Specific pollinators reveal a cryptic taxon in the bird orchid, Chiloglottis valida sensu lato (Orchidaceae) in south-eastern Australia

Abstract

Orchid species belonging to the sexual-deception pollination syndrome exhibit highly specific, usually one-to-one, relationships with their pollinators. This specificity is mediated by the orchid’s mimicry of the sex-attractant pheromones emitted by females of the pollinator species. Chiloglottis valida D.Jones sensu lato is a widespread, sexually deceptive, terrestrial orchid found in south-eastern New South Wales, and eastern and southern Victoria from sea level to at least 1600 m in the Australian Alps. Flowers from 38 C. valida s.l. populations from throughout this area were compared in field choice experiments for the specificity of attracted pollinator species. Four potential pollinator wasps in the thynnine genus Neozeleboria Rohwer were attracted. The data demonstrate the existence of two attractant odour types among C. valida s.l. and its pollinators, and support the recognition of two partially sympatric cryptic species in the orchid, each with two potential pollinators. The copheromone pollinator pairs replace each other on the altitudinal gradient, albeit with some overlap. In alpine areas the pollinators of the two cryptic orchid species are themselves sibling species within Neozeleboria monticola Turner s.l. The results indicate that C. aff. valida, the sister species of C. valida s.s., has two geographically replacing pollinators.