well, i don’t want to launch into my same taxonomy rant so will spare you that :) I just hope if people split the dandelions into a million cryptic species they at least create sections that can be used in the field.
1 Like
Right, now new taxonomy still doesn’t know what itself it is, so we should wait.
Personally I know that there are dandelions in nearly every spot of mowed grass around here, so documenting where they are doesn’t interest me. Learning that there are different sections in my area and where they occur does seem interesting though, because I’ve always just assumed every dandelion is essentially the same.
1 Like
I was talking more about Polypodium example, but still, the habitus of seen dandelion can be interesting for a researcher, why not.
We field collect them and GIS the samples
I just don’t have time to individually
Post on here it takes up to a week
To get positive IDs back on some of
The samples
I have no idea they were so different
To me they all look the same Lol
5 Likes
I had a look around the internet for information from Europe about identifying dandelions to section, if anyone wants to take a stab at some… I figured more perspectives and comparison photos is probably helpful and our species are presumably introduced from there anyway. They are in a journal post here: https://www.inaturalist.org/journal/upupa-epops/48329
Let me know if you find anything else, I’m also curious if anyone is able to try it out successfully!
1 Like
I am skeptical of there being more than 100 look-alike species. I would, however, be willing to concede these sections as 9 species, if they are sufficiently well-marked to be consistently seperable.
Can he back it up with consistent, well-marked differences? How much individual variation is he allowing?
BINGO!!!
If I go by that, I still conclude that all dandelions I have seen are, indeed, Section Taraxacum. I certainly have not seen them with olive-green leaves, or blue-green leaves, or purple-spotted leaves.
1 Like
Dandelion leaf shapes are pretty variable based on growing conditions, e.g. growing in shade vs sun, mown grass or not, and they produce different leaves in the summer than in the spring. From what I’ve read dandelion researchers generally deal with this by cultivating them before describing them, since consistent conditions produces consistent results. The keys try to focus on bracts, which are more consistent, and broader details of the leaves. So the short answer is yes, the question is whether we care. Like you can consistently identify individual people even though they change appearance from day to day.
The question is what to do with the other sections when we do find them, because assuming they’re all sect. Taraxacum without checking is definitely inaccurate. The paper suggests that sections Celtica, Erythrosperma, Hamata, and the fulvicarpum group are all decently common in urban areas in coastal BC, and at least the latter more common than sect. Taraxacum. From UK sources it seems that Hamata is pretty common there too. Presumably further south in North America there are Mediterranean sections that aren’t as well covered in northern European literature.
POWO seems to be accepting all the microspecies that European and other taxonomists are describing (it currently has 2363 accepted species in the genus). Should iNat instead only accept the type species of each section?
POWO also has 2970 Hieracium species. Apparently Rubus, Sorbus, Ranunculus etc. have similar situations. How are those treated?
Edit: It seems like there are 2 competing taxonomies for Heiracium; species groups vs broad species with subspecies etc. http://www.preslia.cz/P042CChr.pdf
1 Like
I would keep all the microscopecies in our taxonomy. It is unlikely but, otherwise, if an expert would join iNat it would be impossible for him to start uploading observations of uncommon specis.
1 Like
Is it even possible to ban taxa that are accepted in POWO? We don’t have all those species in taxonomy now, but anyone can add them. We can add them as synonyms of other species, but it still can’t prevent adding them again.
I hope it is possible. POWO is good but not perfect and with such critically genera the necessity of making deviations is not unlikely.
As always, it would be desirable that the addition/deletion of taxa would follow a rigorous literature.
Anyway, the absence of taxa for the genus Tarxacum is less “dangerous” then for other genera since it is unlikely that observations of every described taxa of dandelions will be uploaded here.
My understanding is that powo just forms the “default” framework that we follow, and that we can deviate from that if there is a good reason to. I’ve never had to do it so I don’t know the process required, but if you contact any of the curators that work heavily with plants I’m sure they’ll put you on that path…
if microspecies act so differently from ‘macro’ species and also are not generally recognizable in the field, aren’t they in fact just populations? I don’t see any benefit of describing them as full species at all, other than perhaps people wanting to ‘describe’ their own species.
Does it make any difference whether we call them species groups with species, or species with subspecies and varieties? Within a genus are they not both arbitrary heirarchies? In either case identifying T. erythrospermum in North America would be incorrect since that “subspecies” doesn’t occur here.
For a technical answer, I think your question was answered above if you replace “subspecies” with “population”.
I don’t know what iNat should do, I’m just trying to understand/explain why people are doing it this way… How much choice does iNat have if POWO is accepting microspecies and no one has suggested an alternative taxonomy in literature?* Either way, identifying to sections (or broad species concept) seems better than choosing 2 random species out of the bunch.
(*Edit: This paper says this, what does it mean?):
Richards and Sell (1976) overcome the problem illegitimately by employing a macrospecies name equivalent to the section (and by implication the type of it) which is the earliest agamospecies name of certain status. … This practice seems contrary to the Code and should be ignored unless formal lectotypification has occurred.
Another detail I found in my readings that might help with the discussion…
This is from a 1972 edition of the Richards British dandelion book, does it help answer that question?
https://archive.bsbi.org.uk/Wats9suppl.pdf#page=10
The BC paper says “Sexually reproducing European Taraxacum species seldom show weedy tendencies, and are not expected to occur in British Columbia or anywhere else in North America.”
I don’t know if I’m familiar enough with apomixis to know what the implications of that are. If only asexual plants were imported to North America and not sexual species, would the asexual populations not continue to remain genetically consistent with the source population?
2 Likes
“microspecies” is not an “official” rank in plant taxonomy and there is not a rule to define a species a microspecies. As regards, whenever there is a sort of splitting inside a genus into a large number of species more or less all extremely similar one can think that they are microspecies. But they taxonomically have the same dignity as the other species. It is not even a matter of agamospermy or not.
Yes, it is unlikely that many of these microspecies will be identified in iNat unless a specialist won’t look after one user that will demonstrate to be willing to get more insight. For the other cases there are the sections as far as Taraxacum in concerned.
1 Like
From Journal Post https://www.inaturalist.org/journal/danielatha/48774-on-the-status-of-red-seeded-dandelions-taraxacum-erythrospermum/edit
This is a rough draft of a paper I hope to publish someday when I have time. I am not analyzing the entire genus Taraxacum and every segregate section, species and microspecies. This post concerns the entity called Taraxacum erythrospermum.
On the status of Red-Seeded Dandelions (Taraxacum erythrospermum)
By Daniel Atha
Introduction
Everyone knows that trust in science, scientists and scientific institutions is at a low point. It’s not surprising the public is skeptical. The masses have been excluded from the language and practice of science. The public has little say in the goals of science. And the products of science have made our world more dangerous and inhospitable.
What I love about natural history is that it is comprehensible to everyone with a desire to look. The natural world is there for everyone to enjoy and study equally. There are no barriers to access and the possibilities for learning are infinite. You don’t need a Hubble telescope or a particle accelerator to study natural history.
We in the iNaturalist community know that we would all be better off if the “public” had a greater appreciation for and understanding of nature and the earth system processes that make life possible. iNaturalist is democratizing science by empowering everyone to participate in the practice and process of natural history science. Every observation records what we find interesting and meaningful. And the totality of our observations reflect our values individually and collectively.
It’s also important to remember that science is driven by curiosity and scepticism. When it is based on observable facts and informed by mature and reasoned analysis, science can reveal processes and patterns that may be hidden to the casual observer. The basics of science are the formulation of a hypothesis, testing the hypothesis (including the null hypothesis) and repeatability. Much of what the public thinks of as science deals with abstract concepts and astronomical values. But we must remember that a flora of a given area is really a whole series of hypotheses. Our concept of a species is really just a hypothesis and that we can tell it apart from others reliably by use of a key is a hypothesis and a test built into one. And because we are dealing with plants in the landscape, our floristic hypotheses can be tested and tested by virtually everyone, regardless of their training or prior knowledge. That’s the beauty of a flora and the fun of writing keys.
As scientists (and citizen scientists) we must be careful not to make uninformed judgements or appear overly certain about our interpretations of natural phenomena. In our haste, carelessness or ignorance, we may base a hypothesis on insufficient evidence or poor interpretation of the evidence that is available. In such cases, when the hypothesis is overturned by evidence that should have been considered or analyzed properly, the public’s trust is eroded.
The subject of this post, the common Dandelion, is an example where careful studies carried out by scientists over decades can and should help us interpret and appreciate what we can all see in our lawns and gardens every day. My goal here is to demonstrate (by presenting solid evidence) that the Red-Seeded Dandelion is not a species as commonly understood by botanistas and the public, but rather is nothing more than a color morph that arises spontaneously from a large pool of genetic variants-- similar to an albino Rat.
Like the common Brown Rat, the Common Dandelion (Taraxacum officinale s.l… Including the Red-Seeded Dandelion) is nearly ubiquitous across North America in areas disturbed by humans. The Common Dandelion thrives with ample sun, moisture and nutrients, especially in lawns, garden beds and exposed urban soils.
Red-Seeded Dandelions (Taraxacum erythrospermum) are treated as a species in most floras of North America, including the Flora of North America. Yet there has been no critical analysis of its validity as a species.
The literature on species concepts in biology is vast. Generally, most people would agree that a plant species is a lineage that has diverged from a common ancestor and has some genetic and morphological cohesion. A species is generally accepted as a reproductively independent lineage (Rieseberg et al., 2006) with corresponding morphological traits. Disputes arise over reproductive capacity and how well genetic markers (genotype) are correlated with morphological character states (phenotype). See Mayer and the biological species concept (Mayr, 1992).
We might successfully classify a species using one or the other or both genotypic and phenotypic characters without knowing everything about the basic life history and reproductive mechanisms of an organism. In fact, most species are named before a great deal is known about their basic biology. But when either data set or the data in combination are ambiguous, we must seek additional data sets, such as reproductive strategy, chemical productions, chromosome number, etc… See Stewart-Wade et al., 2002 for a broad overview of Taraxacum biology.
In the common Dandelion, leaf morphology (ie length:width ratio and degree of lobing) varies as the plant ages (Sanchez, 1971) and is influenced by light intensity (Wassink 1965; Sánchez 1967). Rounded leaf blades develop in low light and deeply lobed leaf blades develop in high light (Sánchez 1967; Slabnik 1981). Increasing light intensity increases the leaf lobing and decreases the leaf length:width ratio (Slabnik 1981).
Discussion
In North America, nearly all Common Dandelion plants are triploid and apomictic (Lyman and Ellstrand, 1984), meaning that they have three sets of chromosomes and reproduce by parthenogenesis (a process called apomixis whereby seeds are formed without fertilization). Common Dandelions with a “normal” complement of chromosomes (diploid, 2n=16) capable of sexual reproduction with other diploid Dandelions and with triploids (2n=24) are known from Europe, where the species is native. Diploids are extremely rare in North America (Verduijn et al., 2004; Lyman and Ellstrand, 1984) and most plants studied in North America are triploid clones, reproducing asexually by apomixis.
Taraxacum erythrospermum Andrz. ex Besser, Enum. Pl. [Besser] 75: 106. 1822.
The Red Seeded Dandelion (Taraxacum erythrospermum) was first named in 1822.
A study of 20 individuals from several populations across Wasington, Oregon, Idaho, Montana, Wyoming, Utah and Nevada representing plants identified as Taraxacum officinale and Taraxacum erythrospermum (Taraxacum laevigatum) found that there was no correlation among twenty-five character states of achenes, involucres, receptacles, leaves and phenolic (chemical) profiles. In fact, these characters showed more variation within populations than between them (Taylor, 1987, citation and abstract below). Achene color-- the single most consistent character state used to distinguish Taraxacum erythrospermum-- was found to be independent of any other character, including shape and degree of leaf lobing. As Taylor points out, it is improbable that the many previous studies have overlooked hitherto untried character combinations to distinguish these entities (e.g. micro-characters). Additionally, as an overwhelmingly asexual, apomictic triploid in North America, it is improbable that hybridization and introgression (back crossing) between putative Taraxacum officinale and Taraxacum erythrospermum has blurred species distinctions creating a continuum of character states bridging one species to the other. Finally, the author’s work and several works cited therein demonstrate a correlation between environmental stress and phenotypic (anatomical) expression including leaf lobing and achene color and that this variation is best explained by a single, weedy species exhibiting a range of phenotypic expression in response to environmental conditions.
Morphological and chemical (phenolic) variables were used in principal components and cluster analyses to determine patterns of variation among and within 22 wide-ranging populations of dandelions. Intrapopulational morphological variation was as great as or greater than interpopulational variation. Morphological variables were poorly correlated, and plants failed to cluster into the two described species, Taraxacum officinale and T. laevigatum [Taraxacum erythrospermum]. Phenolic distinctions existed among populations but not between species-types, and chemical variables did not correlate with morphological variables. The data, therefore, suggest that morphological variation is largely due to phenotypic plasticity. This conclusion was supported by the observation of a strong relationship between microhabitat and morphological phenotype, with characteristics of T. laevigatum being expressed under conditions of environmental stress. The pattern of phenolic variability reflects the existence of chemical biotypes. – Taylor, 1987
Another study of 518 individuals from 22 populations across North America found that there were up to 13 enzyme clonal profiles discernible within a single population of Taraxacum officinale, demonstrating considerable genetic variability within a single population (Lyman and Ellstrand, 1984). In fact, Taraxacum officinale was shown to have a total of 47 enzyme and morphological clonal types among all populations sampled and the highest number of clones per individuals sampled (0.091) of any plant known. By comparison, 108 clonal types have been identified by enzyme analysis for Oenothera laciniata, but only 0.051 clones per individuals sampled. Based on these data and the work of others cited by Lyman and Ellstrand, the authors suggest that multiple introductions of Taraxacum officinale from Europe and Asia have contributed to the high genetic diversity found in North American plants.
In yet another study of 318 Dandelion individuals, Lynn Mertens King found 145 chloroplast (cp) and ribosomal (r) DNA profiles among them. In her work, King states….
North American dandelions with red achenes do not form a natural group based on either rDNA or cpDNA, so lack of differentiation between North American aggregate species T. officinale and T. laevigatum [Taraxacum erythrospermum] in rDNA and cpDNA is consistent \with Taylor’s (1987) observations based on morphology and phenolic compounds and suggest they are not separate evolutionary lineages. - King, 1993
Another study found that achenes actually sort into seven color morphs, but these occur independent of other character states (citation needed).
If Taraxacum erythrospermum is a species, where did it originate?
No objective data has been presented to support the recognition. What descriptive data is available does not support recognition. I have found no taxonomic study that supports recognizing Taraxacum erythrospermum as a species, only floristic descriptions.
Citizen science data from iNaturalist demonstrate that the characters most often used by flora writers to distinguish Taraxacum erythrospermum do not stand up to the test. The characters are: 1. leaf lobing correlated with achene color; 2. phyllaries with horn-like appendages correlated with achene color.
The following observations show with empirical evidence that achene color is not consistently correlated with any of the traditionally used morphological characters. These observations were culled from a review of approximately 300 of 17,000 global Taraxacum officinale observations.
https://www.inaturalist.org/observations/identify?page=102&verifiable=true&place_id=any&taxon_id=47602. Observations were reviewed quickly and some which are ambiguous may remain.
Achenes red but phyllaries without horns
https://www.inaturalist.org/photos/47571589; https://www.inaturalist.org/photos/73078829
https://www.inaturalist.org/observations/46074005; https://www.inaturalist.org/observations/45680775; https://www.inaturalist.org/observations/45305683; https://www.inaturalist.org/observations/45241684; https://www.inaturalist.org/observations/44993437; https://www.inaturalist.org/observations/44992893; https://www.inaturalist.org/observations/45680775; https://www.inaturalist.org/observations/44870840;
https://www.inaturalist.org/observations/44545929; https://www.inaturalist.org/observations/44515723;
https://www.inaturalist.org/observations/44416050; https://www.inaturalist.org/observations/44218822;
https://www.inaturalist.org/observations/43544408; https://www.inaturalist.org/observations/42918761
https://www.inaturalist.org/observations/42200603; https://www.inaturalist.org/observations/41687607
https://www.inaturalist.org/observations/41633065; https://www.inaturalist.org/observations/40355663
https://www.inaturalist.org/observations/38709065; https://www.inaturalist.org/observations/38195521
https://www.inaturalist.org/observations/30666920; https://www.inaturalist.org/observations/27168210
https://www.inaturalist.org/observations/24093003; https://www.inaturalist.org/observations/22916353
https://www.inaturalist.org/observations/22439535; https://www.inaturalist.org/observations/21959839
https://www.inaturalist.org/observations/21910431; https://www.inaturalist.org/observations/19276795
https://www.inaturalist.org/observations/14042249; https://www.inaturalist.org/observations/13356869
https://www.inaturalist.org/observations/13013560; https://www.inaturalist.org/observations/12069364
https://www.inaturalist.org/observations/5708934; https://www.inaturalist.org/observations/4935390
Red cypselae no horns and variable leaves
https://www.inaturalist.org/observations/30449058
Sympatric red and brown seeds
https://www.inaturalist.org/observations/40355663
https://www.inaturalist.org/observations/40355599
https://www.inaturalist.org/observations/40333898
https://www.inaturalist.org/observations/26018331
https://www.inaturalist.org/observations/18144048
reddish brown seeds
https://www.inaturalist.org/observations/22916353
https://www.inaturalist.org/observations/48937056
https://www.inaturalist.org/observations/46463545
https://www.inaturalist.org/observations/46366025
https://www.inaturalist.org/observations/43585532
There are plenty of observations with olive-seeded achenese and with highly divided leaves. Of the observations where you can see both the seeds and the leaves, there are just about as many with olive seeds and highly divided leaves.
https://www.inaturalist.org/observations/6104316
https://www.inaturalist.org/observations/55330874
https://www.inaturalist.org/observations/55135826
https://www.inaturalist.org/observations/51994588
https://www.inaturalist.org/observations/50983759
https://www.inaturalist.org/observations/46723114
https://www.inaturalist.org/observations/46700686
https://www.inaturalist.org/observations/46623799
https://www.inaturalist.org/observations/44853618
https://www.inaturalist.org/observations/43719170
https://www.inaturalist.org/observations/43659943
https://www.inaturalist.org/observations/43585532
https://www.inaturalist.org/observations/43308757
Conclusion
Baesd on the evidence presented here, it is clear that the common Dandelion, nearly ubiquitous across North America, is an apomictic triploid species that has very high rates of morphological, chemical and genetic variability within and among populations, but especially within a population. The author has seen no evidence that the red achene character state is anything but a mutant color morph that can and does appear randomly wherever Dandelions occur. Until there is convincing evidence for the validity of the species, the available evidence argues for treating the common, weedy Dandelion as a single species (Taraxacum officinale).
Literature Cited
King, L.M. 1993. Origins of genotypic variation in North American dandelions inferred from ribosomal DNA and chloroplast DNA restriction enzyme analysis. Evolution 47: 136–151.
Lyman, J.C. and N.C. Ellstrand. 1984. Clonal diversity in Taraxacum officinale (Compositae), an apomict. Heredity 53: 1–10.
Mayr, E. 1992. A local flora and the biological species concept. American Journal of Botany 79: 1537–2197 https://bsapubs.onlinelibrary.wiley.com/doi/abs/10.1002/j.1537-2197.1992.tb13641.x
Riesberg, L., T.E. Wood and E.J. Baack. 2006. The nature of plant species. Nature 440: 524–527. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2443815/
Taylor, R.J. 1987. Populational variation and biosystematic interpretations in weedy dandelions. Bulletin of the Torrey Botanical Club 114: 109–120.
Solbrig, O.T. 1971. The population biology of dandelions. Am. Sci, 59, 686—694.
SOLBRIG. 0. T. AND SIMPSON, B. B. 1974. Components of regulation of a population of
dandelions in Michigan. J. EcoL, 62, 473—486.
SOLBRIG, 0. T. AND SIMPSON, B. B. 1977. A garden experiment on competition between
biotypes of the common dandelion (Taraxacum officinale). J. Eco!., 65, 427—430.
Verduijn, M., Van Dijk, P. & Van Damme, J. The role of tetraploids in the sexual–asexual cycle in dandelions (Taraxacum). Heredity 93, 390–398 (2004). https://doi.org/10.1038/sj.hdy.6800515
8 Likes
Interesting, thanks! I will have to take a more in-depth look this as I may be misunderstanding things. However, based on a quick look is it possible that the critique might apply more to the oversimplistic North American dichotomy than to the more nuanced (perhaps overcomplicated) European taxonomy?
If “T. officinale” actually represents multiple European sections, which among them contain a variety of leaf and bract morphologies (and seed colour), and “T. erythrospermum” represents a section with some variation within it, wouldn’t a poor distinction between them be expected? Maybe the chemical and genetic tests go further than that though.
The most confusing thing for me is the differences in results and interpretation between North Americans and Europeans. I guess I just don’t understand how they could have a heirarchy of taxa like they do if there isn’t even consistency within sections as those papers suggest. To pull one example, this paper seems to claim to find reliable morphological and genetic differences between microspecies, which shouldn’t be possible if every weedy dandelion is the same extremely variable species.
1 Like
Just because one can discern patterns of variation within a highly variable plant, does mean every morphological variant is a species. Human beings are all one species, but we can certainly discern traits within geographic groups and even within families. But that does not make us different species. I would also like to challenge some of the proponents of microspecies to a blinded trial and see how consistently they can apply the characters in their keys. I have tried to use them and most of the character states are so ambiguous as to be impossible to use.
What is a species is an age old debate. But in the end a “species” is a human and artificial construct for convenience. I think we should aim for the truth, but recognize that any system we construct will be imperfect. I think its also important to balance the desire for precision with accuracy. The general public is looking for accuracy. Scientists often get obsessed with precision and lose sight of the bigger picture. That’s when the public gets frustrated and walks away. Have you heard of “plant blindness”?
4 Likes