Creator of species: How what lives on us and in us drives evolution.

Cover article in New Scientist: The other you, 12 January 2013. Carrie Arnold

This is a must for all who attended John Spicers lectures on evolutionary biology. This article touches on one of the deepest philosophical problems that has plagued man since self-reflection became a tool available to us, who are we? The article, by Carrie Arnold, highlights some key examples where microbiota may be key players in the evolutionary process. Most recognisable among these, is the holobiont hypothesis put forward by Eugene Rosenberg for the interaction between corals and their micro-organisms. What I was unaware of was that Rosenburg had also conducted work on fruit flies in the field of evolutionary biology. Inspired by Rosenburgs belief that there is a Lamarckian aspect to the hologenome hypothesis, that is, that sometimes animals evolve via acquired characteristics, Eugene and his wife set about to find evidence in the literature that this may be the case. The pair came across a paper by Diane Dodd, a post Doc at the University of Yale, who found that changing the diet of a fruit-fly could alter the flies mating choice. Rosenburg then set Phd student Gill Sharon to work to try and replicate this experiment.  After two generations of flies fed on molasses it was observed that they would no longer mate with flies fed on regular starch. Next, Sharon gave flies rifampicin to kill off their gut bacteria. Following this, the flies fed previously on starch copulated with those fed on molasses, showing that bacteria were responsible (Dodd et al, 1989).

Another interesting study put forward as evidence for the role of bacteria in the evolution of their larger ‘hosts’ was conducted on the development of mice. The 2011 study suggests that mice need their gut flora for their brains to develop normally (There was no reference for this study but I am searching for it).There are other studies highlighted in the article, but I don’t want to ruin it for you.

The two key players highlighted in this article are Richard Jefferson and Eugene Rosenburg, who, as the article explains, were working individually on the impacts of the microbiome in evolutionary biology independently until Jefferson made contact in 2010.

The purpose of this blog was not to inform on a specific piece of published literature, but more, to spark discussion among the members of the blog. I have had several stimulating conversations on this topic with members of BIOL 3309 and I encourage members to read this article (I’ll try to upload it to the blog) and join in the discussion. I believe that the best thing about this article is that ‘the case remains to be proven’ and I am sure that there are good models in the marine environment to enhance the evidence for this way of thinking. One thought I had on this subject is the implications for laboratory cultures, for example, the pond snail, Lymnea stagnalis. It is common to feed these pond snails lettuce or spinach during culture. Can we be sure that this alien diet is not effecting development or behaviour of the species in some way by modifying the gut bacteria as exemplified by Dodd et al (1989) in fruit flies? Do these snails have microbial gut flora that is passed on purely from the parent, or is some bacteria brought in from the environment post hatching? Will this aspect bias any experiments, I’m not sure, but I think it highlights the message I’m trying to get across. Also, could microbiota have enough of an impact on an organism to be considered a functional trait when looking at the impacts functional diversity in ecological studies? Personally, I really believe that this will be a revolutionary, and controversial, area of research that will redefine our thinking on how to see evolution, and ourselves.

So on that note, I leave the door open for discussion. Do you believe we are ‘I’ or we are ‘us’?