Ice Age in the Tropics: Bees Paint a Clearer Picture

07 May 2014

Homalictus fijiensis bee. Courtesy Museum Victoria.

Homalictus fijiensis. Photo courtesy Museum Victoria.

Scientists have uncovered some of the key impacts of the last Ice Age on tropical island ecosystems in the South West Pacific.

Tropical bee species have proved to be effective markers of the effects of climate change, as shown by researchers at Flinders University and the South Australian Museum’s Senior Research Scientist Dr Mark Stevens.

In a study published today in the journal Proceedings of the Royal Society B, Dr Stevens, Dr Mike Schwarz and PhD student Scott Groom from Flinders University, have shown that bee populations on the separate Pacific archipelagos (Fiji, Samoa and Vanuatu) experienced similar evolutionary responses to the changing climate since the last Ice Age.

The team also uncovered some fascinating and useful results in relation to introduced bee species and their impact on native populations.

Under funding from the Australia Pacific Science Foundation, Rufford Foundation, and an Endeavour Fellowship for Mr Groom, the team has been exploring the DNA of bees on the Pacific islands for the past three years. They wanted to understand how populations have changed and why.

They found that for a particular bee genus (Lasioglossum) in Fiji, Samoa and Vanuatu, there were parallel responses to historical climate change.

“The colder climates of the last glaciation dramatically affected populations of bees on these tropical islands” said Dr Stevens. “Some bees were able to adapt to the colder climates while others retracted to smaller, warmer areas and continued to decline until the climate started warming again.”

The ‘DNA barcoding’ techniques used offered more complex information and results than other morphology-based methods. By studying the mitochondrial differences in species, they could understand how long the bee species had been in particular areas and how the population changed over time.   

Dr Stevens says “We were able to work out where things have come from and when that occurred – that is a very powerful tool. Because of the timeframe that we pinpoint to: the last Ice Age, understanding that gives us an insight into what has happened, what might happen in the future and the importance of the bee fauna on these islands.”

The study also looked at the impact of foreign bee species to the islands, which might have travelled from parts of Asia in plant material.

Introduced species, like honeybees, provide financially, major pollination services for many agricultural crops, but recent global spreads of diseases that can decimate honeybee populations can have grave consequences for crop yields.

Fiji. Photo: S Groom.

Fiji. Photo: S Groom.

The research team has also uncovered other bee species, unrelated to honeybees but not affected by the same diseases that affect honeybee populations globally; one has been recently introduced to Fiji by accident. This species, Braunsapis puangensis, may be an effective crop pollinator, and could provide insurance against future declines in honeybee populations.  However, this species may also pose threats to native Fijian ecosystems.  Research on this, and other newly introduced species has been recently published in the journals Biological Invasions and Insect Science

The team will study whether these species are potential ‘saviours’ of agriculture, or a threat to endemic ecosystems. Results from the study will help decide whether these bee species should be encouraged to spread or if they should be constrained.

The team from the South Australian Museum and Flinders University has long-term research interests to ensure that the evolutionary and population changes of bees are being mapped in the Pacific. On a recent trip with the Waterhouse Club from the South Australian Museum, Dr Stevens and Mr Groom collected more species from islands across Micronesia. Another student will continue the Pacific work; Ms Carmen da Silva from Flinders University recently received funding from the Playford Memorial Trust Honours Scholarship and from AJ & IM Naylon Honours Scholarship, and leaves for Fiji in June.

 “The only archipelago for which there is a comprehensive taxonomic treatment is New Caledonia.  Furthermore, a complete taxonomic picture for most of the bee faunas from South East Asian and the Indo-Malayan regions are also lacking,” Dr Stevens said. “We want to understand more thoroughly the biodiversity of bees in the tropics that fringe Australia and the influences on their populations.”

The Museum has an extensive collection of bees as part of its Entomology stores. High resolution imagery of the species is being compiled for an online database as part of the Atlas of Living Australia.