Symbiosis Between Fungi And Flies
February 6, 2013

‘Pirate’ Flies Have Symbiotic Relationship With Fungus

Brett Smith for — Your Universe Online

By studying tiny flies, biologist Jeffrey Joy, from Simon Fraser University located just outside of Vancouver, Canada, was able to gain insight not only into a symbiotic relationship the flies have with a fungus, but also how evolutionary pressures have allowed the flies to exploit this relationship to the benefit of their species.

According to Joy´s paper in the Proceedings of the Royal Society of London Series B, two categories of gall-inducing flies -- Diptera and Cecidomyiidae -- are examples of how prolific diversity can be a characteristic of symbiotic relationships.

In his report, Joy noted one group of flies was in a symbiotic relationship with a fungus called Botryosphaeria. Another much larger group used as an experimental control had no relationship with the fungus.

While scientists are uncertain how the symbiotic relationship began, Joy said his genetic analysis suggests the relationship has evolved at least four different times since its inception.

The relationship involves the flies picking up the fungi, storing them on their body and depositing them onto plants. There, the fungi convert plant tissue into a gall, or tumor-like structure, that can be more readily utilized as food.

“The flies are like pirates,” Joy explained in a statement. “They use the fungi as boats to float across a genomic sea and board a plant that is genetically far removed from what they would otherwise be able to feed on.”

Because the fungi can feed on a wide array of plant material, they enable the flies to have a more expansive diet. This conclusion suggests symbiosis can enhance diversity as much as competition and predation.

“Symbiotic lineages of these flies have undergone a more than seven-fold expansion in the range of plants they can feed on relative to the lineages without such fungal symbionts,” Joy said. “Also, one genus of gall-inducing flies utilizing fungal symbionts is 50 percent more diverse than its brethren without the symbiotic relationship.”

Joy noted his study was able to not only describe a symbiotic relationship, but also shed some light on the evolutionary activities occurring throughout the relationship and the benefits this evolution conveys.

“The goal of this work was to test predictions of evolutionary theories of diversification and symbiosis,” Joy said. “The theory I observed in action is that the evolution of symbiosis catalyzes niche expansion -- an organism´s use of more resources -- and diversification -- increased species in lineages.

“These findings expand our understanding of how biological diversity is generated and how processes, such as symbiosis, lead to some remarkable examples of biology, such as the symbiotic mutualism between clownfish and sea anemone,” he added.

Joy´s latest study expands on his previous work, which was also published in the Proceedings of the Royal Society of London Series B. That earlier work, performed under SFU biologist Bernard Crespi, discussed the diversity among plant feeding insects.

Currently a post-doctoral researcher at SFU, Joy´s work “integrates genetic, population genetic, phylogenetic, ecological and comparative approaches to study unresolved evolutionary questions in disparate groups of organisms across the tree of life.”