A Study On The Phylogenetics Of Petrocodon S. L.(Gesneriaceae)

Petrocodon s.l., a genus in the subfamily Cyrtandroides of Gesneriaceae, was involved merge the8genera of the original classification system in recent research results. These genera are Petrocodon, Paralagarosolen, Calcareoboea, Tengia, Dolicholoma, Lagarosolen, Didymocarpus, and Wentsaiboea. The systematics of Petrocodon s.l. was discussed base on evidences from gross morphology, leaf epidermal micromorphology and molecular character. The results were summarized as follows:1. Anatomy of leavesThe leaf of14species in Petrocodon s. l. and5species in Primulina s.l. were studied. It is shown that the leaf epidermal cells are usually irregular or polygonal in shape. The patterns of anticlinal walls are straight, arched or undulate. The stomatal apparatuses are anisocytic type and are usually found on abaxial, not adaxial, epidermis. The results show that:The leaf epidermal cells, patterns of anticlinal walls, stomatal index and stomatal distribution pattern of these leaf epidermal characters have important taxonomic and phylogenetic significance. The characters of transverse anatomic leaf structures were observed, include leaf thickness, leaf epidermal thickness, vascular bundle number, leaf palisade tissues and spongy tissues thickness. We found that the evolution of these characters is difficult to trace, but some of them can be used as diagnostic characters.2. Molecular of systematicsBased on DNA sequence data from nuclear ribosomal ITS and chloroplast trnL-F space for19species of Petrocodon s. l. and14species of other genera in Gesneriaceae, the phylogeny of these genera was investigated. Molecular data were analyzed using Bayesian, Maximum Parsimony (MP) and Maximum Likelihood (ML) methods. The results show that Petrocodon s. l. is divided into three clades. Monophyly of the three clades had some of the morphological and anatomical evidence to support. The sister relationship of Lagarosolen hispidus and Didymocarpus niveolanosus got higher support. The resolution of the second clade is poor. Petrocodon dealbatus, Lagarosolen coriaceifolium, Tengia scopulorum, Petrocodon multiflora and Petrocodon ferrugineus form a subclade, which has also been supported by morphological and leaf anatomical characters. The third clade included Lagarosolen integrifolius, Paraisometrum fangianum, Lagarosolen lui and Wentsaiboea tiandengensis. Their close relationships are supported by anatomical characters. Three suspected new species are nested in Petrocodon s. l., but the resolution about them is poor and their phylogenetic positions are still unclear. Further researches are needed to do from the morphology, anatomy and other aspects.