1. syyskuuta 2021

An examination of Research Grade Observations in the genus Callirhoe

Introduction

The genus Callirhoe is a genus of showy, mostly reddish and sometimes white flowering plants in the Malvaceae family native to North America. The most recent study of the genus was by Dorr in A Revision of the North American Genus Callirhoe (Malvaceae) published in 1990 and revised for the Flora of North America (FNA) in 2015.

In the spring of 2021, I began informally examining a number of different type of observations in the Callirhoe dataset for various reasons, sometimes to annotate lesser known species, sometimes to verify identifications or sometimes to add identifications. The occurence of some observations of Callirhoe leiocarpa in the Dallas area (outside their known range) in 2020 had sparked my interest in the genus and I returned to it in 2021. Over the course of a couple of months I noticed a non-trivial number of incorrect observations among Research Grade(RG) observations. At some point, my focus switched to looking for incorrect identifications and I began looking through Callirhoe observations in Texas chronologically, spot checking images in the grid view of the iNaturalist explore window, but I did not track how many were incorrect. After looking through numerous observations and getting part way through the year of 2018, I finally decided that it might be interesting to know what sort of error rate was occurring. Given the relatively large number of observations of Callirhoe (over 10,000), I decided to initially examine a small subset, though eventually examined all RG observations from Texas for the years of 2018 and 2019, including some which were likely RG before I previously made an identification, for a total of 1521. I adjusted the set under examination to exclude RG observations where an identification I had made affected the status and to include Needs ID observations where my identification had changed the status from RG. The error rate for the two years combined was about 19.1%.

Species

There are nine species in the genus, of which the following six are found in Texas: C. alcaeoides, C. involucrata, C. leiocarpa, C. papaver, C. pedata, and C. scabriscula, which has not yet been observed on iNaturalist due to its rarity. C. involucrata is the most common and widespread Callirhoe species in North America. It ranges throughout most of Texas, encompassing the ranges of all the other species in Texas except for parts of the range of C. papaver in east Texas. Two additional species, C. bushii and C. digitata, have historically been found close to or along the Texas Oklahoma border, but are not thought to occur in Texas (Kartesz 2015).

Selection of observations

While I did examine all RG observations from Texas from 2018(594) and 2019(937), I was primarily interested in observations which were Research Grade without my interaction. This required some manipulation of the dataset, removing RG observations where my identification was critical to the observation acheiving RG status and adding to the dataset observations where my identification had changed the observation from RG to Needs ID. Observations that were RG where I simply agreed with the previous identifications which made the status RG were left in the totals since my identification had no effect on achieving RG status.

Limiting the observations to the years of 2018 and 2019 in Texas was mostly based on convenience. I initially started with the year 2019, which was attractive because it was a reasonably large data set and also the year for which I had made the lowest percentage of identifications. I initially intended to evaluate only a small subset of the 2019 observations in order to get a rough figure for the error rate, but I eventually examined all of them and added observations from 2018 for comparison. Limiting the observations to Texas was based mostly on my own familiarity with Texas species and comfort with identifying them. With that said, most Callirhoe observations are currently from Texas and it also contains six of the nine known species, five of which have observations on iNaturalist.

Observation numbers were download as CSV files from iNaturalist by filtering by the genus Callirhoe in Texas for the years 2019 and 2018, repectively, accessed on June 3, 2021 and July 9, 2021. Observations were viewed through the iNaturalist web interface. I examined the observations in random order, first from 2019 and then 2018, but made no attempt to mask other data such as the observer or identifiers names, location and so on.

Standard for correctness

I decided to track whether an identification was incorrect rather than correct. The vast majority of observations, even Research Grade ones, do not show the features one would normally use for identification in a taxonomic key, and so it is often not possible to prove what species a specimen is. However, one can sometimes see a feature which disproves the identification. Most often this was something like the presence or absence of an involucel, but a number of features can be used. For species descriptions and identifying characteristics, I referred to the works of Dorr(1990,2015) and Diggs et al (1999). The reader can refer to my previous post "A Short Guide to Callirhoe in Texas" for methods of identification. On rare occasions I would defer primarily to location, typically only in cases where an observation was identified as C. alcaeoides well outside of its known range.

Given the approach of tracking only incorrect identifications, the results here likely represent a lower bound for the error rate for this data set as there are numerous Research Grade observations which likely don't contain enough information to actually prove or disprove a species level identification. Additionally, even though it is sometimes possible to tell if an identification is incorrect, it is not always possible to make a species level identification in these cases. A common example would be an observation identified as C. involucrata, which upon examination shows a lack of an involucel or the presence of a valvate bud. This would disprove the identification of C. involucrata, but may not offer enough proof to distinguish between C. leiocarpa and C. pedata.

There is a larger discussion to be had about what should constitute enough information for an identification, and this discussion unfortunately can devolve into a broader discussion about the purpose and structure of iNaturalist itself which is beyond the scope of this post. As mentioned, most Callirhoe observations do not show the morphological features one would normally use for identification. To be rigourous, one would likely need to identify those observations only to genus level, and this would remove a significant percentage of Callirhoe observations from RG status. For the time being, for this endeavor at least, I have chosen to track and offer identifications on only those which are fairly clearly incorrect (or in the rare case correct) and leave the rest alone. This unfortunately leaves a fair number of observations at RG status which may or may not be correct, which is not a very satisfying solution given that RG status has implications such as affecting the iNaturalist Computer Vision model and observations being exported to external services such as GBIF. Ironically, for Callirhoe, due to the sheer abundance of C. involucrata compared to the other species, there is probably a high likelihood that something identified as C. involucrata actually is C. involucrata, even if it does not show the features one would need for a positive identification.

Results

The error rate for the adjusted dataset for the two years combined was 19.1%. There was a noticeable difference between the two years, at 15.6% for 2018 and 21.4% for 2019.

Incorrect Research Grade Identifications
Year RG Observations Adjusted RG Observations Incorrect Percent Incorrect
2018 594 617 96 15.6
2019 937 904 194 21.4
2018+2019 1531 1521 290 19.1

The identifications which were not deemed incorrect(approximately 80.9% or 1231) were not necessarily correct. They ranged from merely being possible as in cases where only the non-distinguishing features of a flower were shown all the way to correct where all of the distinguishing features required for an identification were clearly shown, though these appeared to be only a small minority. With most of these observations I found it difficult to decide how to separate those which should be identified only to genus and those which could be identified to species based on what morphological features were shown, and I ultimately could not come up with a good solution for the problem. As an initial assessment, I arrived upon the following rough categorization of the non-incorrect identifications, but I found even my own application to be inconsistent and so this is a rough estimate only, possibly to be revisited in the future.

Categories of Possibly Correct Identifications
Category Number Percent Description
Plausible to Likely 647 42.5 Observation showed one or more features supporting the identification which ruled out some but not all other possibilities found in or near the state. Examples could range from partially visible hairs on the sepals to presence of an involucel.
Possible 372 24.5 Observation showed no or only very weakly distinguishing features. Examples were those that showed only the corolla petals or maybe corolla petals appearing close to the ground.
Correct 141 9.3 Observation showed enough features to rule out other possibilities found in the state.
Uncertain 50 3.3 Observation had some quality, sometimes unclear, which warranted raising the identifcation to genus level, though which did not make it clearly incorrect.
Rosette 17 1.1 Observation showed only leaves.

Trends

A closer examination of the results revealed at least two trends. First, the majority of erroneous identifications were identified as C. involucrata. This trend is unsurprising. C. involucrata is the most common and widespread species of Callirhoe in North America, and so it as not surprising that observers and identifiers might erroneously identify a specimen as C. involucrata. Also, C. involucrata would most likely have been included in the earliest Computer Vision models due to the number of observations, and it, along with C. pedata may have been the only two Callirhoe suggested by the iNaturalist system.

The second trend is that the species most commonly misidentified was C. leiocarpa. It is difficult to determine the ultimate cause of why C. leiocarpa was misidentified so often, but at least two reasons seem possible. First, though I have not examined the data in detail, it is clear that the range of C. leiocarpa seems to be expanding, and numerous observations of it occurred around major metropolitan areas like Dallas, Fort Worth, and Houston, all areas where it was thought not to occur previously (Dorr 1990). It seems plausible that naturalists in those areas were not familiar with C. leiocarpa and were thus identifying it as other species such as C. involucrata and C. pedata. In addition to that, it is likely that C. leiocarpa was not included in the earliest versions of the Computer Vision model on iNaturalist, so that it would not have occurred as a suggestion by the iNaturalist system and observers and identifiers may not have even known it was a possibility. More research might reveal the answer.

Most commonly assigned species in incorrect identifications
Species Times used as incorrect ID
C. involucrata 247
C. pedata 35
C. alcaeoides 6
C. leiocarpa 2
C. papaver 0
Total 290

Most Common Misidentifications where species could be identified
Actual Species Identified as Occurences
C. leiocarpa C. involucrata 95
C. leiocarpa C. pedata 18
C. pedata C. involucrata 18
C. papaver C. involucrata 10
C. involucrata C. alcaeoides 3
C. alcaeoides C. pedata 2
C. involucrata C. pedata 2
C. pedata C. leiocarpa 2
C. papaver C. pedata 1
Total 151

As stated above, in many cases there is enough information to disprove the identification but not enough to prove which other species the specimen is. The most common case of this occurring is when a specimen is identified as C. involucrata but it has a valvate bud or lacks an involucel. I suspect the vast majority of these cases are C. leiocarpa, with a minority of them being C. pedata and a few being C. papaver, as is the case with those which can be identified to species, but I have not attempted a rigorous analysis of this set of observations.

Most commonly assigned species in incorrect identifications where species could not be identified
Species Times used as incorrect ID
C. involucrata 124
C. pedata 11
C. alcaeoides 3
C. leiocarpa 1
C. papaver 0
Total 139

Discussion

There does appear to be a significant error rate for the data examined, and it seems plausible that a similar error rate may have continued without some intervention. The difference in the years could be attributable to any number of factors such as differences in the dataset itself and differences in the iNaturalist observer and identifier community. A significant portion of these errors seems to be attributable to ignorance of C. leiocarpa, and perhaps this could at least partially be rectified by simply correcting the erroneous identifications, which I plan to do. There could however be a significant number of erroneous identifications in the data for other years, which I have not examined rigorously. I have also created a guide, "A short Guide to Callirhoe in Texas", as a starting point to help the iNaturalist community better identify Callirhoe specimens in the future. Hopefully, some difference will be made by identifications that have already been corrected. Additionally, updates to the iNaturalist Computer Vision system may already be helping the issue. Four of the six Texas species (including C. leiocarpa) are now included in the iNaturalist Computer Vision model, though one somewhat common species,C. papaver, is still excluded. It will likely be included in future models as there are almost enough observations to meet the previous criteria to be included in the models.

The question of what to do with the large number of Research Grade observations which do not appear to have enough evidence to support a species level identification remains unanswered. There may be incorrect identifications among them which might raise the error rate, but I suspect the majority of them probably are in fact C. involucrata. However, it would be nice to have some middle ground between Needs ID and Research Grade to indicate that they may be likely to be C. involucrata but that there is not enough proof to fully support that claim. This is an issue with iNaturalist itself though and there does not appear to be any solution on the horizon as far as I can tell.

References

Diggs, G. M., Lipscomb, B. L., O'Kennon, B., Mahler, W. F., & Shinners, L. H. (1999). Shinners & Mahler's Illustrated Flora of North Central Texas. Botanical Research Institute of Texas.
Dorr, L. J. 1990. A Revision of the North American genus Callirhoe (Malvaceae). Mem. New York Bot. Gard. 56: 1–75.
Dorr, L. J. 2015. Callirhoe. In: Flora of North America Editorial Committee, eds. 1993+. Flora of North America North of Mexico. 20+ vols. New York and Oxford. Vol. 6. http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=105128
Enquist, Marshall. 1987. Wildflowers of the Texas Hill Country. Lone Star Botanical, Austin, Texas.
iNaturalist. Available from https://www.inaturalist.org. Accessed [2021].
Kartesz, J.T., The Biota of North America Program (BONAP). 2015. North American Plant Atlas. (http://bonap.net/napa). Chapel Hill, N.C. [maps generated from Kartesz, J.T. 2015. Floristic Synthesis of North America, Version 1.0. Biota of North America Program (BONAP). (in press)].
McDaniel, R.T. “A short Guide to Callirhoe in Texas.” iNaturalist, https://www.inaturalist.org/journal/rymcdaniel/54356-a-short-guide-to-callirhoe-in-texas. Accessed August 2021.

Revisions

1.0 - September 1, 2021 - Original revision.

Lähetetty 1. syyskuuta 2021 22:40 käyttäjältä rymcdaniel rymcdaniel | 5 kommenttia | Jätä kommentti

6. elokuuta 2021

A short guide to Callirhoe in Texas


Introduction

The genus Callirhoe is a genus of mostly reddish and sometimes white flowering plants in the Malvaceae family native to North America. The most recent study of the genus was by Dorr in A Revision of the North American Genus Callirhoe (Malvaceae) published in 1990 and revised for the Flora of North America (FNA) in 2015. Of the nine species in the genus, six species are found in Texas, five of which have observations on iNaturalist with the sixth being a rare endemic found in only a few counties of the southern Rolling Plains. A seventh species occurs in Oklahoma along the Texas border in southeast Oklahoma.

The reason for providing this short guide is to educate iNaturalist observers and identifiers about the ways to identify the different species in Texas. In the spring of 2021, I began checking various research grade observations and noticed a significant number of incorrect observations. At that point I decided to perform a more rigorous examination of research grade(RG) observations, starting with RG observations from Texas for the year 2019 which I had not already identified as the initial data set. Preliminary results indicate that as high as 19.6% (168 of 856) of those observations were misidentified. While I plan to explore those results and others in a future post, it became clear that an article illustrating some of the concepts used in identification might be helpful for the iNaturalist community.

Species in Texas

A mentioned in the introduction, six species of Callirhoe occur in Texas. Relatively accurate distribution maps for these species can be found on the Biota of North America Program (BONAP) website, though the distribution of one species, C. leiocarpa maybe somewhat erroneous and currently seems to be in flux. The six species as ordered by their prevalence on iNaturalist are (vegetation areas as found in Shinners & Mahler's Illustrated Flora of North Central Texas (1999) (FNCT) :

  • C. involucrata: The most widespread of all Callirhoe species, it occurs throughout most of Texas, except for part of the Trans-Pecos in west Texas and parts of northeast Texas where it gives way to C. papaver.
  • C. pedata: Occurs in central and north central Texas from the Edwards Plateau north to the Oklahoma border in the Cross Timbers and Prairies and Blackland Prairies
  • C. leiocarpa: Historically occurred in central and south central Texas from the Edwards Plateau south to the Gulf Coast in the South Texas Plains and Gulf Prairies and Marshes. Recent iNaturalist observations have placed it in additional areas, typically around the major metropolitan areas of Houston, Dallas, and Fort Worth, where it was not found before
  • C. alcaeoides: Restricted to the northern sections of the Cross Timbers and Prairies and Blackland Prairies, starting just south of the DFW area and running northward into Oklahoma
  • C. papaver: In east and southeast Texas, primarily in the Piney Woods and Gulf Coast Prairies and marshes possibly into Post Oak Savannah and Blackland Prairies
  • C. scabriscula: A rare endemic known from only a few counties along the Colorado River in the Rolling Plains. It has not been observed on iNaturalist as of this time and I will not discuss it in detail.

A seventh species, C. bushii, occurs in southeast Oklahoma along the border with Texas. It has not been found in Texas, though it seems plausible that it might occur along the Red River in northeast Texas. One notable exception to this list is C. digitata, which is no longer treated as being found in Texas. Earlier generic treatments apparently included the species now known as C. pedata within the species concept of C. digitata, but that is no longer the case. C. digitata is now only known to be found outside Texas in states like Arkansas, Oklahoma and Missouri, though BONAP maps do show them close to the Oklahoma Texas border. The last species, C. triangulata, is found outside of Texas, primarily in Illinois and Wisconsin but also sporadically in the southeast.

Identification

Identification of the different species of Callirhoe in Texas is not difficult if the appropriate features are photographed. Of course, as with many species on iNaturalist, this is the problem. A significant percentage of Callirhoe observations consist of one or maybe two photos of the flower, which generally is not sufficient for a high confidence identification, at least not one based on the morphological features.

Keys to the genus can be found in both the Flora of North America online (efloras) and also in the Flora of North Central Texas (omitting C. papaver and C. scabriscula), which is also available online at the BRIT website. The reader can reference those keys; I will try to illustrate some of the important differentiating features found in them below. While corolla color can be helpful, some other important features are the buds, the involucel, the stipules, the fruit, the inflorescence and the sepal hairs.


Useful features for identification of common Callirhoe species in Texas
Species Petal
Color
Involucel Buds
Valvate
Stipules
Auriculate
Fruits
Large Beaked
Sepal
Hairs
C. involucrata reddish purple basally white, white, white with reddish vertical stripes yes no - no long simple
C. papaver reddish purple usually yes - no long simple
C. leiocarpa reddish purple basally white no yes yes yes glabrous
C. pedata reddish purple to purple basally white or lightened, white, rarely pink no yes no no mostly glabrous
C. alcaeoides white to light pink no yes - yes short simple

Petal color

Callirhoe in Texas are predominately reddish purple in color, though white species and forms also occur as well as more rare pink ones. The reddish purple ones range from a reddish purple to purple, often within each species. All species in Texas have a red purple form except for C. alcaeoides, though it can appear light pink. Almost all red species of Callirhoe in Texas can have some lightening of the color near the base of the petals, which can sometimes be completely white. This is sometimes referred to as a basal spot. Typically C. involucrata has a basal spot, often larger than in other species. C. leiocarpa generally has a smaller basal spot, while C. pedata and C. papaver often have a mild lightening of color, rarely completely white. Given the variation of this feature, it cannot be used as a diagnostic feature on its own, but is sometimes helpful in conjunction with other features. The literature indicates that C. pedata does not have a basal spot, but it seems specimens on iNaturalist apparently do (TBD).

Red forms of Callirhoe: C. involucrata, C. leiocarpa, C. pedata (C. papaver not pictured)


Three species of Callirhoe have white or light colored forms. C. alcaeoides is predominately white but sometimes light pink. Two of the predominately reddish species, C. pedata and C. involucrata have light forms, which are often initially identified incorrectly as C. alcaeoides. Like C. alcaeoides, the mostly reddish purple C. pedata can also be white and rarely light pink, with all three colors sometimes occurring in the same population. Light forms of C. involucrata also occur, chiefly in areas of central Texas. In Williamson county, a white form with variable large reddish vertical stripes is the predominant form, and it is probably the only one which can be identified on the basis of the corolla color alone. White color forms also occur on parts of the Edwards Plateau such as Kimble and Menard counties (Enquist 1987).

Light forms of Callirhoe: C. alcaeoides, C. pedata, C. involucrata, C. involucrata var. lineariloba (see discussion on varieties)

Involucel

The Flora of North America(FNA) key for Callirhoe starts with the presence or absence of the involucel, which for Callirhoe consists of a whorl of bracts (usually three, sometimes one) subtending the sepals. This feature separates the species into those with an involucel (C. involucrata, C. papaver, C. scabriscula, and C. bushii) and those without (C. pedata, C. leiocarpa, C. alcaeoides). The involucel is most easily visible on the buds, but can also been seen, sometimes with greater difficulty due to proximity of the sepals, on open flowers and fruiting heads. In many parts of Texas, C. involucrata is the only species with an involucel and a somewhat confident identification can be made based on the presence of that feature. Where C. involucrata comes in contact with other species that have an involucel (in Texas mostly C. papaver in east and southeast Texas but also potentially northeast Texas close to C. bushii) other features need to be used for identification, such as the bud (see next section).

C. involucrata with an involucel (other species not pictured)


In treatments previous to Dorr, the spacing between the involucellar bracts and the base of the calyx was sometimes used to differentiate C. involucrata and C. papaver, with that space being larger in C. papaver than C. involucrata. However, according to Dorr (1990), though this is generally true, it is apparently not always consistent or clear, so he uses the buds to differentiate the two species.

There is some variation in the size and shape of involucel bracts. Outside of Texas, this variation is useful for differentiation of various species such as C. papaver,C. bushii, and C. triangulata. Within Texas, the variation is one of the characters used in differentiation of the varieties of C. involucrata.

Species without an involucel C. leiocarpa, C. pedata, C. alcaeoides

Bud

The bud is a useful feature to capture for identification of Callirhoe in Texas, though it is rarely photographed on purpose. Buds in C. involucrata are unique among Callirhoe in that the tips of the sepals/calyx lobes do not come together to form a point; there is always at least some small amount of visible separation. When the calyx lobes do come together in the bud, the bud is called valvate and all Callirhoe species besides C. involucrata have valvate buds. The FNA key only uses this feature to differentiate C. involucrata from other species with involucels, but it can be used to differentiate C. involucrata from all other Callirhoe species. The presence of a non-valvate bud provides evidence that the specimen is C. involucrata whereas the presence of a valvate bud rules out as a C. involucrata possibility.

An added benefit of capturing the bud is that the presence or absence of an involucel is often more obvious on buds than on flowers.

Non-valvate bud of C. involucrata with sepal tips widely separated


Valvate bud of C. leiocarpa and C. alcaeoides with sepal tips coming together


Stipules

The stipules (leaf like appendages at the base of the leaf petioles) are useful for distinguishing two of the taller species in Texas, C. leiocarpa and C. pedata, which are somewhat similar in their lack of involucel and typically erect or ascending habit. C. leiocarpa has auriculate stipules whereas C. pedata does not. This feature needs to be used with other features for identication such as the absence of an involucel, as C. involucrata can have somewhat auriculate stipules as well. Though this differentiating character was included in Dorr's original treatment, it was not included in the key for Callirhoe in the Shinners & Mahler's Illustrated Flora of North Central Texas, which references Dorr's work. It is possible that is not completely definitive as I have seen some examples of C. pedata with small projections at the stipule base, but it does generally seem to be true and is present in Dorr's FNA key. The auriculate stipules of C. leiocarpa are often noticeable even from a distance and in blurry photographs. This may be because their inner face (adaxial) tends to spread away from the stem and face upward like a sessile leaf or because the auricles often encircle much of the stem.

C. leiocarpa stipules


C. pedata stipule

Fruit

The fruit is primarily helpful in distinguishing C. leiocarpa from other species in Texas due to its distinctive appearance. The fruit (shown in pictures below) is usually seen from above and visually has three distinct regions from this perspective: a whitish central column, a variable size greenish ring (appears to correspond to the beak), and lastly a variable size greenish yellow to white ring on the outside (which can correspond to the seed bearing portion or the collar depending on species). In C. leiocarpa, the green region (corresponding to the beak) is quite large compared to the encircling white ring (in this case a small projection called a collar which subtends the beak). Most other species in Texas, except C. alcaeoides, have a smaller green region in mature fruit (a smaller beak), similar to that shown in the C. pedata example below. Note however, that C. pedata is described as having a larger beak in areas outside of Texas, so the this difference may not apply there. Also note that immature fruit of C. pedata often have a large green area relative to the surrounding white area, so it is important to observe a mature fruit.

Fruit of C. leiocarpa, C. pedata


Inflorescence and Sepals Hairs - C. pedata and C. alcaeoides

Both C. pedata and C. alcaeoides are species without an involucel and both can have white corollas, which can make differentiation difficult in areas where they overlap as Dorr noted(1990). While the inflorescence of C. alcaeoides is typically more compact (Dorr's FNA key describes the racemes as "appearing corymbose or subumbellate"), it can be difficult to ascertain this in photos, especially in younger plants where the first open bloom may be close to unopened buds. The FNCT uses an additional character to differentiate the two species, the vestiture of the calyx. In C. alcaeoides it is described as "hispid-pubescent" and in C. pedata as glabrous or sparsely pubescent. Neither of Dorr's treatments use this as a differentiating character between the two species, though the species descriptions in his earlier work do seem to agree with this difference.

Early compact inflorescence of C. alcaeoides

Pubescent sepals of C. alcaeoides


Glabrous sepals of C. pedata

Varieties of C. involucrata

C. involucrata is described as having three varieties, two of which occur in Texas and which Dorr indicates are weakly separated(2015). The two which occur in Texas are C.i. var. involucrata and C.i. var. lineariloba. These two varieties are differentiated by qualities of the leaves, stipules, involucellar bracts and lastly, only partially sometimes, color. Determination of the variety for the most part requires close examination and measurement of these features, so it is typically not possible to make a variety determination based on photos alone. It is probably the case that most observations of C. involucrata in Texas are in fact C.i. var. lineariloba as attested to by Dorr's range maps(1990) for C. involucrata which show that C.i. var. lineariloba is found throughout much of Texas with C.i. var. involucrata apparently only occurring in a few areas in north central Texas, predominantly close to the Oklahoma border.

Some confusion exists around identification of C.i. var. lineariloba in central Texas where the variety has become associated only with the color form found mostly in Williamson county (sometimes referred to by locals as the "Williamson county winecup"), where the petals typically have a central broad vertical reddish purple region borded by white margins. I don't know if earlier research restricted the variety to this color form, but it is implicitly done in Marshall Enquist's popular Wildflowers of the Texas Hill Country (which predates Dorr's work). Ironically, though C.i. var. lineariloba probably mostly consists of reddish purple specimens, only this different color form is easily identifiable as C.i. var. lineariloba since it does not apparently occur in C.i. var. involucrata (or any other species of Callirhoe for that matter). Thus the misconception is perpetuated, but I don't see an easy way around it.

iNaturalist Observations


Observations used in the guide
Taxon Observation
Number
Features Illustrated
C. alcaeoides 88741669 white color, lack of involucel, valvate bud, sepal pubescence
C. involucrata 80169982 red color
C. involucrata 78509404 white color
C. involucrata 50584755 involucel
C. involucrata 83043800 involucel
C. involucrata 78382364 bud
C. involucrata var. lineariloba 89098715 light color with reddish regions
C. leiocarpa 88464887 red color, lack of involucel, valvate bud, auriculate stipules, fruit
C. pedata 88721978 red color, glabrous sepals
C. pedata 88745685 white color, lack of involucel, fruit
C. pedata 89107758 non-auriculate stipule

Other useful Observations
Taxon Observation
Number
Features Illustrated
C. papaver 34204774 involucel, bud

References

Diggs, G. M., Lipscomb, B. L., O'Kennon, B., Mahler, W. F., & Shinners, L. H. (1999). Shinners & Mahler's Illustrated Flora of North Central Texas. Botanical Research Institute of Texas.
Dorr, L. J. 1990. A Revision of the North American genus Callirhoe (Malvaceae). Mem. New York Bot. Gard. 56: 1–75.
Dorr, L. J. 2015. Callirhoe. In: Flora of North America Editorial Committee, eds. 1993+. Flora of North America North of Mexico. 20+ vols. New York and Oxford. Vol. 6. http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=105128
Enquist, Marshall. 1987. Wildflowers of the Texas Hill Country. Lone Star Botanical, Austin, Texas.
Kartesz, J.T., The Biota of North America Program (BONAP). 2015. North American Plant Atlas. (http://bonap.net/napa). Chapel Hill, N.C. [maps generated from Kartesz, J.T. 2015. Floristic Synthesis of North America, Version 1.0. Biota of North America Program (BONAP). (in press)].

Copyright

All photos used in this post are the property of Ryan McDaniel, all rights reserved.

Revisions

1.0 - August 6, 2021 - Original revision.

Lähetetty 6. elokuuta 2021 19:14 käyttäjältä rymcdaniel rymcdaniel | 9 kommenttia | Jätä kommentti

5. kesäkuuta 2020

Differentiation of Gutierrezia texana and Amphiachyris species in North Central Texas

Introduction

Gutierrezia texana is often confused with two Amphiachyris species with which it is sympatric, Amphiachyris dracunculoides and Amphiachyris amoena, and they have historically sometimes been treated in the same genus. For whatever reason Amphiachyris dracunculoides seems to have become the default choice both in the minds of amateur botanists and for the algorithm on iNaturalist (apparently because the other two have not met the requirements to be included in any of the computer vision models as of yet). All three plants have similar small capitula with yellow ray and disc flowers. The branching patterns can also be similar and the sizes often overlap. Amphiachyris dracunculoides often has a distinctive appearance when it exhibits its classic rounded shape with heads in dense corymbiform arrays, while both Gutierrezia texana and Amphiachyris amoena typically have more open paniculiform arrays. However, variations in the number of capitula caused by any range of factors can cause the appearances to be similar enough to be easily confused. Due to these similarities, it is necessary to examine other details of the plants to make a correct identification.

Differentiation via the phyllaries

The most convenient way for observers to differentiate the two genera in north central Texas is by observation of the phyllaries. As noted in the Flora of North America treatment of Amphiachyris, Amphiachyris species have "abaxial nerves of the phyllaries without green borders." The result is that the phyllaries on Amphiachyris species appear to have a uniform color from edge to edge, and thus often appear wider than the phyllaries on Gutierrezia species. Unfortunately, the green nerve borders in Gutierrezia texana are not always present. They often do present as a narrow dark green band bordering the phyllary nerve for much of the length of the nerve, but many times it also only occurs at the phyllary tips or under some weather and seasonal variations it may not be noticeable at all. The overall result however is the edges of the phyllaries on G. texana are often difficult to discern at all, and at best the phyllaries actually look a lot narrower than they really are.

Phyllaries of Gutierrezia texana


Phyllaries of Amphiachyris amoena


Phyllaries of Amphiachyris dracunculoides


Differentiation via the pappus

The best way to differentiate the genera in Texas is to examine the pappus of the disc flowers. In Amphiachyris, the pappus of the disc flowers consists of a few noticeably long scales. A hand lens may be useful to see them more clearly, but they are often visible with the naked eye.


In contrast, on Gutierrezia texana the pappus on both ray and disc flowers is short or absent, often not noticeable at flowering time. It is most easily noticed on achenes, if one is lucky enough to find a specimen with some intact.

Corymbiform versus Paniculiform arrays

While these flowering patterns don't differentiate the genera, they can still be helpful for differentiating A. dracunculoides, which is corymbiform, from the other two species, which are paniculiform. A corymbiform array is one in which all the flowers (or in this case heads) appear to be roughly at the same level. Specimens like these appear flat topped or rounded. Paniculiform arrays are more difficult to describe, but in general the heads do not appear at the same level. In practice, this can be difficult to ascertain when a photo simply appears to be a mass of yellow flowers, but sometimes one is able to isolate a specific branch and see which description applies. More often than not one can see heads much further down on a branch, making it paniculiform, and ruling out A. dracunculoides.

Corymbiform A. dracunculoides - note how the heads are roughly the same level


Paniculiform G. texana - note how there are heads at various levels of the branches

Disc Flower Style Branch Appendage Length

According to Nesom, the disc flowers of Amphiachyris species are functionally staminate and he also notes that the style branch appendages are fused. What this means visually is that the style branches in Amphiachyris disc flowers (when exposed) appear quite short. On the other hand, this is not the case in G. texana, so if one happens to find a capitulum where the style branches are exposed, they appear quite long. While presence of these longer style branches on disc flowers is indicative of G. texana, its absence may simply indicate that no flowers are in that stage of pollination. Additionally, one has to be certain of looking at a disc flower and not a ray flower where both genera can have long style branches.

Longer style branches of G. texana, often forming sort of a loop


Habitat and Distribution

In my experience, in the Austin area (Travis, Williamson, and Burnet counties), G. texana is much more prevalent than either Amphiachyris species in areas accessible by the public, and is often weedy on the borders of hiking trails. Amphiachyris dracunculoides is more often found in grazed pastures. All three plants do occur in the general area.

Observation Links

Amphiachyris dracunculoides
https://www.inaturalist.org/observations/36339681
https://www.inaturalist.org/observations/8626126
Amphiachyris amoena
https://www.inaturalist.org/observations/8486953
Gutierrezia texana
https://www.inaturalist.org/observations/33987832
https://www.inaturalist.org/observations/35425536
https://www.inaturalist.org/observations/35765857
Russell Pfau's comparisons
https://www.inaturalist.org/observations/34926031
https://www.inaturalist.org/observations/34926032
https://www.inaturalist.org/observations/35627415
https://www.inaturalist.org/observations/35627414

Sources

Nesom, Guy L. 2006. Amphiachyris. In: Flora of North America Editorial Committee, eds. 1993+. Flora of North America North of Mexico. 20+ vols. New York and Oxford. Vol. 20. http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=101427
Nesom, Guy L. 2006. Gutierrezia. In: Flora of North America Editorial Committee, eds. 1993+. Flora of North America North of Mexico. 20+ vols. New York and Oxford. Vol. 20. http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=114211

Lähetetty 5. kesäkuuta 2020 22:41 käyttäjältä rymcdaniel rymcdaniel | 16 kommenttia | Jätä kommentti

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