Are small populations larger than they seem? Genetic insights into patchily distributed populations of Drakaea glyptodon (Orchidaceae)

Abstract

Abstract Many orchids are characterized by small, patchily distributed populations. Resolving how they persist is important for understanding the ecology of this hyper-diverse family, many members of which are of conservation concern. Ten populations of the common terrestrial orchid Drakaea glyptodon from south-western Australia were genotyped with ten nuclear and five plastid simple sequence repeat (SSR) markers. Levels and partitioning of genetic variation and effective population sizes (Ne) were estimated. Spatial genetic structure of nuclear diversity, together with plastid data, were used to infer the effective number of seed parents per population. We found high genetic diversity, Ne values that generally exceed predictions based on the number of flowering individuals and moderate levels of gene flow. Two populations were founded by less than five colonists suggesting some populations are colonized by few seeds, with growth largely resulting from in situ recruitment. A value of 3.65 for mp /ms indicates that pollinators play a greater role than seed in introducing genetic diversity to populations via gene flow. Our results highlight that D. glyptodon is highly effective at persisting in patchily distributed populations. However, it is important to examine how insights from this common, widespread species transfer to species that are rare and/or occur in fragmented landscapes.