The future of DNA barcoding, and its use in citizen science

My approach is always to make the most of whatever I have available to me. The best step forward overall would be for more basic taxonomic work to be funded, but that seems unlikely. It is ironic that one of the best uses for DNA would be for associating dimorphic sexes and/or assocating different life stages without having to rear. Oddly, this is very rarely done or even talked about!

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I disagree somewhat with the necessity for specimen vouchering across the board. Botanists have twigged (no pun intended) long ago that you can’t voucher every record from every locality (or else herbaria would be overflowing with Bellis perennis and other common plants). The key here is that iNat observations are not limited to photos of live specimens in the field, and may include diagnostic photos of dissected specimens or spores or whatever which then makes the specimen unnecessary to retain in most cases. Voucher what might turn out to be critical, by all means, but otherwise just take good diagnostic photos.

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If I had to place a bet on the availability 100 or 300 years from now of a digital photo on the Internet, versus a preserved specimen in a natural history museum, I know where my money would be going (having worked extensively with both).

And if we are talking physical photos, there’s really not much practical difference between conserving those and conserving the specimen from which they came, so why not retain the primary evidence instead of (or along with) secondary derivations?

I do agree that vouchering can be overdone, and should not be. (After all, I’m here on iNaturalist, and believing wholeheartedly in the value it is adding to human knowledge and interaction.) But the more frequent cases I have noted are when vouchering is underdone, rendering impossible the repeatability of a scientific study.

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Interesting! You know that the Brazilian Natural History Museum recently burned to the ground, destroying all specimens? I wonder how many other such losses can be expected in the next 300 yrs? What problems do you foresee for the continued availability of iNat observations in the long term?

If you don’t work in a biological curational facility (i.e. a “collection”), then there are major practical difficulties associated with conserving specimens! I can find a specimen in the field, kill it, dissect it and make good diagnostic photos available to the world via iNat in less than 30 minutes! It costs me nothing but a bit of time. Vouchering is a much bigger problem.

My point was that if you photograph the same features that anyone looking at the actual specimen needs to check, then you don’t need the specimen! Of course you need to know what those features are, and there may turn out to be problems in something like 1% of cases, but overall it seems like the best approach to me.

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Certainly nothing is permanent, and specimens have sustained their proportion of losses over the centuries. But at least we can talk about their track record in terms of centuries. What is the track record of Internet web sites over the last 3 decades?

Not wishing ill will to iNaturalist or any other such endeavor, just that with existing track records, the jury is still out on our digital infrastructure. I would be hugely and joyfully surprised if I could come back 300 years from now and find all of your and my iNaturalist observations and IDs still serving the cause of biodiversity in that world. I wouldn’t be here if some part of me didn’t think that possibility existed. But would I bet life or treasure on it right now? Hmmm… no.

I am certainly a huge proponent of the “photo-vouchering” work that I and all of us are able to do here on iNaturalist and in other venues. Its value cannot be overestimated, especially in situations like you mention where specimen vouchering is impractical, or would be “overkill” (pun intended). My point is that photo-vouchers versus specimen vouchers should not be a zero-sum proposition. I will push back against any notion that the value and need for specimen vouchers decreases in proportion to the creation of diagnostic photographs and DNA barcodes. (Maybe that is not what you are suggesting, but it can be heard that way…) In fact, I would say it is exactly the opposite. Each contributes value to the other.

Trying to bend back to the original topic of DNA barcoding…

Taxonomists continue to learn new things all the time about what pieces of evidence are critical to understanding species boundaries in nature. If one doesn’t happen to capture the right evidence in a photograph, or in a DNA bar code, those pieces of evidence can’t be reconciled with new knowledge. But with a well-prepared specimen, you have the whole organism, including the DNA, to go back to and re-sample.

One recent example in plants – over the past decade, there has been a huge leap forward in understanding the difficult genus Boechera (formerly in Arabis) of western North America. It was discovered through chromosome counts and careful study that one could tell the sexual diploid versus apomictic triploid status of a specimen using pollen size and shape. Once species boundaries were better understood on that basis, it further became apparent that basal lobing of the mid-stem leaves is a very good corollary distinguishing feature among species. Until these discoveries, I never thought to photograph the mid-stem leaves of Boechera plants (much less the pollen, which I still don’t!). Without all of the existing specimens (and especially, of course, the type specimens, some almost 200 years old), it would never have been possible to reconcile this new knowledge with the previous taxonomy for these plants.

I think we are both valuing the same two things here. I just don’t see the value of one as being in the position of diminishing the value of the other. I see them as enhancing each other. Specimens will remain just as important as ever, and the value of photographs and DNA barcodes will continue to increase, and to augment the value of the specimens on which their very identity ultimately rests.

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Imagine if, after having sketched illustrations of the specimens found, all early vouchered material was discarded as no longer needed.

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That’s not quite a fair comparison Mark! Taxonomy has now reached the stage where we know what we are doing much better than in the early days and we can now have high confidence in most of what characters are important taxonomically for most groups. Even in your scenario, we would still be able to manage. Many Linnean type specimens are lost and the descriptions useless, but many of those names are still used for taxa that we recognise today. Imagine your scenario without the illustrations! That would be even worse!

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Not sure how on-topic this is but I could imagine an economic crash, international conflict, or big natural disaster (electromagnetic pulse?) affecting it, but perhaps I don’t have a good enough understanding of how the internet works.

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Of course, tho’ I assume that they have at least some sort of contingencies in place? More than one copy of all the data and images stored in widely separate servers, or something like that? I think Wikipedia is copied on maybe 6 servers worldwide?

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As a taxonomist that’s an overly optimistic view of my science. A big part of taxonomic research is figuring out which characters are actually important, and revisions are made when we discover that the characters we used to use weren’t as useful as he had assumed.

Which characters are useful also changes as technology changes. Bits of leaf that were irrelevant 50 years ago now provide critical DNA data. Pollen that Linnaeus could see at 10 or 20x magnification I can examine with an electron microscope. None of this is possible with an image.

I curate a large herbarium, and we’re very excited to get our specimens imaged. But we are also constantly defending the value of the physical specimens against people who seem to think that images (and DNA extractions) will somehow render the specimens irrelevant. I’ve got projects that depend on access to the digital data, and I’ve got projects that depend on the physical specimens. And increasingly I’ve got projects that use both.

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I’m more worried about more mundane things. Support for file formats changes. I have trouble sharing Word documents with colleagues who use a program that’s only a few versions different than the one I use. We’re getting better, but we’ve only been doing this on a large scale for a few decades.

Museum technology has the benefit of simplicity. I routinely work with vouchers collected 150 years ago, and have access to older material if I need it. Imagine if you needed to find a copy of Word1757 to read Species Plantarum!

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yeah, in reality they both make each other more important. It isn’t an either-or, we now have more resources to do both, if less funding and political support in some cases. Pretty much none of my inat data replaces vouchers, instead it’s data i just wouldn’t have collected otherwise.

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I’m fairly new to botany (coming from a background in entomology), but it strikes me that actually a high proportion of botany is based on field IDs by botanists who are pretty confident of their ability to recognise species in the field. To my mind, photo obs from the field are a step up from that, in terms of science, as they provide some degree of independent verifiability that was otherwise lacking completely. Of course there will always be a need for vouchering in some cases, but really not that many cases, I suspect! In particular, I don’t see the need for vouchering in most cases if we just want to map distributions (within known boundaries) or determine presence/absence at a site of known species with no known taxonomic difficulties. Vouchering is not such a big problem in botany as in entomology, because you don’t have to voucher the whole individual as you do in entomology, so you are not changing the system that you are trying to document so much. Developing robust field ID for threatened animals/insects is potentially something for which iNat could be valuable.

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In some of the groups I’ve looked at, such as ladybeetles/bugs, and even in plants, I’ve learned how easy it can be to reliably separate some species pairs in the field. In some cases, these are species pairs that are either highly difficult or technical to identify in a key, or ones that the authors have lamented as “unseparable” without dissection. This is certainly the age of learning how to identify species from field gestalt and appearance, but I am happy to agree that specimen vouchering is (at this point in time) still the best way forward for many cases.

Now if only more specialists would photograph what they collect, before pinning and pressing it…

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yeah, our brains evolved over millions of years to be able to identify plants. Those of us who couldn’t sometimes ate the wrong ones and died. There’s a lot more to it than you can fit in a key.

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I think that the same evolved skill can be extended beyond plants. The important thing is familiarity with the local fauna/flora, which is a mix of experience and knowledge. I find that I rarely use keys for anything.

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Again, this assumes that we have ‘finished’ the taxonomy of a particular group. In the 1990s we knew that Phragmites australis was the only species of Phragmites in Canada, and it was easily recognized from a photo. If we were interested in documenting its range, we’d have been quite happy to do so with images, and they wouldn’t have had to be very good photos.

We discovered in 2002 or so that there were actually several different genotypes (now subspecies), and they can be distinguished by DNA markers or fairly subtle morphological characters. Now we have a situation where the images you collected in the 1990s are useless, and without vouchers we have no way to remedy the situation.

There’s a common misconception that botany is largely solved, so we can get away with less rigorous documentation now (i.e., photos vs specimens). That’s really not the case. As Charlie said somewhere up thread, photos and vouchers compliment each other - we still need both.

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These are really a nightmare, said morphological characters are pretty much bogus in my opinion, as the best botanist I know can’t even tell those apart (and he’s a way better botanist than I). And they’ve been elevated to full species in some taxa! The real question here, which may be diverging off topic some, is how does field ecology (not just iNat, all of it!) deal with this propensity of recent taxonomists to create species that can’t actually be identified in the field! In some cases we have sections we can use but in a lot of cases… they are basically breaking field ecology and what ends up happening in practice is people just don’t use the new taxonomy.

Botany definitely isn’t solved, but we still need ‘handles’ to connect with what we can view during monitoring tasks, whether they are called species or something else.

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Interesting! Possibly related, I’ve noticed that ecologists have a propensity to ignore any organisms they can’t easily identify ;)

Plant taxonomy doesn’t exist primarily to make life easier for field ecologists. Our primary goal is to describe what’s actually happening in the world. And sometimes what’s actually happening is that species with very different evolutionary and ecological roles happen to look very much the same.

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Ha! an age old struggle i suppose

Well, we all know a species is a human constructed concept and the reality of it is much, much fuzzier. Evolutionary convergence is also sticky and magical and weird and if you think it’s bad now just wait until we someday find another planet with life on it and the stuff there looks a lot like the stuff here but from a totally different genesis! In any event… field ecology is imperfect like anything else but field ecology is most of our boots on the ground, so it is what it is. I can tell you that for myself, i have two different types of field work I do. Sometimes i do focused plots where I try to identify every plant in the plot, in those cases that involves taking samples and bringing them back to the lab, etc, so if it can be distinguished under a scope hopefully i will do it. Other times I am doing mapping or rapid assessments, or people are doing permitting tasks, monitoring, a wide range of other stuff. With these, for better or for worse there isn’t time to do scope work and such. We are looking at a situation where we have 10-30 thousand wetlands in our state which have never had an ecological assessment of any sort, at least of the type we can use here. And often if no one has been to the wetland to do that, it’s harder to protect it. So adding 20 more wetlands to the map does often take priority over a day of picking apart sedge dongles in the lab while the bulldozers roll through yet another site. And when i’m doing iNat on my own time, i skip the annoying species a lot of the time because it’s my own time and i get to be lazy :)

The root issue of course is just that we are all working with much, much less resources than we should be, and so we have to triage. it sucks, but I doubt that changes any time soon.

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