May 16, 2021

Why Confirm the ID When the Observation is Already Research Grade?

Several reasons:

  1. Confirmation by a specialist adds value.
  2. So far, I have found 43 plants misidentified as Sea Grape, Coccoloba uvifera: That's almost one percent of all those I've reviewed. 510 plants misidentified as American Jumpseed, Persicaria virginiana: That's 4.6 percent of the 11,000 I've reviewed.
  3. Of course, I have made a mistake or two myself, but I learn the genus better by seeing many observations.

The same reasons I add annotations confirming identifications on herbarium specimens for species I am familiar with. And in this case, the "annotation" doesn't even take up any real estate on the "specimen".

Posted on May 16, 2021 01:07 AM by danielatha danielatha | 1 comment | Leave a comment

April 05, 2021

On the status of Red-Seeded Dandelions (*Taraxacum erythrospermum*)

By Daniel Atha


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 many of 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.

As naturalists we know that we would all be better off if more people 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.

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. The offspring inherit genetic, anatomical and behavioral traits from the parents. Put more simply, a species is 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.

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 that an organism is definable by a set of traits and that we can tell it apart from others reliably by use of a key. And because we are dealing with plants in the landscape, our floristic hypotheses can be 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-- the common Dandelion. My goal here is to determine (by empirical evidence) whether the Red-Seeded Dandelion is a species as commonly understood by botanists and the public or whether it is 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 in the broad sense) 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.

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). In other words, they are clones. 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.

Red-Seeded Dandelions (given the name Taraxacum erythrospermum in 1822 by Antoni Andrzejowski and Joseph Besser.) is treated as a species in most of our floras, including the Flora of North America.

In floristics and systematic botany science, we use taxonomic keys (among other methods) to test our hypotheses. The key is a series of choices that are meant to be mutually exclusive. An organism (taxon) is supposed to fit the characteristics presented in one choice, but not the other. Sometimes key are long and have multiple series of choices that narrow down the options until we are finally presented with just two choices-- one leading to our organisms. Most keys are dichotomous, meaning that each set of questions consists of just two choices, as in the key below.

Every flora treats the "species" in nearly the same way. The detailed descriptions of the two entities (when provided) differ slightly, but the characters in the key here are the ones almost always used to distinguish the species.

A. Leaves usually deeply cut throughout their length, the lobes sharp and narrow, usually pointed back; flower heads smaller; floral bracts (phyllaries) hooded and/or with horns near their tips; seeds (cypselae) reddish or purplish at maturity..... Taraxacum erythrospermum.

A. Leaves less deeply cut, particularly toward the base, the lobes less sharp, not pointed back; flower heads larger; the floral bracts (phyllaries) not hooded and without horns near their tips; seeds (cypselae) brown, olive or tan at maturity..... Taraxacum officinale.

The material presented here demonstrates that these are continuous characters (subject to bias and observer interpretation) and are not correlated with each other or other traits. All research specifically designed to test the hypothesis that Red-Seeded Dandelions are a valid species have found that they are not.

Materials and Methods
Research on the leaf morphology of the Common Dandelions shows that leaf length to width ratio and degree of lobeing varies as the plant ages (Sanchez, 1971) and is influenced by light intensity (Wassink 1965; Sánchez 1967). Rounded leaf blades with less lobeing develop in low light and deeply lobed leaf blades develop in high light (Sánchez 1967; Slabnik 1981). Increasing light intensity increases the leaf lobeing and decreases the leaf length:width ratio (Slabnik 1981). These studies show that the character used by every flora writer to distinguish the two Dandelions (leaf lobeing) is not a trait inherited from the parents, but is rather is a response to environmental variables.

Another study found that achenes actually sort into seven color morphs, but these occur independent of other character states (citation needed).

A study of 20 individuals from several populations across Washington, 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 Taraxacum 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 Taraxacum officinale and Taraxacum laevigatum [Taraxacum erythrospermum] in rDNA and cpDNA is consistent with Taylor’s (1987) observations based on morphology and phenolic compounds and suggests they are not separate evolutionary lineages." - King, 1993

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 lobeing correlated with achene color; 2. floral bracts (phyllaries) with horn-like appendages correlated with achene color.

The following observations show with empirical evidence that seed (cypselae) color is not consistently correlated with either of these commonly used morphological characters. Rather it appears to occur randomly within populations of "regular" Dandelions. (Field studies here in New York City will be designed to test whether distinctly red seed color occurs randomly in populations and is correlated with any other objective character.)

The following observations were culled from a review of approximately 300 of at least 17,000 global Dandelion observations. Observations were reviewed quickly and some which are ambiguous may remain.

Seeds (achenes or cypselae) red but floral bracts (phyllaries) without horns

Seeds red but floral bracts without horns and variable leaves

Red and brown seeded plants growing in mixed populations

Seeds reddish brown

There are many observations with olive colored seeds 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. This is an excellent series of photos with olive achenes, highly divided leaves and phyllaries with small projections.

I have found no scientific studies that support the recognition of Taraxacum erythrospermum as a valid species-- only descriptive accounts using continuous, qualitative characters that are subject to bias. It appears that every study actually testing the validity of the hypothesis with objective and quantitative criteria found that there is no basis for recognition of Taraxacum erythrospermum as a valid species. Don't get me wrong. I love all plants, including the ones we call weeds and invasives. An artificial ranking as species does determine the inherent worth of Red-Seeded Dandelions as living beings worthy of our love and respect.

Based 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 may appear randomly wherever clonal 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).

This is how science is supposed to work. Someone has a hypothesis. That gets tested independently and objectively and either the evidence supports the hypothesis or doesn't. To ignore the evidence and persist with the unsubstantiated hypothesis is not scientific at all.

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: 36–151.

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

Riesberg, L., T.E. Wood and E.J. Baack. 2006. The nature of plant species. Nature 440: 24–527.

Solbrig, O.T. 1971. The population biology of dandelions. Am. Sci. 59: 686–694.

Solbrig. 0.T. and B.B. Simpson. 1974. Components of regulation of a population of dandelions in Michigan. J. Ecol 62: 473–486.

Solbrig. 0.T. and B.B. Simpson. 1977. A garden experiment on competition between biotypes of the common dandelion (Taraxacum officinale). J. Ecol. 65: 427–430.

Stewart-Wade, S., S. Neumann, L. Collins and G. Boland. The biology of Canadian weeds. 117. Taraxacum officinale G.H. Weber ex Wiggers. Canadian Journal of Plant Science 82: 825–853.

Taylor, R.J. 1987. Populational variation and biosystematic interpretations in weedy dandelions. Bulletin of the Torrey Botanical Club 114: 109–120.

Verduijn, M., P. Van Dijk & J. Van Damme. 2004. The role of tetraploids in the sexual–sexual cycle in dandelions (Taraxacum). Heredity 93: 390–398.

Wassink, E.C. 1965. Some Introductory Notes on Taraxacum officinale L. as an experimental plant for morphogenetic and production research. Mededelingen Van De Landbouwhogeschool, 65–16. Wageningen: Veenman.

Posted on April 05, 2021 11:30 PM by danielatha danielatha | 5 comments | Leave a comment

January 30, 2021

Daniel's iNat Tips and Tricks

Tony Iwane's iNaturalist search tips

Tips and tricks compiled by others


My yearly stats

Observations in a 48 kilometer (30 mile) radius around City Hall, New York, New York

All White Snakeroot observations in New York City

All Shaggy Soldier and Gallant Soldier in the world,48178

Map of Spicebush and Spicebush Swallowtail Butterfly in NYC

Species observed in New York City by others but not by me

Observations in a 30 mile radius around City Hall, NY that need identification

My identification stats

My identifications of a particular species

My identification differs from community id (for Common Reed)

My identifications of Sea Grape from API with any potential disagreements

Common responses

Any comment containing “Smartweed”

Comments by me

Comments that tag me

Comments by me containing “Smartweed”

Comments on my observations

New York City White Snakeroot with Leaf Miner annotation

with Leaf Miner annotation = Yes

with Leaf Miner annotation = No

with Leaf Miner annotation = Unclear

with Leaf Miner annotation = null

How to mark an observation captive/cultivated in the mobile app.

Posted on January 30, 2021 12:42 AM by danielatha danielatha | 0 comments | Leave a comment

December 18, 2020

Community Scientists Make Important Discoveries

Community scientists make important plant discoveries around New York City

December 2020

New York City EcoFlora community scientists recently discovered two plant species never before documented in our region. Local residents Susan Hewitt, Sara Rall and Zihao Wang discovered a new plant for North America and a new species (and genus) for New York State. They made the discoveries this fall while observing the flora and fauna in the greater New York City region. Their discoveries are published in the latest issue of the online botanical journal, Phytoneuron.

On September 7, 2020, Sara Rall, self-taught naturalist and a resident of New Jersey observed an unusual Smartweed growing in the floodplain of the Delaware River and made note of its distinct features. And by the most improbable coincidence, Daniel Atha observed the same species on the very same day, just hours apart, but 85 miles north on the upper reaches of the Delaware River in Sullivan County, New York. That evening, noting each other's observations on iNaturalist, the two started a conversation about the plants and their unusual features. Herbarium specimens of the New York plants were used to compare with known North American species and possible introductions. A match was eventually found in the Flora of China and the Flora of Taiwan: Persicaria posumbu, a species heretofore never found anywhere in North America. This significant finding is published today in the online botanical journal, Phytoneuron. See: First Report of Persicaria posumbu (Polygonaceae) for North America.
Susan Hewitt, resident of Manhattan and the most prolific observer of plants and animals in New York City and Zihao Wang, resident of Brooklyn, environmental engineer and discoverer of numerous rare plants and animals in the New York City area, independently discovered populations of Tropic Croton, Croton glandulosus, a member of the Spurge family (Euphorbiaceae): Wang in Queens in the fall of 2019 and Hewitt in Manhattan in September 2020. They posted their observations to iNaturalist and their identifications were confirmed by Nathan Taylor, the Euphorbiaceae specialist. Noting the significance of the discoveries for the region, Daniel Atha visited both sites and confirmed that the plants were indeed a new addition to the flora of New York State. Just in time for the holidays, Tropic Croton is closely related to the Pointsettia we all know. Read more about their discovery published today in the online botanical journal Phytoneuron: First Report of Croton glandulosus (Polygonaceae) for New York.
Posted on December 18, 2020 03:10 PM by danielatha danielatha | 11 comments | Leave a comment

November 16, 2020

Yams (Dioscorea) of Northeastern North America

Wild Yam, Dioscorea villosa Chinese Yam, Dioscorea polystachya

Key to the Dioscorea Species of Northeastern North America

1a. Vine from rhizomes; leaf axils without aerial tubers; mature petioles nearly circular in cross section; leaves ovate-cordate, the sides evenly convex, basal lobes absent; fruits winged..... Dioscorea villosa

1b. Vine from woody tuber; leaf axils often with aerial tubers; mature petioles strongly channeled; leaves hastate, sides with some concavity, basal lobes usually present; fruits unknown in North America..... Dioscorea polystachya

Dioscorea polystachya Turcz. – Chinese Yam, Cinnamon Vine
Introduced; NYS Prohibited; present in NYC. Description. iNaturalist observations from New York City. GloBI interactions.
Indiana non-native plant invasiveness ranking form. Pest Risk Management Document for Dioscorea polystachya (Chinese yam) in Canada

Dioscorea villosa L. – Wild Yam
Indigenous; (CoC 6); present in NYC. Description. iNaturalist observations from New York City. GloBI interactions.

Posted on November 16, 2020 06:11 PM by danielatha danielatha | 2 comments | Leave a comment

October 29, 2020

NYBG Science, Conservation and Humanities Webinars

Everyone is invited to these free Science, Conservation and Humanities Webinars from NYBG

Conserving the Rare Plants of New York (Friday, Nov. 6)

First Nations: Ethical Landscapes, Sacred Plants (Friday, Nov.13)

Here Today, Gone Tomorrow: Plant Extinction Now and Conservation Strategies for Tomorrow (Tuesdays, Nov. 17 & 24):

Sign-up to hear about upcoming NYBG Science, Conservation, and Humanities seminars.

Posted on October 29, 2020 09:15 PM by danielatha danielatha | 0 comments | Leave a comment

October 26, 2020

American and Asian Jumpseed in North America

American Jumpseed, Persicaria virginiana

Asian Jumpseed, Persicaria filiformis (photo by Reuven Martin)

Persicaria virginiana (L.) Gaertn. American Jumpseed is a perennial herb to 1.5 m tall, from knotty rhizomes; stems are erect, slender and few-branched; ocreae strigose or tomentose, the apices ciliate; leaf blades ovate, 5–17 × 2–10 cm, reduced apically, the bases rounded, the apices acute to acuminate, strigose above and below, the margins setose; inflorescences to 45 cm long, very slender; flowers solitary or 2–3 per ocreolate fascicle; tepals 4, white, greenish white or rarely pink; achenes brown with hooked, persistent style. 2n=44.

The species is found across the eastern United States (and southern Canada), east of the 100th meridian, from southern Minnesota to Texas and Quebec to Florida, disjunct in central Mexico; found in rich deciduous forests, floodplain forests, dry woodlands, thickets; flowering July to October.

Synonyms include Polygonum virginianum, Tovara virginiana, Antenoron virginianum, Tovara virginiana f. rubra, Tovara virginiana var. glaberrima

The deflexed pedicels are under strong tension and when disturbed can propel the fruit 3–4 m from the plant (hence the name Jumpseed). The persistent hooked styles aid in animal dispersal. The plants are easy to recognize when young by the relatively large, ovate leaves and often very prominent maroon chevron that disappears as the leaves age. Small flies, bees and wasps are observed visiting the flowers and Robber Flies use the plants to hunt prey. Herbivory by Sawflies in the genus Allantus creates holes in the leaves (

Persicaria filiformis (Thunb.) Nakai, Asian Jumpseed is sister to the American Jumpseed. They may share a common ancestor, but millenia of isolation, drifting continents and changing vegetation patterns caused the two species to diverge genetically, anatomically and chemically. But some taxonomists don't consider these differences enough to divide the species and treat them as two varieties of one species or just one species (under the oldest name, Persicaria virginiana). The one-species concept prevailed several decades ago and is often used in older literature and in the horticulture trade. Today there is ample data from multiple lines of evidence and strong support for separating the two as distinct species (Park et al., 1992; Mun & Park, 1995; Suh et al., 1997).

Cultivars of the Asian Persicaria filiformis ‘Painter’s Palette’, ‘Lance Corporal’, ‘Variegata’ and ‘Bat Wings’ are escaping from cultivation in the eastern United States and becoming naturalized. These introduced, artificial hybrids may interbreed with the indigenous Persicaria virginiana, eroding its genetic integrity and possibly compromising fitness and survival of this important indigenous American plant. The aggressive growth of the Asian Jumpseed also threatens other biodiversity by forming large, monocultural stands that crowd out other species.

Morphologically, Persicaria filiformis and its cultivars can be distinguished by the elliptic leaves that are widest at or above the middle and with persistent purple markings, whereas Persicaria virginiana has ovate leaves, widest below the middle and purple markings only on young leaves.

I recommend supporting the indigenous species and all its ecological benefits and removing the cultivar wherever found.

Suh, Y., S. Kim and C.W. Park. 1997. A phylogenetic study of Polygonum sect. Tovara (Polygonaceae) based on ITS sequences of nuclear ribosomal DNA. Journal of Plant Biology 40: 47–52.

Park, CW., M.G. Lee and H. Shin. 1992. A systematic study of Polygonum sect. Tovara (Polygonaceae): analysis of morphological variation. Korean Journal of Botany 35: 385–392.

Mun, J.H. and C.W. Park. 1995. Flavonoid chemistry of Polygonum sect. Tovara (Polygonaceae): a systematic survey. Plant Systematics and Evolution 196: 153–159.

Please notify me at if you find the Asian Jumpseed and any of its cultivars like 'Painter's Palette', 'Lance Corporal', 'Variegata' or 'Bat Wings' growing wild in North America, apart from a planted population— especially in natural areas. Thank you.

Posted on October 26, 2020 04:40 PM by danielatha danielatha | 8 comments | Leave a comment

October 21, 2020

The Cosmopolitan Quickweeds (Galinsoga) of the World

Quickweeds. Shaggy soldier, Galinsoga quadriradiata (L), Gallant Soldier, Galinsoga parviflora (R), Photo 528808, (c) Kyle Jones, some rights reserved (CC BY-NC). Shaggy Soldier, Galinsoga quadriradiata. Two disc flowers and fruit with acuminate pappus scales (L); one ray flower and fruit with pappus scales nearly as long as corolla tube (R).Photo 9072390, Daniel Atha, public domain.

Galinsoga (Quickweed) is a genus of 15–30 species indigenous to the Americas and centered in Mexico (Canne, 1977; Canne-Hilliker, 2006). Two species are cosmopolitan, occurring in disturbed places in most countries of the world: Galinsoga quadriradiata and Galinsoga parviflora. Currently, only these two species are known from the continental US (USDA NCRS, 2020). Judith Canne-Hilliker who studied these plants for decades published works on the taxonomy of the genus and her work is the basis for modern floras that treat the species. A few additional studies have been done as well. For example, Braden and Cialone found that achenes of Galinsoga quadriradiata are significantly shorter and wider than those of Galinsoga parviflora (Braden & Cialone, 1971). Based on the literature and what could be observed in the field it was clear that the two species were distinct, but I was frustrated by the challenges in separating them, especially from fresh material in the field and from photographs on iNaturalist. The study described here was my attempt to address this problem. See the observation here for images of seedling development.

Materials and Methods
I examined all the herbarium specimens of Galinsoga quadriradiata and Galinsoga parviflora from North America at the New York Botanical Garden (NY) and the Brooklyn Botanic Garden (BKL) (over 300 specimens). Using a compound microscope and strong light, I sorted all specimens by the characters used by Judith Canne-Hilliker and flora writers to separate the two species. I ignored identifications and used only the traits of: rays with well-developed pappus about equaling the tube vs. rays with vestigial pappus scales or scales absent; pappus scales of the disk flowers awn-tipped vs. blunt.

Here is a good view of the pappus scales of the disk flowers and the pappus of the ray flowers in Galinsoga quadriradiata. In Galinsoga parviflora the ray pappus is absent.

I ended up with three piles, one much larger than the other two. The smallest pile consisted of specimens for which it was not possible to determine nature of disc and ray pappus scales. I then examined the two larger piles for hair and leaf teeth character states.

All of the specimens (100%) that sorted by lack of ray pappus and blunt disc scales (the middle sized pile) were found to have very short (<0.5 mm), unicellular hairs (on stems and leaves) and narrow-ovate leaves with mostly entire or merely crenate margins. The larger pile with ray pappus scales present and acute or awn-tipped disc pappus scales were all found to have long (> 0.5 mm) multicellular hairs (on stems and leaves) and wider leaves with definite acute teeth. It was then possible to sort the smaller, undetermined pile on the basis of hair and leaf characters alone so that all specimens were identifiable as one or the other species.

Outside of Mexico, Galinsoga quadriradiata is the most common of the two species. On the continent of Europe, the species occurs at just over twice the rate of Galinsoga parviflora (2,296 to 988, as of 17 Nov 2020). But in the United States, the species occurs at over ten times the rate of Galinsoga parviflora (2,214 to 214). In Asia it is 537 to 120. On the continent of Australia there are thirty-six observations of Galinsoga parviflora and no Galinsoga quadriradiata--so far.

Key to the Cosmopolitan Quickweeds of the World

1a. Stems and leaves pubescent with multicellular hairs 0.5–1(-2) mm long; leaf margins dentate, the teeth obtuse to acute; limb of ray flowers 2–5 mm long, the pappus scales about as long as the tube; pappus scales of disk flowers sharp-acuminate, lacerate..... Galinsoga quadriradiata

1b. Stems and leaves glabrous to sparse pubescent with unicellular hairs 0–0.5 mm long; leaf margins crenate, the teeth rounded; limb of ray flowers 0–2 mm long, the pappus scales minute or absent; pappus scales of disk flowers truncate to obtuse, fimbriate..... Galinsoga parviflora

The results obtained here and those of previous work elucidate several traits that are discrete, objective and unambiguous. Further, these traits are consistently correlated with each other to form a distinct assemblage of character states that unambiguously and consistently define the species. Each couplet (1a and 1b) in the dichotomous key above is a series of characters (separated by semicolons). The two species share these characters (such as pubescence or leaf margins) but not the values or attributes of that character. The values of each character are called character states. The character states exhibited by a species (such as hairs longer than 0.5 mm or shorter than 0.5 mm) are discrete and unambiguous for the two species. They are true for one species or the other, but not both. Each couplet is thus a summary of the assembled traits (characters and values) that define that species and can be used as a brief description (often called a diagnosis in older literature).

The process undertaken in the present study can instruct others seeking to distinguish taxa based on simple terms understood by a general audience and what can be observed with the naked eye or a hand lens. In photographs and often even in the field, it is not possible to dissect the specimen to examine minute and often highly technical features. But monographs, floras and even field guides may rely solely on minute and difficult characters to distinguish species (as in Galinsoga). For nearly all photographs of Galinsoga in iNaturalist, these characters are impossible to see and thus only tentative identifications were possible prior to this study. Working with preserved specimens I could examine under a microscope, I used the technical characters in a process of reciprocal illumination to find other, more easily observable traits by which the species could be identified. Based on the simple traits described here and summarized in the dichotomous key above, it is now possible for anyone to confidently identify Galinsoga in the field and from photographs such as those on iNaturalist.

This procedure may fail to reveal easily observable traits to distinguish cryptic species in other genera, but I have used it with success in Smartweeds (Persicaria) and in genera of other families.

Outside their native range, the two weedy species, Galinsoga quadriradiata and Galinsoga parviflora are often found growing side by side in mixed populations. Care should be taken when taking multiple photos in a single population.

It may only be a matter of time before additional Galinsoga species are found in the continental United States, especially in areas adjacent to Mexico, center of diversity of the genus.

Canne-Hilliker, J. 2006. Galinsoga Ruiz and Pavón, Pp. 180–182. in Flora of North America Editorial Committee (eds.). Flora of North America North of Mexico, Vol. 21. Magnoliophyta: Asteridae, part 8: Asteraceae, part 3. Oxford Univ. Press, New York; Canne, J.M. 1977. A revision of the genus Galinsoga (Compositae: Heliantheae). Rhodora 79: 319–389; USDA NCRS. 2020. Galinsoga. United States Department of Agriculture, Natural Resources Conservation Service accessed 21 October 2020; Braden, D.A. and J.C. Cialone. 1971. Characterization of two Galinsoga R. & P. species from New Jersey by achene length/width ratio and the presence of marginal cotyledonary hairs. Bulletin of the Torrey Botanical Club 98: 50–52.


This post is dedicated to Judith Canne-Hilliker, student and master of Galinsoga, who passed away in Guelph, Canada on October 27, 2013.

Posted on October 21, 2020 05:22 PM by danielatha danielatha | 14 comments | Leave a comment

October 20, 2020

The Case for Recognizing Persicaria amphibia and Persicaria coccinea as Distinct Species

The following information is presented to the community so that they may know more about these beautiful plants and appreciate their unique attributes and inherent value as living beings worthy of respect and protection.

I began studying Smartweeds, Persicaria, over a decade ago when I found a plant right outside my office door and all over New York City that had been in North America for fifty years, yet was unrecognized by all botanists (Persicaria extremiorientalis). Since then, I have collected hundreds of Persicaria specimens and examined thousands more in major herbaria. I have read the literature old and new, been a peer-reviewer for journals and corresponded with the handful of Polygonaceae specialists practicing today. I know the North American species pretty well and can recognize most from photographs.

Smartweeds are a genus of about 100 species primarily of the north temperate zone of both hemispheres. Most species are annuals with simple, alternate, entire ovate or elliptic leaves and spicate inflorescences and flowers of usually five perianth parts. Hybridization, introgression and polyploidy are especially common in the core “Eupersicaria” group of the genus. There are few autapomorphies (unique traits) that clearly distinguish one species from another. Often a suite of characters are necessary to define a species and distinguish it from others. In addition, the species can be quite variable and morphologically plastic in response to environmental conditions, especially periodic inundation (as are the two species discussed here). The Pale Smartweed Persicaria lapathifolia and Lady’s Thumb Persicaria maculosa can also form inflated, floating stems when flooded

The “Amphibious” Smartweeds, Persicaria amphibia and Persicaria coccinea attracted my attention early on because they are such beautiful plants, yet no one seemed interested in them, perhaps because of their tortured taxonomic history. The more I learned about them and the sorry state of our professional conclusions, the more I wanted to “understand” them and reveal their unique qualities and relationships to each other and their surroundings. Ultimately, I want to protect these plants as much as possible from further human harm.

Water Smartweed, Persicaria amphibia var. stipulacea (photo by Reuven Martin)

Scarlet Smartweed aka Longroot Smartweed, Persicaria coccinea (photo by Henggang Cui)

Persicaria amphibia var. stipulacea and Persicaria coccinea (Persicaria amphibia var. emersa) are perennial North American natives that inhabit high-quality, oligotrophic wetlands (especially Persicaria amphibia). They are both adapted to fluctuating water levels (hence the “amphibious” epithet). Persicaria amphibia is normally an aquatic with floating leaves, but when stranded on dry banks can grow aerial shoots (with flared ocreae). Persicaria coccinea is normally a palustrine species with aerial shoots, but can tolerate flooding for periods of time and may sometimes develop floating stems and leaves. Persicaria amphibia var stipulacea does not grow south of the Laurentide Ice Sheet except in the mountain west and Mexico. The fidelity is amazing as can be seen in this map. Persicaria coccinea grows nearly throughout North America except the southeast coastal plains and Mexico.

The vast majority of specimens across North America will key out clearly with the key below. But there are populations that don’t, especially in the mountain west. These anomalies are probably genetic mixtures from hybridization and introgression, both phenomena common and well-documented in the genus. Each species’ extreme anatomical plasticity and the existence of intermediate specimens has thrown botanists for 200+ years into taxonomic fits, lumping the entire range into one artificial super-species (e.g., R. Mitchell) or dividing every minor morphotype into a separate species (e.g., E.L. Greene). Persicaria amphibia has over 100 heterotypic synonyms just in North America!; and Persicaria coccinea almost as many. The hypothesis that there are two distinct species and one or more hybrid swarms (cited below) is the most plausible and parsimonious way to make sense of these beautiful and important plants. It is also the only way to ensure that each species (and its genetic diversity) is wisely and effectively conserved.

Key to the species (currently treated as varieties in most works, but see Reveal, J. L. & D. E. Atha. 2012. 8. Persicaria (L.) Mill. Smartweed, pp 236–250. in Cronquist et al. (eds), Intermountain Flora. The New York Botanical Garden Press, Bronx, NY).

1a. Plants palustrine, usually with emergent leafy stems; ocreae never with flared apices; aerial leaves petiolate with acuminate tips; inflorescence spikes terminal, usually 2 (unequal), > 4 cm long...… Persicaria coccinea (Persicaria amphibia var. emersa).

1b. Plants aquatic, usually with floating stems and leaves; ocreae with flared apices (when stranded); aerial leaves (when present) nearly sessile with somewhat cordate bases and blunt apices; inflorescence spikes usually 1, < 4 cm long...…Persicaria amphibia var. stipulacea.


  1. Distinct geographic ranges. This is becoming more and more clear as the observations accumulate. There are now over 2000 observations of the two species and they clearly have different distributions. There are no Persicaria coccinea in the far north. And there are no Persicaria amphibia south of the Laurentide ice sheet in the eastern US.
  2. Distinct morphologies. The vast majority of plants clearly exhibit a number of discontinuous character states consistent with one species or the other.
  3. No single plant has ever been found to possess the characters of Persicaria coccinea at one end and Persicaria amphibia at the other, even though there is ample opportunity for them to do so based on level of inundation. There are many examples of Persicaria amphibia with floating leaves at one end and erect shoots at the other. I have seen most of the herbarium specimens of both species in North America and all the iNaturalist observations and I have never seen a plant with erect shoots and long inflorescences on the stem portion out of water and oblong floating leaves and short inflorescences on the stem portion in the water.
  4. If they are one species with blended genetics, how can it be that no Persicaria coccinea like plant has ever been found with flared ocreae? That character is found exclusively in Persicaria amphibia var. stipulacea.
  5. The presence of intermediates does not "prove" they are a single species. The most parsimonious explanation is that the intermediates are hybrids. To consider them as one species is the least good explanation. R.S. Mitchell did not consider this possibility (as the null hypothesis) when he lumped them for his Ph.D thesis in 1968.
  6. Taken all together these data are consistent with the consensus definition of a species in botany.
  7. Lumping them as a single species has very serious conservation implications. Conservation plans should conserve distinctive genetic lineages and conflating the two species could lead to the extinction of one or the other in the false belief that the "species" is preserved by the presence of at least some Persicaria amphibia s.l. We all know that most people ignore varieties and even heritage botanists and environmental surveyors will use the species name for convenience or uncertainty. U.S. Army Corps of Engineers data forms often omit subspecies or varieties, compromising the integrity and usefulness of EIS surveys that might include “Persicaria amphibia”
Posted on October 20, 2020 07:08 PM by danielatha danielatha | 4 comments | Leave a comment