Unusual bee-haviour among natives

Australian native bees have evolved complex social structures and foraging behaviours that help biologists answer longstanding questions, such as the origins of social behaviour and the drivers of increased biodiversity.

In European honeybees, the queen governs the hive with her sterile female workers. But most Australian bees are different.

Some are solitary. Others live in cooperative, egalitarian societies where individuals share and jointly defend a nest. There is no clear division into queen and worker castes.

New research led by Flinders University experts, published in the journals Biology Letters and Apidologie, reveals fresh insights into the evolution and ecology of Australian bees.

“All bees face pressure from parasites and predators. But we discovered a unique strategy in one Australian species known as the capricious masked bee (Amphylaeus morosus),” says entomology researcher Dr Lucas Hearn.

“Of the more than 2,000 species in the highly diverse Colletidae bee family, only the capricious masked bee is known to be social.

“Females that choose to cooperate can dramatically improve their defence against enemies such as parasitoid wasps and flies.”

In these cooperative groups, one female protects the developing brood while the mother is away on foraging trips.

The guards do not produce their own offspring. However, guarded colonies do tend to produce more offspring –  and the extras are always males.

However, having too many nest guards in the population can lead to an excess of males. When males greatly outnumber females, far fewer males (compared to females) will reproduce and pass on their genes. This reduces the genetic “value” of males and in turn cooperative behaviour.

“Eventually, the relative benefit of cooperative nesting is diminished. We suggest this limits the frequency of the nest guard strategy, putting the brakes on further social evolution,” says Dr Hearn.

Social Australian stem nesting bees are surprisingly complex, even though their colonies rarely contain more than four or five females.

Plasterer bees, the most biodiverse group of bees in Australia, only exploit a limited range of native plants – mostly in the Myrtaceae family. Photo: James Dorey

Flinders University researchers also took a close look at the diet of other Australian colletid bees (also known as plasterer bees due to the way they smooth the walls of their nest cells with secretions that dry to a cellophane-like lining) to discover that one group in particular only visited a very restricted range of plants.

“This group, the euryglossines, account for almost a quarter of all Australian bee species. So why are they so fussy?,” asked postgraduate researcher Patricia Slattery.

The answer may lie in the nature of the food itself, she says.

Euryglossines clearly prefer plants in the family Myrtaceae. These include the gums, melaleucas, and tea trees that dominate Australian landscapes and provide massive amounts of pollen and nectar. Their shallow, brush-like flowers are also easy for small bees to access.

These same distinctive flowers are heavily used by parrots such as ringnecks, lorikeets and rosellas – who also love pollen and nectar.

This floral system has likely been shaped by co-evolution of parrots and gum trees, and we suspect it was later exploited by euryglossine bees and helps account for their high species diversity.

This research supports what many have suspected for years. Natives typically need other natives to flourish. Our native bees rely on our native plants, even if some have more flexible diets than others,” says co-author Professor Mike Lee.

Australia has more than 1,650 native bee species.

“These little animals have a lot to offer us in terms of how we understand the world, in addition to being vital parts of the ecosystem. And importantly, they are our responsibility to understand and protect,” adds Flinders University PhD Dr James Dorey, who has photographed many of the native species.

Read the full article in The Conversation: Move over, honeybees: Aussie native bees steal the show with unique social and foraging behaviours

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