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Speciation by Symbiosis

How do microbes interact with animals?


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Research Summary

In nature, there are no animals without a microbiome, and most microbes are beneficial or harmless to their hosts. This newly appreciated complexity in host-microbe associations is an inflection point for the life sciences that few could have predicted just ten years ago. Looking further back, Darwin and the 20th-century pioneers of biology would have been astonished to see the countless roles that symbiosis and the microbiome play in animal evolution. A major line of research in our laboratory harkens back to Darwin’s Origin of Species, but in the present-day light of symbiosis. We ask:

  • How do closely related animal species vary in their microbial communities?
  • Does host genetic variation affect these differences?
  • And what is the role of bacterial symbiosis in animal speciation?

To put this work in context, the origin of species is often studied with genetic approaches that quantify the number and types of nuclear genes involved in reproductive isolation. Yet in 1927 after discovering that mitochondria were bacterial derived, Dr. Ivan Wallin suggested that bacterial symbionts were fundamental to host evolution. In the 1970’s, Dr. Lee Ehrman showed for the first time that hybrid sterility between fly species could be cured with antibiotics. In the 1990’s, Dr. Lynn Margulis advocated that microbial symbiosis is central to speciation, though she never conducted experiments on this topic. The field then lay dormant with few exceptions. We are now pursuing a comprehensive set of studies on how symbiosis and the microbiome help drive the origin of new animal species.

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