Mertensia in New Mexico

The key below may or may not work. It is my current best guess as to how to deal with Mertensia in the state and I offer it not because I have any particular confidence that it is correct, but because I think the other available treatments of Mertensia in New Mexico (and Colorado, for that matter) are worse!

Back in 1937, Louis Otho Williams published “A monograph of the genus Mertensia in North America” (Annals of the Missouri Botanical Garden 24(1): 17-159). There are problems with his treatment, but so far as I can tell it basically works. Nearing 80 years later, it appears still to be the best (and only synoptic) treatment of the genus in the U.S. Subsequently, names have been synonymized without any coherent rationale, characters have been misinterpreted, the distributions of various species have been expanded based on dubiously identified specimens, and so on and so forth. As a result, our understanding of Mertensia has been slowly and steadily mangled. The situation with Mertensia abundantly illustrates a general rule in taxonomy: After any monographic treatment of a genus, our understanding of its taxonomy doesn’t just stagnate, it declines. Whatever level of clarity and insight was achieved is slowly lost and buried under the compounded, piecemeal modifications (some well-justified, some not) of subsequent authors. This is not an absolute rule by any means and monographers can’t possibly get everything right. It is, however, a good guess that they got more right than anyone else. The problem, of course, is that the later dilettantes (myself included!) tend to assume they know better and, through being more recent if nothing else, tend to be believed. One way or another, a coherent synoptic view eventually disintegrates into a jumble of smaller taxonomic works, varying regional treatments, etc.

This brings me to the present. After a very long wait, someone has finally taken up the challenge of Mertensia. Mare Nazaire, presently of Rancho Santa Ana Botanic Garden, has completed a PhD on the genus and is working on the Flora of North America treatment for Mertensia. Based on what she has published thus far, it appears that Williams sometimes included distinct and relatively distantly related lineages either as varieties within a species or even lumped together within a single variety. Hopefully we will soon have a solid new synoptic treatment of Mertensia. In the interim, the key below is based primarily on Williams’ monograph, with adjustments in nomenclature based on the work of Nazaire. It may at least reduce some of the confusion. Or it may not!

1. Cauline leaves with prominent lateral veins; stems usually more than 4 dm tall; flowering late spring and summer
    2. Leaves minutely strigose on the adaxial surface, glabrous or with spreading pubescence on the abaxial surface; sepals 2.5–5 mm long, acute – Mertensia franciscana
    2. Leaves glabrous on both surfaces (minutely ciliate on the margins, often papillate on the adaxial surface); sepals 1.5–3 mm long, obtuse – Mertensia ciliata
1. Cauline leaves without lateral veins, or lateral veins very inconspicuous; stems usually less than 4 dm. tall; normally flowering in early spring, as soon as temperatures permit
    3. Stamens entirely within the corolla tube (filaments attached in the corolla tube and anthers not projecting beyond the throat) – Mertensia alpina
    3. Stamens mostly beyond the corolla tube (filaments attached near the throat of the corolla tube, anthers well beyond the throat)
        4. Cauline leaves glabrous abaxially, pubescent or glabrous adaxially
            5. Adaxial cauline leaf surfaces strigose, the hairs pointing towards the leaf margin (at a 45–90º angle to the central vein); sepals definitely strigose on the abaxial surface
                6. Sepals connate half or more of their lengths – Mertensia fendleri var. fendleri
                6. Sepals free to the base or nearly so (look carefully–they may be overlapping in the lower third and appear connate without close inspection) – Mertensia ovata var. ovata
            5. Adaxial cauline leaf surfaces strigose, pustulate, or glabrous (if strigose, the hairs directed toward the apex of the leaf, ± parallel to the central vein); sepals glabrous or very nearly so on the abaxial surface (but ciliate on the margins and, rarely, with a few very sparse trichomes on the abaxial surface)
                7. Corolla tube 3–6.5 mm long, the corolla limb equal in length or slightly longer; cauline leaves usually strigose adaxially – Mertensia lanceolata
                7. Corolla tube 7–9 mm long, the corolla limb slightly shorter; cauline leaves glabrous adaxially – Mertensia ovata var. caelestina
        4. Cauline leaves pubescent on both surfaces
            8. Sepals connate one half or more of their lengths – Mertensia fendleri var. pubens
            8. Sepals connate only at the base, free most of their lengths – Mertensia bakeri

Of the species known in New Mexico, Mertensia franciscana and Mertensia fendleri are by far the most abundant. Three others, Mertensia brevistyla, Mertensia fusiformis, and Mertensia oblongifolia, have been erroneously reported in the state. With the exception of Mertensia franciscana, misidentifications, misapplied names, and baffling synonymies abound in herbarium collections and southwestern regional treatments of Mertensia.

Thelypodium in New Mexico

A key to Thelypodium in New Mexico that I wrote a year ago, after finding existing keys for the genus in our area somewhat unsatisfying:

1 Stem leaves sessile, entire or rarely denticulate; pedicels stout, ca. 0.5 mm wide – Thelypodium integrifolium subsp. gracilipes
1 Stem leaves petiolate, at least the lower pinnately lobed; pedicels slender, ca. 0.25 mm wide (or stout in T. texanum)
    2 Sepals ascending at anthesis, bases of petals and stamens not directly visible; stamens erect, tetradynamous (the outer two conspicuously shorter than the other four); replum constricted between the seeds — Thelypodium laxiflorum
    2 Sepals and stamens spreading at anthesis, bases of petals and stamens directly visible; stamens ascending, equal in length; replum not constricted between the seeds
        3 Uppermost stem leaves pinnately lobed; mature fruits stiffly horizontal to ascending, usually 1.3 mm wide or more – Thelypodium texanum
        3 Uppermost stem leaves entire or toothed, rarely with a couple of lobes near the base; mature fruits horizontal to reflexed, often drooping, usually 1.2 mm wide or less – Thelypodium wrightii

Some brief notes:

Thelypodium integrifolium subsp. gracilipes is basically a species of relatively moist, salty places (playas, alkaline flats, salty springs or washes, etc.) and is definitely present in the northwest corner of the state (San Juan County, probably Rio Arriba and McKinley counties as well) but has been reported from a number of other areas. Probably most of these are misidentifications, but I have not seen the specimens.

We have only one record of Thelypodium laxiflorum in the state, in San Juan County. Thelypodium integrifolium also has ascending sepals and fairly “closed” flowers; this feature is quite obvious on live plants but can be obscured in pressed specimens.

Thelypodium texanum has generally been known under the name Sibara grisea in New Mexico. It is found on and near limestone cliffs in southeastern New Mexico (Eddy and Otero counties).

Thelypodium wrightii occurs in a range of habitats, but I have seen it mostly in moist canyons at intermediate elevations (ca. 6000-7000 feet). This is the most abundant Thelypodium in the state by a wide margin. Consequently, misidentifications of Thelypodium in the state consist mostly of calling Thelypodium wrightii something else. This is the same kind of mistake that is common with Erysimum. I think this is a general rule: If one species in a genus is dramatically more abundant than the others, variation within that species is likely to be misinterpreted as representing the other, relatively rare, species. I think this results from an overestimation of one’s thoroughness in sampling. Surely, after seeing several hundred Thelypodium in New Mexico, you must have seen all four species in the state! Therefore, any variation you can observe must be the same variation discussed in taxonomic works on the genus. Of course, if one species is far more abundant than the others… you might have only seen that species. You might then spend hours trying to figure out how the variation within that one species can be forced to correspond with the published taxonomic work on the genus, which says there are four species in your area. And thus you are led astray. This, by the way, is why access to a comprehensive herbarium is often a necessity. Many errors can be avoided if you have specimens of the relevant species available to compare side-by-side. That said, misidentifications in Thelypodium are understandable with fragmentary specimens. For instance, the leaves of Thelypodium wrightii are progressively reduced as you move up the stem, becoming entire and nearly sessile near the bases of the inflorescences. If only the upper parts of the stems are collected (which is common, because Thelypodium wrightii can be 5-6 feet tall and will not easily fit on an herbarium sheet), this can easily lead to a misidentification of the specimen as Thelypodium integrifolium. The lower petiolate, pinnately lobed leaves can also senesce later in the season, causing the same confusion even if you have the whole plant in hand. In such cases, the narrow pedicels and widely spreading sepals of Thelypodium wrightii (vs. stout pedicels and ascending to erect sepals in Thelypodium integrifolium) should allow correct identification. Or, if in doubt, calling everything in the genus “Thelypodium wrightii” will result in the correct identification 90+% of the time!

Common southwestern NM plant families

Related to the last post, here are the 28 most frequent plant families in my plant community dataset. Plant families follow the Angiosperm Phylogeny Group III treatment.

Poaceae: 3119
Asteraceae: 2643
Fabaceae: 684
Cactaceae: 586
Amaranthaceae: 511
Euphorbiaceae: 416
Pinaceae: 369
Zygophyllaceae: 361
Brassicaceae: 357
Rosaceae: 314
Asparagaceae: 308
Polygonaceae: 301
Solanaceae: 235
Fagaceae: 199
Nyctaginaceae: 192
Malvaceae: 173
Boraginaceae: 168
Cupressaceae: 138
Convolvulaceae: 104
Plantaginaceae: 102
Ephedraceae: 100
Anacardiaceae: 94
Polemoniaceae: 93
Geraniaceae: 93
Ranunculaceae: 88
Portulacaceae: 83
Pteridaceae: 75
Lamiaceae: 71