Origin, evolution and conservation of Cycas panzhihuaensis and its relatives

摘要

In present paper, a species is considered as an information system and information of its ontogenetic program has been stored successively in cloned or reproductive cells. The phenotypic characters exhibited by a species are systematic records of interaction of genotype and environment on each other. The records, more or less, transmit historic information of systematic development and environmental changes in a given group of taxa. Considering information of characters from anatomy of ovule and seed of Cycas revoluta and Cycas panzhihuaensis, alternative theory of seed origin, peritelome tissue fusion, is developed to explain origin of the most primitive seed, rather than telome fusion theory. Based on evidence from fossil and molecular data, the time of origin and divergence of Cycas is estimated and from phytogenetic geography point of view, the place of origin and late migration between lands are discussed. Possibility of stem base with roots conserved as relict via catastrophe is discussed and finally measures of conservation of natural population of Panzhihua cycad are suggested.