Ecological Differentiation In Mosla Species

Mosla (Benth.) Buch.-Hamilt. Ex Maxim. is a small genus (Lamiaceae) ranging from the west-Himalayas eastwards to Japan, and from the Far East of Russia southwards to Indonesia. Its speciation patterns are the key objective. The present dissertation reports the results of three-year-period ecological differentiation studies on this genus. Intensive field surveys and observation were conducted and thereafter 36 plots were sampled. The common garden experiment was made, and control experiments of soil water availability, light intensity and different nitrogen forms were made. Morphological, anatomical, physiological traits and biomass yield of seven Mosla species were measured. Based on all results, the habitat differentiation patterns, the major functional traits of ecological differentiation, adaptive capability of future climate changes, and speciation patterns were investigated in detail.1) Differentiations of species distributions along environmental gradients and phenotypic specialization help explain the co-presence of seven Mosla species that might otherwise be expected to competitively exclude one another. Field investigation results showed each of the seven species appeared to have a unique realized niche, when niche dimensions were defined by soil moisture, gradients in soil texture, soil fertility and light. The species also differed in how broadly or narrowly they were distributed along each gradient. Some species were practically never found in the same sites, whereas others co-occurred with a high frequency, in spite of showing clearly different abundance patterns among sites. 2) The data of control experiments of soil water availability and light intensity show significant morphological and physiological differentiation among the closely related species of Mosla. There is clear evidence for ecological sorting among the Mosla species as species partition environmental gradients more than expected by chance, and most functional traits of species correspond to species distributions as predicted based on a priori understanding of trait function. Across phylogenetic lineages, species showed evolutionary convergence in function and habitat preference. By contrast, leaf-level traits were conserved within phylogenetic lineages and were not well correlated with local habitat factors, but rather with the broader geographic distributions.3) Human intervention in the nitrogen cycle is presently adding more reduced nitrogen to the biosphere as the result of intensive agricultural activities. N input has more than doubled since the 1950s in many areas. This additional N input has led to the N saturation of many natural ecosystems and has affected species composition, forest contraction, while phenomena as important as large-scale forest decline have been linked to anthropogenic NH4~+ input and associated soil acidification. In order to determine the effects of nitrogen forms on Mosla species, the control experiment of different proportion of nitrogen forms was conducted. Mosla species had different response to different proportion of nitrogen forms. With the treatment of different proportion of nitrogen forms, morphological, physiological and growth characteristics of Mosla species differentiated. And species RGR (relative growth rate) were well correlated with their function traits. Mosla pauciflora can survive from complete ammoniac nitrogen form treatment, and RGR was great with the high proportion of ammoniac nitrogen form treatment. Form this we can see that Mosla pauciflora can well adapt the future environment of high ammoniac nitrogen. However, other five species showed evident symptoms of NH4~+ toxicity (eg: the chlorosis of leaves and the overall suppression of growth and so on) with high proportion of ammoniac nitrogen form treatment. These data show the other five Mosla species can not well adapt the future environment of high ammoniac nitrogen.