Climate change, phenology match and the big unknown

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.

New paper out: Pollinators, pests and soil properties interactively shape oilseed rape yield

We have a new paper showing that processes like pollination or pest attacks are not independent process, but one process affects the other. But the title and abstract are quite explicative, so I’ll explain a few other things here.

First, this an example of a cost-opportunity paper. Vesna was already planing to collect data on pests, so she already had selected the fields, contacted the farmers, etc… so adding the pollinator (and soil) surveys was really cost effective, and allowed talking an important question (in addition to her studies on pest control).

Second, I posted a pre-print of this paper 11 months ago. This is how long it took to submit it to a couple of journals (which didn’t review it and rejected it quickly), and to go through the review process (three reviewers, two rounds!) and editorial typesetting. During this time not only I could share a citable pre-print with a couple of interested colleagues, but also get > 500 views and > 200 Downloads from bioRxive. Moreover, the preprint allows you to compare the submitted version with the accepted version. We removed one analysis and added a couple more. The main conclusions are unaltered, but its nice to see the process from an historical point of view.

Why do we need to protect bees?

This is a very tricky question. Recent media coverage and policy makers are increasingly using the “ecosystem services” argument to justify the conservation of bee populations. Bees are indeed providing us with a precious service, the pollination of 75% of our crops. However, “bees” are a diverse group of more than 20.000 species. David Kleijn had the wonderful idea to check how many of those bee species are responsible of crop pollination and I was more than happy to help him find out. This is the resulting paper. Surprisingly very few species made most of the crop pollination job. Moreover, those species are the ones of least conservation concern, as I already showed here.

What does this means? We should enhance agro-ecosystems to maximize crop pollination by bees. There is no doubt about this and repeated papers had shown that more green infrastructure enhance pollinator densities and thereby pollination. BUT if we want to protect the bee species that really need our help, other measures and incentives are needed beyond ecosystem service delivery. Those threatened species pollinate wild plants, parasite other bees (potentially regulating populations) or are part of larger food webs. Conserving rare bees and other animals should be done without an economical incentive in mind, otherwise, conservationists selling the idea that biodiversity should be conserved because it provide us with services may end up shooting them selfs in the foot by allowing policy makers to protect only the species that are of any immediate use.

Book: A sting in the tale (D. Goulson)

I don’t even remember why I chose to read the book, but I did. I thought I know quite a lot about bumblebees, and I am familiar with Goulson papers, so I was not expecting much. I was wrong. I learnt a lot about bumblebee biology (e.g. bumblebees has 16 ovaries!). And Goulson explains his research with bumblebees with such a passion that got me hooked for two weeks, devouring all 11 chapters. Things I like include that he explains several failed experiments, and not only the ones that worked, and that he explains stories from which I know the protagonist first hand, so you can perfectly picture Jane Stout, with whom I collaborated, in the middle of Tazmania. But the best part is possibly the feeling you end up with. A feeling that saving bumblebees (and other pollinators) is possible with some effort from the society.

Here in Spain we lack the UK tradition of valuing natural history, but in the other hand we conserve more natural habitats. Today I am encouraged that a generalized love through nature will arrive here sooner than the destruction of the remaining (semi-) natural habitats. I am already thinking on how to encourage bee friendly Spanish gardens.

Are exotic plants good for pollinators?

Answer quickly. Do you think most pollinators can use exotic plants, and hence will probably benefit from them? My gut feeling was to answer yes, but I am not convinced after seriously reviewing the available evidence.

A while ago I accepted to write a book chapter on the interface between behaviour and invasive species. I really like the idea that pollinators behaviour mediates its responses to environmental changes, including plant invasions. Hence, the main point of the book chapter is that “not all pollinators respond equally”. Yes, the idea of winners and losers of the global change is becoming a leitmotiv in my research.

Doing a book chapter allowed me to do a review, an opinion paper, and throw in some re-analysis of old data for supporting  my claims all in one. I am pretty happy about the result because it crystallise a lot of thoughts I had since my PhD and identifies important knowledge gaps.

If you want to read a draft before the book gets published, you can find a pre-print here: Invasive plants as novel food resources, the pollinators’ perspective.

Which plants are the influencers in plant-pollinator networks?

My PhD looked at two invasive plants that has contrasting effects on the native plant-pollinator network. Since then we advanced quite a lot on understanding why superabundant invasive plants with high reward levels can influence others via its shared pollinators, but other less abundant or rewarding exotics don’t. Today, we have a new synthesis paper (Open Access!) formalizing this ideas for any plant species in the network. We analyze lots and lots of plant-pollinator networks to find some generalities. The catch is that we use an index that calculates the potential for one plant to influence another plant. For example, if two plants share only one pollinator and this one do not visit anything else except this two plants, the influence will be very high. On the other hand, if this pollinator also visit lots of other plants, the influence will be lower (see the paper for details). The nice thing is that we can identify some plant traits that make them “influencers”, like plants offering abundant resources and open flowers. It’s a shame that we couldn’t tell (yet?*) if the influence is positive or negative, but at least we can identify key influential plants within the network.

*It may be a way to test for that and at some point we talked about a follow-up, but who knows…

Is Uppsala city a Bumblebee hotspot?

Sorry, no data to backup my thoughts today… but I feel that the number of bumblebees I saw in the last two years doubles the previous 30 years of my life. Uppsala is a smallish city in Sweden. Has lots of flowers (along all the season), cool summers (from my spanish perspective I may even say cold) and patches of semi-natural grasslands and forests mixed within the city. And lots of bumblenees. Mostly B. terrestris, and B. lapidarius, but I also see frequently B. pascuorum and B. hypnorum, and is not rare to see B. hortorum*.

I don’t make an effort to look for them, but I saw them waiting for the train to pass (yes, railroads have a lot of flowers) or when I am playing with the kids. Walking in spring in the forest patches within the city implies watching your feet to avoid steeping into queens. I even spotted two different bumblebee nests (B. terrestris and B. lapidarius) using man-made structures in playgrounds. Common! I’ve not seen any another natural bumblebee nest in the rest of my life, despite looking for them in several occasions.

I was talking yesterday with a colleague that is surveying bumblebee in grasslands and forests around the city and he is frustrated because he sees very few bumblebees**. So it’s not only Sweden which has lots of bumblebees, but particularly small “green” cities. Maybe cities are really good habitat after all, at least for a few species (See also NYC bees). The same pattern can be seen in bird species, where a few species thrive in cities, so probably I am not saying anything new.


*Id’s on the fly
**4 individuals /8 hours in an area with some flowers in a nice sunny day! that’s the worst day, usually he gets ~20 though

Invasive plants and plant pollinator networks

We have a new article revisiting the topic of my PhD thesis, but with a twist. Invasive plants effects on network modularity. Back then I already explored a bit the effects of invasive plants on the modular structure of the plant-pollinator community, but I never published any result, among other things because I didn’t understand well what I was doing. That’s why when Matthias asked me to join his paper addressing this question with a bigger dataset I was very happy to give it a second try.

Now (6 years later!) I understand two key things way better. First, that invasive plants have different roles in the network than natives, not because they are not native, but because of its different characteristics (i.e. very abundant and generalized). Second, that it is more interesting to understand how the roles that different species play within the network change, than how the overall network structure change, mainly because very different networks can present very similar structures (i.e. nested and modular). I think we nicely present this two points in the paper. See the figure below, and read the paper if you a curious about knowing more.

Ntw

Winners and losers of land use intensification

We have a new paper out showing which pollinators are more affected by land use intensification and which can cope with it quite well in New Zealand. There is a clear agreement that we should move beyond general species richness patterns, and understand each species specific response. Probably is not surprising that e.g., the invasive Bombus terrestris is doing great while bees in the native genus Leioproctus are struggling with land use intensification. However, most pollinator studies are still mainly based on richness and abundance metrics (Winfree et al 2011). That’s why we really wanted to see not only compositional changes, but also functional changes. At the end, identifying the traits of the winners and losers was the most interesting part of the paper.

As usually happens to me, I entered this article on the analysis phase, which means I can not tell you how cool is NZ, because I’ve never been there. However, I can tell you that the stats cover a lot of ground (may be too much and we lose a bit of focus?) and try to make a good use of functional diversity metrics (see here the code used to separate FD and richness effects) and species identity sensitivity to land use intensification.