Transmission dynamics of bee parasites
TRANSMISSION OF BEE PARASITES ON FLOWERS
If feces of a bee infected by an intestinal parasite fall on a flower, the next bee that visit that flower could get infected. Because of that, flower fields can become hotspots for parasite transmission. Given the wide variety of flower shapes and sizes, I wanted to know how the morphology of the flowers affect different steps of the transmission process, including 1) the probability of a flower of catching bee feces, 2) survival of the parasite on the flowers, and 3) acquisition of the parasite by new bees. I found that flowers with long and narrow corollas have the higher transmission potential. Models based on the plant’s species identity are better at predicting deposition and survival of the parasite, but models that use floral traits are better at predicting acquisition.
Check out this video with the preliminary results and the paper with the final results.
WITHIN-COLONY TRANSMISSION OF PARASITES
Bee colonies are pretty dense and there are lots of interactions between individuals, giving parasites a chance to spread within the colony. I tested how fast two different parasites spread within bumble bee and honey bee colonies, and how the initial number of infected bees in the colony affects the spread of the parasites. I used the parasites Crithidia bombi for bumble bees and Nosema ceranae for honey bees, and found that for both parasites, when the initial number of infected bees is small, the social immunity of the colonies is able to control the spread of the parasites. But when the initial number of infected bees is about 30%, the parasites will spread really quickly in the colony. This means that if we can control the exposure to parasites in the environment, we can also reduce within-colony transmission of parasites.
Check out a video about that experiment and the paper with the final results
TRANSMISSION TO OTHER BEE SPECIES
Many species of bees share the same flower resources, so it is expected that when a parasite is on a flower, it could come in contact with other bee species. Being exposed to alternative host can affect the evolution of parasite virulence, as the parasite would need to adapt to this new host. Previous studies found that C. bombi can infect the leaf-cutter bee Megachile rotundata, so I wondered, how would the virulence and infectivity of C. bombi changes after passing through leaf-cutter bees several times? And what would happen when C. bombi isolated from leaf-cutter bees infect a bumble bee again? I found that serial passes of C. bombi on the leaf-cutter bees increase its infectivity, but not the virulence on this alternative host. The virulence and infectivity of C. bombi on bumble bees initially decreased after passing the parasite on leaf-cutter bees. These results support the idea that increasing host diversity can prevent parasite specialization on a single host species.
You can read the full report here.