Unresolved Malva In San Marcos

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Unusual Malva pseudolavatera? ("Malva X") From San Marcos, San Diego Co., CA
   © W.P. Armstrong & Steven Disparti
   14 July 2012 Updated 17 Aug 2019
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Brief Synopsis: Flowers & fruit key out close to Malva pseudolavatera; however, smaller flower size & low-growing, spreading (procumbent-decumbent) growth form do not fit M. pseudolavatera. [In decumbent growth form the tip is ascending.] M. neglecta & M. nicaeensis have decumbent growth form and smaller flowers, but epicalyx bractlets of M. neglecta & mericarps of M. nicaeensis do not fit. Is this an unreported species for California & the U.S., or a fertile, ruderal Malva possibly of hybrid origin? See Summary & Conclusions. According to Christopher Davis (personal communication, March 2013), this is a low-growing morph of M. pseudolavatera.
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Annual & Perennial Malva Species With Petals Less Than 15 mm Long

The above criteria excludes North American native & naturalized species with larger, showy flowers, such as M. alcea, M. arborea, M. assurgentiflora and M. moschata. Petals of M. pseudolavatera are 15 mm long, but this is an upright shrubby plant, not at all decumbent.

Malva X has the following characteristics which just do not fit the Malva keys in the Jepson Manual Vol. 2 (2012) and Flora of North America by Steven R. Hill:

  1. Growth form decumbent.
  2. Petals 10-12 mm depending on water & soil; smaller than M. pseudolavatera & with paler veins.
  3. Epicalyx bractlets widely lanceolate to ovate; bases fused to each other or to calyx (not like M. neglecta).
  4. Mericarps smooth or faintly net-veined (not like M. nicaeensis).

Table Comparing Major Characteristics Used To Key Out Malva Species
In Revised Jepson Manual Of California Vascular Plants Volume 2 (2012)

Shape of bractlets subtending the calyx &
Extent of calyx lobes subtending fruit.
Calyx lobes spreading,
not enclosing the fruit.
Calyx lobes generally
enclosing the fruit.
Bractlets narrow-linear to threadlike.
M. parviflora
----------
Bractlets widely linear to narrow lanceolate;
free from each other and from the calyx.
M. neglecta
Acc. to illust. in Jepson Manual.
M. neglecta
M. verticillata
Bractlets widely lanceolate to ovate;
bases fused to each other or to calyx.
Mericarp strongly net-veined.
----------
M. nicaeensis
    (Growth Decumbent)    
Bractlets widely lanceolate to ovate;
bases fused to each other or to calyx.
Mericarp faintly net-veined to smooth.
----------
Growth Erect:
      M. pseudolavatera
      
    Growth Decumbent:    
Malva X*; Resembles
Italian M. multiflora**

*Based upon key characteristics in the Jepson Manual On-Line Edition (2019).
**Accepted species in Kew Plant List & International Plant Names Index (IPNI)

Field observations and numerous plants grown in test plots by Steven Disparti clearly show that Malva X develops a low, decumbent growth form. M. nicaeensis also develops a decumbent growth form; however, its mericarps are very different from Malva X. The mericarps of M. nicaeensis are strongly net-veined & pitted on back with sharp outer edges, and they remain tightly connected in wheel-shaped schizocarp. Mericarps of Malva X are smooth to faintly ridged on back, similar to those of M. pseudolavatera, with outer edges +- rounded. Mericarps of Malva X readily separate (shatter). These characteristics are illustrated in the following images.

Based upon information and images on this web page, Malva authority Christopher Davis (personal communication, 20 July 2012) states that "Malva X" is a decumbent growth form of Malva pseudolavatera: "I had a look at your atypically decumbent Malva, which is indeed M. pseudolavatera. This can often happen to Malva species that are otherwise more erect, if the main stem is damaged early on (and this is the typical habit for M. neglecta and M. pusilla). " In addition, Mr. Davis said that M. multiflora is a superfluous synonym of M. pseudolavatera.

Note regarding observations by Christopher Davis: Seeds from "Malva X" grown in test plots by Steven Disparti consistently grew into decumbent (prostrate) plants without any damage to the main stem. See the following images.

  Other Malva Species In San Diego County  

Malva X in field in San Marcos. Growth form is decumbent although main stalk appears to have been cut. The petals are 10-12 mm long. 23 March 2012

Malva X grown from seed clearly retained the decumbent growth form. The plants are vigorous, prolific seed-producers. The petals are 10 mm long. 13 July 2012

Malva pseudolavatera and Malva X growing side-by-side in test plots (24 July 2012). Although their flowers and fruits are similar, their growth form is completely different.

Parental San Marcos Malva X at its original site in San Marcos in December 2012 showing procumbent growth form of dead stems. Numerous seedlings with heart-shaped cotyledons appeared around this parental plant. It will be interesting to see if they also develop the decumbent growth form during the following spring and summer of 2013. See next image taken the following May 2013!

Malva X flowers are pale in color. Veins not as dark purple as in M. pseudolavatera.

A. Malva X. B. Malva pseudolavatera. The petals of M. pseudolavatera are 15 mm long.

Epicalyx bractlets are too wide for M. neglecta.

Fruit segments (carpels) partially covered by calyx lobes.

Calyx lobes of Malva parviflora are reflexed outwardly. Malva X calyx lobes are partially folded over mericarps.

The flowers of Malva X are similar to M. pseudolavatera except they are smaller and lighter in color. The petals are about 10 mm long,

The mericarps of Malva X are similar to M. pseudolavatera. They have faint but visible cross-ridges (net veins) on back, unlike the prominent ridges of M. nicaeensis. They lack the thin-winged, toothed edges of M. parviflora. The outer edges appear +- sharp-rounded. M. neglecta has smooth to weakly ridged segments with rounded edges.

Mature fruit segments (mericarps) of Malva X.

Seedlings of Malva X that recently sprouted from a cluster of seed-bearing carpels.


Malva nicaeensis From Twin Oaks Valley, San Marcos, CA

Decumbent Malva nicaeensis in parched, dry field near horse corrals & track at Walnut Grove Park, San Marcos, CA. The flowers were small (10-12 mm in diameter). Mericarps distinctly reticulate & pitted in back.

Close-up view of flower & fruit of Malva nicaeensis at Walnut Grove Park, San Marcos showing small size of flower compared with calyx and fruit (schizocarps). The distinctly reticulate & pitted mericarps are characteristic of this species.

Comparison of the fruits (schizocarps) and individual carpels (mericarps) of three naturalized annual (biennial) species of Malva in San Diego County. Mericarps of M. nicaeensis are strongly net-veined-pitted on back with sharp outer edges. Mericarps remain connected in wheel-shaped schizocarp. Mericarps of M. pseudolavatera are faintly net-veined or cross ridged on back and with outer edges +- sharp. Mericarps of Malva X are smooth to faintly ridged on back, similar to those of M. pseudolavatera with outer edges +- rounded. Mericarps of Malva X readily separate (shatter).


Malva neglecta From Jerome & Prescott, Arizona

The growth form of Malva neglecta is generally low-growing (spreading), unlike the erect M. parviflora and M. pseudolavatera. Mericarps are finely pubescent and smooth on the back, without distinct pits or net-veins as in M. nicaeensis. The mericarps separate from each other at maturity, unlike M. nicaeensis. Calyx lobes generally do not enclose the mature schizocarp. Epicalyx bractlets are narrow-linear, free from each other and the calyx (unlike M. pseudolavatera). Flowers are white to pale pink with pale veins, roughly intermediate in size between M. nicaeensis and Malva X.


Summary & Conclusions (Updated 11 Oct 2019):

Note: I have placed these comments in chronological order starting with the original conclusions and proceeding to newer conclusions based on additional scholarly references. It is obvious to me that the taxonomic status of Malva pseudolavatera & M. multiflora is exceedingly complex & confusing!

1. The epicalyx bractlets of Malva X are widely lanceolate to ovate with bases fused to each other or to calyx, similar to M. pseudolavatera; however, the flowers have paler veins and are smaller. The decumbent growth form is similar to M. neglecta and Malva nicaeensis; however, M. neglecta has epicalyx bractlets that are widely linear to narrow lanceolate, free from each other and from the calyx. The smooth mericarps of Malva X are very different from the strongly net-veined and pitted mericarps of M. nicaeensis. The general flower size with pale veins is similar to M. neglecta.

2. Another interesting revelation is Malva multiflora. The following website has images tentatively identified as M. multiflora that look practically identical to Malva X, including the broad epicalyx bractlets and decumbent (prostrate) growth form. Some on-line references consider this species synonymous with M. pseudolavatera; however, the Kew Plant List (2012) treated both of them as "unresolved." The International Plant Names Index (IPNI) lists Malva multiflora (Cav.) Soldano, Banfi & Galasso with only one synonym Malope multiflora Cav. The IPNI also lists Malva pseudolavatera Webb. & Berthal. with three synonyms: Lavatera cretica L., Malva linnaei M.F. Ray, and Malva hederifolia Vis. Therefore, according to IPNI Malva multiflora and M. pseudolavatera are two separate species! However, according to Malva authority Christopher Davis (personal communication, 20 July 2012) M. multiflora is a superfluous synonym of M. pseudolavatera.

  Images Of Decumbent Malva In Italy Tentatively Identified As Malva multiflora  

When I checked the Kew Plant List in Aug. 2019, it listed both Malva multiflora and M. pseudolavatera as accepted species; however, Kew Plants Of The World Online lists M. pseudolavatera as a synonym of M. multiflora:

    Search The Kew Plant List       Kew Plants Of The World Online       International Plant Names Index  

3. Malva X is a prolific seed-producer, typical of a weedy, annual. The original plant was growing in a field near the location of an old grain silo in San Marcos west of Palomar College. I have found many interesting naturalized weeds in this area. Seeds from the original location were planted in test plots in Escondido. They all developed into nearly identical decumbent plants with little or no variation in flowers or fruits. Could this be a fertile hexaploid hybrid ("ruderal malvoid hybrid")? See the following article by P.E. Garcia, P. Schönswetter, J.F. Aguilar and G.N. Feliner (2009):

  • Garcia, P.E., Schönswetter, P., Aguilar, J.F., and G.N. Feliner. 2009. "Five Molecular Markers Reveal Extensive Morphological Homoplasy and Reticulate Evolution in the Malva Alliance (Malvaceae)." Molecular Phylogenetics and Evolution 50: 226-239.

    "Among the closely related small-flowered ruderal malvoids, different accessions of M. neglecta do not form a cohesive group, but group either with M. nicaeensis and Lavatera cretica (data not shown) or with M. verticillata. This is probably due to hybridization, a well known phenomenon among the hexaploid small-flowered mallows (M. neglecta, M. nicaeensis, M. parviflora and M. sylvestris), which has caused a high number of names describing the variability and morphological diversity of hybrids (see Sennen, 1910, 1932)."

4. According to Malva authority Christopher Davis, Dept. of Plant Sciences, University of Cambridge (personal communication, March 2013), Malva X is a low-growing morph of M. pseudolavatera. After studying the growth of Malva X seedlings and comparing them with other Malva species, I tend to agree with Christopher Davis that our Malva X is a decumbent variation; however, I am puzzled that M. multiflora & M. pseudolavatera are now listed as accepted species on the Kew Plant List and they are both listed for California on some plant databases but not in the Jepson Manual. I must admit that tentative images of M. multiflora from Italy look remarkably similar to our decumbent Malva X. In addition, Mr. Davis also that stated that M. multiflora is a superfluous synonym of M. pseudolavatera

5. Malva pseudolavatera is naturalized in California along the coast and is apparently spreading. The current synonym in the on-line Flora of North America is Lavatera cretica L. (1753), not Malva cretica Cavanilles 1786. According to addendum for Malva pseudolavatera in current Flora of North America, the name Malva multiflora (Cavanilles) Soldano, Bamfi & Golasso based on basionym Malope multiflora (Cavanilles) 1786 has been proposed as the correct name.

6. Flora Europea Vol. 2 (1968) has an interesting statement under Malope multiflora Cav.: "Malope multifora Cav. from S. Spain has never been seen since its original discovery and may belong to some other genus. It is said to have 3-4 small, white flowers in each leaf-axil." According to Flora Iberica, Lavatera cretica L. is the accepted name for Malope multiflora. In fact, Malva pseudolavatera is not listed in the database.

Lavatera cretica L. is correct name for Malope multiflora: See Flora Iberica

7. In "Notes On Systematics and Taxonomy For The Italian Vascular Flora. 2." (Atti Soc. it. Sci. nat. Museo civ. Stor. nat. Milano, 152 (II): 85-106, Novembre 2011), Enrico Banfi, Gabriele Galasso & Adriano Soldano list Malope multiflora Cav., Lavatera cretica L., and Malva pseudolavatera (1836) Webb & Berthel. as synonyms for Malva multiflora (Cav.) Soldano, Banfi & Galasso. [They use 3-bar equal sign ≡ for Malope multiflora & Malva pseudolavatera presumably referring to names based on same type specimen.] Malva pseudolavatera dates back to 1836, 50 years after Malope multiflora. These publication dates are mentioned in the following references:

Lavatera cretica (Caroli Linnae I Species Plantarum, 1753); Malope multiflora (Secunda Dissertatio Botanica, 1786); Malva pseudolavatera (Histoire Naturelle des Iles Canaries, 1836).

8. Another scholarly Italian reference lists synonyms with 2 & 3-bar equal signs for Malva multiflora (Cav) Soldano, Banfi & Galasso: "A New Nomenclatural Combination in Malva L. (Malvaceae)" by Ana Juan & Manuel B. Crepo (2011), Flora Montiberica 48: 3-6 (VI-2011). ISSN 1138-5952: 3-bar equal signs ≡ are reported for Malope multiflora (1786), Malva pseudolavatera (1836), Anthema cretica (1787), Althaea cretica (1862) and Malva cretica (1889); and 2-bar equal sign = for Lavatera cretica L. (1753) .

9. On-Line Information From Global Biodiversity Information Facility (GBIF) 16 October 2019:
   Go To The Global Biodiversity Information Facility (GBIF) Home Page For A Species Search

Malva multiflora L. GBIF Search: www.gbif.org/species/3933415

Accepted Name. Malva multiflora (Cav.) Soldano, Banfi & Galasso: According to this accepted binomial the original author is Cavanilles and the basionym is Malope multiflora Cav. published in 1786.

Malva pseudolavatera Webb. & Berthel. GBIF Search: www.gbif.org/species/3940998

Accepted Name: Malva multiflora (Cav.) Soldano, Banfi & Galasso. The binomial M. pseudolavatera is listed as a synonym of Malva multiflora (With basionym Malope multiflora 1786). GBIF also lists Lavatera cretica L. as a synonym of Malva multiflora (Cav.) Soldano, Banfi & Galasso. For some reason, the original name Lavatera cretica L. is not the basionym even though it was published by Linnaeus in 1753. Perhaps it violates one of the rules of International Botanical Nomenclature. In some references it is listed as 2-bar synonym rather than 3-bar synonym. It is listed as a different species (not a synonym) in Cavanilles original 1786 publication where he provides the 1st (original) name (basionym) of Malope multiflora Cav.

  In the scientific name of organisms, basionym means the original name (binomial) on which a new name is based; the author citation of the new name should include the authors of the basionym in parentheses. Type specimen is the single original specimen designated as the "type" or holotype when the plant was collected. It is deposited in a special herbarium. Duplicates of the type (isotypes) are deposited in other herbaria. Only one specimen may be selected as the type, otherwise there could be chaos. Two types of synonyms are recognized, those based upon the same type specimen (with the 3-bar symbol ≡) and those synonyms based upon different type specimens (with the 2-bar symbol =).
[Chaos In Arizona: Araucarioxylon arizonicum with 3 type specimens.]
10. The bottom line here after reading all these confusing taxonomic references is that during the past two centuries many names have been used for Malva multiflora and Malva pseudolavatera. Some of these may be valid synonyms listed in the literature and data bases and some may be superfluous. There appears to be considerable disagreement among authorities in Europe and the U.S.

11. Another fascinating reference on Malva & Lavatera comes from Martin Forbes Ray (1995, 1998) "Systematics of Lavatera and Malva (Malvaceae, Malveae) - A New Perspective." Plant Systematics and Evolution198:29-53 and Novon 8: 288-295. The cladograms on pages 40-41 of Ray (1995) show Lavatera cretica and Malva nicaeensis as sister clades. In the Jepson Flora of California (2nd Ed., 2012), most of the species originally classified as Lavatera have been transferred to Malva primarily based on Ray's molecular (DNA) data. The morphological key in Jepson Manual uses mericarp characteristics to separate these 2 closely related genera. The degree of fusion of epicalyx bractlets used in some keys are just too variable & overlapping in my opinion. For example: The couplets: "Bractlets Fused ± 1/2" in Lavatera vs. "Bractlets Free or Fused ± 1/2" in Malva are not too useful for some species.

12. Links To Databases Showing Different Citations By Authorites Regarding Synonyms & Species Status of Malope multiflora, Lavatera cretica, Malva pseudolavatera, and Malva multiflora:

1. Plants of the World Online
2. International Plant Names Index (IPNI)
3. The Kew Plant List
4. Flora of North America
5. Consortium of California Herbaria (CCH1)
6. Data From the California Phenology (CCH2)
7. Jepson Herbarium, University of CA Berkeley
8. Global Biodiversity Information Facility (GBIF)
9. Flora Iberica (Iberian Peninsula of SW Europe)

Malva pseudolavatera Is Correct Name; Malva multiflora Invalid Binomial
From C.J. Davis At Cambridge University (Personal Communication, 6 November 2019)

... "Yes, the nomenclature has been a bit tricky. It started when Martin Forbes Ray did his PhD on the circumscription of Malva, and realised that Lavatera cretica (and others such as L. arborea) was really a species of Malva, very close to M. sylvestris (type species, as well as M. neglecta & M. nicaeensis), all occurring in California as introductions. He renamed L. cretica as Malva linnaei, but this wasn't really necessary, since the species had already been named."

"Unfortunately, Devesa had included the obscure name Malope multiflora as a synonym of Lavatera cretica. I corresponded with him, and we attempted to track down any evidence such as type material, to no avail. However, even the description as it stands cannot refer to Lavatera cretica. I had imagined this description (attached) referred to something like Malachra fasciata, but it's really impossible to tell. I've also attached my old correspondence with Devesa. Please feel free to use any of this. For this reason, Malva multiflora is an invalid combination, and Malva pseudolavatera (an ugly mouthful to be sure) stands."


Addendum: (19 July 2019)

Field Where Malva X Was Discovered: No Trace Of Malva X, But Entire Field Covered With
Naturalized Weed Positively Identified As Stinkwort (Dittrichia graveolens--Asteraceae)

Identified as stinkwort (Dittrichia graveolens), a fall-blooming, naturalized weed in the sunflower family (Asteraceae) native to Europe, Mediterranean, southwest Asia and Africa. I confirmed ID when it flowered in September. This species is considered to be a serious, aggressive weed in San Diego County and especially in California wine country. The stems and leaves are covered with minute, globose, sessile, sticky resin glands and dense hairs that provide insulation against dehydration and allow the plant to survive the heat & drought months of summer & fall. Reported to cause allergic contact dermatitis in some people. Allelopathic effects on other weeds & cultivated crop plants has also been reported.

Stinkwort (Dittrichia graveolens) in full bloom (24 September 2019). It belongs to the family Asteraceae, tribe Inuleae along with arrowweed (Pluchea), everlasting (Gnaphalium), nest-straw (Stylocline), and cudweed (Filago). Species in this tribe have distinctive anthers that are tailed at base.

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