Chromosome Number and Genome Size Evolution in Brasolia and Sobralia (Sobralieae, Orchidaceae)

Abstract

Despite the clear circumscription of tribe Sobralieae (Orchidaceae), its internal relationships are still dubious. The recently delimited genus Brasolia, based on previous Sobralia species, is now assumed to be paraphyletic, with a third genus, Elleanthus, nested in it. The morphology of these three genera is significantly different, indicating the necessity of new data for a better genera delimitation. Though morphology and molecular data are available, cytogenetics data for Sobralieae is restricted to two Sobralia and one Elleanthus species. Aiming to evaluate the potential of cytogenetic data for Brasolia-Elleanthus-Sobralia genera delimitation, we present chromosome number and genome size data for 21 and 20 species, respectively, and used such data to infer the pattern of karyotype evolution in these genera. The analysis allowed us to infer x = 24 as the base chromosome number and genome size of average 1C-value of 5.0 pg for the common ancestor of Brasolia-Elleanthus-Sobralia. The recurrent descending dysploidy in Sobralieae and the punctual genome upsize suggest a recent diversification in Sobralieae but did not allow differing between Brasolia and Sobralia. However, the basal position of tribe Sobralieae in the subfamily Epidendroideae makes this tribe of interest to further studies clarifying the internal delimitation and pattern of karyotype evolution.

Taxonomic revision of Sobralia section Racemosae Brieger (Sobralieae, Orchidaceae)

“…The inflorescence contains several flowers at various stages of growth, with the youngest ones on its top. The distinct morphology is supported by the results of the molecular study, which can be seen in the phylogenetic trees (Neubig et al, 2011;Baranow et al, 2017). Also, the karyotype evolution analysis with the phylogenetic study as the background (Baranow et al, 2022) as well as niche conservatism and ecological tolerance evolution study (Kolanowska et al, 2022) have confirmed the consistency of the group.…”

“…The distinct morphology is supported by the results of the molecular study, which can be seen in the phylogenetic trees (Neubig et al, 2011;Baranow et al, 2017). Also, the karyotype evolution analysis with the phylogenetic study as the background (Baranow et al, 2022) as well as niche conservatism and ecological tolerance evolution study (Kolanowska et al, 2022) have confirmed the consistency of the group. Thus, the section appears to be welldefined and distinct from the other groups of the genus.…”

“…However, the development of molecular methods revealed that the nominal section of Sobralia is more closely related to other genera of Sobralieae than to the remaining groups of Sobralia. As the nominal section is also different in the morphological characters, such as branching and often lateral inflorescence, it was elevated to the rank of a separate genus Brasolia (Baranow et al, 2017, see also Dressler et al, 2011;Neubig et al, 2011).…”

Karyotype analysis in nine <i>Uraria</i> Desv. and <i>Christia</i> Moench (Fabaceae: Papilionoideae) species from China

“…However, inconsistency between this study and previous studies also existed, such as C. vespertilionis (2n=20) which was previously reported as 2n=22 (Goldblatt 1981), and U. picta (2n=22) was previously reported as 2n=16 (Löve 1977) or 2n=22 (Gill and Husaini 1986). Intraspecific variation in chromosome numbers is common in angiosperms due to population diversity (Moraes et al 2012), synonyms (Moraes et al 2012), dysploidy (Moraes et al 2017, Baranow et al 2022, and ancient hybridization (Almeda and Chuang 1992).…”