title: The community-level effect of light on germination timing in relation to seed mass: a source of regeneration niche differentiation.
abstract: Within a community, species may germinate at different times so as to mitigate competition and to take advantage of different aspects of the seasonal environment (temporal niche differentiation). We illustrated a hypothesis of the combined effects of abiotic and biotic competitive factors on germination timing and the subsequent upscale effects on community assembly. We estimated the germination timing (GT) for 476 angiosperm species of the eastern Tibetan Plateau grasslands under two light treatments in the field: high (i.e. natural) light and low light. We also measured the shift in germination timing (SGT) across treatments for all species. Furthermore, we used phylogenetic comparative methods to test if GT and SGT were associated with seed mass, an important factor in competitive interactions. We found a significant positive correlation between GT and seed mass in both light treatments. Additionally, small seeds (early germinating seeds) tended to germinate later and large seeds (late germinating seeds) tended to germinate earlier under low light vs high light conditions. Low light availability can reduce temporal niche differentiation by increasing the overlap in germination time between small and large seeds. In turn, reduced temporal niche differentiation may increase competition in the process of community assembly.
authors.affiliation: State Key Laboratory of Grassland Agro-ecosystems, School of Life Sciences, Lanzhou University, Lanzhou, Gansu, 730000, China.|Key Laboratory of Adaptation and Evolution of Plateau Biota, Northwest Institute of Plateau Biology, Chinese Academy of Sciences, Xining, Qinghai, 810008, China.
authors.forename: Chunhui
authors.initials: C
authors.lastname: Zhang
authors.affiliation: Center for the Environment, Harvard University, Cambridge, MA, 02138, USA.
authors.forename: Charles G
authors.initials: CG
authors.lastname: Willis
authors.affiliation: Department of Biology, Duke University, Durham, NC, 27708, USA.
authors.forename: Liana T
authors.initials: LT
authors.lastname: Burghardt
authors.affiliation: State Key Laboratory of Grassland Agro-ecosystems, School of Life Sciences, Lanzhou University, Lanzhou, Gansu, 730000, China.
authors.forename: Wei
authors.initials: W
authors.lastname: Qi
authors.affiliation: State Key Laboratory of Grassland Agro-ecosystems, School of Life Sciences, Lanzhou University, Lanzhou, Gansu, 730000, China.
authors.forename: Kun
authors.initials: K
authors.lastname: Liu
authors.affiliation: Departamento de Botânica, Universidade Estadual Paulista, Rio Claro, São Paulo, 13506-125, Brazil.
authors.forename: Paulo Roberto
authors.initials: PR
authors.lastname: de Moura Souza-Filho
authors.affiliation: Key Laboratory of Adaptation and Evolution of Plateau Biota, Northwest Institute of Plateau Biology, Chinese Academy of Sciences, Xining, Qinghai, 810008, China.
authors.forename: Zhen
authors.initials: Z
authors.lastname: Ma
authors.affiliation: State Key Laboratory of Grassland Agro-ecosystems, School of Life Sciences, Lanzhou University, Lanzhou, Gansu, 730000, China.
authors.forename: Guozhen
authors.initials: G
authors.lastname: Du
mesh_terms: D017753:Ecosystem; D018525:Germination / Q000502:physiology*; D008027:Light; D010802:Phylogeny; D063245:Plant Development / Q000502:physiology; D010944:Plants / Q000145:classification / Q000235:genetics*; D012639:Seeds / Q000502:physiology*; D018609:Tibet
keywords: Tibetan Plateau; community assembly; competition; phylogenetic community structure; phylogenetic diversity; phylogenetic signal; resource limitation; temporal niche
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