Germination behaviour and desiccation tolerance of Coprosma (Rubiaceae) seeds from a remote oceanic island

Abstract

Seed banking can be an efficient approach to conserve plant species ex situ . Research into the suitability of long-term seed banking for (sub)tropical species is limited and urgent, especially for taxa with limited distributions such as those endemic to oceanic islands. Here, we combine a stepwise experimental methodology with non-parametric and survival analyses to assess the germination requirements and desiccation tolerance of three species of Currant Bush Coprosma (Rubiaceae) from Lord Howe Island, a remote island in the South Pacific. All species germinated best under temperatures equivalent to submontane spring/autumn conditions, consistent with temperatures during ripe fruit dispersal. Although warmer temperatures inhibited germination in all species, the species with the broadest elevational range was the least affected. Consistent with the wider literature, we found a negative relationship between seed size and drying tolerance, with the larger seeds of Coprosma huttoniana and C. ptotopetra sensitive to the drying required for conventional seed banking, while the smaller seeds of C. lanceolaris were tolerant and potentially bankable for long-term conservation.