Nahuatlea: a new genus of compositae (Gochnatieae) from North America

Abstract In the course of a detailed molecular study of the tribe Gochnatieae (Compositae: Gochnatioideae) it became apparent that the genus Gochnatia (sensu Cabrera) was not monophyletic but composed of a number of morphologically, geographically, and molecularly distinct clades. All but one of these clades had previously been recognized at the generic or sectional level and therefore had a name that could be applied. However, one clade, whose members are from Mexico and adjacent parts of the United States, had never been recognized as a distinct taxon. The Mexican clade is the sister group of the Caribbean clade which seems to indicate a dispersal event from Southern South America to Mexico and from Mexico to the Caribbean. Here we provide the Mexican clade with a genus name, Nahuatlea, and make the necessary new combinations. The name is derived from Nahuatl, the major indigenous language that is spoken in the area where most of the collections were gathered. A genus description, key to species, images, and a short, species descriptions, are provided.


Introduction
in his comprehensive treatment of Gochnatia Kunth recognized six sections in the genus all mainly from the Americas. He placed all known species of Gochnatia from Mexico, in the section Hedraiophyllum (Less.) DC. along with two southern South American species: G. palosanto Cabrera and G. cordata Less., which are now part of Gochnatia s.s. and Moquiniastrum, respectively. Although one species from 3) Mexican Gochnatia: A group of seven species that had never been recognized as a separate genus nor had they been placed in a section by themselves was recovered as a monophyletic group. 4) Anastraphia: The 33 Caribbean species fell into one strongly supported clade that had previously been recognized as a genus and a section (re-established as a genus by Ventosa and Herrera 2011a; Robinson and Funk 2012). 5) Moquiniastrum: The 21 species that form this clade are mainly from central and southern Brazil and previously formed the majority of Gochnatia sect. Moquiniastrum (Sancho et al. 2013). 6) Richterago Kuntze: A clade of 16 species, all endemic to the campos rupestres of Brazil (redefined by Pirani 2001, 2014). 7) Cnicothamnus Griseb.: A genus of two species found in Bolivia and northwestern Argentina: it has never been included in Gochnatia. 8) Cyclolepis Gilles ex D. Don: A monospecific genus that has never been included in Gochnatia: found from Paraguay to the northern Patagonia area of Argentina. This lineage was regarded as "incertae sedis" in Funk et al. (2014) and so it remains.
A key to the genera of Gochnatieae along with additional discussion on the tribe is contained in a upcoming paper (Funk et al. in prep).  N. magna, N. obtusata, N. purpusii, and N. smithii. In the Funk et al. biogeographic analysis (2014), it was hypothesized that the tribe had a southern South America origin (including the Central and Southern Andes, Argentina, and southern Brazil). Based on this, plus the fact that the Mexican clade is the sister group of the Caribbean clade (Anastraphia) suggests, or is best explained by, a dispersal event from Southern South America to Mexico and from Mexico to the Caribbean. We order the dispersal events in this direction because the Mexican Gochnatia are morphologically more similar to the Andean genus Gochnatia s.s. than the Caribbean species. This Mexican + Caribbean clade (MCC) is believed to have separated from the rest of the Gochnatieae between 11 and 23 mya at a time when there was a gradual climate warming (early Miocene;Petuch 2003, Zachos et al. 2001. MCC is the sister group of a large clade containing Richterago + Moquiniastrum (RM) which is mainly from Brazil and Southern South America. The sister groups to these two large clades (MCC + RM) are from the Andes (Gochnatia s.s., Pentaphorus, Cnicothamnus), so just where in southern South America the MCC clade originated is uncertain especially since some of the sister group relationships are not well supported, although all of the segregate genera are individually clearly monophyletic.
The Mexican members of Gochnatia clearly do not belong in the genus Gochnatia s.s., therefore, we are here describing the genus Nahuatlea for these seven species.

Materials and methods
All types and other specimens deposited at LP and US were examined. The remaining types were viewed on line using the JSTOR-GP portal (http://plants.jstor.org; Fig 3).

Taxonomy
Nahuatlea V. A.Funk, gen. nov. urn:lsid:ipni.org:names:60475585-2 Description. Shrubs or trees, monoecious. Leaves sessile or with a short petiole of no more than 5 mm long, alternate, chartaceous or coriaceous, entire, margins revolute, usually discolorous (silvery or cinereous-tomentose beneath), clustered near the ends of the branches especially late in the flowering cycle. Heads arranged in clusters, rarely solitary, most branches with an apical cluster; sessile or short-pedunculate, peduncles commonly densely scaly-bracted resembling the lowermost involucral bracts, homogamous (flowers bisexual), discoid; involucre obconic (turbinate) or campanulate, shorter than the flowers; phyllaries imbricate, 4-10 seriate, graduate, coriaceous or subcoriaceous. Flowers with corollas homomorphic, white or yellow, actinomorphic, deeply 5-lobed, lobes equal or shorter than the tube, revolute; anthers calcarate, caudate, anther apical appendages apiculate, tails 1-3 mm long, entire or fimbrillate; styles rounded at apex, glabrous, style branches concave. Achenes 5-ribbed sericeous, cuneate-cylindrical, carpopodium conspicuous. Pappus of scabrid bristles, uni-or biseriate, graduated (varying in length) and equally wide throughout or rarely flattened at the tips, ca 1 cm long. [7 species] Remarks. Nahuatlea, with some exceptions, is characterized by a combination of characters: short leafy branchlets, entire and revolute blade margins, clusters of sessile or short-pedunculate heads at or near the tips of branches; densely scaly-bracted peduncles (when present); and a pappus that is biseriate, graduated, and equally wide throughout. Most of the exceptions are found in the recently described Gochnatia hiriartiana (Medrano, Villasenor & Medina, 2004) which has solitary heads, and a uniseriate pappus with bristles that are flattened at the tips. However, recently produced sequence data including those of G. hiriartiana support Nahuatlea as monophyletic (Funk, unpublished). Etymology. The genus name was selected to honor the indigenous people of eastern central Mexico by naming it after their language. The name is derived from Nahuatl, a language of the Nahuan branch of the Uto-Aztecan language family (known informally as Aztec). It is spoken by an estimated 1.5 million people, most of whom live in Central Mexico. Nahuatl has been spoken in Central Mexico since at least the 7th century AD and it was the language of the Aztecs who dominated what is now central Mexico during the Late Postclassic period of Mesoamerican history. Today the Nahuatl language is spoken in the Mexican states of Durango, Guerrero, Hidalgo, Mexico, Michoacan, Morelos, Oaxaca, Puebla, Tlaxcala, and Veracruz. The distribution of the new genus, Nahuatlea, in central Mexico has substantial overlap with the area so it is appropriate to use it for the name of the new genus (http://en.wikipedia.org/wiki/Nahuatl). Description. Shrub or small tree 2.5-4.5 m tall; leaves chartaceous, blades 5-10 × 4.1-6.2 cm, widely elliptic, glabrescent adaxially, wooly abaxially; heads short pedunculate in clusters of 3-5 at the apex of branches, surrounded by leaves, few clusters per plant; involucre campanulate (especially at early flowering), 13-15 mm tall × 10-12 mm wide, bracts in 5-7 series, woolly adaxially; flowers ca. 50 per head; corollas yellow, 12 mm long; anther base caudate, tails ca. 1 mm long, entire; pappus ca. 9 mm long, bristles uniseriate, broadening, flattened, and somewhat darker at the apex.

Key to species of Nahuatlea
Distribution. Mexico: Tamaulipas and San Luis Potosi.

RSA 0001214). [Specimens at P (P00703338 & P00703339) and E (E00413001)
have the correct collecting number but incorrect dates and may or may not be type material; Cabrera (1971) cites isotypes at G, MO, and MEXU that are not found in JSTOR-GP. MO has confirmed that the specimen is not in their collection but there is no information on the others. Description. Shrub of unknown size (one isotype has what appears to be "5-6 m" written on the label); leaves coriaceous, petiole minute (1-2 mm), blade 1.8-3.0 × 0.5-1.4 cm, elliptical or slightly lanceolate or oblanceolate, glabrescent adaxially, white flocculent-tomentose abaxially; heads sessile, in few clusters of 8-15, clusters all at apex of branches; involucre campanulate (especially at early flowering), ca. 10 mm tall × 5-6 mm wide, bracts in 5-6 series, densely wooly abaxially; flowers 12-18 per head; corollas yellowish, ca. 8 mm long; anther base caudate, tails ca. 1 mm long, fimbrillate; pappus ca. 7.5 mm long, bi-seriate with slender bristles.
Remarks. Cabrera (1971) and Jervis (1954) disagree somewhat on the size of the leaf blade: Cabrera lists it as 18-30 mm × 5-14 mm and Jervis has 2.0-2.5 cm × 0.5-1.0 cm. Our measurements, taken from the Holotype, fall within those given by Jervis, however, the isotypes may show the greater range given by Cabrera.
Distribution. Mexico: known only from four collections all from Puebla. ( Note. Determining what may or may not be type material is difficult; all proposed types are Purpus s.n. collections but there are different collection dates and locality information. The Holotype is one of two different collections mounted on the same sheet one of which is annotated as "n. sp." and "type". That specimen also has a hand-written note that says "The year doubtless 1901 RM" indicating that the date on the sheet January-March 1898 is not correct. The information found on the three possible isotypes is nearly identical (Lower California, San Felipe, Cape Region Lower California, Jan-Mar 1901) but the information is different from the locality information on the Holotype. All of the "type material" specimens are the same species so there is little doubt that this is the correct name for this entity but someone more familiar with the work of Purpus (who seems to have confusing dates and numbers) and Brandegee will need to investigate this further to determine if the three listed specimens are actually isotypes.  Cabrera 1971.] Description. Tree 3-8 m tall, trunk 20-30 cm in diameter; leaves chartaceous, blades 3.5-6.5 cm × 2.5-4.5 cm, ovate to elliptic, cuneate or rounded at base, glabrescent on both faces; heads short-pedunculate, solitary or more usually in loose clusters of 2-20 at apex of branches, few clusters per plant; involucre cylindrical to narrowly ob-conic depending on age, 10-15(20) mm tall × 6-8 mm wide at anthesis, bracts in 8-10 series, glabrous; flowers 13-20 per head; corollas yellowish, 12 mm long; anther base caudate, tails ca. 3 mm long, entire; pappus ca. 11 mm long, bristles slender, biseriate.

Nahuatlea arborescens
Remarks. Cabrera (1971) and Jervis (1954) disagree somewhat on the size of the leaf blade: Cabrera lists it as 35-65 mm × 25-45 mm and Jervis has 5 cm × 3-4 cm. Specimens available to us agree with the range given by Cabrera.

Nahuatlea obtusata
Distribution. Mexico: Puebla and Oaxaca. Remarks. Gochnatia obtusata was described by S. F. Blake (1924) and accepted as a good species by Jervis (1954). Cabrera placed it as a subspecies of G. hypoleuca as did Freire et al. (2002). The difference of opinion is based on the importance one gives to the characters that separate the two entities. Blake stated that G. hypoleuca could be separated from G. obtusata by the following characters: leaves chiefly elliptic, apex acute or acutish and mucronate, 20-50 mm × 8-15 mm; involucre 5-6 mm tall, phyllaries obtuse to acute or obtusely acuminate. We have added some additional characters: shrub or small tree 3-7 m; heads arranged in short clusters or panicles; involucre with bracts in 3-5 series; corolla 10-12 mm long; style branches 0.7-1 mm long; pappus up to 6.5 mm. In contrast, G. obtusata has the following: leaves broadly elliptic, apex broadly rounded to obtuse, not mucronate, 4.5-20 mm × 3-13 mm; involucre 6.5-7.5 mm tall, involucral bracts acute to sharply acuminate; style branches 0.5-0.7 mm long. Additional characters for G. obtusata include: shrub of 1.0-2.6 m; heads glomerate at tips of branches and in clusters of 1-several in the subterminal axils; involucre with bracts in 5-6 series; corollas 6.5-7.5 mm long; pappus up to 7.5 mm long. In the field the difference is striking with the larger more robust G. hypoleuca contrasting with the smaller, more compact G. obtusata. Therefore we have chosen to recognize G. obtusata as a separate species.  [There is a second specimen at NY that is a possible isotype NY 00230666; the specimen from HAL 0112991 may be an isotype but the dates don't match and the number is listed at "1391 s.n."] Description. Shrub or small tree, 2-5(-7) m tall; leaves coriaceous, 2-5 × 0.9-1.5 cm, narrowly elliptic, apex obtuse, mucronate, attenuate at base, glabrous adaxially, cinereous-tomentose abaxially; heads sessile or very short pedunculate, in clusters of 5-15 heads at apices and axils of branches, many clusters per plant; involucre narrowly obconic, 4-7 mm tall × ca. 3 mm wide, bracts in ca. 3-5 series, ciliolate-tomentose on the margins but otherwise glabrous; flowers 5-7 per head; corollas white, 10-12 mm long; anther base caudate, tails ca. 1 mm long, fimbrillate; pappus ca. 6.5-7.5 mm long, bristles biseriate, of various lengths and broadening slightly at the tips.
Remarks. According to the Texas A&M University website (http://aggie-horticulture.tamu.edu/ornamentals/nativeshrubs/gochnatiahypole.htm) the common names for this shrub in Texas are Chomonque and Ocote. The website goes on to say that it is an "attractive, little-known shrub native to extreme South Texas, Chomonque flowers in the winter and has striking bi-colored leaves, very dark green on top and white and feltish underneath. The white flowers that appear from November to February are weakly fragrant and attract bees and many species of butterflies. It grows on gravel and caliche in South Texas shrub lands, and is extremely drought and heat tolerant. A specimen at the San Antonio Botanical Gardens has proved cold hardy and evergreen, but its cold-hardiness farther north is untested." The website lists the USDA hardiness zone 9.  Description. Shrub of undetermined size; leaves clustered near the ends of the branches, sub-coriaceous, 3-5 × 0.8-1.8 cm, ovate, obtuse, cuneate at base, glabrescent adaxially, cinereous-tomentose abaxially; heads slender, short-pedunculate, in dense clusters at the ends of branches, sometimes several clusters in a dense panicle, many clusters per plant; involucre narrowly obconic, 6-8 mm tall × ca. 3 mm wide, bracts in 5-7 series, ciliolate on the margins otherwise glabrous; flowers (3-)5-7 per head; corollas white, 8.5-9.0 mm long; anther base caudate, tails ca. 1.5 mm long, entire; pappus ca. 6.5-7.5 mm long, bristles biseriate, not obviously broadened at tips.
Remarks. According to Jervis (1954) the "…small branches are less wooly than most other species." Distribution. Mexico: known only from Oaxaca.