Positive Multifunctionality ≠ All Functions Are Positive

Positive Multifunctionality ≠ All Functions Are Positive

I was dismayed this morning to read Bradford et al.’s recently accepted paper Discontinuity in the responses of ecosystem processes and multifunctionality to altered soil
community composition
in PNAS for several reasons.

The paper itself is really cool. They manipulated community complexity and nutrient conditions in the Ecotron, and then looked at five soil ecosystem functions. They then looked at whether complexity influenced multi functionality (as well as N), and found, indeed, it did! They went on and, as recommended in our paper on multifunctionality analyze single functions to understand what is driving that multifunctionality relationship, and then…

Then they fall off the boat completely.

Disappointment #1
They find that, while some functions were affected positively, some were not, and one more was affected negatively. They conclude, therefore, that multifunctionality metrics are not useful.

…multifunctionality indices may obscure insights into the mechanistic relationships required to understand and manage the influence of community change on ecosystem service provision.

The mismatch between our community and fertilization effects on multifunctionality and the individual processes, however, cautions against using the framework as a predictive tool for achieving desired levels of functioning for multiple, specified ecosystem services.

What is frustrating about this is that the authors completely miss what multifunctionality actually tells us.

I’m going to say this once very simply, and then in much more detail –

high multifunctionality ≠ every single function performing well

To quote from my own work, multifunctionality is “simultaneous performance of multiple functions.” No more, no less. A positive relationship between a driver and multifunctionality does not imply a positive relationship between that driver and every function being monitored. But rather that said driver will be able to increase the performance of more functions than are decreased.

Some More Detail
Indeed, in the example in Byrnes et al. 2014, we look at the data from the German BIODEPTH experiment. Some of the functions have a positive relationship with richness. Some do not. One has a trending negative relationship. But, put together, multifunctionality is a powerful concept that shows us that, if we are concerned with the simultaneous provision of multiple functions, then, yes, biodiversity enhances multifunctionality.

In our paper, we advise that researchers look at single functions – precisely because they are likely not all related to a driver in the same way. We state

The suite of metrics generated by the multiple threshold approach provide powerful information for analysing multifunctionality, especially when combined with analyses of the relationship between diversity and single functions.

We say this because, indeed, one has to ask – is the driver-MF relationship as strong as it could be? Why or why not? How can we pull the system apart into its component pieces to understand what is going on at the aggregate level?

The approaches are not in opposition, but rather utilizing both provides a much more rich picture of how a driver influences an ecosystem – both through an aggregate lens and a more fine-scale lens. The similarities and differences between them are informative, not discordant.

Disappointment #2
UPDATE: See comments from Mark and Steve below. This #2 would appear incorrect and a tale of crossed paths not scene. While I cannot find anything in my various inboxes regarding communication, it’s possible either a bad email address was used, or it went missing in my transition between nceas and umb. If this is the case, I’m in the wrong on this. An interesting quandry of how do we resolve these things outside of the literature, and worth pondering in this our modern age of email. I leave my comments below for the sake of completeness, and as there are still some ideas worth thinking about. But, wish that email hadn’t disappeared somewhere into the ether! Now the more my disappointment in technology!

Perhaps the bigger bummer is that, despite this being a big critique of the idea of multifunctionality that our group spent a *huge* amount of time trying to figure out how to quantify in a meaningful and useful way, as far as I know, none of us were contacted about this rebuttle. The experiment and analysis of the experiment is excellent, and it gets into some really cool stuff about soil biocomplexity and ecosystem multifunctionality. But the whole attacking multifunctionality as a useful concept thing?

That entire controversy could have been resolved with a brief email or two, tops. For this group to go so far off base is really kind of shocking, and dismaying.

Dismaying because the advice that would seem to stem from this paper is to go back to just looking at single functions individually and jettison the concept of multifunctionality (no other alternative is provided). That places us squarely back in 2003, with fragmented different types of analyses being used in an ad hoc manner without a unifying framework. Precisely what we were trying to avoid with our methods paper.

And all it would have taken to prevent is a little bit of communication.

References
Bradford, M. A., S. A. Wood, R. D. Bardgett, H. I. J. Black, M. Bonkowski, T. Eggers, S. J. Grayston, E. Kandeler, P. Manning, H. Setälä, and T. H. Jones. 2014. Discontinuity in the responses of ecosystem processes and multifunctionality to altered soil community composition. PNAS. link

Byrnes, J. E. K., L. Gamfeldt, F. Isbell, J. S. Lefcheck, J. N. Griffin, A. Hector, B. J. Cardinale, D. U. Hooper, L. E. Dee, and J. Emmett Duffy. 2014. Investigating the relationship between biodiversity and ecosystem multifunctionality: challenges and solutions. Methods in Ecology and Evolution. 5: 111-124. doi: 10.1111/2041-210X.12143

Getting it Right – after Publication: A Multifunctional Journey?

Sometimes, you have to publish a paper to have the hit-yourself-in-the-head revelation of the real right answer.

Earlier this year, along with a great cohort of colleagues, I birthed a really neat piece summarizing how you can look at simultaneous change in multiple ecosystem functions. We were interested in how changes in diversity can affect the simultaneous performance of multiple functions, but, really, anything can be put on the X axis – warming, fertilization, lemony-fresh-scentedness – it doesn’t matter.

This was a problem that had been vexing the field of biodiversity-ecosystem-function, or, really, anyone who wanted to look at multiple functions. Our group spent multiple sessions bashing our heads against a wall trying to derive a solid analytic strategy to look at changes in so-called multifunctionality and in the end came up with something that I’m pretty proud of. The basic idea of our approach was to look at the slope of the relationship between a predictor and the number of functions ≥ some threshold of their maximum – but then do it for lots of thresholds. Why is it important to looks at lots of thresholds? Well, if you look at the lines for each choice of threshold, you get something like this:

lineplot

Note, that’s from the multifunc R package vignette, and its the analysis from our paper.

Anyway, you can see how the slope and intercept change with different threshold choices. We eventually looked at how slope changes with threshold, and used that to divine a fingerprint of multifunctionality. But, a plot of threshold v. slope – it’s kind of abstract, and can be hard to parse. It was the best we could do, though, as we thought and thought about it.

While working on a recent analysis, I began to wonder – one of the key numbers we want is something like, how does multifunctionality change with the addition or removal of one species? We can look at how one function changes with diversity – but we still don’t have a good something with our predictor on the X-axis. And yet, the question I want to answer is key if we want to think about the consequences of, say, losing species for a multifunctional world.

Discussing this with Jon Lefcheck, I was suddenly struck by something he had done in a figure on a manuscript. He drew a plot like the one I showed above, only, he also put a line across the top at the maximum number of functions observed in an experiment. I noticed that as my eye moved across the plot – from low to high diversity – I could see the color change along the line, indicating that the maximum number of functions were able to hit progressively higher levels of function. At low levels, nothing was able to hit any threshold. At high levels, a few were. So…one could in theory plot diversity against the highest threshold that all of the observed functions could hit all at once.

Lines drawn on top of the same figure for 5 functions and for 2 functions. Let your eye wander along them and note the change in color. Also, note the weird optical illusion at F=2. Yes, that line is actually straight.

Lines drawn on top of the same figure for 5 functions and for 2 functions. Let your eye wander along them and note the change in color. Also, note the weird optical illusion at F=2. Yes, that line is actually straight.

Moreover, if I were to, say, draw a line at a lower number of functions, I would see the same pattern – but the relationship would change. Now, higher thresholds could be reached by a lower number of functions – but, eyeballing it, it looked like the linearity changed. In some ways, it made me think of, in the BEF literature, if we have only one function, we get a saturating curved relationship between diversity and function. But for multifunction, a few of us have long wondered if we might get a more linear relationship.

So, for the German example, I decided to whip up some simple code to explore the relationship between diversity, number of functions, and maximum threshold those functions can achieve. I used the fitted model, and then just calculated which thresholds could achieve some number of functions at a given level of diversity, and grabbed the maximum. The results are interesting.

newmf

You can see that fewer functions can simultaneously achieve a higher threshold – this is predictable. But there’s a suggestion that the curvilinearity of the relationship switches from linear to concave-up as more functions are considered. That’s it’s linear to begin with is notable, as with few functions I would expect more concave-down-ness. And you kinda get that if you run it down to one function, but, this site in general in earlier papers didn’t have an incredibly strong saturating relationship compared to some other classic examples.

Overall, while it takes a bit of a moment to realize what’s going on, I think this is a far more interpretable graph than what we presented in the paper. I haven’t subjected it to the same in-depth can-this-be-fooled simulations that we did for the MEE paper, but, I have to admit…I kind of like this, and think it might be the answer we tried to get at oh so long ago.

A Kelpy Time Machine

This is x-posted from my guest post at Deep Sea News about the new Floating Forests citizen science project I’m part of. If you’re excited about it, go check out http://www.floatingforests.org/!

avatar_kelpThere’s something I’ve always wanted. Something that would take kelp forest science to a new level. Something that would let me do the kind of work that I dream about, quietly, secretly, peering into the mysteries of kelpiness.

It is something impossible.

It is a time machine.

And now I have one. But with a catch. For you, my dear friends, are its pilot.

OK, OK, first, why use a time machine as a tool of science, and not, I don’t know, to right wrongs and make the world a better place? Well, first off, temporal paradoxes, y’all. Come on. Be realistic. Has Doctor Who taught us nothing? Or decades of Star Trek? Or Primer? (seriously, see that last one, as it will hurt your brain in a good way).

But then, why, kelp? What? Hear me out.

There are so many things that we as marine biologists want to know about the state of ecosystems in the past. For many things, we hardly ever have records that are older than ten usually for just one small area. This is really problematic – especially for something like Giant Kelp.

You see, Giant Kelp (that’s Macrocystis to you!) is kind of the bad-ass of the algae world. It’s pretty damn huge – up to 60m long in some places – and grows up to a foot or two a day. It’s so damn big, we can see it from orbit1.

https://seaweedindustry.com/

Photo courtesy of the Seaweed Industry Association

It’s also everywhere – from Alaska to Baja to South Africa to much of South America to New Zealand to the sub-Antarctic islands. And, according to the Lane et al. phylogeny, it’s all one species2. It gets *around*. And wherever it is, it feeds, houses, and nourishes much of the life in the sea around it.

So, where does the time machine come in, and why are you piloting it?

Simply put – Keeeelllppp Innnnnn Spaaaace!

The Landsat family of satellites have been orbiting earth, taking photos of the whole globe twice a month since the early 1980s. Photos where we can see kelp. They are a time machine we as scientists can use to go back and see how kelp has changed over thirty years.

Can we see the near-extinction of giant kelp from Tasmania? Can we see it moving around the coast of South Africa? Has it been walking away from the warming equator? Is there more or less now than there was in the past?

OK, this sounds pretty cool. But where do you, our time-traveling pilots come in?

Basically computers suck.

OK, no, really, we love them. *pets shiny Apple laptop* BUT – they cannot tell kelp from waves or clouds in the Landsat images. My collaborators (the real remote sensing part of this team) have tried. It’s a no-go. We actually need people – kelp hunters, if you will, to peer at the millions of images of potential kelp habitat and help us discover these Floating Forests.

We need you.

Working with the Big Momma of online citizen science, Zooniverse, my collaborators from the Kelp Ecosystem Ecology Network (KEEN) and I have created an online citizen science project called Floating Forests. In it, we ask you to take a look at images. Help us cull out bad ones (they’re satellites – they take pictures cloudy cloudy rain or (often still cloudy) shine, or take pictures of more than we think.

And if you see kelp, circle it!

We'll give you images of coastline - like this July 2001 picture of Santa Cruz on the left. You circle the kelp beds, and that yields data about kelp abundances, as you can see on the right.

We’ll give you images of coastline – like this July 2001 picture of Santa Cruz on the left. You circle the kelp beds, and that yields data about kelp abundances, as you can see on the right.

It’s really quite meditative to see images of the land and see whisk by, pausing periodically to lasso a green bed of kelp.

Maybe you’ll see a wave-swept vista of Point Lobos. Maybe you’ll see the Googleplex (I did – by accident). Maybe you’ll see somewhere you’ve never dreamed of traveling, but with that big kelp bed sitting there, you know the destination of your next dive trip.

So, please, go hop into the pilot’s stick of this magical kelpy time machine. Poke around. And ask questions! We scientists are there to talk to you! What are you waiting for?

Yes, this is the entrance to a time machine.

Yes, this is the entrance to a time machine.

1.Cavanaugh, K., D. Siegel, D. Reed, and P. Dennison. 2011. Environmental controls of giant-kelp biomass in the Santa Barbara Channel, California. Marine Ecology Progress Series 429:1–17.10.3354/meps09141
2. Macaya, E. C., and G. C. Zuccarello. 2010. DNA barcoding and genetic divergence in the Giant Kelp Macrocystis (Laminariales). Journal of Phycology 46:736–742. 10.1111/j.1529-8817.2010.00845.x

Damn, That’s Some Big Kelp!

I’m not sure what it is this year, but the kelp we’re seeing in the Southern Gulf of Maine is just fracking huge. Last year, yeah, there were kelpy areas, and there were kelps that were ~1-1.5 meters long, which, you know, impressive. But this year…

It started when Team Dive (this summer, we have Team Marsh – #marshlife – and Team Dive going on) hit up the outer Boston Harbor Islands. We hadn’t been out much since winter. They found vasty fields of Laminaria digitata and Saccharina latissima (well, with their super-long stipes, they looked like S. longicruris, but it looks like they are now the same species – e.g., Cho et al. 2000 and others). How big? Twice the size of a grad student!

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But this was at the mouth of Boston Harbor. Maybe a fluke, or eutrophication?

As we kept working up in Salem Sound, though, the kelp seemed…well…big! But, eh, still urban-ish, still maybe an urban thing… (although it was *not* so big last summer).

If anywhere should be free of the urban influence, it should be Appledore Island in the Isles of Shoals. It’s a few miles offshore, and has lots of microenvironments. And yet, everywhere we look – big-arse kelp! Super dense kelp area where last year an intern almost lost her mind counting kelp stipes? Still mind-exploding. Except now you have to count stipes by feel while your face gets wrapped up in the giant lasagna-blades of Saccharina. And it’s just as big.

OK, I’m 6’2″. And a half. (~1.88m). Here’s me, with my fins just barely touching the seafloor.
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It’s everywhere! Even in the wave-protected low-kelp density Heterosiphonia sites, while we do find lots of smaller kelps, the monsters still abound. See how it compares to the size of Team Dive.

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This isn’t to say it’s *all* that huge. A size distribution from the site that piece came from for reference:

14508450178_38a07a7ff0_k

But, still, what is up with this? Big kelps coupled with very cold water temperatures of course has my California trained brain thinking more time with high nutrients, but I don’t know whether that relationship is as strong here in the southern Gulf of Maine. It’s making me very excited to see the oceanographic work that comes out in the next year or so to see just what forces are driving all of this!

And even more curious to know what’s going to happen next year, as we’re seeing massive numbers of tiny urchin recruits (and a lot of sea star recruits) often folded up in the eroding tips of many of these big honkers. Or on Desmerestia, like ornaments on a Christmas tree (240 in a square meter plot yesterday!).

References
Cho, G. Y., H. S. Yoon, S. M. Boo, and C. Yarish. 2000. Atlantic kelp species Laminara longicruris and L. saccharina (Laminariales) are conspecific. Journal of Phycology 36:12–13.

The Launch of the R/V Botryllid

Woohoo! It’s another amazing research season out here at the Shoals Marine Lab. We’re in the midst of our push to sample SML, Salem Sound, and the Boston Harbor Islands. The weather is glorious, and the water is…ok, not warm. 47F this year. Last summer at this time it was a good 5 degrees F warmer. But, either way, here we go on our summer Shoals sampling adventure!

maiden_voyage_of_the_rv_botryllid

Marshall the generalists! Generalize the marshallists!

While working more on the bacterial network stuff, Jen and I realized I was wrong. Yep, I was wrong on the internet. Namely, in my post on bacterial networks, I got the answer wrong on the abundance of OTUs with different degrees of specialization. I had a rowSum after inverting a matrix instead of before, producing wonky vertex sizes. Jen cleverly discovered it when totaling up some of the data by hand, and after alerting me to the issue I produced the following plot which doesn’t agree with the network at all:

Screen Shot 2013-07-02 at 1.29.24 PM

So, I went back in, found the error, and now I give you the corrected network. Still very interesting – and it really shows that in the marsh, generalist bacteria dominate numerically, although they are relatively rare with far more specialists.

Screen Shot 2013-07-02 at 1.23.17 PM

Updating the github soon…

Beautiful Bacterial Networks in the Marsh

“So,” I’m sure you aren’t wondering, how did that creating ‘ecospecies’ from bacterial sequences based on sequence similarity, co-occurrence, and network theory work out for you?”

Quite well, thanks for asking! Heck, have a git repository, why dontcha!

Jen is furiously writing the manuscript, but, the technique indeed seems to indicate that 12% sequence similarity was the optimal number.

Once we got that down, and started plotting the network with individual Operational Taxonomic Units (OTU) each connected to one or more of the 8 plots they were found in, we started seeing some neat things. More more than that, they were just pretty pictures! I mean, come on, these plots are always cool.

Screen Shot 2013-06-26 at 4.18.40 PM

First, you can see that there is indeed some separation of species by plot and treatment (# is plot, letter is treatment). We got really excited about this, and so dug deeper to produce…

Screen Shot 2013-06-26 at 4.19.49 PM

Yes. Not you can see that most OTUs are specialists. True generalists are exceedingly rare.

We had one other piece of information up our sleeve, though. Abundance. We have abundances of OTUs. Playing around with edge widths (abundance in plot) didn’t produce anything striking. But then we looked at total abundance of an OTU across the whole marsh, and resized OTU nodes accordingly. I think this is exceedingly beautiful. And shows some striking patterns with respect to treatment and who is most abundant.

Screen Shot 2013-06-26 at 4.19.10 PM

Jen knows this experiment backwards and forwards, so is writing a much more nuanced discussion of what this means, and analyzing the data in more detail. But it’s pretty awesome. And pretty beautiful.

Just another way of viewing the wonder of nature.

p.s. I am learning to love RColorBrewer in a serious way

Walkin’ in an Invasive Wonderland

Last day of dives before heading back. We hit two sites on either side of the northern head of Appledore. It’s a remarkable break, as on one side you have fairly decent expsore to waves from the West. On the other, things are fairly protected. So, there’s a strong physical gradient. And, though perhaps just a few hundred meters apart, the two sites could not be more different. At the first site, the photos didn’t come out terribly well, but this gives you a general sense –

It was Halosiphon as far as the eye could see - like diving in a bed of furry ropes.  Or very thin muppet arms.  No, wait, that's just odd... although it would fit nicely in  Dark Crystal or Labyrinth.

It was Halosiphon as far as the eye could see – like diving in a bed of furry ropes. Or very thin muppet arms. No, wait, that’s just odd… although it would fit nicely in Dark Crystal or Labyrinth.

Lots of adorable cunner swimming about, but, man, churned up. A little Heterosiphonia about, but, not too bad.

Then we rounded the corner. And saw…

DSCN0105

It’s like somebody defauntated the rumpus room and decided to give the entire subtidal a nice shag carpet. I mean, sure, it hides the stains, but…

More than that, the site was quite bouldery. But what invertebrates were on the boulders?

DSCN0115

Oh, look! It’s my old friend Didemnum vexillum from the Left Coast. It’s here, in force. I’ve seen spots of it all week, but, nothing like the giant area covering colonies of the Bodega Harbor jetty or the docks. And yet, here it is. Sure, there’s some Desmerestia thrown in for good measure, but, more or less, it’s all invasives, all the time down here.

What is going on? How long will this state last?

Undersea Carpets?

The second site of the day was a surprise. 10 years ago, Smith’s Cove was a mixed mussel bed and urchin barren. Previous, it has been a Codium meadow. Now… It’s just a giant red algal carpet. Wall to wall. Thick, easily fragmenting, ubiquitous, invasive red Heterosiphonia japonica. Also, big tufts of Ulva. And some other bushy filamentous algae scattered about, along with a few crabs.

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What a weird landscape. What is that red carpet doing? Smothering things? Creating habitat for mobile invertebrates? Providing food, or is it not that edible? The reef was like this as far as we swam and looked around – hundreds of square meters. Weird.

Yeah, that's 100% cover.

Yeah, that’s 100% cover.

Kelp on a Ledge!

Day 2 of dives with Sarah out at SML. Today we hit two sites that were quite different – both from each other and from Norwegian Cove the other day. The Ledges are in the channel between Appledore and Smuttynose, so, they get good flow running through. This was key, as it blew sediments from the previous day’s storm out fairly quickly. And viz was really quite nice. While it used to be a barren (at least on one side) 10 years ago, it appears that it’s now a mix of kelps and Desmarestia with some Chondrus, filamentous reds, and others thrown in for good measure.

A nice mixed algal assemblage.  And a mix of kelp ages and sizes.

A nice mixed algal assemblage. And a mix of kelp ages and sizes.

Indeed, some parts were super kelpy, although, not dominated by large adults. The mix of sizes was fairly astounding, even where thing were at high densities.

Note all of the little guys hanging about.  I mean, it is still early June, so, it may be recovery.  But how cute are these little ruffled kelpies!

Note all of the little guys hanging about. I mean, it is still early June, so, it may be recovery. But how cute are these little ruffled kelpies!

Note all of the holes you see, though. The site was also packed with little snails like Lacuna vincta that appeared to be doing quite a job on the kelps.

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What will this mean for later in the summer? Particularly with Heterosiphonia around in patches.

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All in all, a nice site to sample. More soon on Smith’s Cove. Which was…