Native bees climb social ladder

Researcher Lucas Hearn and field volunteer Tyla Cousins collect Amphylaeus morosus nests from the Dandenong Ranges. Photo by Georgia Macaulay

A native bee which nests in tree-fern fronds is helping scientists understand how life developed to be social and altruistic — and how bees evolved to purposefully hatch sterile young, a fact which defies Darwin’s natural selection theory.

The Australian bee Amphylaeus morosus only recently made the jump from being a solitary species to a social one — which made them a perfect, and rare, animal to put under the metaphorical microscope.

The bee’s social nests are tiny and rarely contain more than two females, and the females do not use the queen-worker roles seen in other highly social species such as the European honey bee.

The study used genomic data and found each social nest had a single female who laid all the eggs and another related female who guarded the nest but did not reproduce.

Amphylaeus morosus. Photo by James Dorey Photography

Flinders University Associate Professor Michael Schwarz said the extreme reproductive skew to only one female and the high relatedness between the pair was “very unexpected” and challenges theories about how social complexity evolved.

“This provides some of the first evidence that kin selection can promote worker sterility at the initial transition from solitary to social living,” Dr Schwarz said.

“It seems that some species can quickly skip multiple rungs of the evolutionary ‘social ladder’.”

Flinders University PhD student Lucas Hearn was the lead author on the bee study.

“The ramifications of this understanding are very far-reaching,” Mr Hearn said.

The scientists were specifically trying to understand how insects like honey bees, termites and ants made the leap from solitary lifestyles to their altruistic colony systems.

The paper written after studying the tree-fern bees is titled Extreme reproductive skew at the dawn of sociality is consistent with inclusive fitness theory but problematic for routes to eusociality and will be published in the Proceedings of the Royal Society B journal.