Bees and buzzing are common bed-fellows but only a select few species of bees are buzz pollinators.
And studies reveal that the buzzing reverberating nature of buzz pollinators is integral to the reproduction of native plants and in some cases, food plants.
Australian buzz pollinators have also been found to have special abilities and lead the world in buzzing frequencies – also in head banging, but more about that later.
So what is the buzz?
Buzz pollination involves a specialised process where pollen is released from the anther of a flower via vibrations created by a small number of bee species. The bee will hold onto the anther with its mandible and activate its thoracic (flight) muscles to create and transmit these vibrations
As the pollen grains gain energy from the vibrations, they are expelled from the anther onto neighbouring flowers and the bee’s body, facilitating pollination.
A small number of Australian bees can buzz pollinate – carpenter bees (Xylocopa sp.), teddy bear bees (Amegilla bombiformis) and the blue-banded bees (Amegilla cingulata).
Around 24,000 species, or 8 per cent of the world’s flora, depends on buzz pollination for reproduction . This is inclusive of important crop species such as tomatoes, blueberries, eggplants, kiwifruit and chillies, which contribute to global food sources.
The green carpenter bee has been found to be an essential link in the reproduction of native plants such guinea flower, velvet bush and chocolate and flax lilies.
And a South Australian study found that blue-banded bees use buzz pollination to pollinate tomato crops, making them a suitable alternative to fulfill pollination requirements.
Buzz pollination in Australia highlights the evolutionary convergence between flower morphology and pollination behaviour. Buzz pollination allows specific bees to take pollen from plants that other pollinators cannot access, providing them with a competitive advantage in resource availability.
A study by highlights that buzz pollinators have the ability to modify and adjust the frequency, amplitude, and duration of vibrations according to a flowers’ characteristics to increase the success of pollen release, making them highly efficient and specialised pollinators. Interestingly, buzz pollination has only been reported in female bees, as they require pollen resources to feed their larvae.
Other reasons for buzzing
While most bees can’t buzz pollinate, many make a buzzing noise that is associated with a variety of behaviours. The primary reason bees buzz is due to the rapid oscillations of their wings when in flight. These oscillations produce vibrations in the air, which can be interpreted by the human ear as a buzzing noise .
Bees can also buzz for thermo-regulation, and generate heat by flapping their wings to maintain their body temperature. Buzzing is also used as a form of communication between bees to convey information with other members of the colony.
More buzz about buzz pollinators
The blue-banded bee, teddy bear bee and carpenter bees are solitary, meaning they do not live in a hive and instead, build individual nests in underground burrows and small cavities.
Blue-banded bees performs a unique form of buzz pollination, and are often referred to as ‘head bangers’. This species transfers thoracic vibrations to its head and repeatedly strikes its head onto the anther of a flower to release pollen. A joint study compared pollination performance of blue-banded bees and the North American bumble bee, and found that the native blue-banded bees were capable of vibrating the flower at greater frequencies. The study also found they spend less time at each flower.
I Interestingly, the North American bumble bee, which uses its entire body to transmit vibrations, was observed to register a frequency of 240 times per second, whilst the native blue-banded bee was observed to register frequency around 350 times per second
Facing threats
The long-term geographic isolation of the Australian continent has supported the co-evolution between native buzz pollinators and plant species. However, this specialised relationship has been severely threatened by ongoing habitat fragmentation and destruction caused by anthropogenic activities such as land clearing, urban development, and industrial processes.
The green carpenter bee was once abundant across mainland South Australia until the 1950s, where the likely reason for their disappearance can be attributed to native vegetation destruction. In addition to this, introduced pollinators such as the European honeybee (Apis mellifera) can outcompete our native bees and buzz pollinators for resources, leading to population declines. Research conducted in urban bushland and gardens in Western Australia found that resource competition between the introduced honeybee and native bee species was greater in areas dominated by non-native flowering plants
The lack of native plant species in which our native bees and buzz pollinators have co-evolved with, increases resource competition with the honey bees. European honeybees are super-generalists, meaning they are able to visit and exploit an extensive range of flowers, potentially leaving little resources for our native bees. The threats against our native buzz pollinators in Australia can create adverse effects on local biodiversity and ecosystem function.
It is crucial to maintain and regenerate native vegetation in our environment to foster suitable habitats and reduce resource competition for our unique and incredibly important native buzz pollinators.
Author is Amy Wong
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