The origin of the flower is considered one of the most important innovations resulting in the diversity of plant forms present on earth today. The flower components of a typical are flattened and two-dimensional. However, in crested Iris species, the flower components have perpendicular growth giving rise to a three-dimensional, elaborately colored, and fringed flower. The development of this novel, yet morphologically diverse flower, will be studied in an evolutionary context. The study of spatial and temporal factors within the floral bud will examine how novel structures evolve in relation to other floral organs through integrative evolution.
This project will provide information and models for studies on the evolution of novel structures, the genetic bases for development of floral organs, and pollinator-plant interactions. This research will enhance knowledge on the development of the showy crest found in Iris and other floral organ elaborations that are prized in horticulture. Fieldwork will include researchers and graduate students at one USA and three Chinese plant science institutions and will provide an opportunity to inform local Chinese of the importance of conservation of rare Iris species.
One of the most intriguing aspects of angiosperms is the diversity of its flowers. These diversities not only come from variations in flower color, shape, size etc. but also come from the evolution of novel floral characters. The flower components of a typical sepal/petal are flattened and two-dimensional. However, in crested Iris species, the flower components have perpendicular growth giving rise to a three-dimensional, elaborately colored sepal with crest. This novel, yet morphologically diverse floral structure was studied within a phylogenetic context in Iris. This project investigated the morphological, structural, and developmental of sepal crest using dissecting, light, and scanning microscopy. Spatial and temporal factors giving rise to this novel structure were also explored by comparative studies of the flower buds of both crested and non-crested species at different developmental stages. The phylogenetic study indicates that there are at least five independent origins of sepal crest in Iris, which will lead to a taxonomic revision of the traditional polyphyletic subgenus Limniris section Lophiris (rihizomatous crested species). The anatomical studies of the mature morphologies of sepal crests provides a detailed review of morphological diversities of sepal crests in Iris, a formal classification and terminology for sepal crests, and a clarification of the differences between sepal ridge and sepal crest, which was ambiguously used in Iris monographs. The developmental study contributes to a better understanding of the origin of phylogenetic diversification, the timing and mode of dissimilarity or discontinuity and the process of evolutionary innovation. The anatomical study of flower buds of crested and non-crested species provides evidence for an integrative evolution in which all four floral whorls were involved. The findings of this project provided resource information for plant systematics, evolutionary biology and Evo-devo. The results of this study demonstrated that sepal crests could serve as models to study: 1) genetic bases for the development of adaxial meristem of leaf homologues, 2) the establishment of polarity in plant lateral organs, 3) the developmental bases of modifications that contribute to elaborations of floral organs, and 4) the physiological and ecological interactions between plants and pollinators. This project provided the co-PI extensive research experience such as conducting fieldwork, learning lab techniques, analyzing data, preparing and submitting manuscripts and presenting at professional meetings. Fieldwork included researchers and graduate students at three major plant science institutions in China. DNA sequence data generated in this study was uploaded to online databases; specimens collected in fieldwork were deposited in Chinese and USA herbaria, and seeds and living collections were shared with the Beijing Botanical Garden (PRC) and Rancho Santa Ana Botanic Garden (USA). Crested Iris species are showy and horticulturally important. Photographic images were shared with the Species Iris Group of North America (SIGNA) database and CAW’s research website — both open access websites. Fieldwork in China informed the local Chinese people of the importance of conservation of rare Iris species.
