Chromosomal diversity in two synchronopatric species of Hoffmannseggella (Orchidaceae)

Abstract

Hoff mannseggella viridifl ora Verola & Semir (Laeliinae, Orchidaceae) is a recently discovered species in the campos rupestres vegetation of the Espinha ç o Range, MG, Brazil, in synchronopatry with H. bradei (Pabst) V. P. Castro & Chiron. Both morphological and phenological studies indicate that these species are closely related. To substantiate the diff erentiation of these two species we examined their chromosome numbers and morphologies. Th e two species had diff erent chromosome numbers, with H. bradei having 2n ϭ 40 and H. viridifl ora having 2n ϭ 44 chromosomes, an aneuploid number not previously documented in the genus. Meiotic behavioral studies undertaken with H. bradei revealed many abnormalities related to bivalent numbers and chromosome migration, suggesting that meiotic abnormalities could generate aneuploid gametes and perhaps aneuploid zygotes. Karyotype formulas and chromosome morphologies are quite diff erent between the species, so H. viridifl ora was not directly derived from H. bradei through simple chromosome additions. Complementary analyses are necessary to understand the process and species involved in the origin of H. viridifl ora .