Airborne and belowground phytotoxicity of invasive Ageratina adenophora on native species in Nepal

Plant Ecology - Volatile compounds from leaf litter of invasive alien Ageratina adenophora are known to inhibit growth of native species in sub-tropical Asia, but there is not...     

Liparis rubescens sp. nov. (Orchidaceae) from Thailand

In the context of an ongoing revision of the orchid genus Liparis in Thailand, we describe and illustrate a new species under the name L. rubescens Tetsana, H. A. Pedersen & Sridith. Morphologically, it is particularly similar to L. dumaguetensis Ames from the Philippines, but it differs in the shape of the lateral sepals and in several characters of the labellum. Among the Liparis species already known from Thailand, L. atrosanguinea Ridl. bears a certain resemblance to the new species, but not so much as to make misidentifications likely. So far, L. rubescens is only known from Khao Nan National Park in the southern Thai province of Nakhon Si Thammarat, but we suggest that it should also be searched for in other parts of peninsular Thailand, southernmost Myanmar and Peninsular Malaysia.     

Argostemma fasciculata (Rubiaceae), a new species from Cambodia

A new species of the genus Argostemma (Rubiaceae) from Cambodia is described and illustrated. Its relations is discussed.     

How does sampling strategy influence detection of morphological variation in orchids? A case-study of the epiphyte Oberonia hosseusii

Effects of sampling strategy on detection of morphological variation were studied in the epiphytic orchid Oberonia hosseusii in Thailand. We compared the different effects of local versus regional sampling on the one hand and the size of local samples on the other. A local data set was collected by sampling a natural population on Doi Inthanon, during which process a preservation experiment was made. A regional data set was established by measurement of 18 preserved specimens from 12 different localities. Based on the preservation experiment, data from the regional sampling were calibrated (whenever needed) to make the two data sets more directly comparable. Heat drying and spirit preservation significantly influenced measurements for two mutually exclusive sets of characters. Increasing the local sample size from 18 to 52 individuals had no statistically significant effect on the mean value of any character. In contrast, local versus regional sampling significantly influenced the mean value of every character, virtually irrespective of local sample size. In the regional data set only, a difference was found in overall variability in vegetative versus floral characters. Three cluster analyses with equal representation of individuals from the local and regional samples were performed using different clustering techniques. Only in the analysis using neighbour-joining did pure “local clusters” prove to be significantly larger than pure “regional clusters”, suggesting that this clustering technique is particularly sensitive to effects from sampling strategy.     

Character intercorrelation and the potential role of phenotypic plasticity in orchids: a case study of the epiphyte Liparis resupinata

Character intercorrelation was studied in a natural population of the epiphytic orchid Liparis resupinata in northern Thailand, and patterns of morphological variation in relation to the local growth environment of individual plants were mapped. Massive occurrence of character intercorrelation was detected, but clone size only influenced few characters of individual flowering shoots. Variation in vegetative and floral organs was largely independent, but two cases differed from the general pattern: (1) the only character not defined by size (distance between apices of lateral sepals) exhibited largely independent variation; (2) ovary length was positively correlated with nearly all other characters. Major groups of vegetative and floral characters were found to covary with different combinations of ecological parameters. Although our study does not document the existence of phenotypic plasticity in L. resupinata, the overall patterns observed would be congruent with a scenario involving phenotypic plasticity. No positive correlation between variability and apparent morphological susceptibility to environmental influence was found; but floral characters were generally less variable and covaried with more ecological parameters than vegetative characters. Based on our observations, we make a few methodological recommendations for morphometric studies of species complexes.     

Oberonia pygmaea sp. nov. (Orchidaceae) from Thailand

In the context of an ongoing revision of the orchid genus Oberonia in Thailand, we describe and illustrate a new species under the name O. pygmaea Bunpha, H. A. Pedersen & Sridith. Vegetatively, the tiny new species is particularly similar to O. rufilabris Lindl. (widespread in mainland southeast Asia, including Thailand), whereas its floral morphology comes closest to the much larger O. costeriana J. J. Sm. from Sumatra, Java and Sulawesi. So far, O. pygmaea is only known from Pang Ung in the northern Thai province of Mae Hong Son, but we suggest that it should also be searched for in hill evergreen forest in adjoining parts of the Dawna Range, both in Thailand and Myanmar.     

Four new species, a new variety, and a status change in Argostemma (Rubiaceae) from Thailand

Four new species of Argostemma , all endemic to Thailand are described: A. thaithongae , restricted to northern Thailand; A. monophyllum , rather widely distributed in the easern half of Thailand: A. puffii and A. routundicalyx , both endemic to peninsular Thailand. Var. variabile is a new variety of the peninsular Thailand, species A. lobulatum. A. setosum , previously thought to be an endemic species of peninsular Thailand, is now considered to be a subspecies of A. laeve (Malay peninsula and Sumatra): A. laeve subsp. setosum , stat. nov.