Defining conservation units in a complex of morphologically similar, sexually deceptive, highly endangered orchids

Abstract

In plants, rapid speciation attributed to pollination strategy is unlikely to lead to obvious morphological traits for identification or large genetic differences among populations. The species-rich Australian orchid genus Caladenia contains numerous taxonomically difficult species complexes, including the reticulata complex comprising 37 species, many of which are highly endangered with narrow-range geographic distributions as a consequence of severe habitat loss. Here, we test morphological species delimitation in the reticulata complex with a multigene phylogenetic analysis, detailed population genetic analysis and comprehensive data on specific sexually deceived pollinators of species within the complex. Phylogenetic analysis revealed limited species-level resolution within the reticulata complex and no difference between species with different pollinators. Microsatellite data confirmed this result for Victorian populations of the reticulata complex but revealed significant isolation by distance between Victorian and South Australian populations. Pollinator preference tests indicated that 10 reticulata complex morphospecies all shared the thynnid wasp pollinator Phymatothynnus nitidus, yet the microsatellite analysis revealed only limited differentiation between those and three species within the reticulata complex shown to employ different pollinators. The combined molecular and ecological approach revealed that morphospecies that share the same pollinator are likely to be the same biological species. Conservation and taxonomic focus should shift from a ‘microspecies’ approach to capturing key populations across the geographic range of the Caladenia reticulata biological species which will greatly assist the allocation of limited conservation resources.