Inferring population structure and genetic diversity of the invasive alien Nootka lupin in Iceland

Polar and subpolar regions are known for their particular vulnerability and sensitivity to the detrimental effects of non-indigenous species, which is well exemplified by the Nootka lupin (Lupinus nootkatensis) spread in Iceland. Since understanding the population and ecological genetics of invasive alien species offers hope for counteracting harmful biological invasions, the objective of the present study was to investigate interspecific variation in L. nootkatensis in Iceland in relation to a native population in Alaska. Moreover, we aimed to assess whether internal transcribed spacer 2 (ITS2) has sufficient phylogenetic applicability for a large-scale screening of the genetic diversity of a non-indigenous population of this species. This study, which is the first attempt to investigate the genetic diversity of the Nootka lupin in Iceland, included plant samples from eight locations in Iceland and one in Alaska. The analyses included genotyping by sequencing of the 417-nucleotide fragment of the 5.8S ribosomal RNA, ITS2 and part of the large subunit ribosomal RNA (GenBank MT026578-MT026580, MT077004). The main findings showed the presence of five previously unexplained single-nucleotide polymorphisms (SNPs); however, their discriminatory power for Icelandic populations was relatively low, since polymorphism information content (PIC) values ranged from 0.0182 to 0.0526, with average heterozygosity 0.0296. Concomitantly, analysis of multilocus genotypes (MLG) revealed sufficient differences in MLGs variants and their frequency to form genotypic patterns unique for Alaskan and Icelandic populations, revealing an internal genetic structure of the studied group. The proposed SNP panel needs to be supplemented with other nuclear and organellar markers.