The red seaweed Asparagopsis taxiformis represents an iconic species complex of
five mitochondrial lineages (lineage 1 to 5) introduced worldwide as a consequence of human
mediated transport and climate change. Here we compare globally collected mitochondrial
cox2-3 intergenic spacer sequences against sequences produced from multiple Australian
locations and South Korea to identify Asparagopsis lineages and to reveal cryptic
introductions. We report A. taxiformis lineage 4 from Cocos (Keeling) Islands, Australia, and
the highly invasive Indo-Pacific Mediterranean lineage 2 from South Korea and Lord Howe
Island, Australia. Phylogeographic analysis showed a clear haplotype and geographic
separation between western Australian and Great Barrier Reef (GBR) isolates belonging to
the newly described A. taxiformis lineage 5. The same lineage however, was characterized by
a substantial genetic and geographical break between the majority of Australian specimens
and Asparagopsis collections from South Solitary Island, Southern GBR, Lord Howe Island,
Kermadec Islands, Norfolk Island, New Caledonia and French Polynesia. The distinct
geographical distribution and the amount of diversification between these two groups justify
the establishment of a sixth A. taxiformis mitochondrial cryptic lineage.
