Chromosomal evolution in Pleurothallidinae (Orchidaceae: Epidendroideae) with an emphasis on the genusAcianthera: chromosome numbers and heterochromatin

Abstract

In this study, we analysed chromosome number variation and chromomycin A3/4′,6‐diamidino‐2‐phenylindole (CMA/DAPI) banding patterns in 48 species belonging to 12 genera of subtribe Pleurothallidinae (Orchidaceae) in order to understand the chromosome evolution based on recent phylogenetic hypotheses and taxonomic treatments. All species had small chromosomes, with numbers ranging from 2n = 20 in two Specklinia spp. to 2n = 80 in an unidentified Octomeria sp. In Acianthera, the most highly represented genus in this study, a great diversity of chromosome number and pattern of fluorescent bands was observed, showing heterochromatin accumulation in Acianthera section Sicariae subsection Pectinatae. Interspecific ascending and, mainly, descending dysploidy were the main mechanisms of chromosome number evolution in subtribe Pleurothallidinae. For Pleurothallidinae, x = 20 is suggested as the basic chromosome number, the same suggested for the related subtribe Laeliinae and for the whole tribe Epidendreae. The Brazilian species of the mega‐genus Stelis had chromosomes with small amounts of heterochromatin and chromosome numbers based on x2 = 16. These are generally divergent from those reported for Andean and Meso‐American species, but in agreement with the monophyletic hypothesis proposed for Stelis spp. with a Brazilian Atlantic distribution. © 2015 The Linnean Society of London, Botanical Journal of the Linnean Society, 2015, 178, 102–120.

CMA band variability and physical mapping of 5S and 45S rDNA sites in Brazilian Cactaceae: Pereskioideae and Opuntioideae

“…Symmetric karyotypes are frequent in related group of plants, both among monocots, such as Acianthera (Oliveira et al 2015) and in eudicots, as Rutaceae (Carvalho et al 2005). It is difficult to identify individual chromosomes in those karyotypes or to differentiate the karyotypes of different species of a same genus, and they are generally indicative of primitive karyotypes (Stebbins 1971).…”

Heterochromatin and numeric chromosome evolution in Bignoniaceae, with emphasis on the Neotropical clade Tabebuia alliance

“…They have been used mainly to characterize karyotypes with chromosomes that have the same size and morphology, and to differentiate the karyotypes of species with identical chromosome numbers (see Almeida et al, 2007;Barros e Silva et al, 2010;Cordeiro et al, 2016b;Almeida et al, 2016). The different patterns found can help determine taxonomic distinctions and clarify relationships among species (Carvalho et al, 2005;Almeida et al, 2007;Oliveira et al, 2015), as well as contribute to the description of new taxa, such as Epidendrum sanchezii E.Pessoa & L.P.Felix (Pessoa et al, 2014), Ameroglossum manoel-felixii L.P.Felix & E.M.Almeida (Almeida et al, 2016), and Spondias bahiensis P.Carvalho, Van den Berg and M.Machado (Almeida et al, 2007;Machado et al, 2015). Preliminary studies in the tribe Jacarandeae (Cordeiro et al, 2016b) indicated that heterochromatin distribution appeared to follow a specific pattern (8-16 CMA + terminal bands), while in the tribe Bignonieae (Cordeiro et al, 2017) heterochromatin distribution is quite variable among the species.…”

Karyotype evolution in the genus Jacaranda Juss. (Jacarandeae, Bignoniaceae): chromosome numbers and heterochromatin

“…Numerically stable species of Citrus L. (Guerra, 1993;Carvalho et al, 2005), Spondias L. (Almeida et al, 2007), and Acianthera Scheidw. (Oliveira et al, 2015), for example, have been karyotypically characterized based on their patterns of CMA/DAPI bands. Although analyses of CMA/DAPI banding patterns have been important in defining species and investigating karyotypic evolution, this technique has not been widely used in the Bignoniaceae.…”