Synthesizing the relationships between environmental DNA concentration and freshwater macrophyte abundance: a systematic review and meta-analysis.

Environmental DNA (eDNA) analysis can facilitate surveillance of invasive aquatic plant's distribution. However, it is still questionable how accurately eDNA concentration reflects and predicts aquatic plant abundance. Although previous studies investigated relationships between aquatic plant eDNA concentration and their abundance in freshwater environments, the conclusions were not consistent between the studies. Here, a systematic literature search was conducted to summarize previous findings and meta-analyze the relationships between eDNA concentration and aquatic plant abundance. Hierarchical random-effect meta-analyses showed significant positive, but weak, relationships between them (r = 0.45 in average), meaning that eDNA concentration accounted for approximately 20% of the observed variation in plant abundance. Additionally, the relationships tended to be rather stronger in the field than in the laboratory environments, which may be attributed to limited quantifiability and species specificity of plant coverage as abundance metrics, heterogeneous dispersion of plant eDNA particles, and phenology-dependent eDNA production from plant bodies. The finding indicates that aquatic plant eDNA particles could reflect more regional (but not local) abundance, and thus, eDNA-based abundance estimation might be more appropriate at a broader scale (i.e., lower spatial resolution). Further studies focusing on various environmental parameters and plant ecotypes are needed to clarify the relationship. [ABSTRACT FROM AUTHOR]