Niche conservatism, divergence and polyploidy in genus Senna series Aphyllae (Leguminosae: Caesalpinioideae) from arid zones of South America

FEDERICO OMAR ROBBIATI; CORDOBÉS, FERNANDO MORO; RENÉE HERSILIA FORTUNATO; ANTON, ANA MARÍA; URDAMPILLETA JUAN DOMINGO

BOTANICAL JOURNAL OF THE LINNEAN SOCIETY

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2022

0024-4074

This paper aims to integrate cytogenetic and ecological approaches into a phylogenetic framework to better understand the evolution and systematics of the series Aphyllae, an endemic group of arid and semiarid regions of South America. We counted the chromosome number at population level in three species of the series Aphyllae using a conventional technique (GIEMSA) and in situ hybridization (FISH). Phylogenetic reconstructions and inference of chromosome evolution were based on four cpDNA regions and one nuclear marker. A principal component analysis was carried out using environmental data. Finally, ecological niche models (ENM) were implemented i) to recognize the abiotic factors that constraint the potential geographic distribution of the series Aphyllae and ii) to understand the ecological drivers for species diversification. Basic chromosome number is x = 12. Senna aphylla presented three cytotypes with 2n = 24, 48, and 60, and S. pachyrrhiza two cytotypes with 2n = 24 and 48. Senna crassiramea appeared to be polyploid with 2n = 48. In the diploid Senna pachyrrhiza cytotype, two 45S and three 5S rDNA sites were reported and for tetraploid S. crassiramea, four 45S and four 5S rDNA sites. The ENM and ecological speciation tests suggest that in the series Aphyllae several species experienced speciation associated with conservatism and others with niche divergence. Our results contribute to the evolutionary knowledge of Neotropical legumes, and the understanding of a driver of diversification in arid regions in South America.