Cytotaxonomy and geographic distribution of cytotypes of species of the South American genus Chrysolaena (Vernonieae, Asteraceae)

Abstract

Understanding speciation and biodiversity patterns in plants requires knowledge of the general role of climate in allowing polyploids to escape competition and persist with their diploid progenitors. This is a particularly interesting issue in widespread species that present multiple ploidy levels and occur across a heterogeneous environment. Chrysolaena (Vernonieae, Asteraceae) is a cytogenetically very diverse genus, with significant interspecific and intraspecific ploidy level variation and with continuous distribution across South America. No previous studies have summarized chromosome count data of Chrysolaena or addressed the cytogeography of the genus. Ploidy level of Chrysolaena species was determined by chromosome counting during mitosis and/or meiosis; the geographic distribution of cytotypes was examined and the correlations between the distribution of particular cytotypes and current ecological conditions were evaluated. A total of 43 new chromosome counts and five ploidy levels (2x, 4x, 6x, 7x, 8x) were reported. The chromosome number of C. cordifolia (2n ¼ 7x ¼ 70) and a new cytotype for C. propinqua var. canescens (2n ¼ 4x ¼ 40) are reported for the first time. Three geographic areas with high diversity of cytotypes and species were detected. The results obtained do not suggest a clear distribution pattern that depends on climatic factors for Chrysolaena populations. However, a geographic pattern was identified in the distribution of ploidy levels, with diploid species presenting a more restricted distribution than polyploid species.

Aneuploidy promotes intraspecific diversification of the endemic East Asian herb Lycoris aurea complex

“…Cytogeographic patterns may reveal significant amounts of diversity by identifying multiple chromosomal races among related species or within a single taxonomic species and, therefore, contribute to the conservation of rare species and ecological restoration ( Soltis et al, 2007 ; do Pico et al, 2019 ). The cytogeographic data obtained allowed us to find a clear distribution pattern, since the two most frequent cytotypes, II and IV, occupy different areas and do not co-exist in the same area.…”

“…Variations of karyotype and chromosome number, such as polyploidy and aneuploidy, can drive genomic novelty and intraspecific diversification and act as a mode of immediate and sympatric species ( Soltis et al, 2015 ; do Pico et al, 2019 ). Unrecognized cytotype variation can lead to an underestimation of species richness ( Soltis et al, 2007 , 2010 ).…”

Como a variação no número cromossômico pode indicar relações evolutivas entre a Caatinga, o Cerrado e a Mata Atlântica?

“…Polyploids have also been hypothesized to be better adapted to harsh environments than diploids (Hagerup 1931). Comparisons between diploids and natural or synthetic polyploids have shown that polyploids are more tolerant to water deficit Maherali et al 2009;Deng et al 2012;Hao et al 2013), salinity (Chao et al 2013), environments that are xeric (Ramsey 2011), extremely cold Brochmann et al 2004;Deng et al 2012) or extremely hot (Zhang et al 2010;Thompson et al 2014), have wider geographic ranges (Tuler et al 2019;Via do Pico et al 2019) and greater ecological plasticity and invasiveness (Rejlová et al 2019). Polyploidy can also lead to flower morphological differentiation and alter plant-pollinator interactions (e.g., .…”