Sisyrinchieae

Abstract: New data on nectaries in Iridaceae are presented in combination with a literature review, in the context of systematics and pollination biology. Iridaceae are a highly diverse family with respect to nectar production, reflecting the wide range of pollination syndromes within the family. Based on outgroup comparison, presence of septal nectaries is probably the plesiomorphic condition for Iridaceae, despite their absence from the putatively basal genus Isophysis. Within Iridaceae, septal nectaries are present in the largest subfamily Crocoideae (Ixioideae) and also in Diplarrhena, which is putatively sister to all other Iridoideae, but absent from the rest of Iridoideae. Within the paraphyletic Nivenioideae (six genera), septal nectaries are absent from Aristea, Geosiris, and Patersonia and present in the three shrubby Cape genera Klattia, Nivenia, and Witsenia. Perigonal nectaries and elaiophores (oil-producing hairs) are mostly confined to the subfamily Iridoideae, where they take many different forms, although some Iridoideae lack nectaries entirely. In different species of Iris, nectaries are present either on the base of the perianth tube or around the base of the style, or sometimes in a continuous region between the two. In many other Irideae they are located at the bases of the outer tepals (most species of Moraea) or the bases of all six tepals (e.g., Ferraria). In Olsynium douglasii and O. junceum (Sisyrinchieae) nectar is apparently secreted directly from the filament column, and in Sisyrinchium subg. Sisyrinchium elaiophores are present on the lower part of the filament column. Perigonal nectaries may have evolved from septal nectaries by developmentally later formation of nectaries in a more distal position on organ primordia (i.e., heterochrony).

Abstract: Although the South AmericanIridaceae are cytologically diverse, three tribes are distinguishable on the basis of karyotype morphology. TheSisyrinchieae andTrimezieae have variable basic numbers, ploidy levels and chromosome sizes, while theTigridieae are characterized by a relatively uniform basic number and bimodal karyotype. Changes in chromosome size within genera may suggest fluctuations in their DNA amount with latitude and altitude, particularly inSisyrinchium. The results are considered in terms of opportunities for more detailed research.

Abstract: DNA barcoding aims to develop an efficient tool for species identification based on short and standardized DNA sequences. In this study, the DNA barcode paradigm was tested among the genera of the tribe Sisyrinchieae (Iridoideae). Sisyrinchium, with more than 77% of the species richness in the tribe, is a taxonomically complex genus. A total of 185 samples belonging to 98 species of Sisyrinchium, Olsynium, Orthrosanthus and Solenomelus were tested using matK, trnH-psbA and internal transcribed spacer (ITS). Candidate DNA barcodes were analysed either as single markers or in combination. Detection of a barcoding gap, similarity-based methods and tree-based analyses were used to assess the discrimination efficiency of DNA barcodes. The levels of species identification obtained from plastid barcodes were low and ranged from 17.35% to 20.41% for matK and 5.11% to 7.14% for trnH-psbA. The ITS provided better results with 30.61-38.78% of species identified. The analyses of the combined data sets did not result in a significant improvement in the discrimination rate. Among the tree-based methods, the best taxonomic resolution was obtained with Bayesian inference, particularly when the three data sets were combined. The study illustrates the difficulties for DNA barcoding to identify species in evolutionary complex lineages. Plastid markers are not recommended for barcoding Sisyrinchium due to the low discrimination power observed. ITS gave better results and may be used as a starting point for species identification.