ארכיון יומן של אוקטובר 2020

אוקטובר 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.

Summary

  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”

פורסם ב אוקטובר 20, 2020 07:08 אחה"צ על־ידי danielatha danielatha | 3 comments | הוספת תגובה

אוקטובר 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.

Introduction
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.

Results
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

Discussion
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.

References
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.

Acknowledgements

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



פורסם ב אוקטובר 21, 2020 05:22 אחה"צ על־ידי danielatha danielatha | 14 comments | הוספת תגובה

אוקטובר 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.

פורסם ב אוקטובר 29, 2020 09:15 אחה"צ על־ידי danielatha danielatha | 0 comments | הוספת תגובה

אוקטובר 01, 2020

NYBG EcoFlora October EcoQuest Challenge

REPORT MUGWORT

Common Mugwort (Artemisia vulgaris) is a Eurasian perennial in the Sunflower family (Asteraceae). Multiple introductions to North America beginning in the 1600s and subsequent genetic crossing have resulted in a range of morphological diversity, especially in leaf form. Outside its native range it is highly invasive, spreading by seed and underground rhizomes and forming monocultures.

How many Common Mugwort can you find by October 31?

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פורסם ב אוקטובר 01, 2020 08:57 אחה"צ על־ידי danielatha danielatha | 3 comments | הוספת תגובה

אוקטובר 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 (https://www.inaturalist.org/observations/52429526).

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.

References
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 datha@nybg.org 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.

פורסם ב אוקטובר 26, 2020 04:40 אחה"צ על־ידי danielatha danielatha | 6 comments | הוספת תגובה