Karyotypes of Seven South American Species of Vernonia (Asteraceae) *

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1 Cytologia 63: , 1998 Karyotypes of Seven South American Species of Vernonia (Asteraceae) * M. Dematteis and A. Fernandez Instituto de Botanica del Nordeste (UNNE-CONICET), Sargento Cabral 2131, Casilla de Correo 209, 3400 Corrientes, Argentina Accepted May 18, 1998 Summary The karyotypes of seven South American species of Vernonia were analyzed in detail. First chromosome count are reported for V amplexicaulis (2n=34=24m+10sm), V ferruginea (2n= 34=20m+14sm), V pinguis (2n=68=42m+26sm) and V squamulosa (2n=34=20m+2m-sm+ 12sm). Furthermore, the chromosome numbers of V chamaedrys (2n=34=22m+12sm), V fulta (2n=34=24m+ 10sm) and V nudiflora (2n=34=24m+ losm) are also confirmed. The seven species showed similar karyotype symmetry, chromosome size and satellite position, which would support a close relationship among them. Chromosomal data available for the genus and the results obtained here suggests that species with pyramidal or thyrsoid inflorescence have x=17, while entities with scorpioid or seriate inflorescence possess mainly basic numbers x=16, x=15 or x=14. The genus Vernonia sens, lat. contains approximately 1000 species and is considered the central core of the tribe Vernonieae. In the New World, it is represented by about 500 species distributed from Canada to northern Argentina (Jones 1977). From a systematic point of view, Vernonia constitute one of the most complex genera of the Asteraceae family. This complexity is produced principally because the extreme diversity of biological forms that exhibit the genus (Stutts 1988), which ranging from small scapose herbs to large trees. Several authors have attempted to clarify the taxonomy of the genus (Cabrera 1944, Jones 1979a, 1981, Stutts 1988, Robinson 1988, 1992, 1993), however, at the present have not arrived to a satisfactory accord on this subject. Despite the chromosomes are widely variable in number and ploidy level within the genus (Keeley and Turner 1990, Ruas et al. 1991), its have not been mainly applied for systematic studies. Cytologically, the genus Vernonia is barely know, having been analyzed the karyotypes of only 25 species (Gill 1978, Mathew and Mathew 1982, Ruas et al. 1991, Dematteis 1996, 1997). Previous studies in the genus shows that in Old World species, the basic chromosome numbers are x=9 and x=10, while in New World taxa are x=17, x=16, x=15, x=14 and x=10 (Ruas et al. 1991, Dematteis 1997). The purpose of this paper is to report original chromosome numbers and karyotypes of seven Vernonia species from Argentina and Brazil. The significance of the results is discussed in relation to their taxonomic position and to the evolution of the genus. Materials and methods The source of the material examined and collection numbers of the voucher specimens deposited at the Instituto de Botanica del Nordeste (CTES) are the following: V amplexicaulis R. E. Fr.: Argentina. Salta. Dept. San Martin. On the road to Dique Itiyuro, This work is part of a Doctoral Thesis of the first author, which will be presented in the Facultad de Ciencias Exactas, Fisicas y Naturales, Universidad Nacional de Cordoba, Argentina.

2 324 M. Dematteis and A. Ferndndez Cytologia 63 2 km from route 34. Dematteis and Seijo 837. V chamaedrys Less.: Argentina. Corrientes. Dept. Capital. Riachuelo. Dematteis 604. V ferruginea Less.: Brazil. Mato Grosso. Caceres. Serra do Mangaval. Hatschbach et al V fulta Griseb.: Argentina. Tucuman. Dept. Famailla. 9 km N from Famailla. Dematteis and Seijo 725. V nudiflora Less.: Argentina. Corrientes. Dept. Paso de los Libres. Route 126, near route 14. Krapovickas and CristObal V squamulosa Hook. et Am.: Argentina. Jujuy. Dept. Palpald. Cerro Zapla. Dematteis and Seijo 795. V pinguis Griseb.: Argentina. Jujuy. Dept. Valle Grande. San Francisco. Dematteis and Seijo 831. Cytological observations were made primarily on mitotic cells of root-tips obtained from germinating seeds. After a pretreatment of about 4 hr in 8-hydroxyquinoline M solution, the material was fixed in acetic acid-ethanol (1 : 3) and then stained with the Feulgen's technique. Nomenclature used for the karyotype description is that suggested Levan et al. (1964). For elaboration of the idiograms and estimation of the chromosome measures were used ten metaphase plates from 8-10 individuals for each species. Karyotype asymmetry was determined according to the methodology suggested by Romero Zarco (1986). Results The somatic chromosome number, karyotype formula and satellite position of the seven analyzed species are indicated in Table 1. Chromosome measures in um, mean centromeric index and asymmetry indexes are summarised in Table 2. Table 1. Chromosome numbers, karyotype formula and satellite position in Vernonia Table 2. Total chromosome length in,um (TCL), average chromosome length (X), centromeric index (CI), and intra (A1) and interchromosomal (A2) asymmetry indexes in Vernonia species

3 1998 Karyotypes of Seven South American Species of Vernonia 325 Figs Somatic chromosomes of Vernonia. 1) V amplexicaulis (2n=34). 2) V chamaedrys (2n=34). 3) Vferruginea (2n=34). 4) Vfulta (2n=34). 5) V nudiflora (2n=34). 6) V squamulosa (2n=34). 7) Vpinguis (2n=68). Scale=5 pm. All species presented basic chromosome number x=17, six were diploids with 2n=34 (Figs. 1-6) and one tetraploid with 2n=68 (Fig. 7). The chromosomes ranged in size from 1.1,um to 4.3,um. V nudiflora had the smaller mean chromosome length (1.5,um), while Vfulta had the bigger (2.77,um). The idiograms of the analyzed species are shown in Figs The relation between intrachromosomal (A1) and interchromosomal (A2) asymmetry indexes of the species are represented in Fig. 15. Due to the prevalence of metacentric pairs and to the absence of strong differences between smaller and larger chromosomes, asymmetry indexes were in general of low values. Satellites were located usually on the short arm of one or two submetacentric pairs. Their pres-

4 326 M. Dematteis and A. Fernandez Cytologia 63 Fig. 15. Dispersion diagram representing the karyotype asymmetry. ence was not a constant feature in the entities analyzed, since no satellites were found in about 30-40% of the metaphase plates examined. Figs Idiograms of seven Vernonia species. 8) V amplexicaulis (14m+ 10sm). 9) V chamaedrys (22m+ 12sm). 10) V ferruginea (20m+ 14sm). 11) V.fulta (24m+ 10sm). 12) V nudiflora (24m+10sm). 13) V squamulosa (20m+ 14sm). 14) Vernonia pinguis (42m +26sm). Scale =1 ym. Discussion The seven species show rather similar chromosomal features, although some differences in karyotype formula, chromosome size and symmetry can be observed. The karyotypes are composed mainly of metacentric chromosomes, with a lesser proportion of submetacentrics. Karyotype asymmetry is little variable among the species and results in general of moderate order, which is in concordance with previous karyological information available for South American species of the genus (Ruas et al. 1991, Dematteis 1996, 1997). Results obtained in the widespread taxon V chamaedrys agree with two preceding studies made on material from Brazil (Stutts 1988) and Argentina (Dematteis 1996). The number found in V fulta coincides with that reported Jones (1982) and Galiano and Hunziker (1987) for specimens of Peru and Argentina respectively. There are several earlier reports for V nudiflora, most of which indicate n=17 (Jones 1974, Bernardello 1986, Stutts 1988). The single count that differ from its number reports n=16 for material of western Argentina (Covas and Hunziker 1954). The taxonomic position of V fulta has been in dispute during several years. Gleason (1923) based upon the inflorescence type considered it as related to V amplexicaulis (sub. V prenanthoides). Meanwhile, Jones (1979a) taking into account the pollen structure placed V fulta near V ferruginea. More recently, Robinson (1993) segregated it in a distinct genus based on the corolla hairs. Our findings indicate that, although V fulta possess a greater chromosome size, have not another distinctive characteristic respect to the remaining six species. From a cytological viewpoint, the seven entities seems to constitute a relatively homogeneous group with few differences

5 1998 Karyotypes of Seven South American Species of Vernonia 327 between its karyotypes. In this way, the chromosomal data do not support the separation of V fulta in a different group from the others species. Robinson (1992) included all analyzed species, excepting V fulta, in a new genus called Vernonanthura. Morphologically these entities are characterised to possess pyramidal or thyrsoid inflorescence, which distinguish them from the remaining South American species that have scorpioidcymose or seriate-cymose inflorescence. Others species belonging to this group, such as V nitidula, V oligolepis, V patens, V polyanthes, V tweedieana and V westiniana, have been reported to have all n=17 (Jones 1979b, 1982, Stutts 1988, Ruas et al. 1991). The basic chromosome number x=17 might be apparently exclusive of taxa with pyramidal inflorescence. Species with scorpioid forms, according to the literature previously cited, seems to have mostly basic numbers x=14, x=15 and x = 16. The ancestral basic chromosome number of Vernonia was probably x=9, which might have originated x=10 by ascending aneuploidy (Jones 1979b). Higher chromosome numbers present in the most American members of the genus, would be derived from x=9 by duplication to 18 and posterior aneuploid reduction (Jones 1979b, Dematteis 1997). This is in agreement with the hypothetical evolution of the inflorescence suggested for the genus (Robinson 1988), since pyramidal or thyrsoid forms (x=17) are assumed primitive, meanwhile seriate or scorpioid types are considered advanced. Although the cytological information available for Vernonia is still limited, seem undoubted that the chromosomes could provide valuable data to understand the taxonomy and evolution of the genus. Acknowledgements This work has been supported by grants of the Secretaria General de Ciencia y Tecnica- UNNE and the Consejo Nacional de Investigaciones Cientificas y Tecnicas (CONICET). References Bernardello, L. M Numeros cromosomicos en Asteraceae de Cordoba. Darwiniana 27: Cabrera, A. L Vernonieas Argentinas (Compositae). Darwiniana 6(3): Covas, G. and Hunziker, J. H Estudios cariologicos en Antofitas. Revista Invest. Agric. 8: Dematteis, M Estudios cromosomicos en especies argentinas de Vernonia (Asteraceae). Bonplandia 9(1-2): Numeros cromosomicos y cariotipos de algunas especies de Vernonia (Asteraceae). Bol. Soc. Argen. Bot. 33(1-2): Galiano, N. G. and Hunziker, J. H Estudios cariologicos en Compositae. IV. Vernonieae y Eupatorieae. Darwiniana 28: 1-8. Gill, L. S Karyotype of Vernonia aemulans Vatke (Compositae). Adansonia 18: Gleason, H. A The Bolivian species of Vernonia. Amer. J. Bot. 10: Jones, S. B Vernonieae (Compositae) chromosome numbers. Bull. Torrey Bot. Club 101: Vernonieae-systematic review. In: Heywood, V. H., Harborne, J. B. and Turner, B. L. (Eds.). The Biology and Chemistry of the Compositae. I: Academic Press, London. Synopsis and pollen morphology of Vernonia (Compositae: Vernonieae) in the New World. Rhodora 81: Chromosome numbers of Vernonieae (Compositae). Bull. Torrey Bot. Club 106: Synoptic classification and pollen morphology of Vernonia (Compositae: Vernonieae) in the Old World. Rhodora 83: In IOPB chromosome numbers reports LXXIV. Taxon 31: Keeley, S. C. and Turner, B. L A preliminary cladistic analysis of the genus Vernonia (Vernonieae: Asteraceae). Pl. Syst. Evol., Suppl. 4: Levan, A., Fredga, K. and Sandberg, A. A Nomenclature for centromeric position on chromosomes. Hereditas 52:

6 328 M. Dematteis and A. Fernandez Cytologia 63 Mathew, A. and Mathew, P. M Studies on the South Indian Compositae, 4. Karyomorphology of eight species of Vernonia. Cytologia 47: Robinson, H Studies in the Lepidaploa complex (Vernonieae: Asteraceae). IV The new genus Lessingianthus. Proc. Biol. Soc. Wash. 100(4): A new genus Vernonanthura (Vernonieae, Asteraceae). Phytologia 73: Three new genera of Vernonieae form South America, Dasyandantha, Dasyandanthina and Quechualia (Asteraceae). Proc. Biol. Soc. Wash. 106(4): Romero Zarco, C A new method for estimating karyotype asymmetry. Taxon 35: Ruas, P. M., Ruas, C. F., Vieira, A. 0. S., Matzenbacher, N. I. and Martins, N. S Cytogenetics of genus Vernonia Schreber (Compositae). Cytologia 56: Stutts, J. G Taxonomic revision of Vernonia Subsect. Chamaedrys (Compositae: Vernonieae). Rhodora 90: