Beelines: a Pacific mystery solved

It's not often that scientific discoveries in Fiji make the news headlines, but this month, a flurry of articles has appeared. More than one claimed "Michener's Mystery solved" A new mystery for me! My first thought was James Michener, author of Tales of the South Pacific, who frequently stayed at the Grand Pacific Hotel in Suva.

However, the source of this particular mystery is renowned US entomologist Dr Charles Michener who published Bees of the World in 2007. Back in 1965, Michener described tiny (3-5mm) solitary masked bees of the Hylaeus family in the Tuamotu Islands of French Polynesia, thousands of kilometres from their close relatives in Hawaii, and Australia. How they got to the Tuamotus has remained a mystery ever since.

Blue-sky thinking

Before the joint 10-year project between Flinders University in South Australia and the University of the South Pacific, only one species of bee had ever been found in Fiji, the generalist Homalictus, which thrives in areas cleared of forest. This ground-breaking project is a reminder that replicating long-used practices can be dangerous, even to the point of preventing new discoveries. The usual method of sampling bees deploys nets quite low, at shrub-level. But the team leader, evolutionary biologist Dr James Dorey, knew that native Australian bees forage in the canopies of tall eucalyptus, so decided to focus on the forest canopy on Fiji's mountainous Viti Levu, and Taveuni islands. The researchers deployed longer nets higher, with spectacular results.

Source: James Dorey Photography

Eight new species discovered

“As soon as I was able to sample a flowering tree, we were catching Hylaeus,” Dorey says. “It was clear that we had more than one [new] species from that one tree.” (Science News) “[We named veli’s Hylaeus] for the veli of Fijian folklore who are powerful little people associated with forests. Accounts of the veli are varied and they were often seen in a positive light, but they could also be dangerous, for example, if you chopped down their favourite trees. Hence, the name is meant to invoke a sense of responsibility for protecting these new forest-specialist species and their trees.”

So far, eight new species of masked bees have been discovered: six in Fiji: the straight-faced, little yellow-spotted, and Navai’s Hylaeus from the island of Viti Levu, and the white-spotted, open-faced, and veli’s Hylaeus from Taveuni. One new species, Chuuk’s Hylaeus, was found in Micronesia and the golden-green Hylaeus on Tahiti. Their names are as attractive as their tiny bodies, don't you think? The photo shows Hylaeus directus, collected from a canopy-flowering mistletoe in mountainous Viti Levu.

Now their existence in a number of Pacific islands has been established, more new Hylaeus species will probably soon be identified.

Canopy on Taveuni, Fiji. James Dorey Photography

Island-hopping bees?

There are many hundreds of forested islands between Micronesia and the Tuamotus, where the Hylaeus genus was first collected in 1935. It's highly likely these bees travelled between islands, gradually evolving into species endemic to different islands as they did so. The Flinders-USP project has confirmed, by DNA bar-coding and morpholgy, that all the different Hylaeus species are related . However, so far the DNA data is insufficient to tell us the length of time this dispersion took and when it occurred.

But how did these tiny insects hop from one island to another? Their typical flight range is not known precisely but is probably not more than a few kilometres.

Dr Dorey said, “Because most masked bees nest in wood, it’s likely that they rafted between islands, especially when tropical cyclones wash masses of plant materials down rivers and out to sea. It is also possible that they were blown by high winds, but that would have been a much more perilous journey for our little bees.” (Eureka Alert!)

How long ago these dispersal events happened can’t be determined yet from the available DNA data. Nor do the authors know how common the new species are on the islands to which they appear to be endemic.

I was thrilled to hear of this scientific breakthrough by an Australian-Pacific team of scientists. If I'm not mistaken. we'll be hearing much more about these tiny pollinators of Fiji's tallest trees!

Reference: J.B. Dorey et al. Canopy specialist Hylaeus bees highlight sampling biases and resolve Michener’s mystery. Frontiers in Ecology and Evolution, published online February 26, 2024. doi: 10.3389/fevo.2024.1339446.

If you have friends interested in Fiji or Pacific islands in general, I encourage you to share this post.

I look forward to hearing from you!

Bernadette

B.M. Allsopp