Cytological and genome size data analyzed in a phylogenetic frame: Evolutionary implications concerning Sisyrinchium taxa (Iridaceae: Iridoideae)

Abstract

Sisyrinchium is the largest genus of Iridaceae in the Americas and has the greatest amount of cytological data available. This study aimed at investigating how genomes evolved in this genus. Chromosome number, genome size and altitude from species of sect. Viperella were analyzed in a phylogenetic context. Meiotic and pollen analyses were performed to assess reproductive success of natural populations, especially from those polyploid taxa. Character optimizations revealed that the common ancestor of sect. Viperella was probably diploid (2n = 2x =18) with two subsequent polyplodization events. Total DNA content (2C) varied considerably across the phylogeny with larger genomes detected mainly in polyploid species. Altitude also varied across the phylogeny, however no significant relationship was found between DNA content changes and altitude in our data set. All taxa presented regular meiosis and pollen viability (> 87%), except for S. sp. nov. aff. alatum (22.70%), suggesting a recent hybrid origin. Chromosome number is mostly constant within this section and polyploidy is the only source of modification. Although 2C varied considerably among the 20 taxa investigated, the diversity observed cannot be attributed only to polyploidy events because large variations of DNA content were also observed among diploids.

Chromosome number, heterochromatin, and genome size support recent polyploid origin of the Epidendrum nocturnum group and reveal a new species (Laeliinae, Orchidaceae)

“…In addition to karyotype analyses, genome size data in taxonomically complex groups support delimitation of species and identification of natural hybrids (Kron et al 2007;Trávníček et al 2012;Burchardt et al 2018), including those with the same chromosome number and different ploidies, and intraspecific variation has has been found in Gymnadenia R.Br. (Orchidaceae; Trávníček et al 2012), Maxillariinae (Orchidaceae; Moraes et al 2017) and Sisyrinchium L. (Iridaceae; Burchardt et al 2018). However, in Epidendrum, genome size has rarely been studied and is known for less than 1% of the species (Jones et al 1998;Vega et al 2013;Marques et al 2014;Trávníček et al 2015;Pessoa et al 2020;Arida et al 2021).…”