By Jeremy W. Howland, Tristen J. Pasternak

Mar 24 2023

In this collection are some cyanolichens from the NYBG cryptogamic herbarium, some specimens are over 100 years old. Despite their old age, many of these cyanolichens still retain their vibrant color.

Lichens are composite organisms composed of a body, largely constructed of a fungus, and a photosynthesizing algal partner. Also known as a photobiont, this algal partner provides the organism with energy and nutrients. The majority of studied lichens have photobionts that are green algae. Cyanolichens differ from this majority because their photobionts are cyanobacteria, a particular group of bacteria. The benefit of having these bacterial partners is their ability to fix nitrogen, a crucial nutrient for growth. The photobionts fix the nitrogen from the atmosphere through specialized cells. Cyanolichens are particularly sensitive to poor air quality. Since as early as the 1970’s the United States Department of Agriculture (USDA) has been using lichens as an indicator of air quality (Showman 1975). Other studies have focused on using them as an indicator of forest ecosystem health (Merinero et al. 2014).

Most species of lichen have either a cyanobacteria or green alga. Instead of one or the other, some species of cyanolichens can have both types of photosynthesizing partners, forming what is known as a tripartite association, like Lobaria pulmonaria. This life strategy gives the organisms the best of both worlds: they delegate the task of photosynthesizing to the green algae, and fixing nitrogen to the cyanobacteria. What can’t they do?