Evolutionary studies in Iris series Californicae.

摘要

Cladistic analyses of Iris included 18 ingroup taxa from series Californicae and two outgroup taxa from series Sibiricae. The analysis based on 29 morphological characters resulted in three most parsimonious trees of 78 steps, one of which had the topology of the strict consensus tree. The internal transcribed spacers and the 5.8S subunit of 18-26S nuclear ribosomal DNA were sequenced to provide additional phylogenetic information. An analysis of DNA data resulted in a single most parsimonious tree that concurred in part with the morphology based consensus tree. The long floral tube and short floral tube groups in series Californicae that have been informally proposed by previous workers were found to be polyphyletic. Iris tenax is polyphyletic and I. hartwegii may be paraphyletic or polyphyletic as currently delineated. Support for internally resolved clades is low with DNA data, probably due to high levels of homoplasy along some branches. Sequence divergence is high compared to other infrageneric plant groups and narrow endemics have high numbers of unique autapomorphies, indicating that Iris series Californicae may be a relatively old plant group. The inclusion of taxa of proposed hybrid origin (I. hartwegii subsp. pinetorum, I. h. subsp. columbiana and I. thompsonii) did not increase the homoplasy present on the morphology based tree nor did it effect the analysis outcome. Evidence is presented for reticulate evolution involving I. purdyi.;Embryology and reproduction was investigated in two varieties of Iris tenax. Ovule development, including megasporogenesis and initial stages of megagametogenesis, occurs while flowers are still in bud. Final maturation of the seven-celled embryo sac occurs during the male phase of flowering. An earlier report that synergids persist after fertilization, and that nucellar nuclei migrate into the developing megagametophyte was not supported in this study. Reproductive studies used three pollination treatments: outcrossing, selfing and interspecific crossing. Treatment results were compared with results from open pollination. Both varieties of I. tenax are self-compatible and interfertility is less than intrafertility. Fewer than 6% of I. t. var. gormanii ovules develop into seeds. Hand pollinations improve reproductive success suggesting that pollen may be limiting.