Northeastern Naturalist 134 J. Doubt and R.T. McMullin 22001166 NORTHEASTERN NATURALIST 2V3(o1l). :2133,4 N–1o4. 01 Status of Lichens and Bryophytes on Middle Island: Declining Carolinian Habitat at Canada’s Southernmost Point Jennifer Doubt1,* and Richard Troy McMullin2 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. Introduction Middle Island, in Lake Erie, ON, Canada was once thought to be among the best of few remaining examples of Canadian Carolinian habitat (Kamstra et al. 1995). It was home to 258 vascular plant taxa, including 25 nationally and/or provincially at-risk taxa. (Aquila Applied Ecologists 2007, Dobbie 2008, Koh et al. 2012, North– South Environmental 2004). The island, which is 18 ha in size, was privately owned and changed hands many times before it was purchased by the Nature Conservancy of Canada for conservation purposes in 1999. It was then donated to Parks Canada in 2000, becoming part of Point Pelee National Park. There is a history of human disturbance on Middle Island, which includes a lighthouse station (1870–1918), viticulture operations (late 1800s), a prohibition-era mansion and hotel/casino, and an air strip that has been inactive for decades (North–South Environmental 2004). Currently, however, Phalacrocorax auritus Lesson (Double-crested Cormorant, hereafter, Cormorant) presents the greatest challenge to the ecological integrity of the island. The first nesting pair of Cormorants was recorded on Middle Island in 1987, and the population grew to over 6000 nesting pairs (almost 400 nests/ha) in trees throughout the Island. Observations showed that nest density was negatively correlated with forest cover (Boutin et al. 2011, Hebert et al. 2005, Kolb et al. 2012) and vascular plant species-richness (Kolb et al. 2012), and positively correlated with tree-damage indices (Koh et al. 2012), soil acidity, and soil-nutrient levels (phosphorus, nitrogen) (Rush et al. 2011, 2013). These changes transformed resident floral and faunal communities by killing individuals and/or by altering growing conditions. In 2008, Parks Canada initiated a Cormorant-reduction program that 1Canadian Museum of Nature, PO Box 3443, Station D, Ottawa, ON, Canada, K1P 6P4. 2Biodiversity Institute of Ontario Herbarium, University of Guelph, 50 Stone Road East, Guelph, ON, Canada, N1G 2W1. *Corresponding author - jdoubt@mus-nature.ca. Manuscript Editor: David Richardson Northeastern Naturalist Vol. 23, No. 1 J. Doubt and R.T. McMullin 2016 135 decreased nest density to ~200 nests/ha (Hebert et al. 2014), but the current population continues to impair restoration potential on the island (Boutin et al. 2011; Koh et al. 2012; Rush et al. 2011, 2013). Diversity and abundance of vascular plants on Middle Island, including rare species, have declined, presumably due to the effects of Cormorant presence (Aquila Applied Ecologists 2007, Boutin et al. 2011, Hebert et al. 2005, North–South Environmental 2004). Despite the botanical-survey work on Middle Island since 1948 (North–South Environmental 2004), bryophytes and lichens have received little attention. Herbarium records from the National Herbarium of Canada (CANM and CANL, for mosses and lichens, respectively, Canadian Museum of Nature, Gatineau, QC, Canada), the University of Guelph Herbarium (OAC; Guelph, ON, Canada), and the Green Plant Herbarium (TRT; the Royal Ontario Museum, Toronto, ON, Canada), and all records compiled on-line by the Consortia of North American Bryophyte and Lichen Herbaria suggest that in total, 0 lichens and just 9 bryophyte species were documented by 2 separate collectors (M.J. Oldham, Ontario Ministry of Natural Resources and Forestry, Peterborough, ON, Canada and S.J. Darbyshire, Agriculture and Agrifood Canada, Ottawa, ON, Canada) prior to our visit in 2014. Both collectors confirm (through pers. comm. to J. Doubt) that bryophyte collecting was incidental to their main purpose for visiting the island; thus, no comprehensive surveys have been documented. Site Description and Methods On 8 September 2014, we made a 6-h visit to Middle Island, an 18-ha island ~4 km south of Pelee Island in Lake Erie (Fig. 1). We circumnavigated the island on foot and traversed it at 5 roughly equalt intervals through its interior forest. Figure 1. Location of Middle Island, ON, Canada, in the context of western Lake Erie. Northeastern Naturalist 136 J. Doubt and R.T. McMullin 2016 Vol. 23, No. 1 Throughout the survey, we visited all mesohabitat types represented on the island, and examined as many examples as possible of all microhabitat types present within each mesohabitat (Newmaster et al. 2005). We used microscopy and current taxonomic resources (Faubert 2012, 2013, 2014; Flora of North America Editorial Committee 2007, 2014) to identify bryophytes, and microscopy and chemical spot tests following Brodo et al. (2001) to identify lichens. We further examined lichen specimens that could not reliably be identified by these means by using thin-layer chromatography (solvents A and C) following Culberson and Kristinsson (1970) and Orange et al. (2001). We deposited vouchers at CANM (bryophytes) and OAC (lichens). Results We recorded 14 bryophyte (13 moss, 1 liverwort) and 9 lichen taxa (Table 1). Most of these taxa are common and widespread in Ontario; however, 2 mosses, Hyophila involuta (Involute Hyophila Moss) and Fissidens obtusifolius (Blunt Pocket Table 1. Bryophytes and lichens documented on Middle Island during a 1-d survey in September 2014, including their provincial sub-national conservation ranks, or SRanks, and the habitats (F = forest, S = shore) and substrates (L = lignicolous, C = corticolous, S = saxicolous) with which they were associated. Saxicolous species were on calcareous rock; corticolous lichens were on Celtis occidentalis (Hackberry). There was insufficient material to allow for identification of 2 bryophytes beyond the genus level. * indicates the most commonly-encountered taxa in each group. Sub- Species SRank Habitat strate Bryophytes *Hygroamblystegium varium (Hedw.) Mönk. S5 F,S L,S Brachythecium rutabulum (Hedw.) Schimp. in B.S.G S5 F L Bryum s.l. F L Ceratodon purpureus (Hedw.) Brid. S5 F L Entodon seductrix (Hedw.) Müll. Hal. S4 F L Fissidens obtusifolius Wils. S2 S S Funaria hygrometrica Hedw. S5 S S Gymnostomum aeruginosum Sm. S5 S S Haplocladium microphyllum (Hedw.) Broth. S4 F L Hyophila involuta (Hook.) Jaeg. S3 S S Leptobryum pyriforme (Hedw.) Wils. S5 S S Marchantia polymorpha L. S5 S S *Plagiomnium cuspidatum (Hedw.) T. J. Kop. S5 F,S L,S Tortula S S Lichens Amandinea punctata (Hoffm.) Coppins & Scheid. S5 S L Bacidia coprodes (Körb.) Lettau S1S2 S S Candelaria concolor (Dicks.) Stein S5 S C Hyperphyscia adglutinata (Flörke) H. Mayrhofer & Poelt S4 S C *Lecanora dispersa (Pers.) Sommerf. S5 S S Phaeophyscia adiastola (Essl.) Essl. S4 S C Physcia stellaris (L.) Nyl. S5 S C *Xanthocarpia feracissima (H. Magn.) Frödén, Arup & Søchting S5 S S Xanthomendoza ulophyllodes (Räsänen) Søchting, Kärnefelt & S.Y. Kondr. SNR S C Northeastern Naturalist Vol. 23, No. 1 J. Doubt and R.T. McMullin 2016 137 Moss), and the lichen Bacidia coprodes (Dotted Lichen) are rare and tracked by the Ontario Natural Heritage Information Centre (2014). Lichens and bryophytes tended to occur in localized patches. Most surfaces were uncolonized, and even the most common species occupied a small fraction of the substrates that would normally support them. We found the greatest abundance of bryophytes along the water-washed rock surfaces of the island’s northeast shoreline; the rest of the shoreline habitat was largely devoid of bryophytes. In the forested interior of the island and on the ruins of former stone buildings, healthy bryophyte colonies were extremely rare, and we only observed them on a few decaying logs within a small patch of dense understory scrub in the northwest. Lichens were absent from the forest interior, and were restricted to shoreline rocks and forests. We discovered the most common saxicolous lichen species throughout the coastal limestone shelf on the north, east, and south sides of the island, whereas corticolous species were limited to a small forested area on the island’s south side. This area appeared to be less affected by Cormorants than elsewhere on the island. We found 2 lichen species—Amandinea punctata (Tiny Button Lichen) and Dotted Lichen—just once, on the northeast side of the island. Discussion The bryophyte and lichen floras of Middle Island are the most species-poor among the Canadian natural areas we have examined. While additional species may occur in inconspicuous and less accessible microhabitats, the striking absence of bryophytes and lichens from their typical substrates confirms that their current diversity and abundance are extremely low. These organisms are known to be sensitive to changes in environmental chemistry, moisture, and light (e.g., McMullin 2010, 2013; Vanderpoorten and Goffinet 2009). The forest-canopy reduction from 90% to 46% as a result of tree mortality due to the Cormorants (Hebert et al. 2014) has likely caused substantial changes to the moisture and light regimes in all the forest microhabitats. The levels of nutrients and changes in pH, even in areas with a low density of nests where nutrients may be insufficient to be directly toxic, may have shifted growing conditions beyond the tolerance ranges of most forest lichen and bryophyte species. The prospects for forest-habitat recovery are uncertain (Herbert et al. 2014, Koh et al. 2012, Rush et al. 2013), and for sensitive species (such as bryophytes and lichens) it may be particularly slow. In Poland, Żółkoś et al. (2013) observed some recolonization by epiphytic forest-lichen species after nest sites were abandoned by Ardea cinerea L. (Grey Herons), but found that community composition was altered in the long term. One might expect that on Middle Island’s rocky shorelines, contact with lake water (i.e., waves or spray), prevalence of less-permeable substrates, and distance from overhead-nest trees may offer refuge to the subset of resident species—largely bryophytes— adapted to this habitat type. The persistence, in this microhabitat type, of the only 3 rare species detected during our survey, suggests that it may well be the case. Three bryophyte species documented by this study—Hygroamblystegium varium, (Tangled Thread Moss), Funaria hygrometrica (Bonfire Moss), and Northeastern Naturalist 138 J. Doubt and R.T. McMullin 2016 Vol. 23, No. 1 Plagiomnium cuspidatum (Baby Tooth Moss)—were known from the island prior to the dramatic increase in Cormorant numbers. Species that were collected in the early 1980s but not seen in 2014 were Anomodon rostratus (Hedw.) Schimp. (Yellow Yarn Moss), Bryhnia graminicolor (Brid.) Grout (Grass-colored Moss), Ptychostomum creberrimum (Taylor) J.R. Spence & H.P. Ramsay (Scarlet Stalk Moss), Taxiphyllum deplanatum (Bruch & Schimp. ex Sull.) M. Fleisch (Sprouting Silk Moss), and the nationally rare Tortula porteri (James) Brotherus in H.G.A. Engler and K. Prantl (Porter’s Twisted Moss). The potential loss of Porter’s Twisted Moss, which in Canada is only known from small limestone areas in the warmest parts of Ontario (Niagara Peninsula, Pelee and Middle Islands), is particularly significant because its populations on nearby Pelee Island are small and suitable habitat there is rare (COSEWIC, in prep). Several other US and Canadian islands in the Lake Erie archipelago, where this moss has been recorded or is expected to have occurred, are currently also affected by Cormorants (Hebert et al. 2014, Sherman 2007). We can only speculate on the composition and diversity of the former bryophyte and lichen community on Middle Island. Bryophyte surveys in 1945 of 2 limestone-dominated islands in the US portion of the same western Lake Erie archipelago—Green Island (7 ha and ~15 km southwest of Middle Island) and Rattlesnake Island (34 ha and ~13 km west of Middle Island)—yielded 64 species following a 6-h search and 48 species after 4 h, respectively (Schnooberger and Wynne-Hillier 1954). The habitats on Green Island at that time seem to match those on Middle Island, which, prior to Cormorant colonization, included forests dominated by Celtis occidentalis L. (Hackberry), Acer nigrum F. Michx. (Black Maple), Ptelea trifoliata L. (Hop-tree), Fraxinus quadrangulata Michx. (Blue Ash), and/or Quercus muehlenbergii Engelm. (Chinquapin Oak) as well as scrub, pond, and rocky shoreline communities (North–South Environmental 2004). Nearby Pelee Island currently retains remnants of natural forest habitat; thus, studies there may be somewhat useful in hypothesizing the probable original cryptogam biota of Middle Island. 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