Seeds of the nationally endangered shrubby tororaro (Muehlenbeckia astonii) are surprisingly long-lived, research by Moa’s Ark Research ecologist Dr Debra Wotton shows. Shrubby tororaro seeds buried in the soil at Kaitorete Spit in Canterbury can survive for at least four years, although most seeds die within two years. Plants with long-lived seeds can form a soil ‘seed bank’ and disperse their seeds in time, as well as space. A soil seed bank increases seed supply in years with poor seed production, and could buffer small, isolated populations of shrubby tororaro from local extinction, at least in the short term.
Germination of shrubby tororaro seeds was high, especially when seeds were chilled for at least two weeks. In the wild, shrubby tororaro seeds are produced in late summer and autumn, and experience cold temperatures during winter before germinating in spring. A cold period is probably a cue to seeds that conditions will soon be favourable for seedling establishment.
Shrubby tororaro is failing to regenerate in the wild – there are no seedlings and almost no young plants. Seed viability does not appear to be limiting the regeneration of shrubby tororaro at Kaitorete Spit. Shrubby tororaro can resprout, which decreases its dependence on seed for local persistence. However, there may be a trade-off between resprouting and regeneration from seed, making shrubby tororaro vulnerable to any increases in adult mortality. In the face of extensive habitat loss and modification, and ongoing adult mortality (including the recent destruction of several hundred plants at Kaitorete Spit), shrubby tororaro’s lack of regeneration threatens its persistence. Further research is urgently needed on shrubby tororaro regeneration in the wild.
You can read more about this research in the scientific paper published in the latest issue of New Zealand Journal of Botany.