Tuesday, August 21, 2012

Living precariously in Hawaii

bee with deformed wings - Shawn Caza, CC 2.0 license
Recently researchers from the University of Sheffield in Great Britain threw new light on one of the potential causes of honeybee colony collapse disorder. They studied bee colonies in the Hawaiian islands, where the parasitic mite Varroa has only recently been introduced. Because the mite is so new to the islands, there are places where it's not present yet and others where it has been around for a varying number of years. The researchers sampled bees and mites from hives in different places and looked for levels of viruses that honeybees harbor. One virus, called deformed wing virus (dwv), was present in many bees before the mite arrived but rarely caused serious damage to the bees. dwv in mite-free areas was present as many mild strains. As mite infestation levels rose in an area, the mild strains of dwv disappeared, leaving only one strain which evolved to reproduce in the mites as well as in the bees. Bees bitten by mites carrying this dwv strain often had deformed wings, which makes them unable to fly and find nectar and pollen. You can see a good image here of a bee with deformed wings and a mite still clinging to its leg, along with lots of technical details, but for those of you in Canada I suggest going to look at Shawn Caza's post - Shawn is a beekeeper who has some very good pictures, one of which is reproduced above.

Jabuticaba or Brazilian Grape, from Wikipedia
I thought of Hawaiian bees when talking with Mike Marlin (who goes by "just Marlin") and Cynthia Verschuur who recently visited us from the Big Island. Marlin and Cynthia grow an amazing list of plants on a several decades old lava-ash flow, where every plant has to have a hole dug in the ash with organic matter added to get it started. In spite of all the labor, they have cacao, Sharwell avocado, 3 types of bananas, starfruit, dragonfruit, 2 kinds of sweet potatoes, soursop, lychee, jaboticaba (Brazilian grape tree Myrciaria cauliflora), 2 varieties of coconuts, coffee, 5 kinds of citrus (grapefruit, lemon, lime, tangelo, navel orange) , jackfruit, breadfruit, white fig, 2 kinds of mangos, brazilian cherry, white pineapple, papaya, strawberry guava and guaivi, 2 varieties of  passionfruit, kale, collards, basil, pepper, green onions, chives, rosemary, chard, arugula, eggplant, ginger, and many kinds of orchids.  They've made lots of mango wine, which has notes of citrus and strawberry. Sigh! My EnvyMeter just went off!! Not only that, but the idyllic country setting gives Marlin a peaceful place to create his amazing light and dance shows - www.lumatheater.com.
Hawaiian fruit fly: photo Kevin Kaneshiro

Some vegetables lead a precarious existence in their garden though. They said some of the many endemic Hawaiian fruit flies attack any large tomatoes they plant so they only grow cherry-style tomatoes. I'll note that there are invasive Asian fly species in Hawaii that attack fruit. The more than 500 Hawaiian fruit fly species are a textbook study in evolution and adaptation on islands - see the Natinal Academy of Science's Evolution in Hawaii: A Supplement to Teaching About Evolution and the Nature of Science.

Much as I envy Cynthia and Marlin's growing environment, I don't envy them living on the edge of a zone of active lava flows. Looking at their neighborhood from Google Satellite, they pointed out areas where houses had been destroyed by lava in the last 10 years - some of which are being rebuilt. It's a precarious but rich life, just like the precarious life of Hawaiian honeybees. Marlin told us he had a friend whose previously healthy hives had just collapsed. I looked at a map in the Sheffield researcher's Science magazine article, that showed which parts of the islands were infested with the mites in 2009. Sure enough, Marlin and Cynthia's part of the big island of Hawaii was infested then while more northwesterly parts had not yet been infested, so in their neighborhood there has been enough time for the damaging strain of the virus to become omnipresent. A Hawaiian government map from 2007 shows that the mite was not present on the big island then. So, in perhaps 2-4 years after the introduction of the mite, beekeepers have been seeing increased losses.

Varroa mite can't be the whole story in colony collapse disorder, because mites have been present in continental North America for about 30 years while colony collapse has been noticed in the last decade. But this story of invasive flies, mites, and lava flows helps us understand some of the many ways life can be precarious for farmers, pollinators, and home owners.