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Identifying pathways for managing multiple disturbances to limit plant invasions

Andrew Tanentzap, William Lee, Adrian Monks, Kate Ladley, Peter Johnson, Geoffrey Rogers, Joy Comrie, Dean Clarke, and Ella Hayman write:

We tested a multivariate hypothesis about the causal mechanisms underlying plant invasions in an ephemeral wetland in South Island, New Zealand to inform management of this biodiverse but globally imperilled habitat. . . . We found that invasion by non-native plants was lowest in sites where the physical disturbance caused by flooding was both intense and frequent. . . . only species adapted to the dominant disturbance regimes at a site may become successful invaders.

Their keywords are:

causal networks; community dynamics; functional traits, invasive species, kettlehole; megafauna; rabbits; restoration; turf plants

But here’s the part that I like best:

We fitted all our models within a hierarchical Bayesian framework using . . . STAN v.1.3 (Stan Development Team 2012) from R v.2.15 (R Development Core Team 2012).

24 Comments

  1. Nate says:

    I think STAN’s popularity will start to take off. I’m also an ecologist that has used STAN in one published paper (https://peerj.com/articles/376/), one in revision, and one in prep.

  2. Corey says:

    It’s an MCMC wizard
    It samples with a twist
    It’s an MCMC wizard
    Correlations don’t persist

  3. Rahul says:

    Isn’t this a bit like reporting that the middle of the Mojave Desert has a very low incidence of white collar crimes?

    • Phil says:

      I don’t get it.

      • I think he’s saying that the result seems kind of obvious. If stated in the following way I think it makes the obviousness clearer:

        “Species rarely invade wetlands that are frequently inundated unless they are well adapted to frequently inundated wetland locations”

        kind of like

        “white collar crime rarely occurs except in regions where white collar workers work”

        I’m not saying I agree with him entirely, but I do have the sense that maybe there should be something more to the study than is mentioned in the blurb.

        • Rahul says:

          Yes. Nothing against the study but the blurb is interesting.

          • Phil says:

            Either I don’t know what you’re talking about or you don’t know what you’re talking about.

            It is definitely not the case that native species are destined to be the most successful or prolific inhabitants of an area.

            Here in the SF Bay Area, if you drive a bulldozer through an area (to create a fire road, for example) the plant species you are likely to see first are non-native species including Scotch and French Broom for example. Since few local animal species eat them, their roots, or their seeds, these invasive non-native species have a competitive advantage over the native plants with which the fauna co-evolved.

            That could be the case, but is not, in the areas of New Zealand that were studied. One could certainly argue that the study isn’t useful or interesting on the grounds that its results are not generalizable — next year some new introduced species might change the whole picture. But the result is not at all obvious. There are many, many places in the world where non-native species would be prevalent in disturbed areas, including those disturbed by flooding.

            • Chris says:

              I think the assumption would be that environments prone to extremes like flooding would require more specialization to survive, therefore non-native invasions into these areas would be less likely to succeed, making the conclusion in the blurb “We found that invasion by non-native plants was lowest in sites where the physical disturbance caused by flooding was both intense and frequent” the intuitive result, though still worth knowing.

            • Rahul says:

              Isn’t the bulldozer example the opposite of flooding? One is a regular, periodic natural disturbance that has been happening for thousands of years & the other a very recent phenomenon?

              Have species have had enough time for a bulldozer adaptation?

              OTOH, I’d love to hear examples of the assertion: “There are many, many places in the world where non-native species would be prevalent in disturbed areas, including those disturbed by flooding.”

              Are there longstanding, periodic, harsh, intense disturbances that still give an advantage to a non-native species? Where?

              • Phil says:

                I almost wonder if we’re talking past each other in some way.

                Floods occur all over the world. Thousands of species around the world have evolved to tolerate and indeed thrive with periodic flooding. If you introduce one of those plants into some other area, it may or may not have an advantage over the native plants. Replace “flooding” with “fire” or “land disturbance” or “drought” or anything else and this is still the same. And of course no disturbance is necessary at all, sometimes an invasive plant can outcompete the native plants even in the absence of disturbance. This is true all around the world and in all sorts of conditions, so I’m sort of baffled to find it questioned, as though I’m misunderstanding the question.

                You asked for an example involving plants and flooding…this article mentions Purple Loosestrife in the and Japanese Knotweed in the U.S. There are many many more examples.

    • The general point that an invader must in some sense match the habitat it invades is generally pretty well established, but this is an applied paper and they say they show that the effect is more important than herbivory. Without applied studies across a variety of systems in ecology it’s hard to get past back-and-forth arguments like this: person a: “Herbivory controls invasion!”, person b: “Disturbance controls invasion!”, person a: “Herbivory controls invasion!”. Sorting effect sizes across a variety of contexts is useful. It would be even more useful if more studies were conducted with meta-analysis in mind but…

    • JSB says:

      The statement “Species rarely invade wetlands that are frequently inundated unless they are well adapted to frequently inundated wetland locations” is not the best summary. The paper uses the casual analysis to argue that maintaining the conditions that allow for the ephemeral wetlands will reduce the number of potential invasives in the landscape. I am also glad to see this as I hoping to doing something similar with STAN.
      This summary works better from me at least:
      “Synthesis and applications. Predictions of invasions in a world of multiple disturbances clearly need to consider whether the evolutionary history of non-native species predisposes them to invade novel communities. Maintaining hydrological and nutrient regimes of ephemeral wetlands will limit the number of introduced species that are pre-adapted to become invasive.”

  4. jrkrideau says:

    Yesterday I was listening to an interview with a former National Hockey League player who is now part of a paramilitary group guarding the Bruce Nucular facilities in Ontaro and when I say the title I was expecting hints how to deploy the SWAT teams for stikes or the odd terrorist attack.

  5. Joe Bulbulia says:

    Nothing against STAN, but would the practical inference from this study have been different had the authors used MCMCglmm or even (g)mer.

    The article is behind a paywall. I’m on my phone. Apologies if the answer is addressed within the study.

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