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.

Lessingianthus plantaginoides (Vernonieae, Asteraceae) is a small natural tetraploid shrub that inhabits rocky highlands from South America. The population studied inhabits and covers an extensive region of a private reserve with high local biodiversity and animal and plant endemisms. With the purpose of providing insights into the cyto-embryology of this tetraploid species, the aims of this study were: to perform an ontogenetic study of the male and female gametophytes of L. plantaginoides; to carry out detailed meiotic analysis and evaluate the fertility of this species; to document and provide highlights on taxonomic implications of their reproductive aspects. Lessingianthus plantaginoides presented the following male and female gametophyte traits: dicotyledonous type of anther wall development, tetrahedral tetrads, 3-celled mature pollen grains; development of the chalazal megaspore, monosporic embryo sac and Polygonum type of megagametophyte development. The meiotic behavior was regular, the spores were tetrads of equal size and the pollen grains were highly stainable. Lessingianthus plantaginoides is a highly diplodized autotetraploid that reproduces sexually and has high meiotic regularity; which is apparently responsible for its colonization potential. It now seems certain that polyploid speciation plays a significant role in the establishment and diversification of the genus.