Interview with a social insect scientist: Madeleine Beekman

Madeleine in the field

Madeleine in the field.

IS: Who are you and what do you do?

MB: My name is Madeleine Beekman and I study how insect colonies are organised and the ways by which they deal with conflict within their societies. I have done quite a bit of work on foraging behaviour in mass recruiting ants and honey bees as well as nest-site selection in different species of Apis. Currently I continue to work on the amazing Cape honey bee, a subspecies of honey bee in which the workers are capable of cloning themselves. Workers can now produce females instead of males, which completely changes the relatedness within the colony. This change in relatedness in turn leads to very interesting conflicts not usually seen in other honey bees. More recent is my adventure into honey bee virus land. Here the aim is to unravel how honey bee RNA viruses become more virulent and what role exactly the ectoparasite Varroa destructor plays.

IS: How did you end up researching social insects?

MB: While doing my MSc at the University of Amsterdam, people were trying to commercialise the use of bumble bees in glasshouse pollination, particularly of tomato crops. Tomatoes are a funny crop; the plants continuesly produce flowers which can pollinate themselves, but the pollen needs to be actively loosened. When grown outside, the wind does the trick, but not in glasshouses. For a long time every tomato plant had to be touched daily with a vibrating stick to ensure pollination. Enter honey bees….they are much more efficient and cheaper. But honey bees are also picky, so as soon as there are nice plants in flower outside, honey bees ignore the tomato crop (remember they have a very useful communication dance, so only a few workers need to find something better and soon the whole colony knows about it). Obviously glasshouse growers could have screened their glasshouse, but there are other disadvantages to honey bees. Their colonies are large, they poo a lot and they can sting. The bumblebee Bombus terrestris started to look like an interesting alternative. The problem was that bumble bees are annual insects, and tomatoes are grown almost year round. What they needed was a PhD student who was going to figure out how to prevent bumble bee queens from going into diapause, how best to survive artificial diapause, and how to obtain good quality colonies year round. That PhD student was me. I was already obsessed with insects and mites, was an amateur beekeeper and loved the challenge.

IS: What is your favourite social insect and why?

MB: That is a tough question….I think I will settle for the blue-banded bee Amegilla cingulate. It is simply gorgeous and the males have this funny habit of forming social roosts (to be honest the blue-banded bee is not the only one in which the males hang out together at night, but they are the blue-est…).

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Roosting blue-banded bee. Photo: James Niland/flickr

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

MB: I think the most memorable occasion was when I got to work one morning and my then Honours student Alex Jordan said to me: ‘I think I found something really cool’ (or words to that effect; it has been a while). Alex had spent a field season in South Africa working on the Cape honey bee and was analysing his data. When I excitedly asked what that might be, he replied by saying he wasn’t going to tell me until he was certain. Turned out he found that workers of the Cape honey bee parasitise queen cells of other honey bee colonies on a massive scale, a discovery that changed the direction of the research on the lab on this weird bee. Because these workers produce clones, they reincarnate themselves in genetical terms.

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

MB: I teach in a first year unit called Life and Evolution, and in two third year units: Animal Behaviour and Evolution and Biodiversity. In my teaching I am foremost an evolutionary biologist. I do give examples of my own work where relevant, and obviously social insects are ideal if you want to impress first year students, but I am careful in pushing it too far.

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

MB: ‘A Little Life’ by Hanua Yanagihara. One of the most beautiful books I have read, so I most certainly recommened. Science-wise, the last book I read was Frans de Waal’s latest book: ‘Are We Smart Enough to Know How Smart Animals Are?’, also highly recommended as it makes us think about what exactly intelligence is. I look forward to reading Peter Godrey-Smith’s latest book “Other Minds: the Octopus and the Evolution of Intelligent Life” (see a pattern here?) and Menno Schilthuizen’s upcoming “Darwin Comes to Town: How the Urban Jungle Drives Evolution” (so many books, so little time….).

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

MB: Boring anwer I fear, but that must be Richard Dawkin’s ‘The Selfish Gene’ and ‘The Extended Phenotype’. Not very original, I know, but they are extremely influential books.

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

MB: I would love to spend more time reading books, both science and fiction. But I also love exercising and horse riding. My main form of exercise is RPM, where you get on a stationary bike and go nowhere but end up completely exhausted after 45 minutes because there is a trainer shouting instructions such as ‘go faster’, ‘put more gears on’ or (my favourite) ‘suck it up’. I also spend (too little) time on a yoga mat.

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

MB: I exercise or get on a horse.

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

MB: Sunscreen, because I would only go to a tropical island. This is cheating I suspect, but a huge bookchest full of books. And my husband, as I’ll get lonely after a while (and we can swap books if he also takes a book chest….).

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

MB: Different people at different stages in my career, but I can easily single out two. Foremost my PhD supervisor Maus Sabelis, who sadly died too young. He taught me to believe in myself. And ever since I moved to Australia Ben Oldroyd, life partner and close colleague. Without his support I wouldn’t be where I am now.

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

MB: I think these days young researchers need to be much more strategic than I have been. Obviously doing good science is essential, but you also need to make sure people know who you are and what you do. So make sure you give brilliant talks at national and international conferences. Make yourself visible, even as a postdoc. If opportunities arise, people need to know you exist; if you hide in the lab or your office, people may not think of you even if you are the best person. I realise this is not specific to social insect research….

Your baby doesn’t look so well …or the effects of developmental stressors on larvae in a young termite colony

A blog post highlighting the article by T. Chouvenc, M. Basille and N.-Y. Su in Insectes Sociaux

By Thomas Chouvenc

One of the reasons for the success of social insects is that their nest provides a homeostatic fortress for the colony, protecting it from external environmental changes and external threat. This is particularly true in large, mature colonies of ants, termites and bees, where a large worker cohort can provide optimal care for the developing brood and the modification of the nest structure itself provides a safe “home”.

However, like any other organisms, social insects may still be susceptible to developmental stress. Embryos first develop in the womb (or egg), and after birth continue to develop until it reaches maturity (adulthood). During this development phase, an individual is subjected to environmental and epigenetic stressors throughout its growth phase. Fluctuating asymmetry has historically been used as an indirect measure of exposure to developmental stress, and the relationship is that, the more stressful the conditions are for a developing organism, the more it will display asymmetrical traits at the end its development.

In the Asian subterranean termite, Coptotermes gestroi, soldiers sampled from mature colonies display highly symmetrical traits, suggesting that conditions for a developing termite in a large and healthy colony are optimal, and very little stress is imposed on the developing brood (Chouvenc et al. 2014). This is because there is an army of workers taking care of them in the most dedicated nursing behavior. However, in newly started colonies, the king and queen are alone to take care of their initial brood, and for many months, all the young termites hatching and developing in this stressful environment are subjected to limited resources and less than optimal parental care. As a result, the first few termites produced in a new colony are highly deformed and display highly asymmetrical traits. However, as the colony grows and additional workers are produced, the brood receives additional care and the individuals produced are progressively looking more symmetrical. I sent a few termite samples from my incipient colonies to a colleague for identification, without telling him the origin of the samples. His response was: “Tom, your samples are all messed up! You didn’t do a good job conserving the samples.” The fact was I preserved them in the same way that I preserved my other samples but the source of the deformed samples was from a young colony.

termitedevelop

A: C. gestroi soldier from an incipient colony, B: Soldier from a mature colony.

In Chouvenc et al. 2017, we showed that the quality of termites produced in a colony improves over time and that, as the colony grows, termite eggs and larvae develop in better conditions, resulting in “better looking” termites. We were able to identify two independent origins of the stress imposed on very young termite colonies. First, the quality of brood care was found to be critical in producing highly symmetric individuals, and that the more workers present in a colony, the more symmetrical the newly produced termites looked. Second, in the first year of development, the termite colony produces “cheap” soldiers, as their development is accelerated.

These cheap soldiers are a way for the colony to quickly produce a few soldiers to defend the young colony and reach the optimal soldier ratio for the colony (Chouvenc et al. 2015). However, accelerated development imposes a heavy stress on developing soldiers, which display strong asymmetrical traits as a result. Later in the life of the colony, soldiers are then produced through a different developmental pathway, with additional time and resources invested in them, resulting in larger, better looking, and more functional soldiers.

Therefore, a newly established termite colony is extremely limited in its caring capacity, time and resources, and the initial investment in the first brood is very poor, resulting in termites exhibiting morphological evidence of their stress. When the colony grows, the care toward the brood improves and more time and resources are allocated to the new brood, providing stable developing conditions resulting in “good looking” termites.

One could say that the appearance of a termite may not say much about the quality of an individual, however these asymmetric individuals produced early in the life the colony have a short life span, confirming the cost of developmental stress on their individual physiology and metabolism. Workers and soldiers produced from the first initial egg batch laid by the queen usually die within the first year of the life of the colony (Chouvenc and Su 2014). In contrast, termites that developed in a mature colony in optimal conditions can live up to four years. Therefore, the initial parental and alloparental care toward the developing brood can directly be a measure of the initial investment in larvae, and the longevity and functionality of the resulting individual, a measure of the return on investment.

References

Chouvenc T and Su NY. 2014. Colony age-dependent pathway in caste development of Coptotermes formosanus Shiraki. Insectes Sociaux, 61: 171-182.

Chouvenc T, Basille M. Li H-F and Su N-Y. 2014. Developmental instability in incipient colonies of social insects. PloS one, 9: p.e113949.

Chouvenc T, Basille M and Su N-Y. 2015. The production of soldiers and the maintenance of caste proportions delay the growth of termite incipient colonies. Insectes Sociaux, 62: 23-29.

Chouvenc T, Basille M and Su N-Y. 2017. Role of accelerated developmental pathway and limited nurturing capacity on soldier developmental instability in subterranean termite incipient colonies. Insectes Sociaux. In press.

Calling nestmates to the rescue

A blog post highlighting the article by K. Miler & K. Kuszewska in Insectes Sociaux

Written by  Krzysztof Miler

Pit-building antlion larvae are predatory neuropterans which co-occur with some sand-dwelling ants, their main prey. The ants evolved rescue behaviours as means of avoiding antlion predation: when an ant stumbles into the pit and is captured by an antlion larva, its nearby nestmates may act to free it. No one knows how exactly that happens.

ant lions

An example of the “antlion zone” with several antlion larvae pits (conical traps). When an ant stumbles inside one of these pits, its near-by nestmates may come to rescue. Photo: K. Miler [Błędowska Desert, Poland].

In 2002, Czechowski and his co-authors [1] observed that some species of ants rescue their nestmates from the pits of antlion larvae. Since their discovery, several papers about this phenomenon have been published. However, no one knows how exactly rescue behaviour is elicited. The main hypothesis states that when an ant stumbles into the pit of the larva and gets captured, it sends some kind of signal (“call for help”) which summons its nearby nestmates to the site of capture and triggers their rescue behaviour, but the form of this signal remains unknown.

I recently published a paper saying that soon-to-die ants stop calling for help and thus elicit lower levels of rescue than longer-lived individuals [2]. Prof. Martin Collinson tweeted shortly after my publication: “Moribund ants do not call for help. They’re probably too knackered to use their little ant smartphones.” But the call for help likely doesn’t come from a tiny smartphone.

If rescue is indeed elicited by a call for assistance, then in my study species, Formica cinerea ants, the “call for help” signal is most likely chemical, originating from one of glands releasing volatile substances. Together with my colleague, Karolina Kuszewska, we performed two experiments to test whether mandibular gland excretions elicit rescue behaviour. We focused on mandibular glands because they were obvious candidates due to their other communication functions in ants.

In the first experiment, we impaired communication of some ants via their mandibular glands and checked whether they were rescued less frequently than other ants with unchanged mandibular communication skills. In the second experiment, we dissected some ants and checked whether the content of their mandibular glands applied onto dummy-ants made of pieces of toothpicks would elicit rescue from nearby (real ant) nestmates.

Apparently, mandibular glands have nothing to do with the elicitation of rescue behaviour in F. cinerea. Blocking the release of excretions of mandibular glands has no effect on rescue frequency, and applying the content of these glands onto dummies elicited no rescue towards them. Our study is the first one to look into the mechanism of the “call for help” signal. We plan to perform another set of experiments looking into gaster-tip glands, aiming at finding out whether the mechanism of rescue behaviour in ants is as we currently assume it is. We expect that we won’t find a tiny Bluetooth device either.

An ant captured by an antlion larva summons its nestmate to the site. The rescuing ant grabs the victim by its leg and pulls, holding on even when the antlion larva starts to bury deeper in the sand to prevent losing its victim as a result of this rescue action. Unfortunately for the victim, the rescuing ant is not successful. Video: K. Miler [Jagiellonian University, Poland].

 

References

[1] Czechowski et al. 2002, Ann Zool 52:423-431.

[2] Miler 2016, PLoS ONE 11:e0151925.

Find out more in Hollis et al. 2015.

Forced Queen Associations

Highlighting the article written by M. Motro, U. Motro and D. Cohen in Insectes Sociaux

Written by Insectes Sociaux Editor-in-Chief, Michael Breed

Investigations of colony founding by groups start with the question: What happens if an animal that could survive perfectly well on its own is confined with others of the same species? Queens of the harvester ant species Messor semirufus typically found nests on their own, but occasional observations have been made of small groups of queens founding nests together. Many species of ant solitary queens initiate colonies, but in some species groups of queens come together and co-establish a nest. In this issue of Insectes Sociaux, Motro et al. (2017) investigate the outcomes of keeping M. semirufus queens in small groups. This study fits with a growing literature on how social cooperation might emerge when solitary animals are placed in groups by looking at success of group colony foundation in a species which normally does not express this behavior.

When animals have no option but to occupy the same space, the first obvious outcome is battle and possibly cannibalism. Second, the animals could ignore one another, perhaps only interacting if competing for a limited resource. Third, they could start working together to modify their environment, making it more suitable for habitation, and possibly they could collaborate in provisioning and caring for young.

This third outcome is highly significant to our understanding of the evolution of eusociality. If cooperation and division of labor emerges in a forced grouping, then many of the tools needed for successful eusocial living are already at hand. In some species of ant multiple queens come together to found nests. These groups work cooperatively and ultimately either transition to monogynous colonies via queen or worker culling of queens or become fully functional polygynous colonies. In these cases, whether the outcome is monogyny or polygyny, groups have survival advantages over single foundresses.

Motro et al (2017) found that pairs of M. semirufus queens performed less well than solitary queens at nest construction and that mortality was higher in pairs. Aggressive interactions, rather than cooperative behaviors emerged when ants were paired, suggesting that in this species queens attempt to usurp other queens’ nests, rather than joining for the benefits of mutual assistance. Crowding and difficult environmental conditions, exemplified by hard soil, favored co-founding in this species. Motro et al (2017) suggest that such forced associations could lead to selection for mutual tolerance, which is a critical first step in the emergence of cooperation.

Messor is a particularly interesting target for these experiments because similar studies have been conducted in another seed harvesting ant, Pogonomyrmex. The two genera are relatively phylogenetically distinct within the Myrmicinae (Ward et al. 2015) but have similar nesting and trophic biologies. Pogonomyrmex californicus queens found colonies singly at some locations (haplometrosis) and in groups at other locations (pleometrosis) (Overson et al 2014). The behavior of M. semirufus more closely resembles the haplometrotic populations of P. californicus.

Particularly notable about this study is that the data were collected a full quarter-century ago. This shows that careful studies with thorough documentation can retain their value. The value of this study perhaps even increased over time, as the theoretical framework about emergent cooperation developed and data were published on forced associations in other species of ant.

Studies of emergent cooperative behavior in groups of animals will continue to play a key role in improving our understanding of the evolution of social behavior. While this study of harvester ants found no advantage in living in groups, it reminds us that a key gateway to group living is social tolerance, and that even if ecological circumstances force animals into close proximity, there are other barriers to establishing a cooperative relationship. The evolution of the breakdown of those walls should play a key role in studies of social evolution.

References

Motro M, Motro U, Cohen D (2017) Forced associations by young queens of the harvester ant Messor semirufus during colony founding. Insect Soc. DOI 10.1007/s00040-017-0551-1

Overson R, Gadau J, Clark RM, Pratt SC, Fewell JH (2014) Behavioral transitions with the evolution of cooperative nest founding by harvester ant queens. Behav Ecol Sociobiol 68:21–30

Ward PS, Brady SG, Fisher BL, Schultz TR (2015) The evolution of myrmicine ants: phylogeny and biogeography of a hyperdiverse ant clade (Hymenoptera: Formicidae). Syst Entomol 40:61–81. DOI: 10.1111/syen.12090

 

 

 

Interview with a social insect scientist: Katja Hogendoorn

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.

The great carpenter bee (Xylocopa aruana) which is found in Australia. Photo: Alan Wynn/flickr

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.

 

Sex between species: what happens when invasive honey bees meet the locals?

 

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.

A cerana

A swarm of Apis cerana hangs from a branch in its invasive range of Northern Australia, where the species has recently come into contact with A. mellifera. The newly-mated queen will be concealed at the centre of the swarm: but who did she mate with?

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.

The queen is not dead!

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.

marginata

Fig1. A Melipona marginata queen in regular egg laying activity. Photo: M. J. Ferreira-Caliman.

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

 

 

 

 

 

Interview with a social insect scientist: Neil Tsutsui

neil

Neil Tsutsui in the field. Photo: Roberto Keller-Pérez

IS: Who are you and what do you do?

NT: I’m Neil Tsutsui, Professor of Arthropod Behavior at UC Berkeley, in the Department of Environmental Science, Policy and Management.

IS: How did you end up researching social insects?

NT: Maybe a mix of fate and luck? As a child, the first thing I ever said that I wanted to be when I grew up was an entomologist, so I might have a genetic predisposition for it. My route was circuitous, though. I majored in Marine Biology as an undergrad, then started off in graduate school as a cell biologist, studying the Golgi apparatus. After deciding that I wanted to spend my career studying organisms rather than organelles, I jumped over to the lab of an evolutionary ecologist (Ted Case). There, I started working on a project using microsatellites to quantify gene flow across a hybrid zone of whiptail lizards. Andy Suarez was a graduate student in the same lab, and he was studying the impact of invasive Argentine ants on native ants and horned lizards. David Holway joined as a post-doc soon afterward. Since we were always chatting about Argentine ants, and they had colonies in the lab, it seemed like a good idea for me to do something with them, as well. Once I started seeing the genetic data from Californian populations of Argentine ants, it was obvious that something interesting was going on – they had very, very little genetic variation across long distances. Quite opposite to what I was seeing in my lizard data. I started spending more and more time on the Argentine ant project, and have continued with them ever since. I never finished the lizard project.

IS: What is your favourite social insect and why?

NT: Argentine ants have been like Karl von Frisch’s “magic well” for me, so I have great fondness for them. I’m becoming increasingly fascinated with Polyergus, though.

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

NT: Hard to say. Seeing the first population genetic data from native and introduced Argentine ants is up there: I was pretty surprised by the extreme differences in genetic diversity and spatial genetic structure. Later, our experimental confirmation of colony recognition cues was also fun – it was amazing to see Argentine ant nestmates attack each other when we altered their colony odors with synthetic hydrocarbons.

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

NT: I mainly teach Insect Behavior and senior seminars for undergraduates, plus the occasional graduate seminar on chemical ecology or other specialized topics. Social insect examples are very prominently on display throughout my Insect Behavior course.

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

NT: Just finished “The Left Hand of Darkness,” by Ursula Le Guin. Yes, recommended – a nice short read, but quite interesting.

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

NT: I don’t think that there was a single book, but a cumulative influence of National Geographic and Natural History magazines when younger, books by Stephen Jay Gould and Richard Dawkins in high school, and, of course, E.O. Wilson later.

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

NT: Lots of different things, but none of them with any high level of proficiency: urban farming, birding, saltwater aquarium-keeping, parenting.

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

NT: Well, things are often tough in academia. Eventually you accept that sometimes you’ll be in over your head, it’ll just be too much, and you’ll fail. Reviews won’t get done, you’ll miss meetings, classes will go badly, etc. Over time, I’ve learned to say “no” to avoid having commitments pile up, and I’ve grown accustomed to just grinding through the tough patches and not letting the failures upset me too much.

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

NT: You mean that I’m stuck on the island forever? Then it’s gotta be something along the lines of solar still, fishing gear, and magnesium-flint firestarter.

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

NT: Probably my colleagues Andy Suarez and David Holway. Let’s get together for a reunion tour, guys!

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

NT: Well, there are lots of different ways of doing science, so the same formula won’t work for everyone. But I’d say one thing is to make sure that you’re always learning about things outside of your main field of interest. Even if you end up becoming a hyper-specialist in your own research, you’ll benefit from viewing the world through a broader lens.

 

Interview with a social insect scientist: Alex Wild

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IS: Who are you and what do you do?

AW: I am Alex Wild, Curator of Entomology at The University of Texas at Austin. I also run a small insect photography business. I suppose most people know me for the photos.

IS: How did you end up researching social insects?

AW: I wish I had a logical answer for why I’m so taken by social insects. But I don’t. I started early in life, so early that the infatuation seems to have been an inchoate, primordial fixation from a mis-wiring of my brain stem. I was collecting carpenter ants at five, for example, and many of my early childhood drawings depict crude tunnels of ant nests. I didn’t- and still don’t- know why I like social insects, though I can come up with all manner of post-hoc rationalizations.

True story. At age 8 an older cousin I did not know well inquired about my interests, as way of introductory small talk. I think she was expecting some standard answer like “Hockey” or “Video Games” or “Ice Cream” or whatever the kids liked those days. I announced, instead, “I like colony insects!”.

In college (Bowdoin), my ecology professor Nat Wheelwright explained me that one could actually have a career studying ants. I had no idea! Nat started me down a path that eventually led to taxonomy.

IS: What is your favourite social insect and why?

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A turtle ant- Cephalotes multispinosus. Photo credit: Katja Shulz/Flickr

AW: Turtle ants! Or maybe paper wasps? Hard to say. I love Iridomyrmex, in Australia, quietly running the continent while everyone else is distracted by the giant bull ants.

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

AW: I discovered a new genus of ant on Google once, in the early days of the internet. I didn’t do anything with it at the time. A year later, I stopped to watch the sunset in the middle of the Paraguayan Chaco and accidentally happened across a living colony of the same mystery ant. That was exciting- I recognized it right away. I worked with Fabiana Cuezzo to describe it formally as Gracilidris.

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

 AW: I teach Introductory Entomology at UT-Austin. It’s a challenging environment for a bug guy, as UT has no Entomology Department, so my little course is the only entomology most students get and few students have an entomological background. Of course, we use a lot of social insect examples in the lectures and labs.

I taught beekeeping at the University of Illinois for a couple years. It was a tremendous class. Universities would do well to invest more in small courses that combine hands-on activities with general biological theory. We covered both honey extraction and the debates over kin selection.

Mostly, though, I teach photography. Social insects occupy a special place for the insect photographer. Normally, the aesthetic challenge is to make alien-looking species appear relatable to the naïve human audience. Social insects anthropomorphize themselves. It’s much easier to take a compelling photograph of an ant- a photograph that non-biologists can relate to- than of a non-social beetle or fly.

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

AW: “Lab Girl” by Hope Jahren. Recommend!

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

AW: I often return to the concepts in Maynard Smith & Szathmary’s “Major Transitions in Evolution.”

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

AW: I kind of have my hobby for job. So I alternate between sleep, kid care, and hobby.

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

AW: I find point-mounting therapeutic. Doesn’t everyone? But, emotionally, I rely a great deal on my wife and two young children. Having kids has rather mellowed my outlook.

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

AW: Islands can be pretty depauperate. I’m more of a lowland forest guy. Am I allowed a boat with oars?

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

AW: My scientific instincts are moulded on those of my Ph.D. advisor, Phil Ward. But I’d be lying if I didn’t say I am most influenced by my parents, neither of whom are scientists themselves but they knew how to play the long game by encouraging an inquisitive, social-insect obsessed young mind.

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

AW: Normally I’d advise not worrying too much about the particulars of how one enters science- there are many paths to get where you’d like to go, as well as many destinations you may not have thought of. At least, that’s how it’s been in recent decades.

But today? We live in a perilous time, and retreating inward to the lab is capitulation. I advise connecting with local universities, museums, non-profits, and other science organizations to engage aggressively in outreach. You’ll make connections that may prove valuable later in your career, and you’ll help ensure that basic science survives the current mess.

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Interview with a social insect scientist: Jennifer Fewell

j-fewellIS: Who are you and what do you do?

JF: I am Jennifer Fewell. I study the organization, evolution, and ecology of insect societies, primarily focusing on ants and honey bees.

IS: How did you end up researching social insects?

JF: I went into grad school to study the relationships between food and social organization (probably because I like to be social and to eat). My original goal was to study canids, but that became too logistically complicated. I had switched to birds as a focal taxon, but found that birds seem to be much smarter than I am. By my second year, I had switched advisors to the wonderful Mike Breed. One day he took me out to a local park that was covered in harvester ant nests (Pogonomyrmex occidentalis). We watched them for a while; then he gave me a paper by Bert Hoelldobler to read and told me to go home and think about them. The next day I had my dissertation project sketched out and I have never looked back. Social insects are so much more elegant and fascinating in their social organization than any other group.

IS: What is your favourite social insect and why?

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A newly-emerged honey bee. Photo credit: Jon BeesinFrance/Flickr

JF: I can’t answer that. My favorites to watch have been ant queens and solitary bees. For pure attractiveness, I’d have to pick between a harvester ant, a leafcutter ant and a newly emerged honey bee. Honey bees are definitely the cutest, but harvester ants have a sleek but striated look to them that in my mind cannot be matched.

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

JF: My favorite experimental result was showing that normally solitary nest-founding ant queens show an emergent division of labor when forced to be solitary. We repeated and verified the finding in solitary bees. This first experiment tested a then new model of how social interactions affect individual phenotype in the context of division of labor and task organization. It set the stage for most of the work I’ve done since. The original study had fantastic results, but the idea was not well accepted at first. I argue that is okay, because it required a change in how we have to think about social phenotypes and selection. The doubt expressed by the scientific community at the time forced my lab to explore the paradigm in other species, and to test it more rigorously. So, it is a story of initial frustration in how science is discussed and received, but I think with a happy ending…although nothing in science does or should actually have an ending.

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

JF: I teach animal behaviour and sociobiology. One of the things I like about teaching the courses is that they force me to be less insect-centric in my thinking about social evolution, and to be more aware of the diversity of social forms out there. So, my teaching has helped to shape my research as much as my research has helped to shape my teaching.

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

JF: Ah no – I read a lot of science fiction for fun, and so don’t have a very worthy suggestion. I am currently also reading Jim Costa’s “The Other Insect Societies”, which I would recommend any social insect student owning – to remind us that ants, bees, wasps (and termites) do not represent the whole social insect world.

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

JF: The book that most influenced me as an undergrad was Wilson’s book, “Sociobiology: The New Synthesis”. I don’t want to say how far back that was, but I vividly remember reading the book in my advanced animal behaviour class, and I felt that I’d found a new world to explore and a new way to explore it. Wow.

I suppose that now the world has incorporated and moved forward from that text. For the incoming social insect student, Hoelldobler and Wilson’s “The Superorganism” is wonderful. Way back, Hoelldobler’s work set me down my research path, and this book may do the same for some other student.

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

JF: I ride horses.

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

JF: I fuss out and complain a lot to my poor husband. Then I stay up late and get things done.

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

 JF: As a biologist, I would have to say that depends entirely on the ecology of the island.

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

JF: Mike Breed, my grad advisor (as already mentioned) got me started on my research path, and has been a steadying and encouraging presence ever since. My current work traces directly back to the influence of Rob Page, with whom I worked on honey bee division of labor, and whose ideas still shape much of what I do. But my decision to make animal behavior a career started when I took a course in college with Bill Dilger, an ornithologist and ethologist. Bill was the consummate natural historian. We would go for walks in the woods, and Bill would point out songs and behaviors well beyond what I would see…and then explain what was going on around us. I began thinking of the animals around us as a city of arguing, cajoling and romancing individuals, all living interesting lives.

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

JF: Work at it, and learn to design experiments correctly – models and theory are important, but the experiment done well gives you an answer.