Population genomics of Ulex europaeus in the Northern Andes: insights into an invasive species in high-mountain ecosystems

Background and aims – Ulex europaeus is an invasive allopolyploid (hexaploid) plant considered a global threat that has successfully colonized various regions, including the Northern Andes. This study aimed to assess its diversity and genetic structure in six sampling sites from the Central and Eastern Andes of the Northern Andes of Colombia, located in conservation-priority highland landscapes, using single nucleotide polymorphisms. Material and methods – Given the complex inheritance patterns of polyploids, both diploid and hexaploid datasets were analysed to estimate genetic diversity (e.g. H o , H e , F IS , and private alleles) and population structure (using e.g. F ST p, AMOVA, STRUCTURE, PCA, DAPC analyses). Additionally, the introduction history of the species in the Northern Andes, particularly the introduction from the Eastern to the Central Andes, was investigated using ABC-RF. Key results – Diploid and hexaploid datasets showed consistent clustering patterns, supporting predominantly disomic inheritance. Populations exhibited high heterozygosity (diploid: H o = 0.302, H e = 0.252; hexaploid: H o = 0.483, H e = 0.222). Genetic structure analyses showed moderate differentiation ( F ST p = 0.118 for diploid; F ST p = 0.074 for hexaploid) and significant isolation by distance (diploid: r = 0.479, p value = 0.022; hexaploid: r = 0.507, p value= 0.012), but without a clearly defined spatial pattern, suggesting restricted gene flow influenced by external factors. ABC-RF analyses indicated at least two independent introduction events in the Eastern Andes, followed by multiple dispersal events into the Central Andes. Conclusion – Ulex europaeus populations in the Northern Andes maintain high heterozygosity and restricted gene flow. Polyploidy likely contributes to preserving genetic diversity, while multiple introduction events and human-mediated dispersal shape population structure, underscoring the complex invasion dynamics of this species in high-mountain ecosystems.