Multi-Channel Neighbor Interactions Adjust Growth Strategies in the Clonal Plant Glechoma grandis

Background: Plant-plant interactions rely on neighbor-derived cues. Access to multiple cue channels should allow better identity assessment, yet integrative studies-especially on touch between neighbors-remain limited. Methods: We tested how leaf contact and shared rooting space between neighbors influence plant-plant interactions, by measuring growth of Glechoma grandis paired with conspecific, congeneric, or distant heterospecific neighbors. Results: Neighbor effect strength depended on interaction mode: leaf contact alone triggered stronger neighbor identity-dependent growth than shared rooting space alone, and combined channels were strongest. With both channels, plants were a conservative strategy toward conspecifics (reducing stolon allocation), but competitive toward heterospecifics (increasing leaf area and roots, stolons and leaf biomass). The competitive strategy further diverged with phylogenetic distance-congeneric neighbors induced thicker stolons; distant heterospecific neighbors led to longer, thinner stolons. Moreover, interaction mode outweighed neighbor identity: without interactions, neighbor effects differed only between conspecific and heterospecific neighbors (conspecifics induced longer stolons and more ramets, indicating greater expansion, but heterospecific neighbors did not differ); with interactions, leaf contact mainly affected leaf area, shared rooting space affected root allocation, and combined channels eliminated differences in G. grandis among neighbors combinations. Conclusions: Leaf contact triggered the most obvious neighbor identity-dependent growth responses, whereas the combination of leaf contact and shared rooting space caused convergence of growth responses among neighbor combinations.