Unidirectional genomic introgression facilitates the colonization of an invasive orchid in arid, metal-enriched sedimentary habitats.

Genes that introgress between species can influence the evolutionary and ecological fate of recipients exposed to novel environments. However, key questions on the patterns and molecular mechanisms of introgression in perennial herbaceous plants, which enable distantly related invasive species to thrive in extreme habitats, remain largely unanswered. Here, we report unidirectional introgression from the local species Dendrobium huoshanense to the distantly related invasive species Dendrobium catenatum (Dendrobium officinale) in lithophytic habitats of eastern China. The introgressed regions, which comprise approximately 1% of the genome, contain genes that regulate responses to drought, cold, and metal-ion stresses. Notably, introgressed loci such as CDPK, HHP, PIF, BRI1, and FY show distinct selection signatures and differential expression compared with their paralogs, each playing a distinct role in drought and cold-stress responses. In addition, CIPK23, PDR9, and HAM demonstrate differential expression relative to their paralogous genes and alleles within introgressed loci, indicating their potential involvement in responses to metal-ion stress. Introgression thus facilitates the colonization of arid, metal-enriched sedimentary habitats by D. catenatum. These findings enhance our understanding of Orchidaceae evolution and reveal the evolutionary role of unidirectional introgression in the adaptation of perennial herbaceous plants to extreme environments.