Sensitivity of seed germination to temperature of a relict tree species from different origins along latitudinal and altitudinal gradients: implications for response to climate change

Abstract

Seeds of a relict tree species collected from high latitudes were more sensitive to temperature and warming could accelerate germination. Seed germination is a crucial process in a plant life cycle and is highly vulnerable to environmental change. Studying among-population variation in seed germination in response to environmental and geographic gradients is an important tool, allowing us to understand how plants adapt to different environmental conditions and to predict population dynamics under future climate change. Here, we collected seeds of Euptelea pleiospermum, a relict broad-leaved tree species, from six provenances along latitudinal and altitudinal gradients across its distribution in China. We investigated variation in seed germination percentage and germination timing of seeds from these different origins (low, middle, and high latitudes/altitudes) at three incubation temperatures (15 °C, 20 °C and 25 °C). The key results were as follows: first, seeds collected from high latitudes were more sensitive to temperature and was likely to benefit from the higher incubation temperature with increasing germination percentage and shorter germination timing; second, for seeds across latitudes, germination percentage of central populations was lower than that of marginal populations; seed origin and its interaction with temperature were the major drivers of germination percentage variation; germination timing was significantly affected by incubation temperature, and warming could accelerate germination; third, for seeds across altitudes, both germination percentage and germination timing were not significantly affected by seed origin, incubation temperature, or their interaction. Our results indicate that climate warming may influence the population dynamics of relict tree species by altering their seed germination patterns, especially for the leading-edge populations along latitudinal gradient. It is vital to take inter-population variation across species’ geographic distribution into account when estimating the impact of environmental changes on plant species’ distribution and population persistence.