s chemical profile before and during reproductive diapause to verify the occurrence of chemical changes in the signaling of fertility.

We observed that Melipona marginata queens gradually declined the frequency of oviposition in early May, and in the cold and dry months (to May from July) they ceased egg laying completely. Five out of six colonies we observed entered the reproductive diapause, suggesting that this event is facultative in Melipona bees and that this variation is determined by internal factors of the nests, such as the ratio of adults to brood and food stores.

The environmental factors involved in reproductive diapause are commonly associated with photoperiod and temperature (Derlinger, 2002). The photoperiod and temperature seem to be the triggering factor of reproductive diapause in M. marginata in Southeast Brazil, as well as Melipona obscurior in South Brazil. In these two species, the reproductive diapause period coincided with the months of shorter day length and low temperatures, occurring between the months of March and August, suggesting that the reproductive diapause is a mechanism used by Melipona bees to overcome the diminishing resources in the cold and dry season.

The workers did not stop their activities and all behaviors related to colony maintenance were performed, such as queen feeding and food collection (although cell construction was stopped). However, the queens showed conspicuous behaviors. They walked through the entire colony, including in the food pots. The queens’ enlarged abdomen (a typical morphological aspect of post-mating stingless bee queens), did not disappear during reproductive diapause, but we observed that the posterior portion of abdomen decreased, suggesting oocytes were resorbed.

So, faced with the behavioral and morphological changes, why were queens not replaced by gynes when they stopped oviposition? The answer can be related to the chemical communication between the castes, which allows cohesion in the social insect colonies. The chemical analysis of Melipona marginata queens showed that the cuticular hydrocarbons profile does not change qualitatively during the diapause phase. Probably, this may explain why the workers have not killed the queens in this period, and why the workers did not lay eggs, a common occurrence in Meliponini colonies. Chemical and behavioral evidence suggest that two specific groups of hydrocarbons, the methyl-branched alkanes and alkenes, may act as fertility signals. The cuticular profiles of Melipona marginata before and during reproductive diapause had a greater and similar amount of hentriacontene isomers (alkenes). These results reinforce the idea that the chemical signals are crucial to maintaining the organization in insect societies, even in periods of adversity

References

Borges FVB, Blochtein B (2006) Variação sazonal das condições internas de colônias de Melipona marginata obscurior Moure, no Rio Grande do Sul, Brasil. Rev Bras Zool 23:711-715

Denlinger DL (2002) Regulation of diapause. Annu Rev Entomol 47:93-122