Ramirez et al. 2015 (Conference Paper) Hechtia

Phylogeny, evolution and biogeography of Hechtia Klotszch (Hechtioideae: Bromeliaceae)

Author(s):—I.M. Ramírez M., J. Pinzón, G. Carnevali & A. Castillo in Benko-Iseppon, A.M.; Alves, M. & Louzada, R. (2015) An overview and abstracts of the First World Congress on Bromeliaceae Evolution. Rodriguésia 66(2): A1-A66.

Publication:— (2015).

Abstract:—Hechtia comprises more than 79 species restricted to dry or seasonally dry ecosystems of Megamexico III but with most species occurring in tropical Mexico, particularly in Oaxaca, Guerrero and Querétaro; fewer speciesoccur in north-central Mexico or south of the Tehuantepec isthmus into northern Nicaragua. Species range from sea-level to up to 2500 m elevation. Most Hechtia species are saxicolous or terrestrial in well-drained, rocky soils where they are a conspicuous element of xerophytic shrublands, along with other rosetophilous plant groups. Plants are succulent, sympodial to pseudomonopodial rosettes with spiny leaves and terminal or lateral inflorescences, unisexual flowers and dioecy. We tested the following hypotheses using morphologicaland molecular data: 1. Based on a unique set of characters in the genus (unisexual flowers, sessile stigma, and dioecy), Hechtia is monophyletic. 2. The genus is tentatively composed of seven alliances defined by morphological characters associated with geographical distribution; these alliances should be monophyletic as well. 3. If physiographic accidents in Mexico played an important role in the diversification of the genus, the seven proposed alliances should be confined each to a particular biogeographically region. 4. The ancestor of Hechtia invaded Megamexico III from the south, and it featured a strictly sympodial growth habit (central inflorescence) and, therefore, the clade including species with these features and distributed in the southern portion of Megamexico III, should be basal in the resulting phylogeny. Preliminary results based on cpDNA (regions ycf1(6) and rpl32) of 63 Hechtia species, representing ca. 80% of the genus, and 18 species as outgroups, indicate that Hechtia is monophyletic. Internally, the analysis resulted in a trichotomy with a clade including Hechtia guatemalensis and H. dicroantha from Tierras Altas de Chiapas and Tierras Bajas del Pacific provinces; a second clade with species characterized by a strictly sympodial growth pattern, leaves minutely serrate, flowers pedicellate, with lilac or white petals, and found in the provinces of Sierra Madre Oriental, Provincia Veracruzana, and Eje Volcánico Transmexicano (H. tillandsioides Alliance); and a third, poorly resolved clade, including species from the other five alliances.

Keywords:—Hechtia; Phylogeny; Dioecy.