Ochrolechia androgyna (Hoffm.) Arnold
Powdery Saucer Lichen
Basis for Listing
Ochrolechia androgyna (powdery saucer lichen) is widespread in North America, where it occurs throughout the arctic boreal forest and in most major mountain ranges; it is also apparently common along the west coast in California, Oregon, and Washington. The species is, however, absent from the Great Plains and most of southeastern North America (CNALH 2017). Ochrolechia androgyna reaches the western extent of its mid-continental range in northern Minnesota and it was, in fact, unknown in the state until a population was discovered in Itasca State Park in 1972 (Northern Minnesota Drift and Lake Plains Section). Since this original detection, O. androgyna has only been documented a handful of additional times in Minnesota (Northern Superior Uplands Section). Due to the apparent rarity of O. androgyna in Minnesota, it was listed as a species of special concern in 2013.
Ochrolechia androgyna is a small white crustose (crust-like) lichen species that occurs primarily on bark (rarely on rock). The species is not known to produce apothecia in North America specimens but typically has abundant white to yellowish soredia.
In Minnesota, there are quite a few small white crustose lichen species that can look superficially similar to O. androgyna, and so positive identification may be difficult for most amateur lichenologists. One important characteristic that may separate O. androgyna from many other white crustose lichens in our area is that North America specimens of O. androgyna do not produce apothecia (Brodo et al. 2001). This trait alone drops the potentially similar species in our area to only a handful. Additional characteristics that help to further differentiate O. androgyna from other similar species include the fact that O. androgyna typically grows on bark, its thallus has a positive reaction when exposed to bleach (C+ pink), it does not fluoresce under ultraviolet light (UV-), and is sorediate (Lendemer, 2010).
In Minnesota, O. androgyna has only been collected a handful of times, making it difficult to draw conclusions on habitat preference. In our region the species has been collected from a diversity of substrates, including bark and rock. It appears to prefer conifer bark, since populations have been recorded from the bark of Thuja occidentalis (white cedar), Pinus strobus (white pine), Pinus banksiana (jack pine), and Picea mariana (black spruce). Populations have been recorded from both fire-dependent forests (and associated cliff/talus and rock outcrop) and forested peatland communities.
Biology / Life History
According to Brodo et al. (2001,) O. androgyna is not known to produce apothecia in North America, so the species likely reproduces asexually, through the dispersal of soredia. Soredia are reproductive structures that contain both fungal and algal partners and can be dispersed over short distances. This species may also reproduce sexually through the distribution of spores, though this appears to be extremely rare.
Conservation / Management
Although a couple of the known populations of O. androgyna in Minnesota are located in protected areas (Itasca State Park and Boundary Waters Canoe Area Wilderness), the majority of sites are subject to some types of development that can impact the species. Since O. androgyna grows primarily on tree bark, anything that damages this substrate will have a negative impact. Ochrolechia androgyna is also dependent upon a humid microclimate. Opening the canopy would alter that microclimate by decreasing shade, which would raise the humidity level.
Best Time to Search
Ochrolechia androgyna can be observed year-round, whenever lichens are not covered by snow or ice.