Genomic instability within a sympatric complex of South American garlics (Nothoscordum spp., Amaryllidaceae)

Summary

This integrative study demonstrates hybridization between two South American Nothoscordum species (N. montevidense and N. bonariense) growing in sympatry, with morphologically intermediate individuals exhibiting chromosomal variation (2n = 21 and 2n = 25) and meiotic irregularities consistent with interspecific crosses. Chloroplast phylogeny and GBS confirmed N. montevidense as maternal parent and N. bonariense as paternal contributor, with evidence of backcrossing and post-hybridization genomic restructuring evident in reduced 35S rDNA diversity. The findings underscore that morphological similarity can mask profound genomic complexity in cytogenetically labile plant lineages.

Regional applicability

This study concerns wild Nothoscordum species from South America and has limited direct applicability to United Kingdom agriculture or horticulture. However, the methodological approach (integrative cytogenetics, GBS, chloroplast phylogeny, species distribution modelling) may be transferable to characterization of hybridization events in other polyploid or chromosomally unstable crop or wild plant complexes in temperate regions.

Key measures

Chromosome counts (2n), genome size (1C DNA content in pg and Mbp), CMA/DAPI banding patterns, FISH analysis, flow cytometry, GBS genotyping, chloroplast genome assembly, 35S rDNA copy number diversity, species distribution models, phenological data

Outcomes reported

The study confirmed hybrid origin of morphologically intermediate Nothoscordum specimens through integrated cytogenetic, molecular, and phylogenetic analyses. Multiple lines of evidence including chromosome counts, genome size estimation, chloroplast sequencing, and GBS identified N. montevidense as the maternal parent and N. bonariense as the paternal contributor, with evidence of subsequent backcrossing.

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