Identification of determinants of species germination niche breadth on the eastern Tibetan Plateau

Abstract

Studying the germination niches of a diverse array of species at the community level can offer insight into the parameters that govern the structure of these communities. To date, however, few studies have sought to identify determinants of species germination window. As such, we estimated germination niche breadth (GNB) for 476 angiosperm species found in the eastern Tibetan Plateau grasslands under three light treatment conditions (natural, medium, and low light) in the field. In addition, the changes in GNB (CGNB) across these treatment conditions were measured for all analyzed species, and the relationships between life-history traits (seed mass, plant height, adult longevity, onset of flowering, and duration of flowering), environment [maternal habitats (elevation, light, and water habitat), light environment during germination], evolutionary history and GNB/CGNB were further assessed. These analyses revealed that GNB and CGNB were both highly phylogenetically conserved. We found that low light levels during germination were associated with a significant reduction in GNB, whereas larger seeds typically exhibited greater GNB under all three light treatment conditions. High-elevation species and annual species typically exhibited narrow germination niches only under low light conditions. CGNB was negatively related to plant height and was positively associated with elevation. Together, our data suggest that life-history traits, environmental factors, and evolutionary history all can shape the GNB.