Phylogeny and ecological processes influence grass coexistence at different spatial scales within the steppe biome
Phylogenetic analyses are essential for disentangling how environmental filtering and competition determine species coexistence across spatial scales. Inner Mongolia steppe has strong environmental gradients, but how the phylogenetic relatedness of co-occurring species and phylogenetic signals of functional traits change across spatial scales remains unclear. We investigated the phylogenetic structure of grass assemblages along environmental gradients from regional to local scales, and measured functional traits within assemblages. We compared phylogenetic signals of plant traits between the same numbers of species randomly selected from the regional pool and species observed at the local scale, did phylogenetic principal component analysis to infer the main factors driving species coexistence, and examined the key plant trait–environment relationships across the phylogeny to reveal ecological adaptation mechanisms. Regionally, grass species were phylogenetically clustered with contrasting climate preferences. With decreasing spatial scales, species richness declined, changing from phylogenetically clustered to overdispersed, and phylogenetic signals of plant traits became weaker. At the local scale, grass assemblages were structured by soil water content and neighbor density, and the trait–environment relationships were less clear than those at the regional scale. This study demonstrated that at smaller scales, co-occurring grass species in the steppe tended to be more phylogenetically overdispersed, and that phylogenetic signals of plant functional traits became weaker with increasing abiotic and biotic interactions. Our findings contributed evidence for understanding species coexistence and maintenance at scales spanning regional to local communities in the East Asia steppe biome.
KeywordsInner Mongolian steppe Phylogenetic niche conservatism Plant functional trait Poaceae Scale dependence
We thank Chuangye Song, Wenli Chen, Bing Liu, Jin Liu (Institute of Botany, Chinese Academy of Sciences) and Li Chen, who helped with scientific and technical matters during the fieldwork in Inner Mongolia and lab work in Beijing. We also thank Samuel Taylor for technical training and Nasen Wuritu (Zhenglan field station) for assistance. This work was supported by the National Natural Science Foundation of China (31670411, 31300334), the Youth Innovation Promotion Association of the Chinese Academy of Sciences (2019339), and a UK/China Excellence Scholarship (China Scholarship Council and UK Government).
Author contribution statement
HL and CPO designed research; HL, GJ and ML performed research; HL, RPF and DY analyzed data; HL wrote the initial manuscript, while all authors contributed to revisions.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
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