Botanical Journal of the Linnean Society, 2002, 139, 401–408. With 6 figures

Cytotaxonomic analysis of South American species of Vernonia (Vernonieae: Asteraceae) MASSIMILIANO DEMATTEIS* Instituto de Botánica del Nordeste (UNNE-CONICET), Casilla de Correo 209, C. P. 3400 Corrientes, Argentina Received 6 March 2002; accepted for publication 23 May 2002

Chromosome numbers in 48 populations belonging to 31 species of Vernonia from South America have been determined. First chromosome counts are reported for V. propinqua var. canescens (2n = 20), V. sceptrum (2n = 80), V. rufogrisea (2n = 32), V. heringeri (2n = 32), V. hovaefolia (2n = 64), V. hystricosa (2n = 128), V. obtusata (2n = 64), V. pseudoincana (2n = 32), V. rubricaulis var. australis (2n = 64) and V. rugulosa (2n = 30). The basic chromosome numbers x = 10, 14, 15, 16 and 17 were confirmed for New World species of Vernonia. Together with previous records, these numbers suggest that the evolution of Vernonieae has occurred through a combination of polyploidy and aneuploidy. Taxonomic implications of certain counts are also discussed. © 2002 The Linnean Society of London, Botanical Journal of the Linnean Society, 2002, 139, 401–408.

ADDITIONAL KEYWORDS: aneuploidy – chromosome numbers – classification – polyploidy.

INTRODUCTION The genus Vernonia Schreb. includes more than 1000 species and constitutes the central core of the tribe Vernonieae Cass. (Asteraceae). It is distributed widely in tropical and subtropical regions of Asia, Africa and America (Jones, 1977), having more than 350 species in South America which mostly occur in south-eastern Brazil, Argentina, Paraguay and Bolivia (Robinson, 1999). From the taxonomic viewpoint, the tribe Vernonieae has been considered to be one of the most complex groups of the Asteraceae. The main dispute has been commonly centred around the concept and delimitation of the large genus Vernonia, which is still widely discussed to date (Keeley & Turner, 1990; Keeley & Jansen, 1994; Robinson, 1999). The phylogenetic relationships within the genus are poorly understood and the current infrageneric division is mainly the one proposed by Bentham (1873), despite some alternative classifications having been suggested (Baker, 1873; Cabrera, 1944; Keeley, 1978; Jones, 1979a, 1981). *E-mail: [email protected]

According to the traditional infrageneric classification of Vernonia, most of the South American species belong to the section Lepidaploa (Cass.) DC. (Bentham 1873; Baker, 1873). In a recent classification of the New World Vernonieae suggested by Robinson (1987, 1988a, 1988b, 1990, 1999), almost all species in this section have been segregated into new genera, restricting the genus Vernonia exclusively to North America. However, this new classification has not been adopted by several authors (e.g. Hind, 1993; Keeley & Jansen, 1994), who have considered that the elevation of the typical sections and subsections to the generic level is premature and does not resolve the problem fully. Certainly, the status and position of many Vernonieae taxa are still doubtful, due to the lack of information in important areas such as cytology, chemistry and morphological variation (Keeley & Turner, 1990; Robinson, 1999). Cytologically, the genus Vernonia has not been investigated widely, with less than 20% of the species examined for chromosome number. Most of the comprehensive studies on the cytology of Vernonia were done by Jones (1970, 1977, 1979b, 1982), who suggested the base numbers x = 9 and x = 10 for the Old World species and x = 17 for American members of the

© 2002 The Linnean Society of London, Botanical Journal of the Linnean Society, 2002, 139, 401–408

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tribe. Some new chromosome counts and karyotype information from Asiatic species were provided by Mathew & Mathew (1976, 1982) and Gill (1978). Additional base numbers and karyomorphological data of New World species were reported by Keeley (1978), Keeley & Turner (1990), Ruas et al. (1991) and Dematteis (1997, 1998a, 1998b). These studies, in addition to other chromosome number reports (Turner, 1981; Galiano & Hunziker, 1987; Dematteis & Fernádez, 1998; Esteves, Forni-Martins & Semir, 2001), revealed that the genus is heterogeneous, particularly in South America, from which basic numbers have been found that range between x = 9 and x = 19. The present paper reports original chromosome numbers of several South American species of Vernonia belonging to the sect. Lepidaploa. The cytological data are discussed in relation to the taxonomy and the chromosome evolution of the genus.

MATERIAL AND METHODS The sources of the examined plants are presented in Table 1. Voucher specimens are kept at the herbarium of the Instituto de Botánica del Nordeste (CTES) and some duplicates have been deposited in other herbaria, as indicated in Table 1. Meiosis was studied in young inflorescences fixed in lactic acid/ethanol (1 : 5) and stored under refrigeration until examined. Pollen mother cells were macerated and squashed using 2% acetocarmine. Mitotic chromosome preparations were made from root meristems obtained from germinating seeds. The rootlets were pretreated for about 4–4.5 h in 0.002 M 8-hydroxyquinoline solution at room temperature, fixed in 5 : 1 absolute alcohol/lactic acid and then stained using the Feulgen’s technique. In all populations at least 20 counts from seven to ten individuals were made to verify the observations.

RESULTS The chromosome number of 48 populations attributed to 31 species of Vernonia belonging to the sect. Lepidaploa was determined. These include the first count for ten entities and new numbers for three other taxa. The analysed species and their chromosome numbers are given in Table 1, in which the species are grouped according to the traditional subsections suggested by Bentham, (1873) and Baker (1873), while the new genera proposed by Robinson (1999) are enclosed in parentheses. Because the taxonomic positions of several analysed entities are uncertain or need to be reviewed, in this study all the species have been considered as belonging to the genus Vernonia s. l. The analysis revealed 11 different chromosome numbers that ranged between 2n = 20 and 2n = 128.

The chromosomes were mostly small, varying between 1–3.5 mm in length (Figs 1–6). All of the plants in each of the analysed populations showed the same chromosome number, with the exception of a sample of V. platensis that contained hexaploid (2n = 6x = 60) and pentaploid (2n = 5x = 50) individuals (Fig. 2). Although a considerable proportion of the species were diploid, there were several polyploid taxa. Of a total of 31 entities, ten were polyploids or showed polyploid cytotypes, which represents about 30% of the species. Among the polyploid taxa, tetraploids were most frequent (seven spp.), followed by octoploids (three spp.) and hexaploids (one sp.).

DISCUSSION The New World Vernonieae, in contrast with Old World members of the tribe, show a great diversity of chromosome numbers and higher proportion of polyploid species (Jones, 1979b; Ruas et al., 1991). Of the basic numbers reported for American taxa, the present analysis has found five: x = 10, 14, 15, 16 and 17. The base x = 10 was detected in five taxa belonging to the small subsect. Oligocephalae Benth. (= Chrysolaena H. Rob.). Of these entities, the two varieties of V. propinqua were diploid (2n = 20), V. flexuosa tetraploid (2n = 40) and V. sceptrum octoploid (2n = 80). The remaining species, V. platensis, showed four different ploidy levels: 2¥, 4¥, 5¥ and 6¥. According to the available information, the subsect. Oligocephalae is the single New World group of Vernonieae with base x = 10, a number present mainly in Old World species (Jones, 1979b; Galiano & Hunziker, 1987; Robinson, 1999). In addition to the taxa analysed here, there are three other species of this subsection that have been examined chromosomally. For V. lithospermifolia Hieron. and V. verbascifolia Less. 2n = 20 was determined in Argentinian specimens (Dematteis, 1998a), while in V. simplex Less. 2n = 40 has been observed in a Brazilian population (Ruas et al., 1991). The last species was included in the genus Lessingianthus H. Rob. (= subsect. Macrocephalae Benth.) by Robinson (1988a), but it probably should be transferred to the subsect. Oligocephalae because it has pollen morphology that is similar to that of the Oligocephalae species (Robinson, 1988b) and has the base number x = 10 which is lacking in subsect. Macrocephalae. The occurrence of different cytotypes in V. platensis has been well established by some earlier studies (Núñez in Cabrera, 1944; Hunter, 1964; Galiano & Hunziker, 1987; Dematteis, 1997), but the pentaploid level is recorded here for the first time in this species. The existence of pentaploid and hexaploid plants in the same population indicates the occurrence of hybridization between hexaploid and tetraploid individuals, although tetraploids were not found at that

© 2002 The Linnean Society of London, Botanical Journal of the Linnean Society, 2002, 139, 401–408

© 2002 The Linnean Society of London, Botanical Journal of the Linnean Society, 2002, 139, 401–408

Subsect. Macrocephalae (Lessingianthus) V. brevifolia Less.

V. rufogrisea A.St.-Hil.

V. remotiflora L.C.Rich.

V. chalybaea Mart. ex DC.

Subsect. Axilliflorae (Lepidaploa) V. aurea Mart. ex DC.

V. propinqua Hieron. var. propinqua V. propinqua Hieron. var. canescens (Chodat) Dematteis V. sceptrum Chodat

60

30

16

14 14

32 32

32

32*

32 32 28

32

32†

80*

20 20*

40 50, 60†

20

10 10

20

20

40

2n

10

20

Subsect. Oligocephalae (Chrysolaena) V. flexuosa Sims

V. platensis (Spreng.) Less.

n

Species

Argentina. Corrientes. Department Capital. 1 km S of Arroyo Riachuelo. Dematteis 924 (CTES). Paraguay. Department Amambay. Colonia San Luis, 5 km S of San Luis river. Schinini & Dematteis 33621 (CTES, FCQ).

Brazil. Goiás. Mun. Catalão. Route BR-050, km 233, limit between Catalão and Campo Alegre. Hatschbach et al. 70574 (CTES, MBM). Brazil. Goiás. Mun. São Domingos. Route GO-108, 3 km S of São Domingos. Hatschbach et al. 71178 (CTES, MBM). Brazil. Bahía. Mun. Correntina. Correntina river. Hatschbach et al. 71245 (CTES, MBM). Brazil. Bahía. 22 km S of Itiúba, on the road to Filadelfia. Arbo et al. 7239 (CEPEC, CTES). Argentina. Misiones. Department Capital. Arroyo Zaimán. Dematteis 473 (MNES). Paraguay. Department Amambay. National Park Cerro Corá, intersection of Arroyo Aceite and route 5. Schinini et al. 30439 (CTES, SI). Brazil. Goiás. Mun. Agua Fria. Route GO-118, ascending to Torre Repetidora Roncador. Hatschbach et al. 70663 (CTES, MBM). Brazil. Goiás. Mun. Planaltina. Route GO-118, 45 km S of São Gabriel. Hatschbach et al. 70624 (CTES, MBM).

Uruguay. Department Rivera. On the road to Tacuarembó, route 5. Dematteis et al. 493 (CTES, MA, MEXU). Argentina. Misiones. Department Guaraní. Predio Guaraní, Arroyo Paraíso. Tressens et al. 5801 (ASU, CTES, LPB). Argentina. Corrientes. Department Mburucuyá. Route 6, 3 km W of Manantiales. Dematteis et al. 972 (CTES). Paraguay. Department Amambay. Chirigüelo. Dematteis & Schinini 857 (CTES, FCQ). Argentina. Misiones. Department Candelaria. 9 km of the route 12, on the road to Oberá. Krapovickas & Cristóbal 46950 (CTES). Argentina. Misiones. Department Candelaria. Route 15, 21 km E of Santa Ana. Dematteis 592 (CTES). Argentina. Misiones. Department Capital. Arroyo Zaimán. Dematteis 371 (MNES). Paraguay. Department Amambay. 25 km N of P. J. Caballero, on the road to Colonia Estrella. Dematteis & Schinini 869 (CTES, FCQ). Paraguay. Department Amambay. 41 km S of Bella Vista, on the road to the Aquidaban river. Dematteis et al. 909 (CTES, FCQ).

Location, voucher

Table 1. Chromosome numbers of some Vernonia species from South America

CYTOTAXONOMY OF VERNONIA

403

Subsect. Paniculatae (Vernonanthura) V. amplexicaulis R.E.Fries

V. rugulosa Sch.Bip. ex Baker

V. rubricaulis Humb. et Bonpl. var. australis Hieron.

V. pseudoincana (Hieron.) Cabrera V. rubricaulis Humb. et Bonpl. var. rubricaulis

32

34

30*

64

64

64

64*

32

32* 32†

64

64

V. polyphylla Sch.Bip.

128

128

128*

32* 64*

32

32

2n

64*

16

n

V. obtusata Less.

V. hystricosa Cabrera et Dematteis

V. heringeri H.Rob. V. hovaefolia Gardn.

V. dura Mart. ex DC.

Species

Table 1. Continued

Argentina. Jujuy. Department Ledesma. National Park Calilegua. Dematteis & Seijo 824 (CTES, MICH, MO, NY, TEX).

Argentina. Misiones. Department L. N. Alem. National Route 14, 15 km N of San José. Dematteis 595 (CTES, FCQ, TEX, UNSL). Argentina. Corrientes. Department Capital. Molina Punta. Dematteis & Solís Neffa 504 (CHR, CTES, MA). Argentina. Corrientes. Department Lavalle. Route 12, 20 km S of the route 123. Krapovickas & Cristóbal 46518 (CTES). Paraguay. Department Amambay. Route 5, 20 km W of P. J. Caballero. Dematteis et al. 884 (CTES, G). Argentina. Corrientes. Department Paso de los Libres. Route 126, near the Miriñay river. Krapovickas & Cristóbal 46968 (ALCB, CTES, IAC). Brazil. Bahía. Mun. Guanambí. Route BR-030, 15 km N of Guanambí. Hatschbach et al. 65046 (CTES, MBM).

Brazil. Goiás. Mun. Monte Alegre. Route GO-118, near Brejo. Hatschbach et al. 70767 (CTES, MBM). Brazil. Tocantins. Mun. Arraias. Route TO-050, km 415, 6 km W of Arraias. Hatschbach et al. 70856 (CTES, MBM). Brazil. Goiás. Mun. Alto Paraíso. Route GO-118, km 200. Hatschbach et al. 70745 (CTES, MBM). Brazil. Goiás. Mun. Catalão. Route BR-050, km 233, limit between Catalão and Campo Alegre. Hatschbach et al. 70576 (CTES, MBM). Paraguay. Department Amambay. 34 km S of Bella Vista, Arroyo Negla and route 5. Schinini et al. 30446 (CTES, LP). Paraguay. Department Amambay. On the road to Colonia Estrella, 25 km N of P. J. Caballero. Dematteis et al. 911 (CTES, PY). Paraguay. Department Amambay. 30 km S of Bella Vista, on the road to the Aquidabán river. Dematteis et al. 905 (CTES, PY). Brazil. Goiás. Mun. Alto Paraíso. Chapada dos Veadeiros. Route GO-118, km 200. Hatschbach et al. 70719 (CTES, MBM). Paraguay. Department Amambay. 30 km N of route 5 on the road to Bella Vista. Schinini et al. 30444 (CTES, MBM). Paraguay. Department Amambay. On the road to Bella Vista. Dematteis & Schinini 873 (CTES, FCQ). Argentina. Chaco. Department 1° de Mayo. Colonia Benítez. Dematteis 605 (CTES, BAB, F). Argentina. Misiones. Department Capital. Arroyo Zaimán. Dematteis 441 (MNES).

Location, voucher

404 M. DEMATTEIS

© 2002 The Linnean Society of London, Botanical Journal of the Linnean Society, 2002, 139, 401–408

17

17

V. oligolepis Sch.Bip.

V. pinguis Griseb. V. squamulosa Hook. et Arn.

*First count for the taxon †New count for the taxon

34 34 17 V. loretensis Hieron. V. nitidula Less.

68 34

34

17 V. fulta Griseb.

V. incana Less.

17 V. chamaedrys Less. V. ferruginea Less.

34

34 V. echioides Less.

34 34

Paraguay. Department Amambay. 40 km N of route 5, on the road to Bella Vista. Dematteis & Schinini 874 (CTES, FCQ). Argentina. Misiones. Department Capital. Arroyo Zaimán. Dematteis 443 (MNES). Brazil. Mato Grosso. Mun. Chapada dos Guimarães. Agua Fría, 7 km of Rio Manso. Hatschbach et al. 66856 (CTES, MBM). Argentina. Salta. Department General San Martín. Road to Itiyuro, 2 km of route 34. Dematteis & Seijo 834 (CTES). Argentina. Formosa. Department Laishi. Colonia Presidente Irigoyen, 25 km W of San Francisco. Di Giacomo 45 (CTES). Argentina. Misiones. Department San Ignacio. Horacio Quiroga house. Dematteis 511 (CTES, TEX). Argentina. Corrientes. Department Mercedes. Arroyo Ypané, 5 km N of the route 14. Ferrucci et al. 1205 (CTES). Paraguay. Department Amambay. Chirigüelo. Dematteis & Schinini 855 (ASU, CTES, F, G, GH, LIL, LPB, MEXU, NY, SPF, TEX). Argentina. Jujuy. Department Ledesma. National Park Calilegua. Dematteis & Seijo 813 (CTES). Argentina. Jujuy. Department Ledesma. National Park Calilegua. Dematteis & Seijo 829 (CTES, GH, MBM, TEX).

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location. Vernonia platensis shows a wide morphological variability and is taxonomically complex, which could probably be attributed to the variation in its ploidy level. The chromosome number found in V. flexuosa (2n = 40) disagrees with the n = c. 17 recorded by Jones (1979b) among specimens from Uruguay and with the count of n = c. 30–32 established by Hunziker et al. (1990) for an Argentine population. However, the present analysis is in agreement with a previous study on plants collected in southern Brazil (Ruas et al., 1991). Jones (1979b) proposed x = 17 as the single base number for the New World species of Vernonia, considering chromosome number reports of n = 16 or fewer to be doubtful. However, the present determinations in 13 taxa, together with previous records (Ruas et al., 1991; Dematteis, 1998b; Dematteis & Fernández, 2000; Esteves et al., 2001), suggest that x = 16 is a relatively frequent base number in South America. Most species with x = 16 belong to subsect. Macrocephalae (= Lessingianthus), which comprises about 100 taxa distributed widely in south-eastern Brazil, Paraguay, Uruguay, Bolivia and Argentina (Robinson, 1988a). It is characterized cytologically by the basic number x = 16 and possesses the greatest proportion of polyploid entities in the tribe. Chromosome counts already reported in 20 species of the subsection reveal that only nine taxa are diploids and the remainder polyploids (Ruas et al., 1991; Dematteis, 1998b; Dematteis & Fernández, 2000). Among the ten Macrocephalae species analysed, five are diploid with 2n = 32, four tetraploid with 2n = 64 and one octoploid with 2n = 128. The remaining species, V. rugulosa (2n = 30), is diploid with the base number x = 15, which has been noted only for V. cotoneaster Less. (Dematteis, 1998a), a species of the subsect. Axilliflorae distributed in south-eastern Brazil. The relatively high chromosome number found in V. hystricosa (2n = 8x = 128) is in agreement with almost all of its allied species and with the cytological characteristics of the subsect. Macrocephalae. This last taxon is closely related to V. oxyodonta Malme that is also octoploid with 2n = 128 (Dematteis & Fernández, 2000). Nevertheless the two species may be distinguished by flower number, leaf shape and level of pubescence. The chromosome number obtained for V. brevifolia and V. dura (2n = 32) agrees with a prior determination (Dematteis, 1998b) and the tetraploid level observed in V. polyphylla (2n = 64) is the same as that found by Ruas et al. (1991) in plants from the Brazilian province of Rio Grande do Sul. The results observed in V. rubricaulis indicate that the two varieties of the species have different ploidy levels. The typical variety is diploid with 2n = 32, while var. australis is tetraploid with 2n = 64 chro-

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1

2

3

4

5

6

Figures 1–6. Somatic chromosomes of Vernonia. Scale bar = 5 mm. Fig. 1. V. aurea, 2n = 32. Fig. 2. V. platensis, 2n = 50. Fig. 3. V. heringeri, 2n = 32. Fig. 4. V. rubricaulis var. australis, 2n = 64. Fig. 5. V. rufogrisea, 2n = 32. Fig. 6. V. rugulosa, 2n = 30. © 2002 The Linnean Society of London, Botanical Journal of the Linnean Society, 2002, 139, 401–408

CYTOTAXONOMY OF VERNONIA mosomes. A previous count of n = 33 for V. rubricaulis has been recorded in material from Argentina (Jones, 1970), but the author unfortunately did not indicate the existence of any voucher specimen. This record could represents a miscount of V. rubricaulis var. australis which is tetraploid, showing 32 bivalents at meiosis. Vernonia pseudoincana was initially described as a variety of the widespread V. rubricaulis (Hieronymus, 1897) and was recently elevated to specific rank based on morphological and ecological observations (Cabrera & Dematteis, 1999). It is a subshrub 30–50 cm tall with lanceolate leaves, while V. rubricaulis is commonly 60–200 cm tall with linear leaves. Both species also differ in habit, with V. pseudoincana living in clay-like ground, while V. rubricaulis grows in moist lowland soils. The subsect. Axilliflorae Baker (= Lepidaploa Cass.) includes most of the Neotropical species of Vernonia with seriate-cymose inflorescences and comprises more than 110 taxa distributed from Mexico to northern Argentina (Robinson, 1990). The available counts for the group (Keeley, 1978; Jones, 1979b; Dematteis, 1998a, 1998b), indicate that it has four different basic numbers, two of which were found in this study. Vernonia aurea, V. chalybaea and V. rufogrisea are diploids based on x = 16, while V. remotiflora (2n = 28) was diploid with the infrequent basic chromosome number x = 14. The two additional numbers present in Axilliflorae species are x = 15 found in the Brazilian V. cotoneaster (Dematteis, 1998a) and x = 17 reported for numerous taxa in the West Indies (Keeley, 1978). It is interesting to note that almost all the species of this subsection are diploid, with only one hexaploid taxon recorded so far (Keeley, 1978). The number of chromosomes observed in two populations of V. aurea (2n = 32) disagrees with a previous count of n = 17 for Brazilian specimens (Jones, 1982), but agrees with one made on a population from Minas Gerais, Brazil (Dematteis & Fernández, 2000). The counts of 2n = 30 for V. chalybaea and 2n = 28 for V. remotiflora confirm the single previous record for each one (Dematteis, 1998a). The subsect. Paniculatae Benth. (= Vernonanthura H.Rob.) comprises shrubs or small trees with thyrsoid or corymbiform inflorescences and uniform pollen type (Robinson, 1992). All the species of this group have the basic chromosome number x = 17, which has been reported for 24 other South American taxa of the genus (Jones, 1979b, 1982; Stutts, 1988) and most of the Central and North American entities (Keeley, 1978; Jones, 1979b). This basic chromosome number is exclusive to the New World species and constitutes the most common number in Vernonia. The results found in species of this subsection are in agreement with those reported in two previous studies on the

407

group (Stutts, 1988; Dematteis & Fernández, 1998). The available counts for Paniculatae species indicate that they are diploids with 2n = 34 (Jones, 1979b; Keeley & Turner, 1990; Robinson, 1992; Dematteis & Fernández, 1998), with exception of the two tetraploid ones analysed here. The cytological information on Vernonia shows that the New World taxa have a large range of base numbers, including x = 9, 10, 14, 15, 16, 17 and 19. Almost all these numbers are present in the South American species except x = 19, which is restricted to the North American sections Leiboldia (Schlecht.) Benth. and Lepidonia (S.F.Blake) B.L.Turner (Turner, 1981). The chromosome evolution of the American Vernonieae has clearly occurred throughout a complex combination of polyploidy and aneuploidy with no evidence of chromosome fusion or fission. The ancestral basic number of the genus seems to be x = 9, with the higher numbers derived from polyploidy followed by aneuploid reduction (Jones, 1979b). An alternative hypothesis might be hybridization between species based on x = 9 and x = 10 followed by polyploidy and subsequent aneuploid loss, as was suggested by Turner (1981). The subsections of Vernonia exhibit different chromosome patterns. The Oligocephalae group is characterized by a base number of x = 10, with a considerable number of polyploid species. The Macrocephalae species have a base number x = 16, or exceptionally 15 as in V. rugulosa, and also reveal high ploidy levels. The taxa belonging to the subsect. Paniculatae invariably have x = 17 and are diploid, or rarely tetraploid. On the other hand, the Axilliflorae species are mostly diploid, but display four different base numbers: x = 14, 15, 16 and 17.

ACKNOWLEDGEMENTS I would like especially to thank Dr Carmen L. Cristóbal for her critical review of the manuscript. I am also grateful to Gert Hatschbach and Aurelio Schinini for their excellent plant collection made in southern Brazil. This work has been supported by grants from the Secretaría General de Ciencia y Técnica of the Universidad Nacional del Nordeste and the Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), which are greatly appreciated.

REFERENCES Baker JG. 1873. Compositae. I. Vernoniaceae. In: Martius C, ed. Flora Brasiliensis 6 (2): 1–179. Bentham G. 1873. Vernonieae. In: Bentham G, Hooker JD, eds. Genera Plantarum 2 (1): 227–231.

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