摘要:
Sexual deception, entailing the pollination of flowers through mimicry of female insects, is one of the most remarkable pollination strategies to have evolved. This thesis explores two Australian sexually deceptive orchid systems with contrasting patterns of pollinator exploitation. The first three chapters focus on the genus Cryptostylis, a system with a unique case of pollinator sharing - five Australian species, four of which are largely sympatric, all deceive the same male ichneumonid pollinator. In Chapter One, mark-recapture experiments were used to investigate the consequences of ichneumonid pollination on pollen movement in C. ovata. A high pollinator revisitation rate indicated some potential for self-pollination. In Chapter Two, reproductive barriers contributing to the absence of hybrids between Cryptostylis species were investigated. Pre-pollination barriers, assessed in field experiments, did not prevent hybridisation. Hand cross-pollinations conducted among the four common Cryptostylis species in a greenhouse all produced fruits, however seed mass and the percentage of formed embryos were reduced in hybrids. Major differences in ploidy and chromosome number likely explain this post-pollination fitness reduction. Two Cryptostylis species were found to be self-incompatible, marking the first case of self-incompatibility in the Diurideae. The unique reproductive biology of Australian Cryptostylis, encompassing pollinator sharing, self-incompatibility, and post-pollination reproductive isolation driven by large ploidy differences, may indicate that its mode of diversification may differ greatly to those in other sexually deceptive genera. Chapter Three presents the first phylogeny to encompass both Australian and Asiatic Cryptostylis. An Australian origin of Cryptostylis is supported, with a likely single dispersal event to Asia. Ploidy variation and geographic barriers appear to have played a role in diversification across Cryptostylis. In Chapter Four, t