Chromosome Studies in Gomidesia, Marlierea, Myrceugenia and Myrcia (Myrtaceae, Subtribe Myrciinae)

Abstract

In this paper we describe the chromosome numbers of several species of Myrtaceae (subtribe Myrciinae)from south-eastern Brazil, in order to help determine the circumscription and limits of this group. Thechromosomal counts of 20 species were obtained, 17 of which are new. The number 2n = 22 occurs in almost all ofspecies and genera analysed except for the polyploid species Gomidesia gaudichaudiana and two species of Myrcia,with 2n = 44. With these results, our knowledge of the chromosome number in the subtribe Myrciinae increasedfrom 12 (2.2%) to 29 species (5.4%). The occurrence of 2n = 22 in species of the four genera analysed did not helpresolve taxonomic questions relating to the distinction between Myrcia, Marlierea and Gomidesia. Although lessfrequent in Myrciinae, polyploidy appears to have had an important role in the evolution of this family, with highfrequency in Eugeniinae (22.5% of Eugenia species) and Myrtinae (50% of the species, 75% in Psidium).