Comparative Reproductive Biology of Two Sun-Orchids; the Vulnerable Thelymitra circumsepta and the Widespread T. ixioides (Orchidaceae)

Abstract

Two morphologically similar Sun-orchid species, Thelymitra ixioides Sw. and T. circumsepta Fitzg. were studied with respect to their reproductive ecology. Breeding systems were found to contrast strongly. In this study the widespread, T. ixioides is insect pollinated and encourages xenogarny by relying on native Lasioglossum and Exoneura bees for pollination. In contrast, the vulnerable and restricted T. circumsepta was found to autopollinate. These two species differ in floral display and reproductive efficiency. These breeding systems are discussed in relation to the life histories of the two species.