Community-level effects of defensive endosymbionts

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Most insect species on earth carry specific bacteria that are passed from infected females to their offspring. Many of these bacteria are beneficial to their hosts in such ways as conferring resistance to pathogens. Because insects are important members of larger ecological communities, the bacteria they carry may affect the structure and dynamics of these communities. The proposed research will examine several community-level effects of specific bacteria that infect specific mushroom-feeding flies. The bacteria living inside flies confer resistance to the sterilizing effects of a parasitic nematode worm and thus increase the fitness of parasitized flies. In addition, the bacteria dramatically affect the population dynamics of these parasitic nematodes: nematode parasitism increases rapidly in fly populations that lack bacteria, but the nematodes quickly go extinct in bacteria-infected populations. This project will investigate three questions: 1) How do bacteria affect the relative abundance of various species of competing flies, both in the presence and absence of nematode parasitism? 2) How does the presence of bacteria in one fly species affect the rate of nematode parasitism in other fly species? 3) Under what conditions can bacteria spread to new fly species?This research has potential broader impacts in the areas of public health and agriculture. Filarial nematodes cause onchocerciasis (River Blindness) and lymphatic filariasis in humans, with about 160 million people currently infected worldwide. These nematodes are carried from one person to another by insect vectors. If specific bacteria adversely affect nematodes within insect vectors, it might be possible to introduce the bacteria into populations of these insects and thus reduce the transmission, prevalence, and severity of certain diseases. As a potential agricultural application, bacteria or genes derived from them could be introduced to crop plants to provide resistance to root-knot nematodes, which annually cause over $120 billion in agricultural damage around the world. The proposed work includes several projects suited to undergraduate research. The PI will work with the Kearns Center at the University of Rochester to recruit low-income, first-generation, and underrepresented minority students.