Preserving tororaro’s legacy: conservation genetics of in-situ and ex-situ populations of Muehlenbeckia astonii (Polygonaceae)

Abstract

ABSTRACT Tororaro, a Threatened Nationally Endangered species in eastern South Island and southern North Island, New Zealand, is primarily found in coastal or lowland droughty habitats with small, isolated populations, notably the largest on Kaitōrete Spit, Canterbury. Due to recent issues with the conservation management of the Kaitōrete Spit population, the importance of protecting this species has been highlighted. While widely cultivated in gardens for its horticultural appeal and resilience, recruitment failure in wild populations and the genetic structure and variation within wild and cultivated populations is unknown, which raises questions about in-situ and ex-situ conservation strategies. Microsatellite markers were developed to assess the level of natural variation present in wild populations and that of cultivated material present throughout New Zealand. The results reveal natural populations can be grouped into three clusters with a low to medium level of diversity for each cluster (Na = 1.647–3.647, Ho = 0.194–0.457, He = 0.181–0.478), and the diversity of each group is captured in cultivation (Na = 2.471–3.588, Ho = 0.207–0.511, He = 0.173–0.519). Cultivated material largely follows ecosourcing guidelines whereby cultivated plants in Wellington, Marlborough and Canterbury are often sourced from the regional meta-population, however, there are some exceptions that have implications for management of this species. In Otago, where M. astonii does not naturally occur, cultivated populations comprise representatives of all regional populations. An interesting outcome is that we recovered from among the cultivated plants several individuals that are likely to be putative intraspecific hybrids between plants from Wellington populations and those from either Marlborough or Canterbury; these hybrid genotypes are unknown in wild populations. Clonal plants were also represented among the wild and cultivated populations by individual plants having identical genotypes. We also demonstrate the utility of these markers across other Muehlenbeckia species.