Evolutionary and Systematic Studies in South American Endemic Genus Tristagma (Amaryllidaceae)

SASSONE, A. B.

Shenzhen

Congreso; XIX International Congress of Btoany; 2017

IBC Congress Secretariat

Subfamily Allioideae is one of three in family Amaryllidaceae (Chase et al. 2009), and of great economic importance. The closest relatives of Allium L. in South America are represented by the endemic genera of the tribes Gilliesieae and Leucocoryneae. The tribe Leucocoryneae includes 6 genera exclusively distributed in South America, except of Nothoscordum, which is widespread in South America with one species occurring in North America. Most of the genera have presented a controversial taxonomy and species and genus delimitation has been considered problematic. Tristagma was described by Poeppig (1833: 369) with Tristagma nivale Poepp. as type species. Circumscription of Tristagma species has been a source of confusion for various reasons; e.g., generic concepts, nomenclatural inconsistencies, and doubtful species. The aim of this research is to present a multidisciplinary study of Tristagma, in order to define the number of species, contributing to a better knowledge of the subfamily Allioideae in South America, based on morphological, phylogenetic, a complete bibliographic and taxonomic revision, and geographical distribution analyses.Phenetic analyses were performed including 200 specimens of Tristagma on the base of 60 vegetative and reproductive morphological characters. The multivariate analyses performed distinguish 3 complexes of species and morphological characters to define species could be distinguished.Fifty-seven specimens representing species of Tristagma and allied genera were examined. Three molecular markers were sequenced and analyzed individually and combined by Parsimony and Bayesian inference analyses to elucidate relationships within Tristagma and related groups. Exploring molecular marker ITS, Tristagma resolve as monophyletic, when analyzing cpDNA phylogenetic hypothesis the position of Tristagma is not defined, and the combined analyses support Tristagma as paraphyletic being necessary the inclusion of Ipheion to be considered as a monophyletic genus. Also, the optimization of DNA content shows genome size variation among Leucocoryneae genera.As a result of phenetic and phylogenetic studies, the bibliographic compilation, the identification of different species with fresh material and the study of available herbaria specimens of Tristagma kept at American and European herbaria, it is concluded that the genus is composed by 12 species and characterized by uni or plurifloral inflorescences, flowers with fused tepals forming a tube, and staminal filaments disposed in two series.Also, preliminary biogeographic studies were conducted in order to define the environmental requirements of the different species of Tristagma. Specimens of all available species, covering the entire range of distribution of the genus, where georeferenced. Bioclimatic variables and altitude from the WorldClim dataset were associated with each locality of the studied specimens. By the correlation of climatic and geographical information it is concluded that precipitation and temperature of the coldest season are modeling the actual distribution of Tristagma species.