The Lichens and Bryophytes of the Boston Harbor Islands
1,2,*, ELISABETH LAY
1, DOUGLAS GREENE
1, AND MARY LINCOLN
Abstract - A survey of the Boston Harbor Islands national park area yielded 175
lichen species in 67 genera, and 70 bryophyte species in 44 genera. Ten percent
of the lichens represent a maritime floristic element, and 4% represent a coastal
plain element. Caloplaca verruculifera, an orange lichen of rocky shores, is
reported new for Massachusetts. Human disturbance and air pollution seem to
be the major factors limiting the colonization of lichens and bryophytes on the
islands, and specific recommendations for protecting sensitive lichen and bryophyte
communities are presented.
The Boston Harbor Islands consist mostly of drumlins and moraines,
punctuated by occasional ledges of Boston Basin sedimentary rock
(mostly Cambridge Argillite; Cameron 1976). The park area comprises
about 34 separate areas spanning approximately 1600 acres, the furthestmost
point (the Graves) being about 11 miles from Boston (for a
map, see Bell et al. 2005). While documentation of the vascular flora
of this area has begun (Elliman 2005, Levering 1978), the cryptogamic
flora has, until now, been unknown.
The islands are very interesting from a phytogeographic point of
view: they are located within the range of species included in the “coastal
plain” floristic element, and the rocky shores that exist on some of them
are also a suitable habitat for species of the “maritime” floristic element
(Brodo et al. 2001, Ireland 1982). Because of this, a rich cryptogam flora
might be expected. Almost all the islands, however, have endured much
human disturbance, dating to the American Revolution (Snow 1971).
In terms of species numbers, this has probably had an overall negative
impact on the lichen and bryophyte diversity of the park area. In addition,
since these organisms (especially lichens) are extremely sensitive
to air pollution, the growth of the nearby Boston metropolitan area has
probably reduced the flora further. Given the complete lack of historical
reports of bryophytes and lichens from the islands, one of the goals of
1Farlow Herbarium of Cryptogamic Botany, Harvard University, 22 Divinity
Avenue, Cambridge, MA 02138. 2Current address - Herbarium, Department
of Botany, The Natural History Museum, Cromwell Road, London SW7 5BD,
England, UK. *Corresponding author - email@example.com.
Boston Harbor Islands National Park Area: Natural Resources Overview
2005 Northeastern Naturalist 12(Special Issue 3):77–98
78 Northeastern Naturalist Vol. 12, Special Issue 3
this project was to provide a floristic baseline that can be used to measure
future changes in species diversity.
This paper provides answers to the following questions: (1) What
species of lichens and bryophytes are found in the Boston Harbor Islands
park area, and on which islands? (2) Do any of the species belong
to the “coastal plain” or “maritime” floristic element, or are they otherwise
noteworthy? (3) What can we infer about historical and future
impacts on the lichen and bryophyte flora of the park area? The answers
to these questions are discussed in relation to (a) monitoring the overall
environmental health of the islands and (b) conservation and management
of specific areas within the park.
Throughout 2001 and 2002, a total of 107 person-days were spent
collecting lichens and bryophytes on the islands. Thirty-three (33) islands/
areas of the park were thoroughly searched for lichens. The search
for bryophytes, however, was less complete. This is due to the fact that
only one of the investigators (Mary Lincoln) is a bryologist, and she
was personally unable to survey every island/area. Specifically, our bryologist
did not visit the following islands/areas: Button, Deer, Graves,
Green, Lovells, Little Brewster, Little Calf, Moon, Nixes Mate, Nut,
Snake, and Thompson. The rest of us made a few collections of mosses
from five of the islands: Deer, Lovells, Nut, Snake, and Thompson. It
should be noted that, of those islands/areas not visited by the bryologist,
there is very little chance of bryophytes being present on the following:
Graves, Green, Little Calf, and Nixes Mate. This is because of the small
size of these islands, their extreme maritime exposure, and their lack of
suitable bryophyte substrata.
For each island/area, diverse substrata were inspected for lichen
and bryophytes. Specimens were examined using light microscopy and
chemical spot tests. In some cases, lichens were identified using thinlayer
chromatography. The few collections that could not be identified
by these means were sent to specialists at different institutions.
All species, and the islands on which they occur, have been recorded
in the NPSpecies on-line database. At least one voucher specimen for
each species is deposited in the Farlow Herbarium at Harvard University;
complete voucher specimen information will soon be available in
the online NPSpecies database.
A total of 175 species (in 67 genera) of lichens and 70 species (in 44
genera) of bryophytes were identified within the Boston Harbor Islands
national park area. Many of the species were common to the greater
2005 S. LaGreca, E. Lay, D. Greene, E. Kneiper, and M. Lincoln 79
Boston metropolitan area. However, lichens characteristic of both the
maritime and coastal plain floristic elements were also observed; indeed,
about 10% and 4% of the lichens, respectively, belong to these two elements.
(See “Notes on lichen identifications” below.) The remaining
lichens (86%) belong to inland, temperate floristic elements (mostly the
east temperate element; Gowan and Brodo 1988). All of the bryophyte
species, on the other hand, were representative of inland, temperate floristic
elements (Ireland 1982).
A complete list of all lichen and bryophyte species follows. In the lichen
list, non-lichenized fungi that are related to, or affiliated with, lichens
are denoted by an asterisk (*). For each species, we have given generalized
habitat information and phytogeographic affinity (if noteworthy), followed
by a list of the islands on which that species occurs. For each species,
one or more selected voucher specimens are also cited; abbreviated collectors’
names are: DG (Doug Greene); EK (Elizabeth Kneiper); SL (Scott
LaGreca); EL (Elisabeth Lay); and ML (Mary Lincoln).
Acarospora amphibola Wedd.—on rocks. Sometimes lumped with A. smaragdula,
but distinct in the Boston Harbor Islands; see Knudsen (in prep). Bumpkin
(EL 02-0520), Moon, Peddocks, Raccoon, Rainsford (EK BH190), Slate (SL
1032), Thompson, Worlds End (EL 01-0259).
Acarospora fuscata (Schrader) Arnold—on rocks and bricks. All except: Deer,
Graves, Green, Little Calf, Long, Nixes Mate, Peddocks, Raccoon, Sheep,
Snake (DG 21-11-6-1-01, from Calf).
Acarospora immersa Fink—on rocks. Moon (EK BH120), Spectacle.
Acarospora smaragdula (Wahlenb.) A. Massal.—on rocks and cement. Calf,
Hangman, Little Brewster (EL 02-0223), Moon, Rainsford, Webb.
Amandinea milliaria (Tuck.) P. May & Sheard—on bark; coastal plain. All
except: Button, Deer, Graves, Green, Hangman, Little Calf, Little Brewster,
Long, Moon, Nixes Mate, Nut, Outer Brewster, Raccoon, Ragged, Sarah,
Sheep, Spectacle (SL 1040, from Bumpkin).
Amandinea polyspora (Willey) E. Lay & P. May—on bark. Bumpkin, Button,
Georges, Grape, Langlee, Long, Lovells, Moon, Peddocks, Ragged, Rainsford,
Slate, Snake (EK BH477), Thompson (SL 1082), Webb, Worlds End.
Amandinea punctata (Hoffm.) Coppins & Scheid.—on wood, bark, rocks, pebbles
and bricks. All except: Deer, Graves, Green, Little Calf, Little Brewster,
Nixes Mate, Nut, Raccoon, Spectacle, Webb (EL 01-0113, from Lovells).
Arthonia caesia (Flotow) Körber—on bark. Bumpkin, Gallops, Georges (EL 01-
0133), Grape, Long, Lovells, Moon, Peddocks (EL 01-0135), Slate, Snake,
Thompson, Worlds End.
Arthonia lapidicola (Taylor) Branth & Rostrup?—found once on rock. Rainsford
Aspicilia caesiocinerea (Nyl. ex Malbr.) Arnold—on rocks. Button, Calf, Deer
(EL 01-0141), Grape, Langlee, Middle Brewster, Rainsford, Spectacle,
80 Northeastern Naturalist Vol. 12, Special Issue 3
Aspicilia cinerea (L.) Körber—on rocks. Bumpkin, Button, Calf, Grape, Greater
Brewster, Langlee, Little Brewster, Lovells, Middle Brewster, Peddocks, Raccoon,
Ragged, Rainsford, Slate (DG 9-40-5-25-01), Spectacle, Worlds End.
Aspicilia moenium (Vainio) Thor & Timdal—on cement. Moon, Outer Brewster,
Rainsford (SL 1036).
Aspicilia verrucigera Hue—on rocks. Button, Langlee, Raccoon (SL 1053),
Bacidia scopulicola (Nyl.) A.L. Sm.—on rocks and cement; maritime. Georges
(SL 982), Raccoon, Rainsford (SL 1035).
Bacidina arnoldiana (Körber) Wirth & Vezda—found once on rock. Moon (SL
Bacidina delicata (Leighton) V. Wirth & Vezda—found once on brick. Moon
Bacidina egenula (Nyl.) Vezda—on rocks and pebbles. Greater Brewster (EK
Bacidina inundata (Fr.) Vezda—found once on brick in wet areas. Moon (EK
Caloplaca cf. chlorina (Flotow) H. Olivier—found once on rock. Peddocks (EL
Caloplaca citrina (Hoffm.) Th. Fr.—on many substrata: coal, clamshell, brick,
cement, nylon rope. Bumpkin, Button, Calf, Gallops, Georges (SL 648),
Greater Brewster, Little Brewster (EL 02-021), Lovells, Middle Brewster,
Moon, Outer Brewster, Peddocks, Rainsford, Slate, Spectacle, Thompson.
Caloplaca feracissima H. Magn.—on cement. Bumpkin, Calf (DG 21-18-7-9-
01), Greater Brewster, Moon (EK BH69), Peddocks, Ragged.
Caloplaca ferruginea (Huds.) Th. Fr.—found once on rock. Ragged (DG 2-29-
Caloplaca flavovirescens (Wulfen) Dalla Torre & Sarnth.—on cement. Bumpkin,
Calf, Georges, Greater Brewster (DG 30-12-6-1-01), Thompson.
Caloplaca holocarpa (Hoffm. ex Ach.) M. Wade group—on bark. Rainsford,
Sheep (EL 01-0357).
Caloplaca scopularis (Nyl.) Lettau—on rocks in supralittoral zone; maritime.
All except: Bumpkin, Button, Deer, Gallops, Georges, Greater Brewster,
Little Calf, Long, Lovells, Moon, Nixes Mate, Nut, Peddocks, Sheep, Snake,
Spectacle, Thompson, Webb (SL 979, from Calf).
Caloplaca verruculifera (Vainio) Zahlbr.—on rocks in supralittoral zone; first
MA records; maritime. Graves (DG 3-6-9-4-01), Green (SL 651), Little
Brewster (SL 1090), Outer Brewster (EK BH16) .
Candelaria concolor (Dickson) Stein—on bark. Gallops (EL 01-0161), Grape,
Langlee, Lovells, Moon, Thompson, Worlds End.
Candelariella aurella (Hoffm.) Zahlbr.—on cement and mortar; common. All
except: Button, Deer, Grape, Graves, Green, Hangman, Langlee, Little Calf,
Nixes Mate, Ragged, Sarah, Snake, Spectacle (SL 649, from Georges).
Candelariella efflorescens R.C. Harris & W. R. Buck—on bark. Peddocks, Slate
Candelariella vitellina (Hoffm.) Müll. Arg.—on bark. Calf, Gallops, Georges,
Langlee (DG 22-3-8-20-01), Middle Brewster (EL 02-0147), Outer Brewster,
Peddocks, Ragged, Sarah, Sheep, Snake.
2005 S. LaGreca, E. Lay, D. Greene, E. Kneiper, and M. Lincoln 81
Cetraria arenaria Kärnefelt—found once on sandy soil; coastal plain. Peddocks
Cladina arbuscula (Wallr.) Hale & Culb.—on soil. Grape, Langlee, Peddocks
(SL 1060), Raccoon, Snake, Webb.
Cladina mitis (Sandst.) Hustich—on soil. Peddocks, Worlds End (DG 38-45-
Cladina submitis (A. Evans) Hale & Culb.—on soil; coastal plain. Peddocks
Cladina subtenuis (Abbayes) Hale & Culb.—on soil; coastal plain. Greater
Brewster, Lovells, Moon, Peddocks, Ragged (DG 2-27-8-20-01), Rainsford,
Slate, Snake (EL 01-0340), Spectacle.
Cladonia apodocarpa Robbins—on thin soil. Langlee (SL 1040), Little
Cladonia bacillaris Nyl.—on rotting timber. Langlee, Lovells (SL 1005), Moon,
Peddocks, Slate, Worlds End.
Cladonia boryi Tuck.—on thin soil; coastal plain. Peddocks (EL 98-0494),
Cladonia cervicornis (Ach.) Flotow subsp. verticillata (Hoffm.) Ahti—found
once on sandy, gravelly soil. Peddocks (SL 1063).
Cladonia chlorophaea (Flörke ex Sommerf.) Sprengel—on soil. Langlee, Long
(DG 17-2-7-11-01), Nut, Rainsford, Slate, Snake, Worlds End.
Cladonia coniocraea (Flörke) Sprengel—on soil. Bumpkin (DG 20-20-7-30-
01), Button, Gallops, Georges, Greater Brewster, Langlee, Long, Lovells,
Moon, Peddocks, Raccoon, Slate.
Cladonia cornuta (L.) Hoffm.—found once on soil. Worlds End (DG 38-44-6-
Cladonia cristatella Tuck.—on decaying wood. Bumpkin, Gallops, Georges
(DG 8-25-8-18-01), Grape, Langlee, Long, Lovells (SL 1008), Moon, Nut,
Peddocks, Raccoon, Ragged, Rainsford, Slate, Snake, Spectacle, Thompson,
Webb, Worlds End.
Cladonia cylindrica (A. Evans) A. Evans—on rotting wood. Button, Peddocks,
Thompson (SL 1079).
Cladonia farinacea (Vainio) A. Evans—found once on soil. Ragged (EK
Cladonia fimbriata (L.) Fr.—found once on soil. Peddocks (SL 1109).
Cladonia furcata (Hudson) Schrader—on soil; sometimes over rocks. Bumpkin,
Langlee (DG 22-41-8-20-01), Little Brewster (EL 89-0045), Peddocks,
Slate, Worlds End.
Cladonia gracilis (L.) Willd. var. turbinata (Ach.) Ahti—found once on soil.
Moon (DG 24-20-8-27-01).
Cladonia grayi G. Merr. ex Sandst.—on soil or rotting wood. Grape, Langlee,
Lovells, Moon, Peddocks, Raccoon, Ragged, Rainsford (SL 1038), Slate,
Cladonia humilis (With.) J.R. Laundon—on soil. Bumpkin, Button, Gallops,
Georges, Grape, Greater Brewster, Langlee, Lovells (DG 18-25-7-02-01),
Outer Brewster (EK BH10), Peddocks, Slate, Worlds End.
Cladonia macilenta Hoffm.—on soil or rotting wood. Little Brewster, Lovells,
Nut, Raccoon (EL 01-0347), Slate, Thompson.
82 Northeastern Naturalist Vol. 12, Special Issue 3
Cladonia multiformis G. Merr.—found once on soil. Long (DG 17-1-7-11-01).
Cladonia ochrochlora Flörke—found once on soil. Thompson (SL 1070).
Cladonia peziziformis (With.) J.R. Laundon—on sandy soil. Grape, Greater
Brewster, Lovells (SL 1007), Webb.
Cladonia pleurota (Flörke) Schaerer—found once on soil. Nut (DG 1-4-8-28-
Cladonia polycarpia G. Merr.—found once on soil. Thompson (SL 1068).
Cladonia polycarpoides Nyl.—on thin, sometimes sandy soil. Langlee, Lovells,
Nut, Peddocks (EL 90-0141), Snake, Thompson (DG 29-10-7-18-01),
Cladonia pyxidata Flörke—found once on soil. Thompson (SL 1076).
Cladonia ramulosa (With.) J.R. Laundon—on soil. Georges (EL 01-0348), Nut,
Cladonia rei Schaerer—on soil. Georges, Grape, Greater Brewster, Langlee,
Nut, Peddocks (EL 98-0501), Ragged, Rainsford, Snake, Thompson (SL
Cladonia sobolescens Nyl. ex Vainio—on sandy, gravelly soil. Little Brewster
(EL 89-0044), Long (DG 17-6-7-11-01), Nut, Peddocks, Snake.
Cladonia squamosa Hoffm.—on rotting wood or soil. Nut (SL 1043), Thompson.
Cladonia strepsilis (Ach.) Grognot—on thin soil over rock. Little Brewster (EL
89-0046), Nut (SL 1042).
Cladonia uncialis (L.) F.H. Wigg.—on sandy, gravelly soil. Langlee, Peddocks,
Snake, Thompson (DG 29-7-7-18-01), Worlds End.
Collemopsidium halodytes (Nyl.) Grube & B. D. Ryan—common on rocks,
concrete, and barnacles; maritime. All except: Button, Moon, Sheep (EL 01-
0277, from Green; EL 01-0281, from Nixes Mate).
Dermatocarpon luridum (With.) J.R. Laundon—found once on rocks. Langlee
Dimelaena oreina (Ach.) Norman—on rocks. Bumpkin, Button, Calf, Georges,
Grape, Greater Brewster, Langlee, Little Brewster, Lovells, Middle Brewster
(DG 25-36-7-20-01), Outer Brewster, Raccoon, Ragged, Rainsford, Sarah,
Slate, Spectacle, Worlds End.
Diploschistes muscorum (Scop.) R. Sant. subsp. muscorum—parasitic on Cladonia
squamules. Raccoon (SL 1055), Rainsford, Thompson (DG 29-15-7-
Diplotomma alboatrum (Hoffm.) Flotow—found once on rock. Little Brewster
Endocarpon pusillum Hedwig—on bricks and cement. Bumpkin (EL 02-0167),
Gallops, Moon (EK BH117), Thompson.
Evernia mesomorpha Nyl.—on bark. Gallops, Grape, Slate (DG 9-26-5-25-01).
Flavoparmelia baltimorensis (Gyelnik & Fóriss) Hale—on rocks. Grape, Langlee,
Ragged, Worlds End (DG 38-24-6-4-01).
Flavoparmelia caperata (L.) Hale—common on bark. Bumpkin, Button, Calf,
Gallops, Georges, Grape, Greater Brewster, Long, Lovells, Moon, Outer
Brewster, Peddocks, Raccoon (DG 27-11-5-25-01), Ragged, Rainsford,
Sarah, Slate, Snake, Thompson, Webb, Worlds End (EL 01-0179).
Fuscidea arboricola Coppins & Tønsberg—uncommon on bark in shaded areas.
Peddocks, Thompson (SL 1083), Worlds End (SL 1022).
2005 S. LaGreca, E. Lay, D. Greene, E. Kneiper, and M. Lincoln 83
Hyperphyscia adglutinata (Flörke) H. Mayrh. & Poelt—found once on bark;
very uncommon in New England. Long (EL 01-0180).
Hypocenomyce scalaris (Ach.) M. Choisy—on bark. Ragged (SL 1046),
Thompson, Worlds End (DG 38-3-6-10-01).
Hypogymnia physodes (L.) Nyl.—on bark. Grape, Long, Ragged (EK BH261),
Slate, Worlds End (EL 01-0183).
Lasallia papulosa (Ach.) Llano—on rocks. Langlee (DG 22-38-7-25-01),
Ragged, Spectacle, Worlds End.
Lecanora albescens (Hoffm.) Branth & Rostrup—found once on rocks. Thompson
Lecanora caesiorubella Ach. subsp. prolifera (Fink) R.C. Harris—found once
on bark; coastal plain. Worlds End (DG 38-60-6-26-02).
Lecanora congesta Lynge?—found once on rock. Ragged (EK BH703).
Lecanora contractula Nyl.—on rocks in supralittoral zone; maritime. Calf,
Gallops, Georges, Grape (DG I-21-Sept-2002), Graves (DG 3-1-9-4-01),
Greater Brewster, Green, Langlee, Little Brewster, Middle Brewster, Outer
Brewster, Raccoon, Ragged, Rainsford, Sarah, Slate, Worlds End.
Lecanora dispersa (Pers.) Sommerf.—common on various substrata: mussel
shell, brick, cement, rocks, coal, bone, metal, wood, pebbles. All except:
Deer, Grape, Graves, Green, Little Calf, Nixes Mate, Nut, Sarah, Sheep (SL
647, from Lovells; EK BH452, from Snake).
Lecanora hagenii (Ach.) Ach.—on bark and rocks. Georges (EL 01-0015),
Greater Brewster, Hangman (SL 999), Snake (EK BH440).
Lecanora helicopis (Wahlenb.) Ach.—found once on slate. Slate (EL 01-0354).
Lecanora hybocarpa (Tuck.) Brodo—on bark. Bumpkin, Gallops, Grape (SL 988),
Langlee, Long, Lovells, Slate, Snake, Peddocks, Thompson, Worlds End.
Lecanora minutella Nyl.—on conifer bark. Langlee (EK BH651), Lovells (EL
Lecanora muralis (Schreber) Rabenh.—on rocks. Bumpkin, Georges, Grape,
Langlee, Little Brewster, Middle Brewster (SL 1086), Outer Brewster, Peddocks
(EL 01-0052), Rainsford, Sarah, Slate.
Lecanora polytropa (Hoffm.) Rabenh.—on rocks. Calf (EL 01-0054), Georges,
Long, Moon, Peddocks (EL 01-0056), Rainsford, Thompson.
Lecanora pulicaris (Pers.) Ach.—found once on bark. Spectacle (EL 92-0392).
Lecanora saligna (Schrader) Zahlbr.—on wood; commonly found on docks.
Bumpkin, Calf, Gallops, Georges, Greater Brewster, Long, Lovells, Moon,
Outer Brewster, Peddocks (EL 01-0061), Ragged, Rainsford, Sarah, Sheep,
Slate, Snake, Thompson, Worlds End (SL 1019).
Lecanora strobilina (Sprengel) Kieffer—on bark. Gallops (SL 1003), Georges,
Grape (DG 7-22-7-31-01), Greater Brewster, Langlee, Long, Lovells, Moon,
Nut, Outer Brewster, Peddocks, Raccoon, Ragged, Rainsford, Sarah, Slate
(DG 9-6-6-21-01), Snake, Worlds End.
Lecanora symmicta (Ach.) Ach.—on bark. Gallops (DG 23-16-8-6-02), Georges,
Greater Brewster, Langlee, Long, Lovells, Moon, Nut, Outer Brewster,
Peddocks, Rainsford, Slate, Snake, Thompson, Worlds End.
Lecanora xylophila Hue—on rocks in supralittoral zone; sometimes on wood
near shore; maritime. Calf, Georges, Greater Brewster, Langlee (SL 1050),
Little Brewster, Lovells (DG I-24-Jul-2002), Middle Brewster (EL 02-0150),
Outer Brewster, Ragged, Snake, Thompson, Worlds End.
84 Northeastern Naturalist Vol. 12, Special Issue 3
Lecidea cyrtidia Tuck.—on rocks. Button (EK BH426), Lovells (EL 01-0186).
Lecidea tessellata Flörke—found once on rocks. Little Brewster (EL 02-0360).
Lepraria caesioalba (de Lesd.) J.R. Laundon—found once on rocks. Worlds
End (DG 38-20-6-4-01).
Lepraria lobificans Nyl.—on rock, soil and bark. Georges, Rainsford (SL 1100),
Slate (EL 01-0394).
Lepraria neglecta (Nyl.) Erichsen—found once on rocks. Grape (DG 7-17-8-
Leptogium tenuissimum (Dickson) Körber—found once on thin, sandy soil.
Rainsford (EL 01-0028).
Leptorhaphis epidermidis (Ach.) Th. Fr.*—on Betula bark. Long (EL 01-0188),
Peddocks (EL 01-0187).
Melanelia subaurifera (Nyl.) Essl.—on bark and wood. Bumpkin, Button, Gallops
(SL 1002), Georges, Grape, Greater Brewster, Langlee, Long, Lovells,
Outer Brewster, Peddocks, Ragged, Rainsford (EK BH410), Slate, Snake,
Spectacle, Thompson, Webb, Worlds End.
Micarea erratica (Körber) Hertel, Rambold & Pietschmann—on rocks and
pebbles. Bumpkin, Gallops, Grape (EL 01-0195), Lovells, Moon, Peddocks,
Raccoon, Rainsford, Snake.
Mycoblastus sanguinarius (L.) Norman—found once on wood; unusual in New
England outside mountainous areas. Spectacle (EL 92-0186).
Parmelia squarrosa Hale—on bark. Gallops (EL 01-0212), Snake.
Parmelia sulcata Taylor—common on bark, wood, and rocks. All except: Deer,
Graves, Green, Little Calf, Middle Brewster, Nixes Mate, Nut, Raccoon,
Sheep (SL 994, from Langlee).
Parmeliopsis hyperopta (Ach.) Arnold—found once on twigs. Worlds End (EL
Peltigera didactyla (With.) J. R. Laundon—on wet soil. Gallops (DG 23-18-8-
6-02), Rainsford (DG 19-25-8-24-01).
Pertusaria macounii (Lamb) Dibben—found once on bark. Peddocks (SL 1065).
Pertusaria xanthodes Müll. Arg.—found once on bark. Webb (DG 16-16-7-
Phaeocalicium polyporaeum (Nyl.) Tibell*—on shelf fungi. Long, Thompson,
Worlds End (EL 01-0215).
Phaeophyscia adiastola (Essl.) Essl.—on cement and bark. Georges (DG 8-42-
7-24-02). Langlee (SL 993), Lovells, Peddocks, Worlds End.
Phaeophyscia orbicularis (Necker) Moberg—on concrete and rocks. Georges
(SL 986), Peddocks (EL 01-0218).
Phaeophyscia pusilloides (Zahlbr.) Essl.—on bark. Gallops, Georges, Snake
(EK BH485), Thompson.
Phaeophyscia rubropulchra (Degel.) Essl.—on bark. Button, Gallops, Grape,
Langlee, Long, Lovells, Peddocks, Ragged (EK BH278), Rainsford (DG 19-
33-8-24-01), Sarah, Snake, Worlds End.
Phlyctis argena (Sprengel) Flotow—found once on bark. Thompson (SL 1081).
Physcia adscendens (Fr.) H. Olivier—on rocks, cement, and bark. Button
(EK BH400), Gallops, Georges, Grape, Greater Brewster, Langlee, Little
Brewster, Lovells, Middle Brewster, Moon, Outer Brewster, Peddocks,
Ragged, Rainsford, Slate, Thompson.
2005 S. LaGreca, E. Lay, D. Greene, E. Kneiper, and M. Lincoln 85
Physcia aipolia (Ehrh. ex Humb.) Fürnr. var. aipolia—on bark. Georges, Grape
(DG 7-35-8-31-01), Long, Nut (DG 1-3-8-28-01), Peddocks, Thompson,
Physcia millegrana Degel.—common on bark, wood, rocks; found once on a
coal cinder. All except: Deer, Graves, Green, Hangman, Little Calf, Nixes
Mate, Sheep, Slate. (DG 21-3-7-9-01, from Calf; DG 26-8-7-31-02, from
Physcia stellaris (L.) Nyl.—common on bark. Bumpkin, Calf (SL 981),
Deer, Georges, Gallops, Greater Brewster, Langlee, Long, Lovells, Outer
Brewster, Peddocks, Ragged, Rainsford, Sarah, Slate, Snake, Thompson,
Webb, Worlds End.
Physcia subtilis Degel.—on rocks. Button, Calf (DG 21-17-6-1-01), Georges,
Langlee, Middle Brewster, Outer Brewster, Peddocks, Ragged, Rainsford,
Physciella chloantha (Ach.) Essl.—found once on concrete. Bumpkin (EL 02-
Physciella melanchra (Hue) Essl.—found once on a tree. Thompson (SL 1116).
Placynthiella icmalea (Ach.) Coppins & P. James—on soil, bricks, and wood.
Georges, Long, Lovells (EL 01-0249), Moon, Peddocks (EL 01-0255), Raccoon,
Rainsford, Snake, Spectacle, Worlds End.
Placynthiella uliginosa (Schrad.) Coppins & P. James—on soil. Gallops (EL
01-0258), Peddocks, Worlds End.
Polysporina simplex (Davies) Vezda—on rocks. Button, Ragged, Rainsford (EK
BH307), Snake, Spectacle.
Porpidia albocaerulescens (Wulfen) Hertel & Knoph—on rocks. Langlee,
Lovells (EL 01-0260), Ragged, Rainsford, Worlds End.
Porpidia crustulata (Ach.) Hertel & Knoph—found once on rocks. Spectacle
Psilolechia lucida (Ach.) M. Choisy—on shaded rocks and cement. Calf,
Georges (DG 8-15-7-2-01).
Punctelia rudecta (Ach.) Krog—on bark. Bumpkin (EL 02-0174), Button (EK
BH407), Georges, Langlee, Nut, Peddocks, Thompson, Worlds End.
Pyrrhospora varians (Ach.) R.C. Harris—on bark. Bumpkin (EL 02-0217), Button,
Gallops, Georges, Grape, Langlee (EK BH577), Long, Lovells, Moon,
Nut, Outer Brewster, Peddocks, Rainsford, Sarah, Slate, Snake, Thompson
(SL 1080), Worlds End.
Ramalina americana Hale—found once on bark. Snake (EK BH701).
Rhizocarpon distinctum Th. Fr.— on rocks. Little Brewster, Outer Brewster (EL
Rhizocarpon grande (Flörke ex Flotow) Arnold—on rocks. Ragged, Spectacle,
Worlds End (DG 38-23-6-4-01).
Rhizocarpon reductum Th. Fr.—found once on rock. Sarah (EK BH217).
Rhizocarpon rubescens Th. Fr.—found once on rocks. Worlds End (DG 38-36-
Rhizoplaca subdiscrepans (Nyl.) R. Sant.—on rocks. Langlee, Ragged, Slate
(DG 9-35-5-25-01), Spectacle, Worlds End (DG 38-22-6-4-01).
Rimularia badioatra (Kremp.) Hertel & Rambold—found once on rocks.
Worlds End (EL 01-0290).
86 Northeastern Naturalist Vol. 12, Special Issue 3
Rinodina confragosa (Ach.) Körber—found once on rocks. Gallops (DG 23-
Rinodina gennarii Bagl.—very common on wood and rocks; found also on
bone and metal; maritime. Bumpkin, Calf (EL 01-0578), Georges, Graves,
Green (SL 997), Greater Brewster, Hangman, Little Brewster, Long, Middle
Brewster, Moon, Outer Brewster, Peddocks, Raccoon, Ragged, Rainsford,
Sarah, Slate, Thompson, Worlds End.
Rinodina subminuta H. Magn.—found once on bark. Calf (DG 21-29-7-9-01).
Ropalospora viridis (Tønsberg) Tønsberg—found once on bark. Ragged (EK
Sarcogyne regularis Körber—on cement. Snake (EK BH633), Thompson (DG
Sarea resinae (Fr.) Kuntze*—found once on pine resin. Georges (DG 8-40-7-
Scoliciosporum chlorococcum (Stenh.) Vezda—common on bark and wood. Deer,
Georges, Lovells, Nut, Ragged, Rainsford, Slate (EL 01-0293), Snake.
Scoliciosporum umbrinum (Ach.) Arnold—on bricks and rocks. Calf, Little
Brewster, Long, Moon, Nut, Outer Brewster, Peddocks, Raccoon, Rainsford
(DG 19-5-8-24-01), Thompson (SL 1077).
Stereocaulon saxatile H. Magn.—found once on rocks. Spectacle (DG 12-1-6-
Stigmidium marinum (Deakin) Swinscow—found once; parasitic on Verrucaria
mucosa; maritime. Graves (EK BH584).
Thelocarpon laureri (Flotow) Nyl.—on rotting wood, bricks, pebbles, and charcoal.
Gallops, Ragged (EK BH252), Rainsford, Snake (DG 10-17-6-18-01),
Trapelia involuta (Taylor) Hertel—on rotting wood; rocks and pebbles; found
once on nylon rope. Langlee (DG 22-5-7-25-01), Moon (EL 02-0219), Peddocks,
Slate, Snake, Spectacle.
Trapelia placodioides Coppins & P. James—on rocks and bricks in shaded areas.
Button (EK BH359), Calf, Ragged (SL 1049), Rainsford, Snake.
Trapeliopsis flexuosa (Fr.) Coppins & P. James—common on wood. Gallops,
Georges, Greater Brewster, Langlee, Long (EL 01-0302), Moon, Outer
Brewster, Peddocks, Raccoon, Ragged (EK BH298), Snake, Spectacle,
Thompson, Worlds End.
Trapeliopsis granulosa (Hoffm.) Lumbsch—on soil. Ragged, Worlds End (SL
Umbilicaria mammulata (Ach.) Tuck.—on rocks. Langlee (DG 22-19-7-25-01),
Ragged (DG 2-13-8-20-01), Worlds End.
Umbilicaria muehlenbergii (Ach.) Tuck.—on rocks. Langlee (DG 22-17-7-25-
01), Ragged (SL 1051), Spectacle, Thompson, Worlds End.
Verrucaria calkinsiana Servít—found once on rocks. Moon (EK BH100).
Verrucaria degelii R. Sant.—on rocks; maritime. Calf, Graves (EK BH650).
Verrucaria ditmarsica Erichsen—on rocks; maritime. Calf, Graves, Little
Brewster (EL 02-231), Little Calf, Middle Brewster, Nixes Mate, Sheep (DG
13-1-6-7-02), Slate (DG 9-49-6-7-02).
Verrucaria erichsenii Zschacke—on rocks; maritime. Deer, Graves (DG 3-4-9-
4-01), Green, Hangman, Langlee, Little Brewster, Little Calf (DG 6-1-7-9-
01), Long, Nixes Mate (EL 01-0652), Peddocks, Rainsford, Worlds End.
2005 S. LaGreca, E. Lay, D. Greene, E. Kneiper, and M. Lincoln 87
Verrucaria glaucovirens Grummann—found once on brick. Rainsford (EK
Verrucaria maura Wahlenb.—on rocks; maritime. Calf, Graves, Langlee,
Outer Brewster, Ragged (DG 2-8-8-16-02), Sarah (DG 11-3-7-25-01), Slate,
Verrucaria microspora Nyl.—on rocks; maritime. Deer, Little Brewster, Long,
Nixes Mate (EL 01-0629), Peddocks, Rainsford, Spectacle (EK BH188).
Verrucaria mucosa Wahlenb.—common on rocks; maritime. All except: Button,
Calf, Deer, Green, Little Calf, Moon, Nut, Slate, Spectacle (DG 5-3-5-25-01,
Verrucaria muralis Ach.—on rocks and bricks. Bumpkin (EL 02-0225), Gallops,
Grape, Long, Lovells, Moon, Peddocks, Rainsford (EL 01-0603),
Verrucaria nigrescens Pers.—found once on brick. Ragged (EK BH243).
Verrucaria nigrescentoidea Fink—found once on rocks. Rainsford (EK
Verrucaria silicicola Fink in Hedr.—found once on rock. Peddocks (EL 98-
Verrucaria striatula Wahlenb.—common on rocks; maritime. All except: Button,
Calf, Gallops, Green, Little Brewster, Nixes Mate, Sarah, Slate, Spectacle
(DG 8-3-8-18-01, from Georges; EK BH651, from Graves).
Xanthoparmelia conspersa (Ehrh. ex Ach.) Hale—on rocks and pavement.
Bumpkin, Button, Calf, Georges (SL 985), Grape, Greater Brewster, Lovells,
Middle Brewster, Peddocks (EL 01-0319), Raccoon, Ragged, Rainsford (SL
1037), Slate, Snake, Spectacle, Worlds End.
Xanthoparmelia cumberlandia (Gyelnik) Hale—on rocks. Langlee (DG 22-27-
9-25-01), Little Brewster (EL 02-0218), Ragged (EK BH67).
Xanthoparmelia plittii (Gyelnik) Hale—on rocks. Langlee (DG 22-1-7-25-01),
Outer Brewster, Peddocks, Raccoon, Ragged, Rainsford, Slate (EL 01-0321),
Spectacle, Webb, Worlds End.
Xanthoparmelia somloënsis (Gyelnik) Hale—on rocks. Gallops, Langlee,
Lovells (EL 01-0325).
Xanthoria elegans (Link) Th. Fr.—on rocks in supralittoral zone; maritime.
Greater Brewster (DG 30-21-6-1-01), Little Brewster (SL 1096), Slate (SL
Xanthoria parietina (L.) Th. Fr.—common on rocks and bark; found once on
bird down; maritime. Bumpkin, Calf (DG 21-8-6-1-01), Gallops, Georges
(SL 984), Grape, Greater Brewster, Langlee, Little Brewster, Long, Lovells,
Middle Brewster, Moon, Outer Brewster, Peddocks, Rainsford, Slate, Snake,
Thompson, Worlds End.
Xylographa opegraphella Nyl. ex Rothr.—on wood; coastal plain. Langlee (SL
990), Long (EL 01-0337), Peddocks, Raccoon (DG 27-14-5-25-01), Ragged,
Amblystegium serpens (Hedw.) Schimp.—on cement or moist soil. Long,
Worlds End (ML BH55).
Amblystegium varium (Hedw.) Lindb.—on cement; sometimes on wood or
gravel. Bumpkin, Long, Peddocks (ML BH229), Worlds End.
88 Northeastern Naturalist Vol. 12, Special Issue 3
Atrichum angustatum (Brid.) Bruch & Schimp.—on soil. Bumpkin, Georges
(ML BH213), Langlee, Raccoon, Ragged, Slate.
Atrichum crispum (Hampe) Sull. & Lesq.—on soil. Bumpkin (ML BH145).
Atrichum oerstedianum (Müll. Hal.) Mitt.—on soil; disturbed places. Bumpkin,
Grape (ML BH174), Long, Peddocks.
Atrichum undulatum (Hedw.) P. Beauv.—on soil. Bumpkin, Georges, Grape,
Langlee, Peddocks, Slate (ML BH34), Worlds End.
Aulacomnium palustre (Hedw.) Schwägr.—wet soil or wood. Grape (ML
BH179), Peddocks, Worlds End.
Barbula unguiculata Hedw.—on cement or rocks. Georges (ML BH202), Spectacle.
Brachythecium campestre (Müll. Hal.) Schimp.—on soil at base of trees, or on
rotting wood. Peddocks, Worlds End (ML BH69).
Brachythecium curtum (Lindb.) Limpr.—on soil; disturbed places. Bumpkin
(ML BH157), Georges, Peddocks.
Brachythecium oxycladon (Brid.) A. Jaeger—on cement; sometimes on soil.
Bumpkin, Greater Brewster, Long (ML BH118), Outer Brewster, Worlds End.
Brachythecium rutabulum (Hedw.) Schimp.—at base of tree. Worlds End (ML
Brachythecium salebrosum (Hoffm. ex F. Weber & D. Mohr) Schimp.—on rocks
or cement; sometimes on soil, or at base of tree. Bumpkin, Deer, Georges,
Langlee (ML BH248), Nut, Peddocks.
Bruchia flexuosa (Schwägr.) Müll. Hal.—on soil. Grape (ML BH2).
Bryum argenteum Hedw.—on rocks, cement or soil; disturbed places. Deer, Georges,
Grape, Greater Brewster (ML BH39), Nut, Outer Brewster, Spectacle.
Bryum caespiticium Hedw.—on cement or rocks. Calf (ML BH52), Grape,
Bryum capillare Hedw.—on rocks, cement or gravel. Long, Outer Brewster (ML
Bryum lisae De Not. var. cuspidatum (Bruch & Schimp.) Margad.—on cement
or bricks, sometimes soil. Bumpkin, Greater Brewster, Long, Lovells (SL
Callicladium haldanianum (Grev.) H.A. Crum—on rocks, bases of trees, rotting
timber. Grape (ML BH133), Lovells, Peddocks, Worlds End.
Ceratodon purpureus (Hedw.) Brid.—many substrata; the most common moss on
the islands. Calf, Deer (DG BH210), Georges, Grape, Greater Brewster, Langlee,
Lovells, Middle Brewster, Nut, Outer Brewster, Peddocks, Raccoon (ML BH12),
Ragged, Rainsford, Sheep, Snake, Spectacle, Worlds End.
Dicranella heteromalla (Hedw.) Schimp.—on soil, sometimes over rock.
Bumpkin, Grape (ML BH184), Langlee (EK BH189), Long, Nut, Peddocks,
Ragged, Slate, Worlds End.
Dicranum flagellare Hedw.—on soil or rotting wood, sometimes at bases of
trees. Grape, Langlee (ML BH243), Peddocks.
Dicranum montanum Hedw.—on soil, wet rocks, or bases of trees. Grape, Langlee
(ML BH242), Worlds End.
Dicranum scoparium Hedw.—on soil, sometimes over rock. Worlds End (ML
Ditrichum lineare (Sw.) Lindb.—on soil, sometimes over rock. Slate (ML
BH29b), Worlds End.
2005 S. LaGreca, E. Lay, D. Greene, E. Kneiper, and M. Lincoln 89
Ditrichum pallidum (Hedw.) Hampe—on soil. Bumpkin, Grape, Long, Raccoon
(ML BH16), Worlds End.
Entodon seductrix (Hedw.) Müll. Hal.—on cement. Bumpkin (ML BH166).
Fissidens exilis Hedw.—found once on wet soil; uncommon throughout its
range. Worlds End (Ray Abair BH71).
Fissidens osmundoides Hedw.—on soil. Long (ML BH111).
Fissidens taxifolius Hedw.—on rotting timber. Peddocks (ML BH225a).
Funaria hygrometrica Hedw.—on bricks and cement. Bumpkin, Long (ML
BH101), Lovells, Spectacle.
Hedwigia ciliata (Hedw.) P. Beauv.—on rocks. Worlds End (ML BH89).
Herzogiella striatella (Brid.) Z. Iwats.—on rotting wood. Calf (ML BH48).
Herzogiella turfacea (Lindb.) Z. Iwats.—on rotting wood. Peddocks (ML
Homomallium adnatum (Hedw.) Broth.—on tree. Worlds End (ML BH91).
Hygroamblystegium tenax (Hedw.) Jenn.—in drainage ditch. Worlds End (ML
Hypnum cupressiforme Hedw.—on rocks and sometimes cement; shaded areas.
Langlee (ML BH249), Peddocks, Ragged, Slate, Worlds End (ML BH83).
Hypnum pallescens (Hedw.) P. Beauv.—on rocks or bases of trees. Grape, Langlee
Leptobryum pyriforme (Hedw.) Wilson—on cement and bricks. Bumpkin (ML
Leptodictyum trichopodium (Schultz) Warnst.—on cement. Outer Brewster (ML
Leskea polycarpa Ehrh. ex Hedw.—on cement. Long (ML BH115b).
Mnium hornum Hedw.—on soil. Worlds End (ML BH68).
Orthotrichum anomalum Hedw.—on cement. Lovells, Peddocks (ML BH234).
Orthotrichum obtusifolium Brid.—on cement. Long (ML BH115a).
Orthotrichum stellatum Brid.—bases of trees. Langlee (ML BH239b).
Orthotrichum strangulatum P. Beauv.—on cement. Long (ML BH115c).
Physcomitrium pyriforme (Hedw.) Hampe—on wet soil. Calf (ML BH46).
Plagiomnium cuspidatum (Hedw.) T.J. Kop.—on soil, bases of trees, concrete,
and rotting wood. Bumpkin, Georges, Langlee, Long, Outer Brewster (ML
Plagiothecium cavifolium (Brid.) Z. Iwats.—on moist, shaded rocks. Worlds
End (ML BH84).
Plagiothecium denticulatum (Hedw.) Schimp.—on shaded soil. Peddocks (ML
Platygyrium repens (Brid.) Schimp.—on rocks and tree trunks. Langlee (ML
BH241), Worlds End .
Pohlia nutans (Hedw.) Lindb.—on soil. Peddocks, Raccoon, Rainsford, Slate
(ML BH27), Worlds End.
Polytrichum commune Hedw.—on soil; common. Bumpkin (ML BH161),
Grape, Long, Peddocks, Raccoon (ML BH24), Thompson, Worlds End.
Polytrichum juniperinum Hedw.—on soil, often over rock. Grape, Slate, Worlds
End (ML BH77).
Polytrichum ohioense Renauld & Cardot—on soil over rock. Slate (ML
Polytrichum piliferum Hedw.—on rocks. Georges (ML BH205), Long, Nut (SL
BH197), Raccoon, Worlds End.
90 Northeastern Naturalist Vol. 12, Special Issue 3
Schistidium apocarpum (Hedw.) Bruch & Schimp.—on cement and mortar.
Bumpkin, Peddocks (ML BH230).
Steerecleus serrulatus (Hedw.) H. Rob.—on cement. Long (ML BH116).
Tetraphis pellucida Hedw.—on rotting wood. Peddocks (ML BH219).
Thelia hirtella (Hedw.) Sull. & Lesq.—on rocks. Langlee (ML BH247a).
Thuidium delicatulum (Hedw.) Schimp.—at base of tree. Langlee (ML
Tortula muralis Hedwig—on concrete. Thompson (SL BH266) .
Ulota crispa (Hedw.) Brid.—at base of tree. Langlee (ML BH239a).
Ulota hutchinsae (Sm.) Hammar—on rocks. Worlds End (ML BH88).
Weissia controversa Hedw.—on soil; disturbed places. Bumpkin, Deer (SL
BH220), Georges, Greater Brewster (ML BH45).
Calypogeia muelleriana (Schiffner) K. Müller—on shaded soil. Peddocks (SL
Cephaloziella rubella (Nees) Warnst. Raccoon (ML BH20a).
Frullania eboracensis Gottsche—on tree trunks and rocks. Langlee (ML
Lophocolea heterophylla (Schrad.) Dumort.—on soil. Slate (ML BH29a).
Pallavicinia lyellii (Hook.) Gray—on soil. Peddocks (SL BH196b).
Notes on lichen identifications
Some clarifying remarks on the identification and nomenclature of
certain lichen genera need to be made. First, the Bacidia and Bacidina
species on the east coast of North America are poorly known at this
time. We have done the best we can identifying them, but some of these
specimens are difficult to name. Second, Verrucaria is a difficult genus;
we assigned species names as best we could using Taylor (1982) and
Fletcher (1975), in conjunction with Esslinger (1997). We were rather
surprised by the variety of Verrucaria species present in Boston Harbor,
especially considering the Harbor’s long history of use. It is noteworthy
(and reassuring) that our marine Verrucaria species are the same ones
recently reported for nearby Cape Ann by Flenniken and Gibson (2003).
We found a total of seven marine species, which is comparable to that
found in much more pristine habitats, e.g., nine in Newfoundland (Taylor
1982) and eight or nine in the Queen Charlotte Islands, BC (Brodo
and Santesson 1997).
Our overwhelming impression of the Boston Harbor Islands is
that there are few examples of well-developed lichen and bryophyte
communities. Notable exceptions include the gravelly scrub on the
northern spit of Thompsons (lichens); the isthmus between Middle
2005 S. LaGreca, E. Lay, D. Greene, E. Kneiper, and M. Lincoln 91
Head and East Head on Peddocks (lichens); some of the rocky shores
of Calf, Middle Brewster, and Outer Brewster (lichens); and the
Hingham Harbor Islands (namely, Langley, Ragged, and Worlds End;
bryophytes and lichens).
Because of the dearth of well-developed communities of these
organisms, many species reported here were discovered only as a result
of intensive searching. For example, a lone specimen of the moss
Ulota hutchinsae (common elsewhere in New England) was found on
a single rock on Worlds End. Similarly, the lichen Xanthoria elegans
(otherwise common in maritime New England) was located only after
careful searching among similar-looking, orange lichens on Bumpkin,
Great Brewster, Langley, Little Brewster, and Slate. Very few species of
lichens and mosses were ubiquitous; of these, an outstanding example is
the terricolous Ceratodon purpureus—probably the most common moss
on the Boston Harbor Islands.
The long history of human activity on the islands is probably the
best explanation for the low number of well-developed lichen and bryophyte
communities. Docks and battlements along the shorelines have
disturbed the native rocky shore lichen communities, while trampling
and construction have disrupted fragile soil-dwelling cryptogams.
Some lichens and allied fungi which were notably absent from the
islands include: Phaeocalicium curtisii (Tuck. ) Tibell, which grows on
sumac bark; Opegrapha varia Pers. and Phaeographis inusta (Ach.)
Müll. Arg., two common corticolous coastal plain species; and Lichina
confinis (O.F. Müller) C. Agardh, an unusual fruticose lichen that is
found in the upper part of the littoral zone on undisturbed rocky shores
elsewhere in the northeast. In addition, we didn’t find the saxicolous
mosses Schistidium maritimum (Turner) Bruch & Schimp. in BSG and
Ulota phyllantha Brid., both of which are sometimes found in the supralittoral
zone in the northeast (Bates 2000).
Maritime influences may be preventing entire groups of lichens
and bryophytes from inhabiting the islands. For example, there are
very few liverworts present (five species total), probably because salt
and wind create a harsh, desiccating environment which is intolerable
for most liverworts. For the same reason, there are very few cyanolichens—
lichens that contain a cyanobacterial photobiont rather than
a green alga—in the study area. Like liverworts, most cyanolichens
require wet (or at least non-desiccating) habitats. Only three species
of cyanolichens, Collemopsidium halodytes, Leptogium tenuissimum,
and Peltigera didactyla, were found in the present study. Fruticose
epiphytes, which also require humid conditions (Zedda 2002), are
virtually absent from the islands as well.
92 Northeastern Naturalist Vol. 12, Special Issue 3
Most species of lichens, and virtually all the bryophytes, that occur
on the islands are common to the Boston metropolitan area. In
some places in the park, we were surprised to find many common
“inland” lichens and bryophytes successfully growing in the supralittoral
zone, exposed to splashing and high salt conditions. This was
especially true on more sheltered shores, i.e., places with relatively
low wave action. Some examples include Dermatocarpon luridum
and Parmelia sulcata on coastal rocks on Langlee, multiple Cladonia
species in crevasses on the rocky cliffs in a cove on the west side
of Rainsford, and Acarospora fuscata found on rip-rap sea walls on
many of the islands.
On the other hand, in a few cases, wave action appeared to be so
strong that it prevented the growth of lichens, even eliminating some of
the characteristic rocky intertidal species. For example, the steep, northeastern
cove of Outer Brewster is exposed to consistent, strong waves.
No lichens except Verrucaria spp. were found growing on its high walls.
Floating refuse borne by the waves appeared to be abrading these walls,
which could also be preventing lichen colonization.
Lichens of rocky shores: the maritime floristic element. Most
rocky shores on the islands are intermediate between the extremes
of wave exposure: they experience moderate wave action and spray.
These habitats are excellent places to find well-developed examples
of the maritime floristic element—so-called “rocky shore” lichens.
About 10% of the lichens found in the park belong to this element,
and it is these lichens which make the Boston Harbor lichen flora different
from other areas of Massachusetts that we have surveyed. We
suspect that many of these lichens are present on nearby Cape Ann,
but are probably missing from other maritime areas in Massachusetts
because of the absence of rocky shores. The rocky shore lichen communities
are the most consistent, predictable lichen communities on
Rocky shore lichens occur in distinct belts in the supralittoral zone,
as well as the upper part of the littoral zone—much like the algae and
invertebrates that occur below them. This “zonation” phenomenon is
very striking in Europe (Gilbert 2000), but is less pronounced in North
America (Gowan and Brodo 1988). The lichens we found in each belt
are summarized below:
Upper part of littoral zone
Black lichen belt: Stigmidium marinum, Verrucaria spp., Collemopsidium
2005 S. LaGreca, E. Lay, D. Greene, E. Kneiper, and M. Lincoln 93
Orange lichen belt: Caloplaca scopularis, Caloplaca citrina, Xanthoria
parietina, Xanthoria elegans. On certain rocks that have
been nitrified by seabirds, Caloplaca verruculifera will also be
Gray lichen belt: Rinodina gennarii, Amandinea punctata, Lecanora
contractula, Lecanora dispersa s.l., Lecanora xylophila.
In addition, on wooden docks (but not on rock), the lichen
Lecanora saligna is extremely common in the park.
There are some lichen species on our checklist (e.g., Bacidia scopulicola)
that are maritime, but were not found in rocky shore environments
in the park.
There is much variation between rocky shore habitats within the
park. In some places, the distinct lichen belts are clearly evident, while
elsewhere, certain lichen species or entire belts can be absent. This is
due to the highly variable wave exposure gradient, diversified rocky
substrates (e.g., bedrock, boulders, cobble), and variable slopes ranging
from steep cliffs to gradual rock expanses.
It should be noted here that one of the rocky shore lichens identified
during this project, Caloplaca verruculifera, is a new record for Massachusetts.
Our specimens represent the southernmost collections of this lichen
in eastern North America. It has been collected on rocky shores in both
Maine and New Hampshire (Arup 1994), however, so its presence here is
not unexpected. We predict that it may also be found on Cape Ann.
Coastal terricolous lichens: the coastal plain floristic element. On
the east coast of North America, there is a characteristic association of
terricolous lichen species always found in coastal, scrubby areas with
sandy or gravelly soils. These species include Cladina subtenuis and
Cladina submitis; in the Northeast, the lichens Cetraria arenaria and
Cladonia boryi are also typically found. These so-called “coastal plain”
lichens make up 4% of the lichen species found on the islands. As a floristic
element, this coastal plain association reaches its northern limit in
Massachusetts (Brodo 1968), although certain individual species (e.g.,
Cladonia boryi) are found well to the north of the Commonwealth.
Some of the lichens denoted in our list as “coastal plain,” e.g., Amandinea
milliaria and Xylographa opegraphella, are not terricolous. However,
they are included as part of this floristic element because they grow
in the same habitats as the terricolous lichens.
Quantitative measurements of species richness. In general, smaller islands
have lower species counts than larger ones, but this is not always true
due to mitigating factors such as construction/development and proximity
to Boston. For example, Deer is one of the largest islands, but its lichen
flora is very poor due to recent, extensive development. Similarly, Long
and Thompson are two of the largest islands, but they have fewer species
94 Northeastern Naturalist Vol. 12, Special Issue 3
of lichens than many smaller islands. Lichens are extremely sensitive to air
pollution, and these two islands are very close to Boston, which has probably
been the largest source of air pollution for the park.
The air pollution levels in the Boston area, however, have recently
diminished: over the past 15 years, levels of SO
, and groundlevel
have dropped by 55%, 30%, and 30%, respectively (Massachusetts
Department of Environmental Protection 2001). In fact,
one of the DEP-run, Boston-area, SO
monitoring stations is located
in the park, on Long Island. Data from this station collected over the
year 2000 showed a winter monthly average of 14 mg/m3 atmospheric
. On the Hawksworth and Rose (1970) scale, which correlates
lichen presence/absence with winter monthly atmospheric SO
this corresponds to “zone 9”—the second-cleanest air ranking on
their scale. Perhaps because insufficient time has elapsed for the lichen
flora to recover from previous (higher) SO
levels, however, the
lichens present in the park are not yet consistent with those reported
for zone 9.
If these low levels of air pollution continue, though, we expect the
islands closer to Boston to undergo a substantial recovery of their lichen
flora, as has been documented in other areas in North America (Showman
1997) and Europe (Bates et al. 2001). Indeed, some recovery of
the lichen flora may already be taking place in many parts of the park;
many of the species we found appear to have only recently colonized
(e.g., the pollution-sensitive lichen, Ramalina americana, on Snake).
We expect that if human disturbance is kept to a minimum, the lichens
on the islands should continue to grow in abundance and diversity.
The numbers of species are less than those recorded for areas of
comparable size on the mainland. For example, we collected 71 lichen
species on Peddocks (184.3 acres, 74.6 hectares), as compared with 209
species recorded for Wachusett Mountain (225 acres, 91.1 hectares; May
2002). This may be a result of the historically higher air pollution levels
in the greater Boston area than in the old-growth forests of Wachusett
Mountain. Perhaps a more fair comparison can be made with the Sagamore
Hill Solar Observatory, which, like the Boston Harbor Islands, is
located in the greater Boston area. A total of 129 lichen species were
recorded on that 27.5-acre (11.2-hectare) property (Kneiper and Maxfield 1997), but only 52 species were found on 29-acre (15.8-hectare)
Georges Island. The reason for the large difference in species counts
between these two comparably sized areas, both located in metropolitan
Boston, is unclear.
Some factors which influence diversity
Substrata. Initially, abandoned buildings and hard substrate construction
materials can damage cryptogam communities; after a period
2005 S. LaGreca, E. Lay, D. Greene, E. Kneiper, and M. Lincoln 95
of time, however, these items can serve as substrata and actually increase
species diversity. We have found many lichens and mosses growing
on abandoned buildings, docks, and cement fortifications; we have
also found lichens growing on such unusual materials as bone, metal,
feathers, nylon rope, charcoal, brick, barnacles, shells, and pebbles.
Certain species which prefer calcareous substrata, e.g., the moss Schistidium
apocarpum and the lichen Lecanora dispersa, were probably not
as widespread on the islands before human disturbance. And at least
one of the islands—Great Brewster—would have very few lichens if it
weren’t for its cement fortifications. Apparently, the sumac trees there
are too young and too dense for lichens to grow on or under them, and
the sea wall around the island is too new. As a result, the greatest lichen
diversity on Great Brewster is found on the cement.
Birds. High densities of nesting seabirds is another factor that probably
negatively impacts lichens and mosses on some islands. For example,
few lichens, and no mosses, grow on Little Calf and Sheep. It is
true that some saxicolous lichens (so-called “bird rock lichens”) prefer
bird nitrification; for example, on the west shore of Little Brewster, we
observed thalli of maritime Caloplaca spp. thriving in grooves that carried
run-off from bird perches. However, in most nesting areas, guano
coverage is excessive, which seems to prevent the growth of any lichens
or mosses. In addition, trampling by seabirds on soil and grass surrounding
their nests probably prevents the establishment of lichens and
mosses in those habitats.
Table 1. Lichens of Spectacle Island, 1992 vs. present.
Lay’s 1992 survey (voucher specimen) This study (voucher specimen)
Caloplaca citrina (EL 92-0161) Acarospora fuscata (EL 01-0091)
Cladina subtenuis (EL 92-0353) Acarospora glaucocarpa (EK BH176)
Cladonia cristatella (EL 92-0393) Aspicilia caesiocinerea (EL 01-0139)
Cladonia ramulosa (EL 90-0143) Aspicilia cinerea (DG 12-3-6-20-01C)
Lecanora dispersa (EL 92-0271) Collemopsidium halodytes (EL 01-0270)
Lecanora pulicaris (EL 92-0392) Dimelaena oreina (EL 01-0173)
Melanelia subaurifera (EL 92-0022) Lasallia papulosa (EL 01-0185)
Mycoblastus sanguinarius (EL 92-0186) Lecanora dispersa (EK BH186)
Parmelia sulcata (EL 92-0015) Parmelia sulcata (DG 12-3-6-20-10A)
Physcia millegrana (EL 92-0300) Physcia subtilis (DG 12-2-6-20-01)
Placynthiella icmalea (EL 92-0202) Polysporina simplex (EK BH184)
Trapeliopsis flexuosa (EL 92-0226) Porpidia crustulata (EL 01-0361)
Rhizocarpon grande (DG 12-3-6-20-01D)
Rhizoplaca subdiscrepans (DG 12-8-6-20-1)
Stereocaulon saxatile (DG 12-1-6-20-01)
Thelocarpon laureri (EK BH179)
Trapeliopsis involuta (EK BH177)
Umbilicaria muehlenbergii (DG 12-4-6-20-1)
Xanthoparmelia conspersa (DG 12-6-6-20-1)
Xanthoparmelia plittii (EL 01-0324)
Verrucaria microspora (EK BH188)
96 Northeastern Naturalist Vol. 12, Special Issue 3
Historical effects. The long history of human activity on the islands
has probably also had an overall negative impact on the bryophyte and
lichen diversity. Unfortunately, there are no historical reports or specimens
from the islands, so the recovery of the flora over time (i.e., since
the last date of human occupation) cannot be tracked.
On Spectacle, however, the lichens collected by one of us in 1992
(Elisabeth Lay, unpubl. data) can be directly compared with those
recorded in the present study. In the intervening years, Spectacle was
capped by fill from Boston’s “Big Dig” highway project, eliminating
the previous flora. Today, the species present on Spectacle are almost
completely different from the previous species, and there are actually
more of them (Table 1). This is because almost all the lichens present
today were imported from the mainland on rocks used to build the riprap
seawall. We know this because most of these species (e.g., Umbilicaria
muehlenbergii) are, elsewhere, only found on inland rocks—never
in rocky shore environments. In addition, the size of some of the thalli
present on the rip-rap rocks indicate that they are much older than three
years. The future of these lichens in this maritime environment is uncertain
at best; however, the present study provides important baseline
data for use in monitoring the health and success of this unusual island
Conservation and management recommendations
From our observations, it appears that human disturbance and air
pollution are the two most important factors limiting the colonization
of lichens and bryophytes on the islands. Management decisions that
limit such disturbance and pollution can only improve the Boston
Harbor lichen and bryophyte communities. One particular problem
with regards to human disturbance is excess foot traffic, which destroys
soil-dwelling lichens. Walking trails should be clearly identified
to avoid critical lichen areas, such as the west side of Rainsford
(fragile soil lichens such as Leptogium tenuissimum); the Peddocks
isthmus (where the only population of Cetraria arenaria is found);
and the north tip of Thompson (terricolous Cladonia communities).
The well-developed orange Caloplaca zones on Calf, Middle
Brewster, and Outer Brewster also merit special protection, since they
appear to represent the southernmost occurrence of this type of lichen
community in eastern North America. Further, the wetland on the
north peninsula of Worlds End is home to the uncommon moss, Fissidens
exilis, and should be protected. Plans for future development
activities and hiking trails on all the Harbor Islands should consider
the occurrence and continued growth of these special coastal plain,
rocky shore, and wetland cryptogam communities.
2005 S. LaGreca, E. Lay, D. Greene, E. Kneiper, and M. Lincoln 97
We are grateful to the following specialists who identified or confirmed
specimens for us: Ted Ahti, Ernie Brodo, Bill Buck, Ted Esslinger, Sam Hammer,
Dick Harris, Jim Hinds, Kerry Knudsen, Thorsten Lumbsch, Phil May,
Norton Miller, John Sheard, Lucyna Sliwa and Cliff Wetmore. Bryologist Ray
Abair was a great help to us at the outset of this project. We would also like to
thank Don Pfister for assistance and advice. This survey was made possible by
the collaborative efforts of the Massachusetts Natural Heritage and Endangered
Species Program, the Island Alliance, and the National Park Service, on behalf
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