CHROMOSOME STUDIES IN VERNONIA CINCTA AND V. SCORPIOIDES (ASTERACEAE, VERNONIEAE) ESTUDIOS CROMOSóMICOS EN VERNONIA CINCTA y V. SCORPIOIDES (ASTERACEAE, VERNONIEAE)

Vernonia eineta Griseb. and V. seorpioides (Lam.) Pers. (Asteraeeae, Vernonieae) are two closely related taxa which have been considered by different authors either the same species or two varieties of the same species or two different species. In the present study a detailed chromosome analysis was carried out in an attempt to clarify the status and relationships of these two taxa. The cytological study revealed that Vernonia eineta has 2n=60 chromosomes and a karyotype formula composed of 36m + 16sm + St, whereas V. seorpioides presents 2n=66 and a karyotype with 34m + 20sm + 12t. Besides, V. eineta showed two chromosome pairs bearing satellites on the short arms, one m pair with linear satellite and one t pair with macrosatellite; while V. seorpioides presented one mchromosome pair carrying a linear satellite in the long armo In addition to the chromosome number, these species showed certain other karyotypic differences, mainly in theirformula, total chromosome length and asymmetry leve!. Chromosomal information here reported supports the specific status of both taxa. The presence of telocentric chromosomes in V. cincta and V. seorpioides would distinguish them from the remainder New World species of Vernoniawhich commonly have metacentric and submetacentric chromosomes. The karyotypic differences between V. cincta and V. seorpioides may be explained by the occurrence of structural rearrangements such as centric fusions or traslocations. This hypothesis is well supported by the similar total karyotype length of both taxa and the higher mean chromosome length of V. cincta, which presents a lower number of telocentric chromosomes than V. seorpioides. Vernonia cincta Griseb. y V. seorpioides V. (Lam.) Pers.. (Asteraceae, Vernonieae) son dos taxones estrechamente relacionados que han sido considerados por diferentes autores como una misma especie o como dos variedades de la misma especie. En el presente estudio se realizó un detallado análisis cromosómico en un intento de aclarar la situación y las relaciones de estos dos taxones. El estudio citológico reveló que Vernonia cincta tiene 2n = 60 cromosomas y una fórmula cariotípica compuesta de 36m + 16sm + 8t, mientras que V. scorpioides presenta 2n = 66 y un cariotipo con 34m + 20sm + 12t. Además, V. cincta mostró dos pares de cromosomas con satélite en los brazos cortos, un par m con satélite lineal y un par t con macrosatélite; mientras V. scorpioides presentó un par de cromosomas m que llevaba un satélite lineal en el brazo largo. Además del número de cromosomas, estas especies mostraron algunas otras