Sedum chazaroi (Crassulaceae), an endemic new species from southern Jalisco, Mexico

Sedum chazaroi (Crassulaceae), una nueva especie endémica al sur de Jalisco, México

Pablo Carrillo–Reyes^1,3 and José Aquileo Lomelí–Sención²

¹ Departamento de Biología Evolutiva, Instituto de Ecología, A.C. Apartado Postal 63, 91070 Xalapa, Veracruz, México. ³Author for correspondence. E–mail: pcarreyes@gmail.com

² Jardín Botánico y Herbario, Escuela de Biología, Universidad Autónoma de Guadalajara, Apartado Postal 1–440, 44100, Guadalajara, Jalisco, México

Recibido: 27 de julio de 2008.
Aceptado: 13 de octubre de 2008.

Abstract

Sedum chazaroi (Crassulaceae), an endemic new species from southern Jalisco, Mexico, is described and illustrated. This taxon belongs to section Sedastrum (Rose) Berger based on characters such as its basal rosettes, dense pubescence and paniculate inflorescences. Among differentiating characters from the rest of species of section Sedastrum are bigger rosettes (1.5–6 cm in diameter), larger and thicker floriferous stems (57–85 cm long and 1.1–1.8 cm in diameter) and a dense pubescence. Sedum chazaroi is compared with closely allied species like S. ebracteatum, S. hintonii and S. mocinianum.

Keywords: Jalisco, Mexican endemic species, Mexico, Sedastrum, succulent plants.

Resumen

Se describe e ilustra Sedum chazaroi (Crassulaceae), una especie nueva endémica del sur del Estado de Jalisco, México. Este nuevo taxón pertenece a la sección Sedastrum (Rose) Berger por presentar rosetas basales, pubescencia densa e inflorescencias paniculadas. Se distingue de las demás especies de esta sección por sus rosetas de mayor tamaño, las cuales llegan a medir 1.5–6 cm de diámetro, por sus ramas floríferas de 57–85 cm de largo y 1.1–1.8 cm de diámetro, y por su indumento denso. Se le compara con S. ebracteatum, S. hintonii y S. mocinianum, con los cuales parece estar estrechamente relacionado.

Sedum section Sedastrum (Rose) Berger (Crassulaceae) is characterized by dense basal rosettes with usually pubescent leaves, fleshy, thickened rootstocks, numerous stems dying after flowering, paniculate inflorescences and flowers with white, very thin petals that possess a nectarial concavity (Clausen, 1943; Uhl, 1992). This section contains about five species (Pérez–Calix, 1998) distributed from northern Mexico to Honduras, with most diversity in central Mexico (Clausen, 1943; Uhl, 1992).

During botanical exploration to southern Jalisco, we collected a member of Sedum sect. Sedastrum with long and pendulous floriferous stems that cannot be identified as any of the described species of the section. After reviewing the literature (Clausen, 1943, 1978, 1979; Pérez–Calix, 1998) we concluded that this species has never been described. We describe and characterize this new species below.

Sedum chazaroi P. Carrillo & J. A. Lomelí sp. nov. (figure 1). Planta herbacea perennis dense pubescens; caules erecti ad 10 cm longi; folia 25–35(70) in rosula dense et spiraliter disposita, triangularía vel oblonga, 8–33 mm longa; inflores–centia paniculata ad 85 cm longa decumbens vel pendula, ramis 9–26 late divaricatis ad 15.5 cm longis, 3–27 flores ferentibus, floribus sessilibus vel subsessilibus; petala 5 alba, 4–5 mm longa; carpella 5 glabra, 4.5–5–5 mm longa ad basem cavata.

TYPE: México, Jalisco, municipio de Tolimán, arroyo La Ciénega, 19°36'N, 103°54'W, 760 m. Tropical deciduous forest; rocky cliffs of N and NW exposure; 20 Dec 2005; P. Carrillo–Reyes and J. A. Lomelí–Sención 5105. (Holotype: GUADA; Isotypes: IBUG, IEB, MEXU, MICH, MO, NY, XAL).

Herbaceous perennials, densely pubescent (except petals, stamens and carpels), pubescence of hyaline hairs ca. 0.5 mm long. Sterile stems erect, to 10 cm long, 8–10 mm in diameter at the base. Leaves 25–35 (70), rosulate, crowded, spiraled, triangular when young, oblong–elliptic to oblong at maturity, 8–33 mm long, 4–10 mm wide and ca. 4 mm thick, apex acute. Floriferous stems decumbent or pendulous, (30–) 50–85 cm long, 11–18 mm in diameter at the base. Inflorescence a panicle, peduncle to 62 cm long with 9–26 secondary thyrsoid branches 8–15.5 cm long, each branch with 3–27 flowers in cincinnae 6–25 mm long; bracts similar to the leaves, lingulate to oblong, 10–32 mm long, 5–10 mm wide and 5–7 mm thick; bractlets lingulate, 4–8 mm long, 47 mm wide and 2–4 mm thick. Flowers sessile to subsessile, 9–10 mm in diameter, with a fetid odor; calyx pubescent, with 5 free subequal lobes, green–whitish, the lobes deltate to triangular, 2–3 mm long, 1.5–2.5 mm wide at the base, apex obtuse; corolla glabrous, with 5 free white petals, these ovate to elliptic, ca. 5 mm long, 2–3 mm wide; stamens 10, glabrous, 5 of them opposite and adnate to the petals, 2–2.5 mm long, the other 5 alternate to the petals, 4–5 mm long, filaments white, anthers pinkish at predehiscence; pollen whitish; nectaries oblong to ovate, ca. 0.4–0.5 mm long, carpels glabrous, vesciculose, whitish green, 4.5–5.5 mm long including the style, with a concavity at the base when nectarial scale is placed, styles ca. 1.5 mm long, terete. Follicles containing numerous seeds.

Distribution and habitat: Sedum chazaroi is a narrow endemic species from southern Jalisco, it is known only from two localities with populations of a few individuals. It grows on vertical, rocky cliffs with sporadic streams from 750 to 1360 m of altitude. The vegetation in both localities is a tropical deciduous forest with Bursera spp., Cnidoscolus sp., Euphorbia macvaughii Carvajal & Lomelí, E. oaxacana B.L. Rob. & Greenm., Fouquieria formosa Kunth, Hechtia sp., Mammillaria sp., Pilosocereus sp. and Stenocereus sp.

Phenology: Flowering from November to January.

Etymology. The specific epithet honors Miguel de Jesús Cházaro–Basáñez Sedum (Britton and Rose 1905) a researcher of the Universidad de Guadalajara, devoted scholar of the succulent plants from Western Mexico.

Discussion

In a recent phylogenetic analysis of the Acre clade (Carrillo–Reyes et al., in prep.), three species of Sedum sect. Sedastrum were sampled (S. hemsleyanum Rose, S. hintonii R.T. Clausen and S. chazaroi) and they were retrieved in a well supported clade. These results strongly support the monophyly of this section as well as the placement of the new species in this group. Sedastrum Rose was originally described as a separate genus from Sedum. Although additional studies including all representatives of Sedum sect. Sedastrum are necessary to accurately determine the affinities of S. chazaroi, based on morphological features it seems to be most closely related to S. mocinianum Pérez–Calix. Both species are rock–dwelling plants with succulent leaves densely covered by hyaline hairs ca. 0.5 mm long. However, the former species is a more robust plant with rosettes of 25–35 (–70) leaves (vs. 12–18) and paniculate inflorescences to 85 cm long (vs. thyrsoid inflorescences about 10 cm long). These species are not sympatric and are found in different types of vegetation; Sedum chazaroi is distributed in southern Jalisco in tropical deciduous forest between 750 and 1360 m of altitude, whereas S. mocinianum occurs in Guanajuato and northern Jalisco (and probably also in southern Durango) in tropical deciduous forests and in the ecotone with xerophitic scrub, between 1480 and 2400 m of altitude (Pérez–Calix, 1998). S. chazaroi is also similar morphologically to the widely distributed S. ebracteatum Sessé & Moc., both of which are robust plants with thyrse inflorescences that occur in tropical deciduous forests in western Mexico. However, S. chazaroi can be distinguished by the presence of a dense pubescence (vs. moderate pubescence), its oblong–elliptic to oblong leaves (vs. suborbicular to oblong–spathulate) and its very large inflorescences of (30–) 50–85 cm long (vs. 1040 cm long). In addition, although S. ebracteatum is widely distributed, apparently there are no collections known from southern Jalisco. Morphological characters also suggest that Sedum chazaroi is related to S. hintonii, mainly in characters such a dense indumentum and in the shape of leaves. However S. chazaroi is a more robust plant with differentiating characters from S. hintonii like length of hairs (ca. 0.5 vs. to 1.5 mm long), number of leaves per rosette (25–35 (–70) vs. ca. 25), position of the inflorescence (decumbent or pendulous vs. erect), length of the floriferous stem (3085 vs. to 24 cm) and number of branches (9–26 vs. to 10). Both species occur at medium–low altitudes (less than 1400 m) at cliffs in tropical deciduous forests, but S. hintonii is only known from the type collection in the municipality of Coalcomán, Michoacán (Clausen, 1943) and for an additional recent report of another locality in the municipality of Arteaga, also in the Sierra Madre del Sur, in southern Michoacán (Anaya, 2005). There are some other reports of populations of Sedum of this section that could be related to S. hintonii but their taxonomic status needs to be established (Clausen, 1946; Sánchez–Mejorada, 1975). Salient morphological features of S. chazaroi, S. ebracteatum, S. hintonii and S. mocinianum are compared in table 1.

Acknowledgments

We thank Victor W. Steinmann and Emmanuel Pérez–Calix for their valuable comments to a previous version of the manuscript; to Georgina Tinoco–Villa and Hugo Orozco–Jiménez for making available their collections, to Manuel Martínez–Rufino who kindly guided J.A. Lomelí–Sención to Tolimán. We greatly appreciated the latin diagnosis by J. Rzedowski.

Literature cited

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