Overview:

We selected this manuscript for our lab meeting because we are interested in biotic determinants of plant coexistence, particularly using Chesson's framework, as part of our group is working on this topic.
The paper aims to test the effects of competition and pathogens in stabilizing Californian perennial grassland communities invaded by exotic plant species. For that, the authors develop a population dynamical model which accounts for the particularities of the lifespan of 2 native (perennial) and 3 exotic (annual) plant species. Estimates of each parameter of the model are obtained from field observations and experiments. The dynamical population model predicts that native species will be able to persist within the invasion of the exotic grass species.  In this model, priority effects are to a large extent responsible for explaining the persistence of native species. Importantly and contrarily to expects pathogens 
play a minor role in determining the coexistence of native and exotic plant species. 

Positive feedback:

We agreed that the paper was very interesting in exploring the role of pathogens in coexistence. Also, it presents a nice framework to apply principles from coexistence to species with different life-history (annual and perennial plants), with the theoretical and methodological challenges that is supposes. Overall, this makes a very nice contribution to the scientific literature. 

Main concerns:

The main concerns that we discussed in our lab meeting were:

Other thoughts and future prospects:

Overall, we think that in the years to come it would be awesome to advance the development of mathematical tools to estimate niche and fitness differences for other communities besides the annual plant communities as the example of the present native perennial Californian grasslands. We also felt that given the theoretical nature of the paper, the direct conservation implications of this work do not marriage well in the paper, and this section could be shortened. Finally, we congratulate the authors for their work and we hope seen it published in an international journal soon.