Species distribution modelling and seed germination of four threatened snow lotus (Saussurea), and their implication for conservation

Abstract

Plant environmental envelops and seed regenerative traits of high altitude plants may contribute to competitiveness or endangerment under abiotic conditions that enforce a short growing season. Here, we investigate the factors threatening the existence of four, typical snow lotus species (Saussurea laniceps, S. medusa, S. quercifolia, S. gnaphalodes) endemic to the subnival belt of Southwest China at c. 4300 m a.s.l. Through species distribution modelling, we found that the potential areas of these four species would be reduced under future global climate change scenarios. However, their seed germination traits, in the laboratory and field, indicate that fresh seeds have valuable considerable plasticity, lacking deep physiology dormancy and having a wide thermal range for germination. Seeds of all species had low Tb (below 3 °C), and germinated relatively well between 5 and 20 °C (S. medusa) or 5–30 °C (S. laniceps, S. quercifolia, S. gnaphalodes). Dry after-ripening increased germination under alternating temperatures conditions for two species (S. quercifolia, S. gnaphalodes), but there was no light preference. Seed burial experiments suggested the species fail to form a persistent soil seed bank. Seeds could tolerate drying and storage at −20 °C and should be amenable to long-term seed banking. In conclusion, plasticity in the seed regeneration trait may counteract the projected narrowing of the species distribution range based on macro-environmental modelling. However, over-collection threatens opportunities for population adaptation and self-sustainability, indicating an urgent need to integrate in situ and ex situ conservation of snow lotus populations in the subnival belt of Southwest China.