2. Blooming deadly: flowers as dispersal platforms for pathogens in bees

Blooming deadly: flowers as dispersal platforms for pathogens in bees

Research by BSc (Hon) candidate: Terence Purkiss (research grant 2016)

Native stingless bees are crucial pollinators across the Wet Tropics with potential reductions in bee abundancelikely to have adverse effects on agricultural and wild ecosystems. The microsporidian gut parasite, Nosema cerenae (N.ceranae) originally found in Asian honey bees (Apis cerana) has transferred to European honey bees (Apis mellifera). This parasite is known to decrease the longevity and foraging behaviours of bees.  N.ceranae is the most prevalent cause of disease in European bee populations worldwide.

Purkiss’s project used the native stingless bee Tetragonula hockingsi (T.hockingsi)as a model for “Blooming deadly: Inflorescences acting as dispersal platforms for pathogens” which investigated whether stingless bees are hosts for N.ceranae. The study examined three areas; the effect of N.ceranae infection on longevity, the presence of N. cerenae in wild stingless bee populations and whether flowers are the transmission routes for N.ceranae between bee species.

By studying the controlled experimental infection of Tetragonula hockingsi, field surveys and collection of wild stingless bee specimens, the study found that T. hockingsi is susceptible to N.ceranae with 63% of experimentally infected bees having spores present in their digestive tract. N.ceranae infection was also found to reduce stingless bee longevity and is present in T. hockingsi colonies in the Wet Tropics regions with five out of six different hives (sampled at four week intervals over a five month period) experiencing N.ceranae infections.

The study also found that flowers visited by infected European honey bees, can act as a dispersal platform for N.ceranae with nine of fifteen exposed flowers having spores remain on them. It was also found that T.hockingsi can become infected through contact with exposed flowers with an infection rate of 31%.

Asiatic, European and most stingless bee species are generalist flower foragers and in the Wet Tropics forage year-round on many of the same plant species. This research demonstrates that the impact of N.ceranae is not restricted to Asiatic and European honey bees. Because of their foraging behaviours, Australia’s native stingless bee populations are susceptible to infection. Many Australian native trees and shrubs, including endemic orchids of the Wet Tropics rely on pollination by native bees and thus, infection of native bee populations may have serious implications for the ecosystems of the Wet Tropics.