Rare Species Guide

  Synonyms

Alectoria thrausta

  Basis for Listing

Ramalina thrausta (angel’s hair lichen) is an uncommon species throughout its North America range, and it appears to be particularly rare in the Great Lakes region (Bowler 1977). In this region, R. thrausta occurs along the North Shore of Lake Superior in Ontario and on Isle Royale (Michigan), where it is apparently secure. This species was first documented from Minnesota in 1999, when a population was discovered in a cedar swamp in Cook County. Since this first state detection, R. thrausta has only been documented a dozen times in Cook and Lake counties (Northern Superior Uplands Section). Due to its restricted range, habitat requirements, and few known localities in the state, Ramalina thrausta was designated a special concern species in 2013.

  Description

Ramalina thrausta is a fruticose (shrub-like) species, with a greenish-white thallus (lichen body). The branches are typically round in cross-section, though they may be flat near the base of the thallus. The fine branches curve near the end, giving them a hook-like appearance, and most branches have soredia on the tips (Brodo et al. 2001). The thallus grows pendent to decumbent on its substrate and can reach considerable lengths in coastal sites. In our area, the species is typically only a few inches in length, with one robust specimen reaching almost 25 cm (10 in.) in length. In Minnesota, there are no other Ramalina (strap lichen) species that can be confused with R. thrausta; of our ten species, R. thrausta is the only one that has branches that are round in cross-section. In addition, this species is typically longer than most other Ramalina that occur in our area. A few species of Usnea (beard lichen) can look superficially similar to R. thrausta; however, these can be readily separated by the presence of a central axis or cartilaginous cord in the center of Usnea branches. Two Bryoria (horsehair lichen) species, B. capillaris and B. nadvornikiana, can look similar to R. thrausta; however, they never have soredia on their lobe tips.

  Habitat

In Minnesota, R. thrausta has been collected from three distinct habitat types (forested peatland, wet forest, and cliff communities). So far, the majority of populations of R. thrausta have been recorded from forested peatland communities dominated by Thuja occidentalis (northern white cedar). In this habitat, R. thrausta grows on the trunks of T. occidentalis or on the bark of mature Picea mariana (black spruce). When the species grows on T. occidentalis, it is typically found with other species of Ramalina, particularly R. intermedia (intermediate cartilage lichen). In this setting, R. thrausta is often found on the downward-facing side of the trunk, in a fairly dry micro-environment. Ramalina thrausta has also occasionally been found growing on the trunks of T. occidentalis in wet forest communities. 

A recent collection of R. thrausta from Cook County was from a north-facing rock face, adjacent to a large fast-flowing river. At this location, the species was observed with other species of Ramalina. Although this habitat differs from the typical cedar swamp habitats, it is similar in its high humidity, which may be crucial to maintain populations of R. thrausta.

  Biology / Life History

Ramalina thrausta does not produce apothecia, so the vast majority of reproduction in this species likely occurs asexually, through the dispersal of soredia. Soredia are reproductive structures that contain both fungal and algal partners and can be dispersed over short distances. It is also possible that the species reproduces through fragmentation.

  Conservation / Management

Loss of habitat is the primary threat to R. thrausta in Minnesota. The most prominent agents of habitat alteration or destruction include logging, housing/cabin development, and climate change. Any alterations that disrupt the humidity of a site where R. thrausta is found would likely have a negative effect on populations of this lichen.  

  Best Time to Search

Ramalina thrausta can be observed year-round, whenever lichens are not covered by snow or ice.

  References and Additional Information

Bowler, P. A. 1977. Ramalina thrausta in North America. The Bryologist 80(3):529-532.

Brodo, I. M., S. D. Sharnoff, and S. Sharnoff. 2001. Lichens of North America. Yale University Press, New Haven, Connecticut. 795 pp.

Minnesota Department of Natural Resources. 2003. Field guide to the native plant communities of Minnesota: the Laurentian mixed forest province. Ecological Land Classification Program, Minnesota County Biological Survey, and Natural Heritage and Nongame Research Program. Minnesota Department of Natural Resources, St. Paul, Minnesota. 352 pp.