Two new lichenicolous species of Opegrapha (Arthoniales) from Canada

Two new species of lichenicolous Opegrapha are described from New Brunswick, Canada. Opegrapha inconspicua was found once on a rock bluff above a river on the thallus of Verrucaria aethiobola. It is characterized by punctiform, rounded, black ascomata 75-170 mu m diam., an excipulum dark brown to black only in the upper part and (1-)2(-3)-septate ascospores of (12.5-)15.5-25 x 4-5 (-5.5) mu m. Opegrapha parmeliiperda was found in four localities on epiphytic Parmelia squarrosa and P. sulcata. It is characterized by short lirelliform ascomata 70-220(-250) x 70-120 mu m, in +/- loose groups of 5-15(-20) lirellae forming on black necrotic areas on the host thallus, 4-spored asci of 32-40 x 11-15 gm, and persistently hyaline and 3-septate ascospores of (11-)13-15.5(-17) x (3.5-)4-5(-5.5) mu m. Opegrapha lamyi is reported for the first time in Canada, and O. anomea and O. sphaerophoricola for the first time in New Brunswick. One of only two previous reports of O. lamyi for the U.S.A. is based on a specimen from Colorado, revised here to Sclerococcum suburceolatum, the latter record representing a significant range extension for that species. Three of the five lichenicolous Opegrapha species reported here for New Brunswick are so far known in the province only in old mixedwood swamp-forests, highlighting the conservation significance of this forest community type. An identification key to the lichenicolous Opegrapha s.l. species known from Canada is provided. The worldwide diversity and host specificity of lichenicolous Opegrapha s.l. are discussed.