Species and genetic diversity of Fagaceae in northern Thailand based on ISSR markers

The family Fagaceae in northern Thailand consists mainly of three genera: Castanopsis, Lithocarpus and Quercus, each with extensive diversity at species level. A study area of about 550 km(2) in Doi Saket district, Chiang Mai province was selected where Fagaceae can be found in different habitats and forest types. Samples were collected from 146 randomly selected trees: leaves, fruits (acorns) and flowers for taxonomic identification, and young leaves for molecular analysis. Based on the morphological characters, 30 species were identified from this collection. Twelve species of Castanopsis were discovered, with C. acuminatissima being the most dominant species especially in hill-evergreen forests. Eleven species of Quercus were found essentially at lower altitudes and mainly in deciduous dipterocarp forests, with Q. kerrii being the most common. Lithocarpus included seven species and the genus was found in all forest types. However, the most common species, L. harmandianus was found mainly in hill-evergreen forest with pine. Phenetic relationship among these species was analyzed using inter-simple sequence repeats (ISSR) markers. The results showed clear separation of the genera and of most species, supporting the taxonomic classification. Some Lithocarpus samples were found within the Castanopsis group. The study reported here is seen as the first step aiming at characterizing diversity of one of the most important tree families in a region where taxonomic diversity is large and mostly undescribed.