First report of articuliths (free-living geniculate corallines, Corallinales, Rhodophyta) in the northern hemisphere revealed during diversity surveys of Haida Gwaii, British Columbia, Canada

Free-living coralline beds are typically composed of rhodoliths, or unattached non-geniculate coralline algae. In 2017, the first beds comprised primarily of free-living geniculate coralline algae, termed articuliths, were documented in Arraial do Cabo Bay in southeastern Brazil. During routine barcode surveys of the Haida Gwaii, British Columbia, Canada flora, 16 rhodolith-like specimens were collected from a rhodolith bed that DNA sequences assigned to the geniculate taxa Calliarthron tuberculosum and Bossiella sp. 1heteroforma. To our knowledge, articuliths have not been documented outside of Brazil; this discovery thus documents the first instance of northern hemisphere articuliths. Despite disparate gross morphologies to attached conspecific populations, anatomical observations revealed internal anatomies consistent with those of attached forms but with a significant reduction in the number of genicula and increased uniformity in intergenicular shape.