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.