Hypogymnia is a very common and striking worldwide lichen genus. Over 100 species are known and found on all continents, except Antarctica. The 31 species in North America are found across the Arctic, south to the southern Appalachians and Mexico. The Pacific Northwest is particularly rich with 14 species.
The genus is easily recognized by its hollow lobes. The only other hollow-lobed foliose lichen in North America is Menegazzia, which has perforations in the upper surface. Chemical spot test reactions, particularly the P reaction, but also the K and KC reactions of the medulla, are extremely helpful in identifying to species. Many species, however, can be identified to species without chemical tests.
Any physiological or environmental explanation for having hollow lobes, often with ventilation holes, remains a mystery. Some small creatures have been found inside, perhaps finding shelter.
How to Use This Site
This site provides a complete list of Hypogymnia species in North America. To browse, go to the Species List and hover to see a preview, click for details.
The interactive random-access identification key uses probabilitistic methods to calculate most likely species based on location and user selected characteristics. As this key is designed for those with some lichen background, if you are new to lichens or Hypogymnia, it is strongly suggested that you read through the Characteristics before using the key.
Any feedback is much appreciated.