Abstract Dormancy and germination determine when and where plants recruit, and their occurrence reflects current environmental conditions as well as the evolutionary history of the species. As such, they are central to predicting how plants will respond to climate change. Here, we examined dormancy and germination responses in 21 species and subspecies representing four major and endemic Australian plant groups ( Eucalyptus, Callistemon, Brachyscome and Deyeuxia ). Seeds were collected along an elevational gradient (31–1,822 m a.s.l.), focusing on contrasting high- and low-elevation species. To assess physiological dormancy, seeds were subjected to two pretreatments: soaking in deionized water (control) or gibberellic acid (250 ppm) for 8 hours. Seeds were then incubated across six constant temperatures (5–30°C) to quantify germination responses and thermal niches. High-elevation species exhibited stronger dormancy than lowland species, although responses to dormancy-breaking treatments were group-specific, reflecting phylogenetic differences. High-elevation species generally germinated more at warmer temperatures (20–30°C) and less at cooler temperatures (10–15°C), whereas lowland species showed broader thermal niches, with germination across most tested temperatures. These results indicate that elevation-related climatic conditions shape dormancy and germination traits, with implications for species persistence and distribution under climate change.
Hirst et al. (Mon,) studied this question.