Morphological and Citogenetics Studies in Genus Senna Series Aphyllae: Taxonomic and Evolutionary Implications.

FEDERICO OMAR ROBBIATI; RENÉE HERSILIA FORTUNATO; URDAMPILLETA JUAN DOMINGO

Congreso; XIX International Botanical Congress; 2017

Series Aphyllae Benth. belongs to the genus Senna Mill. (Leguminosae) and is comprised of xeromorphic shrubs and subshrubs, with deeply woody roots; the leaves of the adult branch are represented by minute triangular or sublobate scales; the stem is junciform, green, and photosynthetic. In this group the specific and varietal delimitation is still problematic due to the high morphological variation within and among taxa. We assessed the intra and interspecific variability using morphological and citogenetics analyses (in situ hybridization: FISH) to understand the patterns of morphological variation, phylogenetic relationships and to test hypothesis about speciation in the different specific group in series Aphyllae. Based on multivariate analyses two specific complexes were recognized: S. aphylla-S. pachyrrhiza and S. crassiramea-S. rigidicaulis complex. Our results, suggest that x = 12 is the basic number for series Aphyllae. Moreover, this series was revealed as a polyploidy group with 2n = 24, 48. The FISH revealed that in the polyploidy species there is not a missing of ribosomal sites indicating a recent origin of these polyploidy. Moreover, our results suggest that some underlying evolutionary mechanisms such as incomplete lineage sorting and/or reticulate evolution (hybridization and introgression) are shaping the relationships in Aphyllae. A broader cytogenetic survey of a more representative number of populations, along the geographic distribution of the series Aphyllae, should be done to address questions such as if the polyploidization is supported by environmental differences.