Rapid Expansion of the Eastern China Lineage (Haplotype P) of Phragmites australis in Caohai Lake, Guizhou, China

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Abstract
Phragmites australis is a well‐known invasive grass in North America, but its rapid expansion into new habitats within its native range is less documented. Here, we report a rapid expansion event of P. australis over the past decade in Caohai Lake, a plateau lake in China. Remote sensing and field surveys revealed that the reed population now covers 454.09 ha, constituting 3.8% of the protected area (approximately half of the total lake shoreline), with the most significant expansion occurring between 2018 and 2020. Ecological niche modeling with the previous records in China indicated a low habitat suitability (index = 0.354) for P. australis in this region. Despite this, our genetic analysis identified that all sampled individuals belong to haplotype P, an introduced octoploid lineage from eastern China. This finding excludes a natural range expansion from native populations in northern or southwestern China. The expansion is likely driven by anthropogenic habitat modification (e.g., “returning farmland to wetland”) and the introduction of this competitive genotype via constructed wetlands. Our study underscores the risk of “cryptic invasions” by introduced lineages within a species' native range and highlights the need for monitoring intraregional genotype translocations.
Funding Information
  • National Natural Science Foundation of China (32470388)
  • Natural Science Foundation of Shandong Province (ZR2024QC197)

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