Mutualism resulting in range expansion

Professor Bazely hosted a talk today, presented by Michelle Afkhami. For those of you that were not there, I thought I’de share a brief overview of the talk since it was interesting to learn some new stuff, and it directly applies to this course.

A lot of the studies done on symbiosis focus on negative relationships such as competition and predation also correlating with a range compression, whereas Michelle focused on how mutualism among Bromus laevipes, a grass, and fungal endophytes resulted in range expansion of Bromus laevipes. The range expansion observed was about 25,000 km^2 which is about 20% range expansion.


(E+ are the fungal-associated grasses, and E- are grasses that are endophyte free. As you can see, only the endophyte associated grasses occupied areas that had lower water availability)

Range expansion was attributed to endophytes “buffering” the stress of drought in Bromus laevipes, helping this grass expand its range into areas that were more dry. This study is significant because it suggests 1) Generally, the possibility of speciation occurring as a result of this type of range expansion (see figure below)


(Divergence of these two populations/reduced genetic flow= speciation may occur)

and 2) more specifically, the idea that the gradually warming climate may result in less water i.e. dryer soils, suggests that endophytes may be a key factor in the survival ofBromus laevipes in “key habitats”.

Below is a link to the article if you would like to read more about the study and its implications- which I strongly suggest, as it is a meticulous study and the methods are as interesting as the results.


Afkhami, M. E., McIntyre, P. J., & Strauss, S. Y. (2014). Mutualist‐mediated effects on species’ range limits across large geographic scales. Ecology letters, 17(10), 1265-1273

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