High species diversity may result from recent rapid speciation in a 'cradle' and/or the gradual accumulation and preservation of species over time in a 'museum'. China harbours nearly 10% of angiosperm species worldwide and has long been considered as both a museum, owing to the presence of many species with hypothesized ancient origins, and a cradle, as many lineages have originated as recent topographic changes and climatic shifts-such as the formation of the Qinghai-Tibetan Plateau and the development of the monsoon-provided new habitats that promoted remarkable radiation. However, no detailed phylogenetic study has addressed when and how the major components of the Chinese angiosperm flora assembled to form the present-day vegetation. Here we investigate the spatio-temporal divergence patterns of the Chinese flora using a dated phylogeny of 92% of the angiosperm genera for the region, a nearly complete species-level tree comprising 26,978 species and detailed spatial distribution data. We found that 66% of the angiosperm genera in China did not originate until early in the Miocene epoch (23 million years ago (Mya)). The flora of eastern China bears a signature of older divergence (mean divergence times of 22.04-25.39 Mya), phylogenetic overdispersion (spatial co-occurrence of distant relatives) and higher phylogenetic diversity. In western China, the flora shows more recent divergence (mean divergence times of 15.29-18.86 Mya), pronounced phylogenetic clustering (co-occurrence of close relatives) and lower phylogenetic diversity. Analyses of species-level phylogenetic diversity using simulated branch lengths yielded results similar to genus-level patterns. Our analyses indicate that eastern China represents a floristic museum, and western China an evolutionary cradle, for herbaceous genera; eastern China has served as both a museum and a cradle for woody genera. These results identify areas of high species richness and phylogenetic diversity, and provide a foundation on which to build conservation efforts in China.

Coastal wetlands are one of the important ecosystems that play a crucial role in the regulation of climate change. Rare taxa (RT) exist in one habitat along with abundant taxa (AT).

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Exotic species vary in how harmful they are. The earlier we can predict the outcome of an invasion, the more time is available for management. We conducted a “marsh organ” experiment with six elevation treatments to evaluate how the exotic grass Spartina alterniflora, which has invaded almost the entire coastline of China, affects a native (Kandelia obovata) and an exotic (Sonneratia apetala) mangrove in Zhangjiang Estuary, southern China. Survival of transplants in monoculture over two growing seasons in the marsh organ was high except at extreme high and low elevations. All three plants displayed hump‐shaped patterns of biomass across elevation in monoculture, but K. obovata performed best at slightly higher and S. alterniflora at slightly lower elevations, whereas S. apetala performed well across all four intermediate elevations and grew larger than the other two plants. In mixtures, S. alterniflora suppressed growth of mangrove seedlings of both species by up to 90%. The competitive effect of S. alterniflora was greatest at intermediate elevations where its biomass was greatest. When transplanted into adjacent stands of S. alterniflora, K. obovata remained stunted, but S. apetala grew quickly and began to emerge from the canopy of S. alterniflora by the end of the second growing season. At this site, past and ongoing disturbances to mature stands of K. obovata are likely to allow both exotics to increase in abundance. Aggressive management intervention will be needed to prevent estuaries in southern China from transitioning to near complete dominance by the exotic mangrove S. apetala.

Coastal wetlands are experiencing frequent flooding because of global climate changes, such as the rising sea level. Despite the key role of archaea in soil biogeochemical cycles, the assembly processes and co-occurrence patterns of archaeal communities in coastal wetlands in response to increasing inundation frequencies remain elusive. Herein, we established an in situ mesocosm with an inundation frequency gradient to investigate the response of soil archaeal community toward increasing inundation frequencies in monocultures of Spartina alterniflora (SA) and a mangrove species, Kandelia obovata (KO). Both neutral community model and null model analyses suggested that stochastic processes are dominant in governing the archaeal community assembly, and that the stochastic processes are enhanced with increasing inundation frequencies. Increasing inundation frequencies significantly increased the community niche width. Moreover, archaeal community in SA soil displayed lower niche overlap and higher stochasticity than in KO soil. Co-occurrence network analysis revealed that the network complexity increases with increase in the inundation frequencies. Soil water content is the most decisive factor influencing the archaeal communities. Overall, we found that increasing inundation frequencies enhance the stochastic processes and network complexity of the soil archaeal community in coastal wetlands. This study could enhance our understanding on the response of soil archaeal communities in coastal wetlands toward global change. Importance Coastal wetlands, subjected to regular disturbances by periodic tidal, are highly productive and important in the regulation of climate change. However, the assembly mechanisms and co-occurrence patterns of soil archaeal communities in coastal areas remain poorly known, especially for their responses to increasing inundation frequencies. In this study, we aim at unravelling these uncertainties by studying typical estuarine ecosystems in southern China. We show that increasing inundation frequencies enhance the stochastic processes and network complexity of the soil archaeal community. This study offers a new path for an improved understanding of archaeal community assembly and species coexistence in coastal environments, with a special focus on the role of inundation frequency.