Abstract:

The diversification of floral traits is the outcome of evolution by natural selection, and the variation in floral traits between species has a certain correlation with the plant habitats. The northern tropical karst seasonal rain forests have a great habitat heterogeneity, a complex structure of plant community, and abundant endemic components. Analyzing the relationship between the variation of plant traits and their habitats in those forests is helpful to understand species coexistence, coevolution and their adaptations to habitats, and to provide clues for revealing the ecological adaptability of plants and the maintenance mechanisms of biodiversity in karst forests. We conducted a preliminary study at a 15 ha plot of the northern tropical karst seasonal rain forest in Nonggang to examine the differences in floral traits among species and how these traits varied with habitats, when a relatively large number of woody plants bloomed synchronously, with a total of 21 species being found flowering. We divided the 21 species into three preferred habitat types (peak, slope and valley) according to the spatial distribution of species and their habitat associations, and analysed the differentiations among their floral traits. We also divided 21 species into three clustering groups of floral traits, and had a comparison between the habitat types and the clustering groups. The results showed that species dominance had a significantly negative correlation with flower size and flower color vividness, which indicated that it should be a favored trait for trees to have small flower size or unattractive flower color in the community. Only the flower color lightness was significantly different among the three types, while other flower traits were not significantly different. However, there was weak consistency between the three types and the three main groups, with 57.14% species overlapped , which showed that habitats had something to do with flower traits differentiations. In conclusion, we believe that the floral traits are closely related to the dominance of species and habitats in the northern tropical karst forest. Moreover, floral traits might be more deeply affected by habitats than pollination in this region.

Key words: flower size, flower color, trait combination, habitat, adaption, species dominance