Menegazzia terebrata (Hoffm.) Massal.
Hypogymnia pertusa, Menegazzia pertusa, Parmelia pertusa
Basis for Listing
Menegazzia terebrata (port-hole lichen) is yet fairly uncommon across its North American range and is particularly uncommon in the Great Lakes region (U.S. Forest Service 2002). The species was first documented in Minnesota by Bruce Fink in 1902 (Fink 1910) by a single collection from Cook County (North Shore Highlands Subsection). The species was not collected again in the state until 1976, when Dr. Clifford Wetmore rediscovered the species at a site in Cook County. Since that time, the species has been documented about 20 times from Cook, Lake, and St. Louis counties (North Shore Uplands Section). Due to the limited number of collections of this species from Minnesota, as well as its restricted habitat requirements, Menegazzia terebrata was listed as a species of special concern in 2013.
Menegazzia terebrata is a foliose (leaf-like) lichen, with a grey-green thallus. The species gets its common name from holes that form in the upper surface of the thallus that resemble port-holes. This species also forms tube-like structures, with holes at the top that are lined with soredia. The lower surface of the thallus is black.
In Minnesota, M. terebrata resembles species in the genus Hypogymnia but can be easily separated from members of that genus by the presence of the holes in the upper-surface of the thallus. Hypogymnia physodes (tube lichen) commonly form openings into the medulla at the tips of some lobes but never forms holes in the upper surface of the thallus.
In Minnesota, M. terebrata has been collected from two distinct habitat types, forested peatland and cliff communities. The majority of populations of M. terebrata have been recorded from forested peatland communities dominated by Thuja occidentalis (northern white cedar). In this habitat, M. terebrata grows on the trunks of T. occidentalis.
Twice in Minnesota M. terebrata has been collected from rock substrates. Both of these sites are humid and shaded north-facing cliffs. It appears that the species requires a shaded site, with high humidity and a substrate that is not prone to deterioration or sloughing.
Biology / Life History
Menegazzia terebrata can reproduce by spores; however, this species does not regularly produce apothecia. 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.
Conservation / Management
Loss of habitat is the primary threat to M. terebrata in Minnesota. The most prominent agents of habitat alteration or destruction include logging, housing/cabin development, and larger scale environmental changes, such as climate change. Any alterations that disrupt the humidity of a site where M. terebrata is found would likely have a negative effect on populations of this lichen.
Best Time to Search
Menegazzia terebrata can be observed year-round, whenever lichens are not covered by snow or ice.