Seaside bone (Hypogymnia heterophylla) COSEWIC assessment and status report: chapter 3

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Name and classification

Scientific name:    Hypogymnia heterophylla L. Pike

                           Mycotaxon XVI: 157-161 (1982), Figure 1

The common name is seaside bone lichen or seaside tube lichen (Brodo et al. 2001).

Family classification

The genus Hypogymnia has been included in the Parmeliaceae. However, Poelt (1974) suggested that it may be sufficiently distinct from other members of that family to warrant separate family status. Later he appears to have reversed this opinion in favour of assigning Hypogymnia a subfamily rank within the Parmeliaceae (Eriksson 1982). His original proposal was taken up (and validated) by Elix (1979). More recently, Tehler (1996), mainly based on the outline of ascomycete systematics of Eriksson and Hawksworth (1993), has placed the genusHypogymnia in the family Parmeliaceae. The specific distinctness of H. heterophylla has not been challenged since its description (Goward 1996a).

Morphological description

Hypogymnia heterophylla is a foliose (leaf) lichen averaging 5-8 cm across the thallus or lichen body.The inflated lobes or branches are hollow, pliable and variable in width from 1-6 mm, often on the same lobe; the lobes are typically fork-branched at the ends with long, narrow lobules that are perpendicular to the lobe margins and constricted at the base. The greenish grey upper surface usually has the black dots of numerous pycnidia or sacks that contain conidiospores. The lower surface is black, shiny and wrinkled. The medullary cavity or inside of the hollow lobe is dark brown throughout. Trebouxia is the green alga or photobiont partner of this lichen. Soredia and isidia are absent.

Apothecia or fruiting bodies are common in this species, up to 8 mm across, and are raised on short broad stalks. The apothecial disc is brown with spores 8 per ascus, colourless, somewhat elongate, and about 4 µm x 7 µm. Pycnidia contain conidiospores which act as asexual spores and sometimes serve as male sexual cells (spermatia) (Brodo et al. 2001).

Technical descriptions and chemistry are described in Pike & Hale (1982), Goward et al. (1994), McCune & Geiser (1997) and Brodo et al. (2001).

Important diagnostic features of this lichen are:

·       long, narrow lobules that are perpendicular to the lobe or branch and are constricted at the base

·       medulla or inside of lobe is dark brown

·       lichen medulla chemical spot test is PD+ red

Genetic description

GenBank 2006, the comprehensive database for species’ DNA sequences, has no records for Hypogymnia heterophylla.