The Brazilian state of Acre has an extensive natural reserve of bamboo,making it one of the largest in loco gene banks.The aim of this study was to characterize the structure and genetic diversity of Guadua weberbaueri Pilg.in two populations,one native(FAPB)and the other anthropized(FAPBA),using ISSR markers.The results show that the FAPB population exhibited higher values for all estimates of population diversity.However,the FAPBA population also showed high heterozygosity,corroborated by estimated gene flow(Nm = 3.9)between the populations.The study of the association between Nei's genetic distances and the geographic distances between the populations were significantly correlated(r=0.45,p = 0.01),corroborated by the dendrogram revealing two distinct groups corresponding to the collection sites,without mixing classes between popu-lations in the same group.As for the coancestry coefficient,pairs of individuals in the first distance class were positive and significant,indicating that plants that are geographi-cally closer share common alleles with a frequency greater than by chance,which means that there is a tendency that geographically closer individuals are related.Individuals presented similar genetic structure when the geographical distance between them was up to 56 m for FAPB and up to 156 m for FAPBA.It was concluded that anthropized envi-ronments exhibit less genetic diversity than native environ-ments,inferring risks for species conservation if appropriate and planned management techniques are not adopted.