CHROMOSOME STUDIES IN VERNONIA CINCTA AND V. SCORPIOIDES (ASTERACEAE, VERNONIEAE)

Abstract

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 akaryotype 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.