Status of Lichens and Bryophytes on Middle Island: Declining Carolinian Habitat at Canada's Southernmost Point

Abstract

The Carolinian habitats of Middle Island, ON, Canada, have been altered by Phalacocorax auritus (Double-crested Cormorant). On 8 September 2014, we recorded 14 bryophyte and 9 lichen taxa while sampling throughout the 18-ha island. Both bryophytes and lichens were concentrated in highly localized patches. Most species, including 2 provincially rare mosses—Hyophila involuta (Involute Hyophila Moss) and Fissidens obtusifolius (Blunt Pocket Moss)—and 1 rare lichen—Bacidia coprodes (Dotted Lichen)—were restricted to water-washed shoreline rocks. The paucity of historical data about the cryptogam populations on the island limit the ability to document changes that have occurred in community composition and to explain the current low level of species-richness. Many bryophytes and lichens that we expected to occur on Middle island appear to be intolerant of current conditions there.