Cuatrecasanthus (Vernonieae, Compositae): A revision of a north-central Andean genus

Abstract Cuatrecasanthus is native to Ecuador and Peru and although several unusual characters define the genus, such as single flowered heads and corolla throat (limb) divided to the base with lobes that are thickened at the margins, the members of the genus were not recognized as especially closely related until relatively recently. All six species are described, including two new to science (Cuatrecasanthus kingii H. Rob. & V.A. Funk, sp. nov. and Cuatrecasanthus lanceolatus H. Rob. & V.A. Funk, sp. nov.), and one new combination is recognized (Cuatrecasanthus giannasii (Stutts) H. Rob. & V.A. Funk, comb. nov.). A key is provided along with images of the types, SEM photographs of the leaf surfaces, a distribution map, and illustrations of the two new species. All species are given a preliminary conservation status of Data Deficient in regard to the IUCN Red List of Threatened Species.


Introduction
Th e Andean genus Cuatrecasanthus H. Rob., native to Ecuador and Peru, is one of the most readily distinguished genera in the tribe Vernonieae. Th e combination of heads with one fl oret, corollas with the limb divided to the base into fi ve scarcely distorted lobes, lobes with thickened margins, and ten-ribbed achenes is unique in the tribe. Another Andean genus, with similarly deeply cut corolla lobes, Joseanthus H. Rob., diff ers by its opposite leaves and many fl orets in each head. Although the distinctions of Cuatrecasanthus are clear, it has been subject to problems at the species level that have not been entirely resolved until the present eff ort to treat the genus for the Flora of Ecuador.
Given the distinctive characters of the genus, it is surprising that the fi rst few species that were described were not recognized as relatives. Th e fi rst member the group to be described was Eremanthus jelskii Hieron. from Peru. When Vernonia fl exipappa was described by Gleason (1925), the relationship to E. jelskii was not recognized. Yet again, Vernonia giannasii Stutts (1980) was described without mention of the previously described relatives. It was Robinson and Kahn (1985), at the time of the description of Vernonia sandemannii (1985), who fi rst recognized the relationship of the new species to the Hieronymus and Gleason species. At the time of the description of the genus Cuatrecasanthus (Robinson 1989) the three species were placed together, with Vernonia giannasii being treated as a synonym of Cuatrecasanthus fl exipappus. Th e most recent studies have shown some errors in the 1989 treatment, with V. giannasii proving to be a distinct species and two additional species needing description. Th e genus thought to contain three species now proves to contain six with all the additions being based on material from Ecuador.
Although material of Vernonia fl exipappa was collected by Keeley in 1983, it was not reported in the DNA study of Keeley et al. (2007). Nevertheless, a position for Cuatrecasanthus in the subtribe Piptocarphinae near Critoniopsis Sch. Bip. is hypothesized on the basis of the woody habit, branching trichomes on the abaxial surface of leaves, and blunt-tipped sweeping hairs on the styles. Description. Erect branching shrubs, scrambling shrubs or trees (rarely vines) to 3.5 m tall; stems terete, striate, minutely pilose (pilosulous) with evanescent simple hairs or thinly tomentose; pith solid. Leaves alternate, petiolate; blades elliptical or lanceolate, base narrowly cuneate to attenuate, subchartaceous, margins entire to remotely subserrulate, narrowly recurved, apex usually sharply acuminate, adaxial surfaces pilosulous with simple non-septate, thick-walled trichomes, with numerous glandular dots, abaxial surfaces covered with thin whitish tomentum of prostrate myceliiform minutely branching trichomes; secondary veins 4-9 on each side of midvein, ascending basally at 45-60° angles. Infl orescence terminal on leafy stems, rounded corymbiform, branching alternate, with large foliaceous bracts only at lower primary nodes.
In addition to the diagnostic generic characteristics are features of special interest such as the marginal teeth of the leaves that are incurved and appressed against the abaxial surface in all but one species (C. lanceolatus; Fig. 1A-B) and the fi nely branching myceliiform hairs on the abaxial surface of the leaves in all the species (Fig. 1C). In addition, there is variation on the leaf surfaces. Th e surfaces of the leaves have veins that can be exsculpate (above the surface), insculpate (below the surface), or even with the adaxial leaf surface (Figs 2-4). All but one of the species have veins on the adaxial surface that are even with the surface or slightly insculpate; one species has veins that are deeply insculpate (C. giannasii) and all six species have veins that are exculpate on the abaxial surface. Th e style branches are reported on one herbarium label as pale pink almost white; there are no additional data on the color of the styles.
Th e genus occurs in Ecuador and Peru. Th e six known species can be distinguished using the following key: Description. Shrubs or small trees, 1.0-3.0 m tall; stems densely pilose with dark brown trichomes, becoming glabrous with age. Leaves with petioles 0.5-1.2 cm long; blades narrowly to broadly elliptical, mostly 3-9 cm long, 1-3 cm wide, narrowly acuminate at base and apex, margin narrowly but strongly recurved, without evident teeth or with in-turned teeth, adaxial surface dark green, glabrous or with minute appressed pubescence, secondary and tertiary veins insculpate, abaxial surface pale greenish covered with mostly appressed, stiff , brownish trichomes (rarely straw colored) intermixed with less evident whitish prostrate myceliiform branching trichomes, midvein with dense antrorse pubescence mostly on sides; secondary veins ca. 5 pairs, spreading from midvein at ca. 45° angles, strongly curved. Infl orescence scarcely exceeding vegetative leaves; branches densely pilosulous or hirtellous. Heads sessile in clusters of 3-7, ca. 10-11 mm tall × 2 mm wide; involucres cylindrical to fusiform; bracts mostly deciduous, ca. 15 in ca. 5 series, 1.0-5.5 mm long, ca. 1.2 mm wide, apices shortacute, ovate to narrowly elliptical, yellowish or with reddish median stripe, puberulous to nearly glabrous outside. Florets with corollas white to bluish white or lavender, ca. 5.5 mm long, with glandular dots on basal tube and tips of lobes, few small trichomes on lobe tips, tubes ca. 2 mm long, lobes ca. 4 mm long, with some non-glandular trichomes; anther thecae ca. 2 mm long. Achenes 2.0-2.5 mm long; pappus white, of ca. 50 bristles mostly ca. 6 mm long, not or scarcely broadened toward tips. Pollen grains 37-47 μm in diam.
Th e species is the most commonly collected member of the genus but apparently is sympatric with both C. kingii and C. lanceolatus in the area near the border between Loja and Zamora/Chinchipe. Th e species is very closely related to the northern Peruvian C. jelskii (Hieron.) H. Rob. Th e latter diff ers most obviously by the densely hirsute abaxial surface of the midvein of the leaves and erect rather than appressed trichomes of the abaxial blade surface. Th e adaxial leaf surface of the latter also has less strongly insculpate veins. Description. Vines or scrambling shrubs; stems fl exuous, densely pilose with long, mostly single-celled trichomes. Leaves with petioles 0.4-0.7 cm long; blades subchartaceous, elliptical, mostly 3.5-8.5 cm long, 1.0-2.5 cm wide, acuminate at base, acute to short-acuminate at apex, margins appearing entire, narrowly recurved, with infl exed teeth distally, adaxial surface, dark green, bullulate, sparsely shortscabridulous, secondary and tertiary veins insculpate, abaxial surface pale green with thin white cover of myceliiform branched trichomes, minutely pilosulous with pale trichomes on veins, without dark trichomes, all veins and veinlets exsculpate; secondary veins ca. 5 or 6 on each side of midvein, spreading at base at 45-50° angles, curved and more strongly ascending near margins. Infl orescence terminal and from axils of uppermost leaves, not or scarcely exceeding the leaves, rounded corymbiform; branches short, puberulous. Heads sessile with up to 9 clustered in dense glomerules, 8-10 mm tall, ca. 2 mm wide; involucre cylindrical or narrowed distally and fusiform, bracts ca. 16 in ca. 5 series, short-ovate to oblong elliptical, 2.0-5.5 mm long, 1.0-1.5 mm wide, apices short-acute, slightly darkened distally, sometimes with reddish median line, glabrous outside. Florets with corollas pale lavender, ca. 6.5 mm long, with glandular dots on basal tube and tips of lobes, tubes ca. 2.5 mm long, lobes ca. 4 mm long; anther thecae ca. 2.5 mm long. Achenes ca. 2.5 mm long; pappus white, of ca. 40 capillary bristles ca. 6.5 mm long, distinctly broadened toward tips. Th e species is known only from Morona-Santiago and Loja, Ecuador, between 2300 and 3200 m in elevation (Fig. 10).
Camp describes the habit as a vine and this character would easily distinguish the species, but the type specimen has no information on the habit and it appears to be a sturdier plant. Only new collections that document the habit will resolve this issue. Description. Shrubs or small trees, 1.0-3.0 m tall; stems densely velutinous (short velvety) with dark brown trichomes. Leaves with petioles 0.3-0.5 cm long; blades narrowly to broadly elliptical, mostly 3-10 cm long, 1-2.5 cm wide, narrowly acuminate at base and apex, margin narrowly but strongly recurved, with few inturned teeth distally, adaxial surface dark green, glabrous or with appressed puberulence, secondary and tertiary veins insculpate, abaxial surface pale green covered with erect, stiff , yellowish trichomes intermixed with less evident whitish prostrate myceliiform branching trichomes, midvein with dense spreading pubescence; secondary veins ca. 5-6 pairs, spreading from midvein at 45-55° angles, strongly arched. Infl orescence scarcely exceeding vegetative leaves, with intermixed foliiform bracteoles; branches densely pilosulous or hirtellous. Heads sessile in clusters of 3-7 within larger glomerules, 10−11 mm tall × 1.5−2.0 mm wide; involucres cylindrical to fusiform; bracts ca. 9-12 in ca. 4 series, 1-5 mm long, ca. 1.2 mm wide, apices short-acute, ovate to narrowly elliptical, yellowish darkened tip, outer bracts puberulous, inner bracts glabrous outside. Florets with corollas violet, ca. 6 mm long, with glandular dots on tube and tips of lobes, tubes ca. 2.5 mm long, lobes ca. 3.5 mm long; anther thecae deep purple, ca. 3 mm long. Achenes 2.0-2.5 mm long; pappus white, of 32-ca. 50 bristles mostly ca. 6 mm long, not or scarcely broadened toward tips. Pollen grains 37-47 μm in diam.
Additional specimen examined. Habitat. Rodríguez & Campos 1816 was described as having been collected in primary forest. Th e range in elevation that has been reported is 1800-3000 m (Fig. 10).
Th is species was the fi rst member of the genus to be described. At the time of its description, a comparison was made to Brazilian species of Eremanthus, members of the comparatively distantly related subtribe Lychnophorinae. Herbaria that might hold Jelski collections from Peru and therefore might have additional isolectotypes (according to Chaudhri et al. 1972)  Description. Shrubs to 1 m tall, bases erect or decumbent to rhizomate; stems densely lanulate with tawny mostly single-celled trichomes. Leaves with petioles 0.8-  2.0 cm long; blades ovate to elliptical, mostly 3.5-8.5 cm long, 2-3 cm wide; base acuminate, apex short-acuminate, margins appearing entire, narrowly recurved, with incurved teeth distally, adaxial surface dark, epidermal cells often paler in area along veins, surface plane or with slightly insculpate veins, densely hispidulous with stiff trichome bases, abaxial surface densely lanulate to sericeous with tawny trichomes, at surface with dense white cover of myceliumiiform stellate trichomes; secondary veins ca. 5 or 6 on each side of midvein, spreading at base at 45-50° angles, curved and more strongly ascending near margins. Infl orescence distinctly exceeding reduced distal leaves, with few long ascending branches; branches tomentellous with dark hairs. Heads sessile and with up to 12 clustered in dense ultimate glomerules, up to 10 mm tall, ca. 2 mm wide; involucre cylindrical or narrowed distally and fusiform, bracts brown, ca. 16 in ca. 5 series, short-ovate to oblong elliptical, 2.0-5.5 mm long, 1.0-1.5 mm wide, apices short-acute, slightly darkened distally, sometimes with reddish median line, scarious, glabrous outside. Florets with corollas possibly pale lavender, ca. 6.5 mm long, with numerous glandular dots on basal tube and few on tips of lobes, tips of lobes paucipilosulous, tube ca. 2.5 mm long, lobes ca. 4 mm long; anther thecae ca. 2.5 mm long. Achenes ca. 2.5 mm long; pappus white, of ca. 50 capillary bristles ca. 6.5 mm long, not or scarcely broadened toward tips. Pollen grains 35-42 μm in diam.
Th e species has the most broadly elliptical leaf blades of any member of the genus. Th e most distinctive feature, however, is the mostly fl at and hispidulous adaxial surface of the leaves. Th e distribution is restricted to the area near the pass between the Ecuadorian provinces of Loja and Zamora-Chinchipe (Fig. 10) Description. Shrubs to small trees up to 2 m high; stems fl exuous above, hexagonal, densely pilose with brownish trichomes. Leaves with petioles mostly 0.5-1.5 cm long; blades lanceolate, broadest at basal 1/3, 4.0-9.5 cm long, 1-3 cm wide, apex distally narrowly acute, not acuminate, margins not or scarcely recurved distally, with marginal teeth projecting upward or outward (may vary in intensity), not inward, adaxial surface dark green, lamina dotted with gland-like persistent or aborted stumps of small scaber, with weakly insculpate veins, abaxial surface gray-green, tawny-pilose, sometimes contorted, denser on veins, with thin grayish prostrate myceliiform branching trichomes; secondary veins in 4-5 pairs, strongly ascending. Infl orescence distinctly exceeding the reduced distal leaves, main axis and branches mostly defl ected at nodes, rounded corymbiform; branches tomentellous. Heads sessile in clusters of 2-6 congested in larger dense glomerules, 10-11 mm high × 2 mm wide; involucres cylindrical or fusiform, ca. 16 in ca. 5 series, 1.0-4.5 mm long, ca. 1.2 mm wide, short-acute, greenish brown, darkened at tips or along midvein distally, glabrous. Florets with corollas pink-lilac, ca. 6 mm long, with numerous glandular dots on basal tubes, with a few short hairs at apices of tubes, tubes ca. 2 mm long, lobes ca. 4 mm long; anther thecae dark reddish brown, ca. 2.5 mm long. Achenes ca. 2 mm long; pappus white, of ca. 45 capillary bristles ca. 6.5 mm long, not or scarcely broadened at tips. Pollen grains ca. 35 μm in diam.
Preliminary conservation status. Data Defi cient