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Excerpts from Jim Conrad's
Naturalist Newsletter
Entry dated April 20, 2024, from notes taken about 1.5km northeast of Puerto de los Velazquez, Municipality of Pinal de Amoles; N21.138°, W99.665°, elevation ~2780 meters (~9120 feet); oak/pine/fir borderline cloud-forest on limestone bedrock; in the Eastern Sierra Madre Mountains of east-central Querétaro state, MÉXICO
ARCHIBACCHARIS HIERACIOIDES
At the right, at the crest of a wind-swept ridge, a woody bush loaded with pompom-like fruiting heads dangles over a limestone ledge. It isn't clear that the species normally is a dangler, for it's rooted in forest soil at the ledge's top, where certain stems grow upright. Other stems lean outwards. My impression is that the dangling stems, if they were on level ground, also would be leaning, not dangling.
At the left, it's clear that we're dealing with yet another member of the Composite/Aster/Sunflower Family, the Asteraceae. Basic identification features already apparent are that our plant belongs to that minority in the family which is woody, and that atop its one-seeded, cypsela-type fruits pappuses develop composed of slender, white, hair-like bristles which at the current season perform the service of parachuting the windborne fruits to different places.
Younger flowering heads still contained fading corollas amid pappus bristles, which extended a little above the corollas' tops. No flat, ray floret corollas arose along the heads' margins; only cylindrical disc floret corollas were present. Rusty-reddish, greenish, scale-like phyllaries formed urn-shaped involucres which constricted at their tops, and enclosed the florets' lower parts. The phyllaries were of different lengths and overlapped one another. Their slender tips were long and sharply pointed. The phyllaries' bodies were sparsely puberulent with short, erect hairs, and the surfaces glistened with what must have been resinous glands. In the above picture, a couple of hairs may bear glands atop them; under higher magnification maybe more would appear to be glandular.
Amid the pappus bristles, two types of slender, cylindrical, disc-floret corollas were visible, but there were no flat, ray floret corollas. Of the disc florets, some corollas were very slender throughout their lengths, while others had somewhat inflated upper parts. In general, most slender corollas were tightly packed in the head's center, with the ones with enlarged tops appearing along the periphery, though in places the two corolla types mingled.
Above, on the left, several corollas with enlarged upper halfs are seen, some with faded Y-shaped style arms extending beyond the corollas' mouths. A black cypsela with four strong ridges lies atop the mass of pappuses. The cypsela bears 16 or so pappus bristles.
Last season's leaves have fallen off the woody and semiwoody stems but, above, a young leaf's upper surface is seen sparsely hairy with short, erect hairs, some of which may be gland tipped.
Above, a young leaf's undersurface is splotchy with white, cobwebby hairs. The leaf has a definite petiole, and the blade base is somewhat rounded.
Above, emerging leaves at a new stem's base bear petioles. At the right, an inflorescence's peduncle and branches appear to be covered with very short hairs and possibly glands, but it's hard to say.
Noting all the above features was necessary to identify our shrub as ARCHIBACCHARIS HIERACIOIDES, with no English name. The species is endemic just to highland central Mexico from San Luis Potosí, Querétaro and Hidalgo states in the north, to Morelos and Tlaxcala states in the south. It occurs in forests with oaks, pines and firs, from 2750 to 3200m in elevation, so our plant approaches its lower elevation limit.
No flora treatment of Archibaccharis exists for our area, but John Jackson's 1975 work "A Revision of the Genus Archibaccharis Heering. (Compositae - Astereae)," describes in detail the species's features. He uses an older name for the taxon, Archibaccharis hieraciifolia var. hieraciifolia. He mentions the corollas being of two different kinds, one very slender and another blousing out above. He considers the condition to be a transition stage between ancestral taxa producing flowers with both male and female parts (monoecious state), and taxa in which individual plants bear either male or female flowers, but not both at the same time (dioecious).
Otherwise, published literature, except for its phylogenetic status, doesn't say much about Archibaccharis hieraciifolia, probably because of its limited distribution and the difficulty in identifying it. However, the species occupies part of the phylogenetic Tree of Life where branching within the tree is much discussed.
A 2017 study by Oscar Vargas and others entitled "Conflicting phylogenomic signals reveal a pattern of reticulate evolution in a recent high-Andean diversification (Asteraceae: Astereae: Diplostephium)" -- the study included an Archibaccharis species -- concluded this: That there was "... significant incongruence among the nuclear, chloroplast, and mitochondrial phylogenies" of the species. The authors concluded that their evidence supported the idea that a major role in events of rapid diversification can be attributed to "reticulate evolution."
In short, branching of the Tree of Life in the neighborhood of our shrub's location, may not be as neat as we usually think. For example, within the Tree of Life, evolutionary reticulation events potentially can be convergent and divergent at the same time.
So, that's what you can get into stumbling around on an isolated mountain ridge wondering about the beings you meet there.