Behind the scenes of the Maestre lab (IV)

We continue with the series of posts describing the “behind the scenes” of the research presented in the articles we publish (you can find the previous posts of this series here, here and here). In this case we will talk about a paper published online early in Perspectives in Plant Ecology, Evolution and Systematics entitled “Plant-plant interactions, environmental gradients and plant diversity: a global synthesis of community-level studies”, led by our former post-doctoral research associate Santiago Soliveres. Santiago is now a post-doctoral researcher in the Functional Biodiversity group at the University of Bern (Switzerland).

Santiago Soliveres, the lead author of this paper

These are the Q & A for Santiago:

What is this paper about?

In this paper we synthesize available evidence of the importance of plant-plant interactions for the maintenance of diversity, and how predictable are these interactions across contrasting environmental conditions. For doing this, we gathered a large dataset of own and published data at the community level in more than 200 sites scattered across a wide variety of habitat types and environmental conditions.

What are the key messages of this article?

The main finding was that over 25% of the plant species sampled were significantly associated to a nurse plant, which support –and quantify- the importance of positive plant-plant interactions in the maintenance of species diversity. We also found that environmental predictors perform better in alpine than in dryland environments, as the latter likely show higher variety in growth forms and response traits, and more complex environmental gradients. Lately, we found that positive relationships between the frequency of facilitative interactions and environmental harshness are more likely to be found in simpler, shorter gradients.

How did you come up with the idea of conducting this study?

Well, many papers state that plant-plant interactions are of crucial importance for the structure and function of natural communities. However, few studies have critically evaluated this statement or provided a quantitative assessment of this importance. In other words, I always wondered about how many plant species depend on these interactions and it seemed to be the right time to answer this question.

The second line of thought that drove us to conduct this study is the long-standing debate regarding whether or not the frequency of facilitative interactions can be predicted from environmental conditions, whether or not these interactions collapse under extreme conditions, and what exactly are these “extreme” conditions. Regrettably, until now most tests of widely accepted theories were performed using data on pairwise interactions, which made difficult to assess the frequency of these facilitative interactions, and which ignore that species do not interact in pairs, but rather form multi-species interactions. We wanted to overcome these limitations by analyzing research studies conducted at the scale of whole plant communities.

What have you enjoyed the most during the “life cycle” of this article (from its conception to its publication)?

I think what I enjoyed the most was to finally answer one question that obsessed me during my PhD (how important are facilitative interactions in plant communities?). Then, of course, I really enjoyed the opportunity that the BIOCOM project gave to me to travel across several countries while gathering this data. I really enjoyed sampling with the Maestre lab and with new colleagues in Spain, Morocco, Australia and USA. The laughs and fun that we´ve got with you, Pablo, Manu, José Luis, Vicky, Matt or Cristina will be difficult to forget.

What have been the major difficulties you have encountered when conducting the research reflected in this article?

I think that the most challenging part of this study was to find out how to provide some concealing results of when, and when not, facilitation-environmental gradient relationships should be expected. Unfortunately, there are not many studies conducted at the community level and across more than two points along a given environmental gradient to properly assess this.

Publishing today is really hard, how has been your experience with this publication?

Well, as you know better than anyone, it is always hard to publish when your results do not fully support the mainstream theory, and it was quite hard dealing with certain shocking reviews we received. I especially remember two that were among the less constructive and mind-limited reviews I have ever received. The first one stated that this review had too much unpublished data to allow publication. I still cannot find a reason why providing new data to the already published one does reduce the interest of any synthesis! The second one was even more surprising, the reviewer stated that providing a quantitative assessment of these theories widely used in community ecology was not important…well, I thought that this was precisely what ecologists do, to critically assess our theories with quantitative data to see whether or not they fit with nature. Happily, most of the reviews received were much more helpful than these ones and I learned a lot during the process (and I think the paper improved a lot too). I especially appreciate the support and kind words of Claus Holzapfel, the editor of Perspectives in Plant Ecology, Evolution and Systematics that handled our manuscript, during the publication of this work.