Human modifications gave wild bees a boost in Fiji

Human activities often have a detrimental impact on wild pollinators, but a new study reveals that this is not always the case. The researchers have found that a native bee species in Fiji has been thriving since the very first land clearances by humans in the island nation. 

The experts report that the common bee, Homalictus fijiensis, has increased its spread on the main island Viti Levu alongside advancing land clearance and the introduction of new plants and weeds to the environment.

“Earlier research connected the relatively recent population expansion to warming climates, but our study reveals an interesting and positive response from an endemic species to human modifications to the landscape which commenced about 1000 BC,” explained study lead James Dorey of Flinders University.

“This species is a super-generalist pollinator (pollinates many plant species) and likes to nest in open, cleared ground, so one of the most important bee pollinators in Fiji actually appears to have benefited from human arrival and subsequent clearing of land in Fiji.”

The researchers used phylogenetic analyses of DNA to examine changes in native bee populations in Fiji. They determined that bee populations have expanded enormously, beginning about 3,000 years ago. 

According to Dorey, there has been no corresponding change in bee population size on another major island, Kadavu, where human populations and agricultural activities have been historically very low.

“That is too recent to be explained by a warming climate since the last glacial maximum which ended about 18,000 thousand years ago,” said study senior author Professor Michael Schwarz.

“Instead, we argue that the expansion of Fijian bee population better coincides with the early occupation of the Pacific islands by the somewhat-mysterious Lapita people, and this expansion accelerated with increasing presence of later Polynesians in Fiji who modified the landscape with their agricultural practices.”

Professor Schwarz noted that high-resolution population genetic studies such as this are a good way to distinguish between older and “natural” events and those resulting from early human dispersal and colonization.

“A persistent question in studies of ecosystems over the last 60,000 years or so concerns the relative roles of climate change and human modifications of the environment. For example, there is a continuing debate about the extinction of megafauna in Australia – was it due to humans, climate change, or both?”

“Those kinds of questions can be addressed if there are very good fossil records, but what about ecosystems where fossil records are very poor.”

The study is published in the journal Molecular Ecology.

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By Chrissy Sexton, Earth.com Staff Writer