#29: Adam Kranz – The Amazing World of Plant Galls

#29: Adam Kranz – The Amazing World of Plant Galls Nature's Archive


My guest in this episode is Adam Kranz. Adam has a BA in Environmental Studies from Lawrence University in Wisconsin, and a Masters of Science in Natural Resources and Environmental Science from University of Illinois Urbana-Champaign. His thesis was on insect pest ecology in diverse agroforestry plantings, but of late has taken a special interest in plant galls. He’s since founded Gallformers.org, which is a website designed to be the authoritative resource for all plant galls of the United States and Canada.

We start out discussing a bit of background about how Adam got into galls and how gallformers came to be. If you’re listening now and wondering “what’s a gall anyway?” Well, these are beautiful and sometimes bizarre growths on plant tissues induced by another organism, such as a wasp, midge, aphid, mite, or many others. They often develop vivid colors and evocative shapes, and all have fascinating natural histories. These growths occur specifically to support the life cycle of the inducer, and are often induced in amazingly precise ways that you’ll have to hear to believe. For example, Adam explains how the larvae inside the gall may steer the plant response throughout their lifespan! By the way, I have photos of several of these amazing species below in the show notes and on my instagram @naturesarchive. You’ve really gotta check them out.

[UPDATE 14 Sept 2021: I was just made aware of this wonderful paper in the Molecular Ecology journal published 12 September, which shows the extend to which a galling insect manipulates its host plant genome. And here is the corresponding Twitter thread from @wasp_venom.]

[UPDATE #2 16 Sept 2021: Past guest Dr. Merav Vonshak has created “Gall Week 2021”, running from 2021-10-02 to 2021-10-10. This is a global event, and to participate join the iNaturalist project and submit observations!]

[UPDATE #3 18 August 2022: Gall Week 2022 is ON! Sept 3 – Sept 11, 2022. Here’s the new iNaturalist project.]

Disc Gall Wasp Andricus parmula

We also discuss strategies and techniques for looking for galls in the field. They are quite common throughout much of the world, and many can be easily identified. We discuss some of the attributes of a gall that might be helpful to identify them, when and where to look, what makes for an identifiable iNaturalist observation, and other plant growths that might be confused with galls.  And as it turns out, there is still much to learn about galls, so they are a great area of focus for naturalists looking to discover and describe new species.

Adam also gives a nice overview of three extremely interesting galls that are among his favorites. Each of these have fascinating natural histories, including peculiarities like hollow centers with free-rolling cells, and what might be considered a gall threesome, where a second cynipid wasp comes along and entirely changes the gall’s developmental trajectory. Of course, Adam describes this in a much more scientifically accurate way.

Photo by Adam Kranz

You can also find Adam and Gallformers on twitter @gallformers, and Adam on iNaturalist @megachile.

While you are welcome to listen to my show using the above link, you can help me grow my reach by listening through one of the podcast services (Apple, Google, Stitcher, etc) linked on the right. And while you’re there, will you please consider subscribing? Thank you.

Links To Topics Discussed

People and Organizations

Biodiversity Heritage Library


Charley Eiseman’s blog BugTracks

iNaturalist Gall Projects:

Books and Other Things

Plant Galls of the Western United States, by Ronald Russo – HIGHLY recommended

Tracks and Signs of Insects and Other Invertebrates by Charley Eiseman – also HIGHLY recommended, introduces galls, and many other great naturalist topics including leaf mining insects, eggs, signs of feeding, and more.

Weld Cynipid Books: Free via the Biodiversity Heritage Library and Hathitrust

Note: links to books are affiliate links

Previous Podcasts Mentioned

Music Credits

The following music was used for this media project:
Music: Spellbound by Brian Holtz Music
Free download: https://filmmusic.io/song/9616-spellbound
License (CC BY 4.0): https://filmmusic.io/standard-license
Artist website: https://brianholtzmusic.com


Transcripts are automatically created, and are about 95% accurate. Apologies for any errors.

[00:00:00] Michael Hawk: Hey everybody. Before I get into the standard intro, I just wanted to say that I’m super excited about this episode. As naturalist, one of the most fascinating areas of study is Plant Galls. I hope you get a taste as to why that is today, and you might note that my voice is a little well off. I do have a head cold, so hopefully it isn’t too distracting, or maybe you actually like this voice better.

[00:00:20] If so, let me know, but I’m not sure there’ll be much I can do. So my guest today is Adam Krantz. Adam has a BA in Environmental studies from Lawrence University in Wisconsin, and a master’s of Science and Natural Resources in Environmental Science from the University of Illinois urban Banish Champaign.

[00:00:36] His thesis was on insect PEs ecology and diverse agri forestry plantings. But of late, he’s taken the special interest in plant galls. He’s since founded gall forms.org, which is a website designed to be the authoritative resource for all plant galls of the United States. And. We start out discussing a bit of background about how Adam got into Galls and how golf form came to be.

[00:00:56] If you’re listening now and wondering what’s a gall anyway, well, these are beautiful and sometimes bizarre growths on plant tissues induced by another organism such as a wasp amid, or many others. They often develop vivid colors and evocative shapes, and all have fascinating natural histories. These growths occur specifically to support the lifecycle of the inducer and are often induced in amazingly precise ways that you’ll have to hear to believe.

[00:01:21] For example, Adam explains how the larvae inside the gall may steer the plant response throughout the entire life. By the way, I have photos of several of these amazing species and the show notes in on my Instagram at Nature’s Archive. You’ve really gotta check ’em out. We also discussed strategies and techniques for looking for gulls in the field.

[00:01:40] They’re quite common throughout much of the world, and many can be easily identified. We discussed some of the attributes of a goal that might help you to identify them, when and where to look, what you can do to improve your chances of an ID on iNaturalist. And we talked about some of the other plant growths that might be confused with Gus and as if the crazy shapes and colors and interactions weren’t enough.

[00:01:58] It turns out there’s still a lot to learn about Gus, and there are great area of focus for naturalists looking to discover and describe new. Adam also gives a nice overview of three extremely interesting Gus that are among his favorites. Each of these have fascinating natural histories, including peculiarities, like hollow centers with free rolling cells and what might be considered a gall threesome, where a second synopi wasp comes along and entirely changes the Gall’s developmental trajectory.

[00:02:23] Of course, Adam describes this in a much more scientifically accurate way. You can find Adam and golf formers on Twitter at Golf Forms and Adam on iNaturalist at Mega Child. So without further, Adam Kranz. Adam, I really appreciate you joining the show today. Thanks for having me. So the topic of Galls I think is really of a lot of interest to a lot of naturalists and for me here in California, we’re in peak gall season right now as we’re recording this.

[00:02:49] So I’m really excited to have you today and get into the fascinating natural history of gulls. Before we dive into that, however, I want to understand a little bit about how you found goals and maybe we go way back, and how did you get interested in nature in the first place?

[00:03:04] Adam Kranz: I actually came to natural History from an activist political angle.

[00:03:08] I was into like anarchist anti civilization sort of politics as a high school kid, and that sort of gave me this idea that nature was something that I needed as an expression of my personal values. Get to know. That led me to, once you start studying nature, the interest of it takes hold on its own. At that point in my life, I’m interested in nature, but never really got all that far as a natural historian.

[00:03:31] And so for me, it wasn’t until actually I discovered iNaturalist after grad school that I actually started making headway as a natural historian on my own. So I, it was the, the computer vision, which as many of your listeners probably are familiar with, uh, the computer vision on I natural. Provide suggestions about what, you know, your observations are.

[00:03:50] And that just opened up this whole world. It made it the sort of frustrating, difficult activity of finding out what all this stuff I was seeing actually was. Finally that dam broke and I was able to get off and figure out what these things actually were. And that was really exciting for me and it kinda took, took over my life at that point.

[00:04:06] And so ever since I’ve been kind of obsessed with using inet and after that I, you know, I. Getting into different things. I, I got Charlie Eisenman’s book Tracks and Signs of Insects, uh, and I was focusing on all the sorts of different things that he talks about in the book. Leaf Miners, eggs, and. Puy and all these sorts of different interesting things that you see.

[00:04:25] And I realized that of all of those things, plant galls were just this massive world that his book like barely scratches the surface of, and that in terms of the expert community on Inet, there wasn’t anybody out there who was focusing on this and, and there’s just all of this work that needed to be done in terms of identifying old observations and making new species and all of this stuff that once I started.

[00:04:46] Doing that a little bit. It was just a rabbit hole where it kept getting bigger and bigger and I realized how enormous this project was actually gonna be in order to take care of this stuff. And it’s been an obsession for me ever.

[00:04:56] Michael Hawk: Yeah. When I had Charlie on this show, in fact, uh, he said that each chapter of his book could be an entire book in and of itself, which he has gone to prove with his Leaf minor online book.

[00:05:08] In fact, I think each chapter of, of his book could be a whole volume, uh, set of books. I wanted to back up real quick with to the computer vision, the CV part of iNaturalist. As I understand it, that is the machine learning aspect of iNaturalist where there are reference photos that then inform the identification suggestions that I a P provides.

[00:05:33] I from some of our prior discussion in, in preparing for this show, it sounded like you were actually working to fill in some of the gaps there so that the computer vision could be improved for goals. Is that accurate?

[00:05:45] Adam Kranz: Yeah. Yeah, so that’s one of the things I found really exciting at first when I started using i a, is that I realized that there were a couple of really common things that the existing computer vision was already able to identify.

[00:05:56] But then I was finding all of these sort of under observed species that were still relatively common, and I thought, what’s it gonna take to make it so that in the future, those OB observations would be identified correctly? And I talked to the people on the INET team and realized that you just needed to get over a certain threshold that they needed.

[00:06:14] Minimum of a hundred observations for each species to get them included into the next training batch for the CV in the future. And so that was really motivating for me, you know, of the species that I already knew to go out and find more observations in my area, take more pictures, upload them, but also to go through and identify other observations that.

[00:06:32] Would get to that goal from other people in other parts of the country. And like I said, once I started doing that a little bit, I realized, well, there’s all these other species that aren’t even on the site at all. It’s just this huge, uh, backlog of literature and all of these observations that are waiting for identification, that somebody’s just needs to come along and put in the time to, to connect those.

[00:06:53] Michael Hawk: So I had no idea that there was a threshold of a hundred observations are is that research grade observation? There’s.

[00:06:59] Adam Kranz: particular details to it. I don’t want to go on the record with specifically what, what those are. It’s something like 50 research grade plus a minimum of 10 observers. Is it some traits that they, they yeah.

[00:07:09] Apply to make sure that it’s diverse and stuff. Yeah,

[00:07:12] Michael Hawk: that makes sense. You could have one person misidentifying something a hundred times and you wouldn’t want that to to necessarily go into the computer. Yeah. So they have some safeguards to avoid that. Yeah. Makes sense. So you’ve taken this interest, like you identified this niche.

[00:07:26] Needs more help and uh, you’ve actually now developed a site called Golf Forms. Golf forms.org is where you can find it. Can you tell me about what that project is, what your goals with that project?

[00:07:36] Adam Kranz: Yeah, like I said, when I discovered that there’s this huge sort of literature, so maybe a hundred years ago, people were pretty interested in the natural history of golf.

[00:07:44] There’s a lot of publications in the academic literature. There’s a fair number of popular publications. Uh, and so these are all out there. You can access these all on websites like the Biodiversity Heritage Library. Most of them are public domain, but naturalists today, basically don’t know these books exist.

[00:07:59] So I knew of one, the weld book about CIP wasps I got from um, Charlie Isman. But other than that, nobody seemed to be aware that all these publications had been released, that this information was freely available. And so the goal of our website Golf Farmers is basical. To take all of that primary literature information, and for one thing, just to make it like conveniently available for a naturalist today, by combining it with an ID tool that lets users search by field obvious traits, right?

[00:08:30] So if you’re looking at a gall on a plant, If you can identify that plant and then you can answer a few simple questions about what that gall looks like, where you find it on the plant, what color it is, season, stuff like that. Basic field traits that don’t hopefully require a ton of expert knowledge.

[00:08:44] Then that ID tool is gonna present you with a short list with good pictures where available that are gonna let you easily identify that species that you’re looking at in the field. So that’s one of our main goals. And then our other goal is to. Expand that literature. There’s quite a few publications documenting Gus from the past 150 years or so.

[00:09:03] But the work is by no means anywhere and you’re done. And it’s actually an area that if you’re a naturalist who’s interested in finding undescribed species or contributing to the sort of frontier of scientific knowledge, gulls are a great place to do it because we have, even in places that are relatively, you would think relatively well studied, a lot of undescribed species in North America.

[00:09:21] It’s a great place. contribute to knowledge there and our website hopes to facilitate that by collecting and organizing observations of undescribed calls.

[00:09:29] Michael Hawk: So I know it’s a relatively new site, how much progress have you made at this point and uh, what do you see as next steps? Sure. So

[00:09:36] Adam Kranz: we got started around the beginning of 2021.

[00:09:39] We’ve been building the site on the technical side and then filling in data for maybe, I dunno, four or five months now, uh, in sort of a pretty active. at this point, we have almost 2000 gulls listed on the site. Of those, almost half of them, so about a thousand are oak gulls, and we have a complete set of all of the described oak gall species from North America.

[00:10:01] So yeah, at this point we’re just trying to fill in that, that database expanding out to other hosts, plant Jenna, and just looking for other observations to, to fill in and then taking more things from the literature. So for anybody

[00:10:12] Michael Hawk: listening right now that wants to help contribute to golf farmers, what can they do?

[00:10:17] Sure. So

[00:10:18] Adam Kranz: golf farmers is by amateur naturalists for amateur naturalists. So none of us are experts. We’re not in academia necessarily, and we’re all people who are just trying to find information about GS and build this sort of collective area of knowledge. One thing that helps us obviously, is just for people to observe GS and put those observations on iNaturalist or a website like bug guide where we can find them and see if.

[00:10:42] Contribute to our, the knowledge that we’re trying to build. But if people are interested in going beyond just being an observer, we are definitely looking for more people to contribute to the site as admins. So maybe pick off an area, uh, where you live or a taxonomic group that you’re interested in, and to find the literature and to fill in the gaps in our, our database, because our project is pretty ambitious and it’s never gonna get anywhere close to complete unless we.

[00:11:07] Interested active users who are helping us, uh, fill in that

[00:11:10] Michael Hawk: data. And is the scope North

[00:11:12] Adam Kranz: America? Yeah, so our intended scope is the us, the continental US and Canada. Although we do have a little bit of a few OB species that we include from Mexico and other parts of Central America. The problem is that once you get outside of the US and Canada, the literature is.

[00:11:32] Much thinner relative to the diversity of species. And so we just end up having a lot of UND described species, which isn’t undesirable, but it makes the website less useful than it is in the US and Canada. So that’s our main focus. That

[00:11:43] Michael Hawk: would be such a huge undertaking as well. I can only imagine if you’re talking a couple thousand known species here, then you expand that to, to.

[00:11:52] Places like Mexico or the tropics or the whole rest of the world, there’s gotta be tens of thousands. Yeah,

[00:11:56] Adam Kranz: if you look at oaks alone, but the diversity of oak species going from the US to Mexico, like doubles. And that makes everything so much harder because gulls are so host specific that you need to have an ide, a species identity for the host.

[00:12:09] And people don’t know how to do that, and we don’t know how to help them do that. Less resources available. It’s just much more

[00:12:13] Michael Hawk: difficult. So we’ve been talking about goals as if everybody knows what they are, but haven’t really addressed what they. How they’re formed, things like that. Can you tell me what is a plant gall?

[00:12:24] How do they form? Sure. So

[00:12:27] Adam Kranz: a plant gall is basically a novel organ of a plant that can only exist because the plant develops in a way that’s guided by some other organism. So we call these inducers, call inducers. They can be all sorts of things, wasps, midges, mites, aphids, fungi, even nematode. , all sorts of different taxa have developed a strategy.

[00:12:50] And basically it’s a form of herbivory where the plant is induced to create a structure that protects and feeds the inducer. Uh, so it’s an alteration of the plant’s development. It’s not, people often make the mistake of thinking that Gs are some kind of a tumor or like a scar tissue that’s developed in response to like feeding damage, which is something you often see with other kinds of herbivory.

[00:13:13] But Gus Aren, aren’t that sort of like a chaotic response? Right. Aga is a specific design that the plant creates using plant jeans to a design created by the inducer. That’s tricky to wrap your head around, but the idea is that it’s plant gene plants are supplying the sugars. All of the, the compounds that create the, the.

[00:13:37] It’s just that they’re expressing those genes in a way that the plant could never do on its

[00:13:41] Michael Hawk: own. Yeah. And I guess that sort of interaction then explains why for individual species, the galls always look pretty much the same. Yeah. The morphology ends up being consistent, uh, across different individuals of the same species.

[00:13:56] Adam Kranz: Yeah, absolutely. It’s part of, I guess what, what you call the extended phenotype of the gall inducer. It’s just that includes not just the plant itself as a niche that organism lives in, but specifically the genetic information of that plant that they’re altering as a part of their life

[00:14:12] Michael Hawk: history. So you mentioned there’s a number of different families of organisms that can induce skulls.

[00:14:19] they can also induce them in a number of different places on a plant as well. Are there any insights, first of all, like where do you typically see a goal, but are there any thoughts as to why certain strategies maybe are taken on to choose a certain location for for a goal?

[00:14:34] Adam Kranz: So we find plant goals on all different parts of host plants.

[00:14:38] There are leaf gulls, and this is part of what our ID tool@golffarmers.org is built on so that there’s this long, very specific co-evolutionary relationship. that you need to have in order for an inducing organism to specifically play these plant, host, uh, genes in the right order, in the right way to develop this novel organ.

[00:14:59] Right? It’s not something you can just move from one plant to another, but it gets a lot even more specific than that because the, the, uh, genes that they’re stimulating, the, the structures that they’re creating can only be created on particular parts of the planter. So some goals can only be formed on.

[00:15:15] Plant stems. Some are found on uh, flowers, some are on fruit, some are on the roots. Different parts of the roots, rhizomes versus other parts of the root, just the root crown. And then on the leaves you have gulls that are only found on the angle between the veins. Some gauls are only found in the upper side of the leaf, some only on the lower, some only on the midrib.

[00:15:35] Uh, and so we take advantage of all that specificity to, uh, facilitate our ID tool to. Tell people where or what species they’re likely to look at, be looking at based on where it is on the plant.

[00:15:45] Michael Hawk: If we were to maybe look at, say, let’s pick, uh, CIP wasps as one focal, you know, area for this, can you walk me through then when, how, et cetera that they induce the gall?

[00:15:58] Like, uh, it sounds like there’s a very specific timing that has to be followed here for them to be successful in this.

[00:16:05] Adam Kranz: Yeah. Absolut. Each wasp has its own target part of the plant, but they also have particular seasons and parts of the plant’s development. So there’s sort of a temporal, uh, niche partitioning here as well as, uh, physical.

[00:16:18] And so a snippet wasp will lay eggs. So let’s take species that occurs in the spring will lay eggs in the bud tissue before the leaves and stems of the, the New Year’s growth emerge. And then those eggs. We’ll hatch into larvae and those tiny little larvae. This, this is, to the best of my understanding, the larva are primarily responsible for actually inducing the gall as that New Year’s growth grows around them.

[00:16:47] So whether they emerge in the spring or in the fall, those structures develop as the plant tissue grows, and they’re constantly changing the chemicals that they’re emitting into the. To update based on what stage the gull, the growth of the gall is in. So, you know that it, it creates the structure at the right time and in the right place and with the right traits that the inducer wants it to have.

[00:17:08] Michael Hawk: So potentially for a spring gall like that, the adult is laying the eggs very early in the season if it’s still mm-hmm. , uh, in bud form.

[00:17:18] Adam Kranz: Yeah, so here in Michigan I saw a lot of CPI wasps over positing in around March, back when there’s still snow on the ground and they’re actually a relatively easy thing to observe as well.

[00:17:28] Just the wasps themselves because they’re very slow and you know, the cluster on the, the same sort of host plants that you expect them from the Gulf. So

[00:17:35] Michael Hawk: that’s a good point to start looking early then and, and these are typically. , very small wasps. You said they’re, they’re easy to to find, but they aren’t like super dramatic.

[00:17:46] You have to look pretty close, I think, to see ’em still. Right. And the adults that are over positing so early in the year, have they just emerged from the previous year’s, Gus? Where have they been? All

[00:17:57] Adam Kranz: winter. Yeah. So a lot of gall life cycles involve pupation. And overwintering either on the forest floor inside of aal, and sometimes this can last for multiple years.

[00:18:09] So a lot of oak gall wasps, because oaks are, I think this is presumably something to do with the fact that oaks, oaks are a masking species. So the abundance of available acorns at any given year might be very different. And this might also be just to avoid cycles in in parasitoid or predator abundance.

[00:18:24] But many Gus will persist on the forest floor for multiple years, and then the last will emerge from the Gaul. At at the time it’s appropriate for it to over posit will emerge from the gall and go find its target

[00:18:36] Michael Hawk: organ. Yeah. So a number of different strategies then involved in overwintering. And one other thing you said that sort of piqued my interest is the the root gus that could be on different parts of the root.

[00:18:47] And that’s just gotta be so difficult to actually observe because I don’t think there are many naturalists going around, digging up plants to

[00:18:54] Adam Kranz: inspect the roots. Absolutely. Yeah. That’s an area where, Have a pretty good reason to guess that there are a lot of undescribed or never reported species, uh, just because you don’t see ’em, they’re hidden underground.

[00:19:06] To

[00:19:06] your

[00:19:06] Michael Hawk: knowledge, has anyone gone out and actually attempted to do any sort of survey? So I

[00:19:11] Adam Kranz: know because Oak Galls sign NPI galls on oaks are, are particularly well studied. We know that there are quite a few root gus that occur on oaks, and part of that is people looking for. Alternate generation. So not only do sy snippets over winter in Gus on the ground or sometimes in the tree itself, depending on wh where the gull is, but many snippet species have alternating generations within a year.

[00:19:35] So they’ll have what we call an agam generation where there are only female wasps, and then the eggs laid by that generation will contain both male and female wasps. We call that the sexual generation, and those two gulls can be extremely. And so we have something like a a thousand known gulls from oaks right now.

[00:19:56] And of those maybe over 600 of them are named described wasp species. And presumably the majority of those wasps occur in pears. So we know them as 600 different species, but actually they’re may be only 300 species that we don’t realize yet. We haven’t connected that they’re alternate generations of the same species.

[00:20:16] Uh, so that’s an active area of research to try and connect those alternating generations. Uh, and a lot of the root galls are alternate generations of species that also form gulls on leaves or flowers or acorns.

[00:20:30] Michael Hawk: Yeah, that’s just . So like mind blowing and fascinating. You mentioned that there could actually be a.

[00:20:36] Reduction in number of species as we start to figure these things out. At the same time, I know there’s a number of different factors that could result in splitting of species, and there’s all these undescribed species as well. Have you seen cases where there’s a gall that looks very similar, say on a set of western oaks as eastern oaks, but turns out.

[00:20:56] through research, through dna. I, I don’t know, some discovery that they’re actually, uh, different species or I, I, I’m not quite sure what the right question to ask there is, but how do these splits tend to come about?

[00:21:08] Adam Kranz: I, I think at the, at the moment, most of our gulls lean toward, because of the nature of Gauls as a natural history object, they lean toward lumping rather than splitting.

[00:21:18] And we will probably. As DNA comes into to play more, probably see some of that splitting. But the at, at the moment, I think I can’t really come up with a good example for you because, so the, the problem is that this is something we deal with in, in areas that are even less studied than thes wasps a lot where, um, we’ll see a goal that happens in North America on a North American native host species.

[00:21:41] And I can say this looks very similar to a gal that’s found in Europe that has a name in Europe, but I have no way to know without doing the actual. , um, specimen, the genetic or the anatomical analysis to prove that these are actually the same species. So I, I think at the moment we are making some assumptions that things that look the same, that are unrelated hosts are caused by the same species.

[00:22:03] But there’s always the chance that further DNA n a evidence will prove that was a mistaken assumption. Just

[00:22:09] Michael Hawk: goes to show how much there is to learn in this. So you mentioned that there’s, by Far Oaks have the most gall species that have been described. What other plants are prolific or, or maybe not so prolific, but an interesting host to galls?

[00:22:23] Yeah,

[00:22:24] Adam Kranz: so oaks are, are definitely the champion in this respect, as in so many respects for whatever reason. But in North America, the second place winner by far is the, uh, hickory genus. So we have two big groups on Hickory. We have Hickory Midges and Hickory lazera, and both of those have around 50 species.

[00:22:43] And then after that, goldenrod has a ton of gall species. Uh, that’s something that we’re still currently in the process of building out our guide for. So right now the Gulf Farmer’s website is comprehensive for oak galls, hickory galls and hackberry gulls. Hack bras are mostly Midge galls and Sid Galls.

[00:23:00] And we have around 50 species on hackberrys. And then other than that, there’s just a huge list of species that have maybe one or two or five or 10, a Gulf species. Being so

[00:23:12] Michael Hawk: prolific, I’ve seen oak trees that just literally have hundreds, if not thousands of gulls on them as one example. I suspect that these play an important role in the, in the ecosystem in general, and maybe the food web more specifically, can you tell me a little bit about some of the known interactions that exist with gulls in the food web?

[00:23:33] Adam Kranz: So, gulls are a form of obi, so they’re a vector that’s gonna take resources. Primary producers from plants to anything that eats them. And so we know that there’s a huge community of parasitoid. Wasps are the primary known predators of gull inducers, so there’s mostly oid wasps and cpid wasps are gonna be found in all sorts of gulls, whether they’re made by midges or flies, or even mites.

[00:23:58] There’s. At least one parasitoid was species known to inhabit AFI mite calls, which is mind blowing to me because these mites are just so incredibly tiny. You need a scanning electron microscope to actually even take a anatomically useful picture of them. , uh, and yet that there’s still a parasitoid wasp small enough to, you know, make their living specifically seeking these things out.

[00:24:19] But other than parasitoids, gus are a common target of all sorts of things that eat insects, right? That that’s the one of, one of the big selection pressures in the, the design of the gall is to find ways to deter parasitoids and predators. And then there’s, of course, the incentive. The more effective those strategies are, the greater the incentive.

[00:24:40] Other organisms to learn how to get into them. So we know that Mye squirrels will chew into acorns to get at cipd larvae, uh, woodpeckers and other kinds of birds will peck through the woody outer parts of Gus to get at the little larvae inside. And we also know that they’re actually stories of humans eating.

[00:24:59] Gus. Uh, I don’t know what exactly , this is a time when maybe people didn’t have such good food available, but I’ve read stories in the literature of school kids. on their little lunch breaks, throwing out and picking up oak apples, which you hear oak apples if you don’t know what they’re like. That might sound like it might be an appetizing snack, but there are these just extremely thin walled, uh, spheres that are just full of strings and hard to see what the appeal of that would be necessarily.

[00:25:26] But apparently people have eaten them in fast,

[00:25:29] Michael Hawk: as I understand it. There’s a lot of tannins in those and they, yeah, they wouldn’t be too, too appealing, I don’t think, to most people anyway. Yep. , you mentioned that a lot of the design of Gus is to prevent access by some of these predators, and I’ve heard some interesting stories.

[00:25:46] Well, first of all, just looking at some of the Gus that I’ve seen around here, they have these spikes or hairs or things like that cause he would just make physical access difficult. Mm-hmm. But the chambers where like larva might be maturing are, as I understand it also, Distanced from the, from the perimeter of the gall, just far enough to avoid some of the predation.

[00:26:05] Like there’s some of these other, I guess, the co-evolutionary arms race sort of activities that seem to be happening. First of all, are these stories I’ve heard, are they accurate and, and maybe you have more you can elaborate on what’s been observed.

[00:26:16] Adam Kranz: Yeah, so this is an area that I think is definitely understudied, uh, and that we’ll learn more as more research comes out, but we have a fairly confident idea that predation is an extremely strong selection pressure on go inducers as it is.

[00:26:29] most organisms and that we can infer, but maybe not say with scientific proof. In a lot of cases, that particular features are, you know, emerged the way they are in order to avoid parasitism. So for instance, one very common strategy in oak calls and snippet calls is to secrete, which is something that folks don’t do on their own.

[00:26:52] They’re a plant that doesn’t attract pollinators, right? They’re wind pollinated tree, and yet they now have these sort of, Nectar producing glands caused by the, the ga inducer that attract ants. And the reason sen and other, you often see in Michigan analysis, often see bald face tots, yellow jackets, things like that that come to feed on this honey do.

[00:27:13] And we have reason to believe that the reason that the ga inducers cause this honey do excretion is to attract ants that prevent parasitoid access, but the ants defend them in the same way that they might defend. Scale insects or something like that.

[00:27:30] Michael Hawk: So that would be, uh, a tip off. If you see a lot of ants in some honey dew on a oak tree, that’s, uh, something worth inspecting a little bit more closely.

[00:27:38] Absolutely. . So we started to talk a little bit about the, the plants where the most variety of Gus occur on, and, and I guess for the naturalists out there that really want to go out and Yeah, hopefully we can get this published here yet in September. So there’s still a window of time to, to look for Gus.

[00:27:55] Uh, so I, I’d love to talk to you a little bit about. Strategies, where to look, how to look, those sorts of things. And I guess I just gave a little bit of a hint saying that, well, hopefully we can publish this in September, but time of year, you know, what’s the seasonality and how might it change? Like where would you look, say, I’m just guessing Gulls will stick to the leaves when they fall in the autumn, so you could probably look even later into the year still as well in, in

[00:28:15] Adam Kranz: North America, I as a, a.

[00:28:18] Uh, fanatic. You get really familiar with identifying oak trees. Not only just spotting them, identifying them to species, Oaks become this sort of like, Uh, a little delay. Every time you take a walk, you see an oak tree. Oh, there’s something I gotta go look at. Oaks, golden rods, hickies, hackberries roses have a lot of snippet.

[00:28:36] Gulls, grapes have a, a pretty wide variety of Midge Galls. Poplars, you’ll find a few different aphid Gs on Maples, cherries, elms all have a decent golf on in North America. And then just pretty much anything. Grasses don’t tend to have much such as anything like that. As far as I’m aware, not the best, most productive places to look for golfs, but broadleaf plants.

[00:28:57] But in terms of seasonality, it’s like I said, so for with CIP golfs, they have this alternating generational structure. So you’ll see a completely different golf fauna if you look in the spring than you do if you look in the summer or the fall. So it’s actually never really a bad time to look for golfs.

[00:29:15] But right now in the fall, there’s a ton of unique SY snippets and other goals that haven’t quite emerged. In places like California or Texas, you have a much longer time to, uh, to do that. But in terms of dropping off the leaf, you mentioned, so. One, one of the main criteria we, we divide gus by in on golf farmers is whether Gus are integral or detachable.

[00:29:39] So on leaf gus, in some stem gulls, they’ll actually fall off the leaf. Before the leaves fall, the gulls will complete their development and just fall to the ground because that’s where they overwinter. Whereas other gulls that are integral will stay on the leaf and you can find them on the leafs, uh, into the.

[00:29:55] Michael Hawk: Okay, so the, that’s actually a hint then when you find the gall still attached to the leaf, and if you can then identify the host plant. Of course,

[00:30:03] Adam Kranz: yeah. Once they fall on the ground, that makes it tough because you don’t know where they came from. You have to look around and see if you can connect the gall to a likely source.

[00:30:11] Michael Hawk: So you, you mentioned that California, Texas, I assume places like Arizona, I know there’s a lot of interesting sort of scrub oaks, uh, in those areas. Maybe the, the golf season extends a little bit longer. And, and here in California, I was gonna mention a couple plants that, that I tend to look at a lot when I go out.

[00:30:27] In addition to everything you said, willows, I think we see a lot of Midge gus on the on willows here. I have the proper Latin name is escaping me, but we call it a California coffee berry and it gets a flower gull in the spring and uh, , the, uh, coyote brush is another good one that there’s often gulls on as well, and that’s one of the most common plants that you see in California.

[00:30:46] So for those listening, those are also ones to take a look at.

[00:30:50] Adam Kranz: Yeah, you guys are lucky. You have a very totally unique synopi fauna over in California.

[00:30:54] Michael Hawk: It’s super fun too, and, and we get a lot of really colorful gulls this time of the year. The spring goals are fun, but the fall goals tend to be a little bit more over the top in terms of their coloration and shapes and so forth.

[00:31:08] Adam Kranz: That’s ultimately, that’s like the base of the, the appeal of it was the, just the, the fantastic forms and designs that these inducers have come up with that’re just so interesting to look at.

[00:31:19] Michael Hawk: Yeah. And I’ll make sure to link to a few interesting ones, uh, as well. I know we’re gonna talk about some of your favorite goals here in a little bit, so maybe we can get some photos of those too, link to in the show notes.

[00:31:29] Adam Kranz: Yeah, it’s a shame because they’re so, so visual sort of can’t get it quite across. But I, I would invite listeners to go to golf farmers just to. You have to put in a, a host Gina. So if you just put in a corcus or carry and just look at the shapes, you’ll be I think, quite intrigued.

[00:31:44] Michael Hawk: Yeah, great idea. And fully endorse that.

[00:31:46] So continuing on with kind of the, the, how to look for galls. So we’ve covered sort of the win and where, and the types of plants. Are there other sorts of growths that might be confused with calls?

[00:31:59] Adam Kranz: Yeah, so we, thanks to the Inet computer vision, we get a lot of these, uh, sorts of things. The computer vision suggests, Hey, this is probably a gall, uh, and it turns out to be something else.

[00:32:08] The most common one is, is burls. So people think that burls are a subtype of gall, but they’re actually not. They’re more like the normal sort of what you’d imagine as like a tumor or a scar tissue on a tree. People often mistake insect eggs for Gus and maybe more commonly vice versa, different kinds of feeding damage, but mostly it’s other plant structures.

[00:32:29] So if a. Gaul is a novel plant organ. What they’re most likely to resemble is something produced by a plant, uh, rather than an insect. Uh, and so we’ll see people confuse different kinds of seed pods or flower buds, uh, things like that. Advantageous roots, uh, which are little roots that occur on the sides of stems above the ground.

[00:32:48] But we’ve even actually had, I think on at least two occasions now, people have. Uh, tagged me in observations of rabbit poop, , and asked me to identify what kind of gall species they were. . I, I, I suppose

[00:32:59] Michael Hawk: for somebody who maybe doesn’t have a lot of experience with Gus, uh, some of them are super obvious and you see it and you know it’s a gall.

[00:33:06] Some of them really are cryptic, and I, I have a number of observations on iNaturalist myself that I’ve attached to. to the, one of the various gall projects. And, and I have to kind of say I, I think it’s a gall, but , you know, I’m not really sure. And, uh, and in hope that an expert can come along and provides an expert eye to the observation.

[00:33:26] So speaking of observing goals and making the them identifiable, what tips do you have for people say, that are submitting their observations to, in a

[00:33:36] Adam Kranz: So the first question we’re gonna ask anybody who submits a goal, observ. If we can’t tell from the pictures is to tell us what the host plant is, whether you’re qualified amateur botanist to do this on your own or not.

[00:33:48] You can take advantage of the cv. You can take advantage of the expert community on iNaturalist to help you figure out what those plants are, but making sure that you get enough pictures that we can confirm that is extremely helpful. So if you’re really confident you know what you’re looking at, then fine.

[00:34:03] You can just take a picture of the the gall on it. But these relationships are so close that without that confident identification, we basically have to recognize it already, and that is actually something that we do a lot. Once you see a lot of goals, you realize this is a very unique structure. And I would know this anywhere, even if I didn’t know what plant it was on.

[00:34:22] And we can actually do it in reverse. We can use the gulls as a line of evidence to guess at what the host plant is. And that’s often quite fun and satisfying. So it’s not just one or the other, right? You don’t have to learn all of your host plant ID first before you can do the gulls. You can do them sort of both at the same time, and.

[00:34:38] Contribute to this larger sense of familiarity with the plant community. But other than that, for the gall itself, if you have a leaf gall, we really often, and sometimes always, depending on the taxon, need to see the top and the bottom side of the leaf where the gull is attached. I mean, other than that, Cross section.

[00:34:54] So cutting it open to show what the internal structure looks like is something that is always useful. And sometimes we can’t do an ID without it. So if you carry a little knife or sometimes you can use your fingernail just to see what they look like inside can be very

[00:35:07] Michael Hawk: informative. Yeah. Once trap, I’ve found myself fall into, um, and unfortunately I still get lazy at certain times, so I’ll take a picture of a goal thinking it should be easily identifiable and uh, I won’t photograph say the underside of the.

[00:35:21] Maybe I looked at the underside of the leaf and there’s really nothing there. But having the photograph that shows there’s nothing there is really helpful to others to help confirm what it was that you did. See, I have to consciously remind myself still at this sort of early stage of my naturalist development to take more photos than I think are necessary and more angles and, and then, then typically it works out.

[00:35:44] But it, the worst is just to get home and look at something and be like, you know what? I can’t really identify. And I don’t have enough data to, to figure out what it was.

[00:35:53] Adam Kranz: Yeah. It’s a tough balance to strike, to figure out how much evidence together on any one thing versus going out and getting more observations and seeing more different things.

[00:36:01] You have to learn that over time.

[00:36:02] Michael Hawk: Yeah, that’s a good point. Everything’s a trade off. And I guess the other little tip from my own personal experiences here in California, we have a pretty good variety of oaks. Yeah. We focused in this discussion today a lot on oaks. When I first started, I, it was intimidating to identify the oaks and to learn how to distinguish them all from each other, and it’s one of those things, I think, so many things that when you first start, Uh, it seems intimidating, but then you chip away at it for a while and, and next thing you know, it’s not so hard.

[00:36:35] So, I, uh, encourage people to just give it a shot and it’s probably not gonna be as intimidating as it might seem at first.

[00:36:42] Adam Kranz: Yeah. I think goals are, are just a great example of that principle in, in natural history because some of them are so distinctive and so easy to recognize that it gives you that sort of place to start.

[00:36:53] Michael Hawk: Yeah, I did something for the first time two weekends ago, and that was, I took a nature hike specifically looking for goals. Now I’ve done a lot of hikes where I’m looking for everything, like any interesting thing. But this time I was fully focused on goals. And it was one of the more enjoyable hikes I’ve had in a while, partly because I was able to just focus so deeply and observe so closely you get into that mindfulness zone in observing nature.

[00:37:19] I never would’ve guessed I would be doing that a couple years ago, but I’m certainly gonna do it again with all of this in. . Yeah. I’d love to hear, given all of your experience, you’ve seen so many different goals in person and through golf forms. I’d love to hear about what some of your favorite goals are and why, and what their own natural histories are.

[00:37:38] Sure. So I picked

[00:37:39] Adam Kranz: three here that are gonna be things that I’ve seen in person in Michigan. Uh, and so the first one is, Cal Corcus Opera, and this is one of the few golfs that we do actually know both generations of. So in the spring, I first saw this year on the northern pin oak trees in our yard as the tree was flowering.

[00:37:57] You get these big fluffy, they look like big. I stand not that big, but they always look bigger to me in pictures than they do in real life. But look like big cotton bowls, uh, on the, the catkins of the oak. And if you dissect those, you find these tiny little individual cells inside where the larva live.

[00:38:16] And the wool itself is this sort of beautiful, it looks just like normal wool when you see it from a distance. But if you put it under a microscope or a, a close digital camera, each of the, uh, individual strands of Woo is this beautiful clear crystal, and they look like glass. Uh, it’s really lovely. And then those wasps that emerge from those cat canals go to over posit on the young acorns that develop on other unaffected catkins and are on the, the female catkins female flowers rather of the oak.

[00:38:48] And as the acorns grow in the fall, you get these tiny little pips that look like kernels of corn that. Like somebody stuck them underneath the cup of the acorn and they release, honey do, and they attract other organisms. So I think that’s cool just because we know that whole life cycle and we can tell how this particular wasp species is taking advantage of the full life cycle of this oak every year that it’s going from flower to fruit and this wasp is coming along for the ride.

[00:39:15] Michael Hawk: I, I looked it up because I wasn’t familiar with that species. And you’re right. Like I thought at least the spring generation looked a lot. Fuzzy pink cotton candy. And I could see, you know, to your earlier point about people eating gulls and eating the oak apple gulls, that would look pretty appealing to me.

[00:39:32] If I were a kid, it, it would look like something sweet to, uh, take a bite of. . Yeah, I

[00:39:37] Adam Kranz: haven’t tried it. So the other one I was gonna mention, the second species is called the Succulent Oak Gal wasp. So this is Trio Cosmos, corcus Polys, and it’s a very common, very abundant gal found in the spring on Red Group Oaks.

[00:39:51] So Corcus, rubra, and other Oak oaks in that group. And they formed these little green globs. They’re almost perfect spheres. They look like little green grapes. and they, what’s remarkable about them to me is that inside, they’re completely hollow and they have what’s called in literature a freeroll cell.

[00:40:09] So what that means is that the cell that the actual larva lives in is not attached to the plant anymore. It just rolls around. So if you pick up the leaf and shake it, you can’t actually hear it cause it’s too quiet. But if you open it up, you can see this little pellet rolling around inside with the larva.

[00:40:24] And most of the space of the gall is actually completely empty as far as I’m. This is something that doesn’t occur without the aid of an inducer in plants at all. It was maybe always possible, and it’s always exceptions in nature. But as far as I’m worried, this is something that an oak tree can only do because the WASP taught it how to do it, and I just blows my mind that they can.

[00:40:46] yeah. Create such a new ability to have this little loose palette inside of another structure. That’s

[00:40:50] remarkable

[00:40:50] Michael Hawk: to me. I have no idea if this makes any sense to someone like yourself who’s an expert in the area, but I was just thinking about having that free rolling cell in there, and if there was a para toy that came along, trying to like inject its own egg inside, that might make it extremely difficult.

[00:41:05] It would just push that free rolling cell away as opposed to actually being able to inject inside. .

[00:41:11] Adam Kranz: I think it’s a reasonable hypothesis, but I have no, no evidence one way or another whether that’s the reason that those occur. There. There are all sorts of calls in that genus that have free, free lung cells and some of them are much less hollow than this one, much less space in there.

[00:41:24] And I, I don’t know if a significant strategy in that, a reason that strategy developed.

[00:41:28] Michael Hawk: It’s fun to think about anyway, . Absolutely. And your third

[00:41:31] Adam Kranz: one? Sure. So this is also, this is a third species that also is found on Red Group Oaks in Michigan, and it’s called Cal Quickest Jamari. . So these are little green cylinders, little ribbed cylinders that emerge in these really dense clusters in the spring along the stem or twig of red oaks, and they release honey, do.

[00:41:52] And so you’ll often see these covered by ants that are collecting that honey do. Uh, and we, again, we think that’s in order to deter other wasps from coming into OPO on those calls. In this case, there is at least one other wasp that successfully bypasses that security mechanism and lays eggs in there.

[00:42:14] We think that this is a, uh, synergic species, another sy wasp. And so if these gulls get over posited by the synergic wasp, they completely change their developmental tra trajectory. So instead of dropping onto the forest floor like they normally would, they stay on the tree, they get much bigger and they get almost wood.

[00:42:33] and they stay on there for months and they look completely different than what otherwise. And so that’s, I guess what I find interesting about those is that the, not only do you have the plant and the inducer, you then have this third organism and only the three of them together can produce this outcome, this unique org organ on the plant stem.

[00:42:52] Yeah, just

[00:42:53] Michael Hawk: another kind of mind blowing thing in nature that, uh, I think it would be so easily overlooked. Mm-hmm. . Oh, it absolutely has. Yeah. Now we know to look for it. Here’s a request I have for you for each of these. Do you have photos that you’d be able to share with me? I could put in the show notes for people to see.

[00:43:08] Of course. Yep. Awesome. So yeah, the, I, I looked at all of ’em and they are all fascinating. So, uh, highly advise people to take a look. So to wrap things up, I always have a few standard questions I like to ask and, and one of course. . Yeah. What resources do you recommend for people who are interested in learning more about goals?

[00:43:29] We’ve talked about a whole bunch here today, so maybe this is just a recap. Maybe you have some other ones as well. Sure.

[00:43:34] Adam Kranz: Yeah, so our, our website golf form is obviously my, uh, number one recommendation. Our goal is to make that site a one-stop shop for gall identification. So we’re planning to include full passages from the primary literature whenever possible, so that it will not just be our information, but it will.

[00:43:53] all available information. So for instance, a lot of the older sources like the Weld Lewis Heart Weld sign books, uh, that he’s written on the Eastern Pacific and Southwestern United States, those books are all completely redundant relative to our database. We have all of his information, plus a lot more, but outside of what we have, there are, uh, definitely some useful books out there.

[00:44:14] Ron Russo is a California gall. Who recently published a new book. He had a one previous older book, but he’s a brand new book. Just came out this year called Plant Galls of the Western United States. That would be a definite must own for anybody in California, Oregon, Arizona. Charlie Eisenman’s blog has tons of great observations and interesting information about Galls Bug Guide of.

[00:44:39] although at this point most of what they have is gonna be on our, our site as well. If it, it’s not, it will be soon. And then if you find yourself in a position where none of those resources get you the information you need, uh, you can start looking in the biodiversity heritage library for things that we haven’t added to our site yet.

[00:44:55] Yeah. And

[00:44:55] Michael Hawk: earlier you mentioned Charlie’s other book, the, uh, tracks and Signs of Insects and other invertebrates. And I’ll include links to all of these as well, but that, that other book has a good overview on. , do you have any other upcoming projects that you’d like to highlight? So

[00:45:09] Adam Kranz: at this point, we’re just plugging away at filling in the site.

[00:45:13] So short-term plans are just to pick out another genus and find all the literature and put that onto the site. So I, I haven’t, at the moment, I haven’t actually decided where I’m going next. I just finished up with the new, uh, phra on Hickory and in between projects right now.

[00:45:27] Michael Hawk: All right. And if people wanna follow your progress or follow your work, where can they go?

[00:45:31] Adam Kranz: Can go to the website, golfer.org. And you can follow us on Twitter at golf forms. And if you wanna follow me personally on iNaturalist, my handle is mega Kyle.

[00:45:40] Michael Hawk: And one thing we didn’t really talk about on iNaturalist is there are a couple, for those listeners anyway that do contribute o observations.

[00:45:47] There are a couple of gall oriented projects out there. There’s at least the two that I contribute to, to, there’s a California specific one and then, uh, one, I think that Charlie Iceman actually started called Gulls of North America. And these projects

[00:46:01] Adam Kranz: are, are nest. Okay, so I think all of the California calls go into the North America project.

[00:46:06] That’s

[00:46:07] Michael Hawk: really good to know. , that will save me some time. ,

[00:46:10] Adam Kranz: uh, yeah, so if you’re uploading an, an observation to in a, and you think it’s a goal, but you’re not sure what kind of call, you can always just submit it to that project and someone will see it there at some point, whether it’s in the short term or long term.

[00:46:22] You can feel free to tag me as well, and I will try to help you identify your.

[00:46:28] Michael Hawk: Okay. Well, Adam, it’s really been a fascinating conversation. I appreciate all the time that you’ve spent with me here today, and best of luck to you as golf formers fills out, I’ll certainly do what I can to help out in, in making math the resource that you envisioned it to become.

[00:46:44] Adam Kranz: Okay. Thank you so much for having me.

2 thoughts on “#29: Adam Kranz – The Amazing World of Plant Galls

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