Ann. Bot. Fennici 49: 239–247 ISSN 0003-3847 (print) ISSN 1797-2442 (online) Helsinki 31 August 2012 © Finnish Zoological and Botanical Publishing Board 2012 Taxonomy of the Lessingianthus saltensis (Vernonieae, Asteraceae) species complex María Betiana Angulo & Massimiliano Dematteis* Instituto de Botánica del Nordeste (UNNE-CONICET), Casilla de Correo 209, 3400 Corrientes, Argentina (*corresponding author’s e-mail: [email protected]) Received 27 Dec. 2011, final version received 14 Feb. 2012, accepted 16 Feb. 2012 Angulo, M. B. & Dematteis, M. 2012: Taxonomy of the Lessingianthus saltensis (Vernonieae, Aster- aceae) species complex. — Ann. Bot. Fennici 49: 239–247. In this study, three species of Lessingianthus saltensis complex are described and illus- trated, including two new species. The new taxa L. membranifolius and L. coriarius are diploid (2n = 2x = 32), while L. saltensis is tetraploid (2n = 4x = 64). Lessingian­ thus membranifolius is distinguished from the other taxa in the complex by the mem- branaceus leaves, phyllaries with a rounded apex and leaf blades basally obtuse with serrate margins. Lessingianthus coriarius can be easily separated from the other taxa of the group by the combination of coriaceus leaves, phyllaries apically acute and leaf blades acute at the apex, with entire margins. A lectotype is designated for L. saltensis. Introduction and they are tricolporate, echinolophate, with a discontinuous tectum, very long germinal fur- The genus Lessingianthus (Vernonieae, Aster- rows that converge at the poles, lacunae disposed aceae) was initially established to accommo- in a regular pattern, and lacking a polar lacuna date the species originally placed in Vernonia (Keeley & Jones 1979, Angulo & Dematteis sect. Lepidaploa subsection Macrocephalae 2010). The anther appendages in Lessingianthus (Bentham & Hooker 1873). It is widely distrib- commonly lack glands, whereas some related uted in South America, including Venezuela, genera have glandular appendages (Robinson Colombia, Peru, Brazil, Bolivia, Paraguay, 1988, Dematteis 2007). The basic chromosome Argentina and Uruguay (Robinson 2007). The number is x = 16, differing from the majority of species are perennial herbs or shrubs with xylo- the New World Vernonieae which have a base podia, having medium- or large-sized heads and number of x = 17 (Dematteis 2002, Angulo & seriate-cymose inflorescences (Robinson 1988). Dematteis 2012). The genus currently comprises more than 120 There are several closely related and morpho- species that mostly occur in campo cerrado and logically similar species complexes within Less­ campo rupestre habitats (Bremer 1994). ingianthus that may hybridize naturally. Among This group can be distinguished from the these complexes are those formed around L. gla­ other American members of the tribe by its bratus, L. mollissimus, L. rubricaulis and L. salt­ pollen type, anther appendages and chromosome ensis (Angulo & Dematteis 2009a). At present, number, among other features. The pollen grains only the L. rubricaulis complex has been studied of Lessingianthus have been named type “B” (Dematteis 2004). This complex includes four 240 Angulo & Dematteis • ANN. BOT. FENNICI Vol. 49 species, L. rubricaulis, L. laniferus, L. pusillus some morphology was determined using the and L. pseudoincanus, that can be distinguished centromeric index (ci = [short arm] ¥ 100/[total by their habit, underground parts, indumentum chromosomal length]). Accordingly, the chro- type, and leaf size and shape. mosomes were classified into metacentrics (m): In the present study, we analyzed the L. 50–37.5, submetacentrics (sm): 37.5–25 and saltensis complex, which is distributed in the subtelocentrics (st): 25–12.5. The karyological northwestern Argentina and Bolivia and shows parameters, total length of karyotype (TLK), wide morphological and karyological variation. the mean chromosome length (ML), the average The analysis of external morphological features, centromeric index (CI) and the ratio between pollen morphology, microcharacters and chro- the longest and the shortest chromosome pair mosomes revealed three species, two of them (R) were evaluated. The karyotype asymmetry new. These species are described, including full has been determined using the intrachromosomal synonymy and a key to distinguish the taxa. (A1) and interchromosomal index (A2) suggested by Romero Zarco (1986). To examine micro-characters, the florets Material and methods were obtained from herbarium specimens and softened in boiling water to which a drop of This study was based on morphological analysis detergent was added, dissected under a stereomi- of specimens deposited at BAB, CORD, CTES, croscope, mounted in Hoyer’s solution (Ander- G, K, LP and SI (Holmgren et al. 1990). The line son 1954) and studied with a light microscope. drawings were made from herbarium specimens using a camera lucida with a Leica MZ6 stereo microscope. The journal abbreviations are from Results and discussion Botanico Periodicum Huntianum (Lawrence et al. 1968). Chromosome number and karyotype Pollen samples were obtained by removing one or two florets from herbarium specimens of Lessingianthus saltensis was found to be tetra- the species. The pollen grains were acetolysed ploid with 2n = 4x = 64 (Fig. 1A), which agrees according to the procedure suggested by Erdt- with prior counts from a population of Jujuy man (1966). For light microscopy (LM) the (Argentina) by Dematteis (1998). The chromo- pollen samples were mounted in glycerin jelly some numbers of L. membranifolius (Fig. 1E) on glass slides and then examined with a Zeiss and L. coriarius (Fig. 1G) were determined here Axioplan microscope. Permanent slides were for the first time. Both taxa were diploids having deposited at the Palynological Laboratory of 2n = 2x = 32. The somatic chromosome number, the Universidad Nacional del Nordeste (PAL- karyotype formula, mean chromosome length, CTES). The terminology applied for pollen grain total length of karyotype, centromeric index and description in general follows Erdtman (1966) asymmetric index of the species in the L. salten­ and Punt et al. (2007). sis complex are indicated in Table 1 (see also Mitotic chromosome preparations were made Fig. 2). from root meristems obtained from germinating seeds. The roots were pretreated for about five hours in 0.002 M 8-hydroxyquinoline solution Pollen morphology at room temperature, fixed in 3:1 absolute alco- hol/acetic acid and then stained using Feulgen’s The species of the L. saltensis complex all have technique. Permanent microscope slides were type “B” pollen grains (Fig. 1B and C). This type prepared by mounting in Euparal. In all sam- of pollen grain is tricolporate, echinolophate, ples at least 20 counts of 7–10 individuals were with a discontinuous tectum, very long germinal made to verify the observations. Nomenclature furrows that converge at the poles, and lacunae used for the karyotype description is that sug- distributed in a regular pattern but lacking a gested by Levan et al. (1964). The chromo- polar lacuna (Keeley & Jones 1979, Dematteis ANN. BOT. FENNICI Vol. 49 • Taxonomy of the Lessingianthus saltensis species complex 241 Fig. 1. Somatic chromo- somes, microcharacters and pollen grains in the Lessingianthus saltensis complex. A–D: L. salten- sis (Dematteis et al. 2952, CTES). — A: Metaphase plate, 2n = 64. — B: Pollen grain, polar view. — C: Pollen grain, equato- rial view. — D: Glandular trichomes of cypsela. E and F: L. membranifolius (from the holotype). — E: 2n = 32. — F: Corolla lobe apex with glandular tri- chomes. G–I: L. coriarius (from the holotype). — G: Metaphase plate, 2n = 32. — H: Idioblasts. — I: Crystals of achene wall. Scale bars = 10 µm. & Pire 2008, Angulo & Dematteis 2010). The crystals in the achene wall (Robinson 1999). type “B” pollen is characteristic of the genus The species of the L. saltensis complex lack of (Robinson 1988, Dematteis & Pire 2008, Angulo basal stylar node. The anther appendages are & Dematteis 2010). For pollen characteristics eglandular and the species have anthers basally see Table 2. calcarate and sagittate similar to those found in the congeneric taxa. Additionally, they have glandular trichomes on the corolla lobes (Fig. Morphological characters 1F). The surface of the cypselas have eglandu- lar trichomes in L. coriarius, while L. saltensis Previously described Lessingianthus species are has eglandular and glandular trichomes (Fig. distinguished from the other American members 1D) and the cypselas of L. membranifolius are of the tribe by their eglandular anther append- glabrous. The crystals are cubic and prismatic of ages, lack of a basal style node, and cubic varying size on the fruits walls (Fig. 1I). Numer- 242 Angulo & Dematteis • ANN. BOT. FENNICI Vol. 49 Taxonomic treatment A The taxa are described and illustrated below and m they can be distinguished by the following key. Key to species of the Lessingianthus saltensis complex sm 1. Fruits with glandular trichomes; chromosome number 2n = 64 .............................................................. L. saltensis 1. Fruits without glandular trichomes; chromosome number B 2n = 32 ......................................................................... 2 2. Leaves membranaceus, base obtuse, margins serrate; m phyllaries with rounded apex ............ L. membranifolius sm 2. Leaves coriaceus, base attenuate, margin entire; phyllar- ies with acute apex. ..................................... L. coriarius C sm m Lessingianthus