Tag Archives: climate change

Network ecology is dead, long live network ecology!

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Carsten F. Dormann writes a provoking book chapter entitled “The rise, and possible fall, of network ecology” openly criticizing the concept of network ecology. Read it, I enjoyed it.

In fact, despite using network theory in some of my papers, I never liked the term network ecologist, and I never presented myself as such (but I’ve been presented as a network ecologist). For me, being a network ecologist would be like being a GLMM ecologist, or a differential equation ecologist. Networks are tools, not ends.

I believe that things interact with things. While simple systems do not require complex network theory, complex systems can benefit from it, but in agreement with Carsten, only if well applied. Unfortunately, some tools are over-(and miss-)used, such as topological indexes, while others are under-used, such as exploring network dynamics. It is paradoxical that the creator of the bipartite package, which popularized the blind use of multiple topological indexes not necessarily related to processes, is now warning about it.

One of my major concerns about “network ecology” is that many “network” papers are question free. If you don’t have a question, do not use networks. I don’t think answering how index X changes along Y is a valid question as change is the only constant in ecology. I also agree many tools from networks have analogous community ecology metrics, but this is fine with me as it reflects different ways of thinking. So let’s see a few examples of instances where I think network tools can bring exciting complementary veiws:

  • To measure indirect and higher-order interactions. The neighbour of my neighbour can still influence me even if I never meet him/her. How important are indirect interactions in ecology? How do we account for their effects on fitness? Many open questions where a network perspective can help.
  • To assess community stability. There is a lot of work using population dynamic models linked through species interaction networks that can help elucidate which interaction structures are compatible with stable communities and why.
  • To describe entire multi-species communities with different interaction types. We can’t even describe how entire communities look like. Networks are good tools for describing patterns, which is the first step to asking questions about processes.
  • To model the flow of “information”. Diffusion networks are under-used as a tool to model how things move through a network. Like pollen grains*

So I agree with Carsten on the fact that “Network ecology” should fall, but i think network analysis applied to ecological problems should prevail!

* we barely scratch the surface on this topic here: Allen-Perkins et al. (2024), Multilayer diffusion networks as a tool to assess the structure and functioning of fine grain sub-specific plant–pollinator networks. Oikos e10168. https://nsojournals.onlinelibrary.wiley.com/doi/abs/10.1111/oik.10168

Climate change, phenology match and the big unknown

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This year was crazy in Seville with plants flowering 2-3 months earlier than last year. So we went to sample, and guess what: bees were there too. Despite expectations about phenological “mis-match” are raised here and there, we don’t find a big phenological mismatch between plants and pollinators*. I am not talking here of specific species, but taking a community approach. However, this is not the end of the story. Is good that plants and pollinators are in sync, but this alone doesn’t warrants a healthy ecosystem functioning.

Why not? My main worry is that after a mild January and beginning of February, we have now “normal cold days” again. Consequently, we also find little bee activity (today we are sampling at 14ºC just to make sure this is true). Hence, both plants and bees are likely to suffer. The demographic implications of this are hard to predict, maybe is not a big deal if it happens only one year, but if it happens often, I presume can be quite bad. All in all its hard to quantify, but I suspect that we need to go back to population dynamics if we want to understand climate change impacts beyond phenological overlaps.

*Don’t take this blog as word, there are plenty of good papers showing it (here and here), including my own (here and here), and very little showing a clear mismatch, most of those on specialized systems.

Biodiversity insurance hypothesis in the real world

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This year is being great and we have another great publication in Ecology Letters. We use long-term plant and pollinator data to show that high levels of biodiversity ensure plant pollinator matching over time despite climate change.

The story behind the paper starts 2 years ago (yes, it always take time!) when we did a paper showing that in general, plants and bees are advancing its phenology due to climate change at similar rates. The problem of this general patterns is that we don’t present data on any particular case study to show how this “general pattern” translates to a given system. My idea was doing a small follow-up using apple orchards as a case study. I ran the first analysis and saw that indeed, apple flowering and bee pollinators are advancing at similar rates. Cool, We can now provide a case study that validates the pattern observed! But then I went further and tried to see what happens when the main apple pollinators are analyzed one by one. Here the things got interesting because some bee species DO show a phenological mismatch with apple, but the total synchrony is stable at the community level because the effects of individual species cancel out. When I showed the results to Rachael, she immediately related them to the biodiversity insurance hypothesis, and we start working on validating this idea. That meant looking for more data, including a simulation, and a lot of fun reading the biodiversity ecosystem function literature. Is amazing how much of what we know relating biodiversity and ecosystem functioning is based on experiments in grasslands, so applying those concepts to real world trophic interactions was intellectually very stimulating. I like a lot the final paper and I am looking forward to work more on this topic, hopefully with less complex data.

Native bees buffer the negative impact of climate warming on honey bee pollination

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We have a new paper in GCB lead by Romina. In this paper we do a very cool thing. We characterize the daily activity period of a bunch of bee species and how this activity is modulated by temperature. We show that while honeybees decrease visitation to watermelon at very high temperatures (literature suggest that the reason is that honeybees need to go for water more often when hot, hence have less time to visit flowers), some native bees concentrate its visits on the warmer hours. I think that understanding behavioural differences among species is neat to answer BEF questions.

wtbeeIn addition, we play a bit with future temperature scenarios to see if (all else being equal) visitation and pollen deposition will change with warmer temperatures. We show that the visitation reduction predicted for honeybees is compensated by an increased visitation rate by native bees (taken altogether). Despite this predictions should be interpreted with care, it adds up to the several lines of evidence suggesting that conserving all species is needed in order to have flexible ecosystems able to cope with environmental change.