Dr. Amanda K. Gibson an Assistant Professor of Biology at the University of Virginia. Dr. Gibson joins the show to dissect the relationship between parasitism and evolution. In this episode you'll learn:

• About the complex multi-organism environments parasites live in
• About the Pros and Cons of asexual reproduction in parasites
• About the evolutionary change back and forth between parasites and mutualists

Dr. Gibson's lab focuses on the genetic change driven by parasitism on both the parasites and hosts. This evolutionary relationship is challenging to unravel given the complex biotic interactions a parasitic organism encounters. As an example, parasites in humans need to successfully compete with the both the thousands of human microbiome bacteria and viruses as well as the human immune system.

First, Dr. Gibson asked the question how do parasites reproduce, and then linked this idea to the evolution of parasites over time. If fit parasites or hosts were genetically well equipped to produce progeny why would they not reproduce asexually transferring that fitness to their progeny? Why would either engage in sexual reproduction which would change the genetic makeup of their offspring?

Explaining this paradox Dr. Gibson highlights the fact that greater genetic diversity in parasites yields a higher likelihood that some of the parasites are able to infect the hosts available, whereas for the host genetic diversity means a higher chance of being resistant to new versions of parasites. Parasites reproduction may be affected in the opposite way as well, with monoculture crops perhaps encouraging asexual reproduction among parasites.

Supporting this idea Dr. Gibson points out that more monoculture crop fields tend to be destroyed by parasites than fields with multiple genotypes. This effect could be seen with as little as two different genetic backgrounds. Finally, Dr. Gibson extends her research to humans explaining a tantalizing yet poorly studied theory that humans might be drawn to mate with people who have different major histocompatibility complexes than themselves in order to give their children a broader defense against potential parasites.

To hear about more examples of coevolution between parasites and hosts see Dr. Gibson's work at coevolving.org . Available on Apple Podcasts: apple.co/2Os0myK