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3200006Notes of the NortNhOeRNaTHosrEttheAeSraTnsEte RrNnN NaNatAtuuTrUraaRliAsltiLsIStT, Issue 14/2,V 21o03l.( 0114)7:,3 N9–o4. 22
Xanthoria parietina, a Coastal Lichen, Rediscovered in Ontario
Irwin M. Brodo1,*, Chris Lewis2, and Brian Craig3,4
Abstract - Xanthoria parietina, a conspicuous orange foliose lichen, has been doubtfully
recorded as part of the Ontario lichen flora because the previous documented reports were very
old (1868 and 1917) and it had never been reported since. Here, we document a number of new
sightings, all in southern Ontario. A previous report of this lichen from “Longulac” that was
interpreted as Long Lake in Frontenac County is corrected to Longlac in the Thunder Bay
District, and the specimen proved to be Xanthomendoza hasseana. A search for the lichen
around Belleville, one of the original localities, proved fruitless. It is still not clear whether the
new sightings of Xanthoria parietina represent a reintroduction of this coastal species to the
inland sites, or whether the lichen has persisted in southern Ontario for almost 140 years, but
was never reported. Substrate enrichment (eutrophication due to agricultural activity) in the
region is one explanation for the spread of the lichen in southern Ontario.
Introduction. Xanthoria parietina (L.) Th. Fr., as can be surmised by its vernacular
name, “the maritime sunburst lichen,” was considered to be narrowly confined to
coastal areas in North America, although widespread in the rest of the world (Hinds
1995, Lindblom 1997). The distribution map in Brodo et al. (2001) shows it to occur
from the southeastern corner of Pennsylvania to Newfoundland in the east, as well as
in a small area of coastal Texas, with scattered populations in coastal California,
Oregon, Washington, and southwestern British Columbia. Although a specimen of X.
parietina was known to us from southern Ontario (Belleville, “On trunks, very
common,” Macoun, 533(42), Aug. 17, 1868 [National Herbarium of Canada
(CANL)]), it was regarded to be so questionable (perhaps mislabeled) that it was not
even mentioned in a treatment of the lichens of southern Ontario (Wong and Brodo
1992). In her monograph of the North American species of Xanthoria, however,
Lindblom (1997) reported seeing a second specimen from Ontario at the Smithsonian
Institution (US). It is from “H.B. Post, Longulac, Long Lake,” collected by G.K.
Jennings and O.E. Jennings in July1917. In the absence of any such locality name,
current or historic, in Canadian gazetteers, a guess was made that the locality was
actually “Long Lake” in Frontenac County of southern Ontario and was mapped as
such by Lindblom. Nevertheless, because the species had not been seen in recent
years despite its being large, brightly colored, and very conspicuous (Fig. 1), it was
thought to be extirpated from Ontario, and these localities were left off the map in
Brodo et al. (2001). Hinds (1995) mentioned two records from the Great Lakes
region. One (Calkins 13 [US]) reported by Rudolph (1955) from Cook County, IL
(not Michigan, as given by Hinds [1995]), proved to be Xanthomendoza hasseana
(Räsänen) Søchting, Kärnefelt, & S. Kondr. according to an annotation by Lindblom
in 1997. The other, collected by Louis Agassiz in 1868 from “Lac Supérieur” (Farlow
Herbarium [FH]) is true X. parietina, but its vague locality makes it impossible to
know where it was actually found.
It has always been puzzling to North American lichenologists why Xanthoria
parietina, such a widespread lichen, known from Australia, Africa, Asia, and throughout
much of Europe (Lindblom 1997), should be so closely associated with coastal
localities in North America. In Maine, where the species’ distribution has been studied
in detail (Hinds and Hinds 1993, Hinds 1995), the range of X. parietina is almost
invariably coastal. Wherever it occurs, it grows in great abundance, covering not only
suitable bark and wood substrates, but also rocks, cement walls, and gravestones. In
one of the rare California localities, it was covering an Aesculus californica (Spach)
Nutt. (buckeye) rendering all the branches an eerie orange. A cement-walled building
300
2007 Notes 301
in Martha’s Vineyand, MA, was similarly covered (Sharnoff and Sharnoff 1997).
McCune (2003) also mentions its great abundance in a newly discovered and rare
locality in Oregon. This is not a lichen that is easy to overlook, and yet, despite the
considerable collecting efforts of observant naturalists and collectors such as Roland
Beschel, Roy Cain, John Krug, Rupert Warren, and Pak Yau Wong, not to mention
John Macoun, this lichen has been represented in southern Ontario in only a single
locality based on specimens collected almost 140 years ago, and somewhere in the
western Great Lakes region based on a specimen over 150 years old.
Observations. In the process of studying urban lichens as part of a pilot project by
the Ecological Monitoring and Assessment Network (EMAN) using lichens as biological
indicators of air quality in southern Ontario, a small, rather depauperate specimen
of X. parietina was discovered in the University of Guelph Arboretum by B. Craig
(Fig. 1d). Healthier specimens were collected by Craig north of Dunnville and at the
Canada Centre for Inland Waters in Burlington (Fig. 1b). Independently, C. Lewis
found excellent specimens of this species north of Craig’s discoveries: in Hanover
(Fig. 1a), Paisley (Fig. 1c), Arthur, and elsewhere in the region (Appendix 1). The most
extraordinary occurrence was near Orangeville in Dufferin County, where X. parietina
occurred along a drainage ditch, almost entirely covering trees of several tree species,
especially Acer negundo L. (Manitoba maple), but also Fraxinus americana L. (white
Figure 1. Xanthoria parietina specimens from southern Ontario: a. Paisley, b. Burlington,
c. Hanover; d. Guelph. Scale = 1 cm in all photos.
302 Northeastern Naturalist Vol. 14, No. 2
ash) and Salix sp. (willow). Most recently, Lewis discovered some good colonies of X.
parietina growing on Acer negundo near a creek just east of Bowmanville
(Clarington). These localities are mapped in Figure 2.
From Figure 2, one might suspect that the species occurs all over southwestern
Ontario, but field investigations by Lewis northwest of Paisley into Port Elgin and
Southampton did not yield sightings, nor did trips to Owen Sound and Chatsworth.
Brodo also sought it without success on the Bruce Peninsula and Manitoulin Island in
2005. In Brodo’s resurvey of the Belleville region in 2006, Xanthoria parietina was
not seen, although Xanthomendoza fallax (Hepp ex Arnold) Søchting, Kärnefelt & S.
Kondr. and, to a lesser extent, Xanthomendoza ulophyllodes (Räsänen) Søchting,
Kärnefelt & S. Kondr. were found in abundance on a variety of deciduous trees and
lignum. The most recent discoveries of Xanthoria parietina in Reaboro and just east of
Bowmanville, however, extend the range eastward towards Belleville. The striking
NW–SE alignment of localities between Dunnville and Paisley may well be an artifact
of collecting efforts in that corridor, although it somewhat approximates the location of
the Niagara Escarpment, and almost all the localities fall within the Silurian dolomite
belt between the Bruce Peninsula and Niagara Falls (Fig. 2).
The Jennings and Jennings specimen labelled “Longulac,” a locality not listed in
any Canadian gazetteer, was an enigma. We first assumed that “Longulac” was
actually Long Lake in Frontenac County east of Peterborough, which is where
Lindblom (1997) mapped it. However, the labels of a number of bryophyte specimens
at CANM collected between 15–20 July 1917 by Jennings from this locality all
were titled “Flora of Western Ontario.” The label for Plagiomnium medium (Bruch &
Schimp. in B.S.G.) T. Kop. elaborated on the locality “Longulac,” saying that it was
“1 mile south of Revillon.” Unfortunately (and frustratingly), that locality is also
absent from all Canadian gazetteers we consulted. There is, however, a “Longlac” in
the Thunder Bay District at the northern end of Long Lake, deep in the boreal forest,
Figure 2. Distribution of Xanthoria parietina in southern Ontario. = recent discoveries; =
historic collection. Shaded area is the Silurian dolomite belt (Ontario Ministry of Northern
Development and Mines 2003).
2007 Notes 303
and the bryophytes collected from Longulac are indeed boreal species (e.g., Bryum
pseudotriquetrum (Hedw.) Gärtn.; Meyer & Scherb., Plagiomnium ellipticum (Brid.)
T. Kop.; P. medium; and Aulocomium palustre (Hedw.) Schwaegr.) that are not
normally found in southern Ontario (Linda Ley, Canadian Museum of Nature,
Ottawa, ON, Canada, pers. comm.). Since Long Lake is also mentioned on the label,
this is almost surely the locality of the Xanthoria specimen, which would put a record
of Xanthoria parietina deep into the boreal forest, far out of its normal range. We
therefore borrowed the specimen from the US National Museum (US) and quickly
determined that it was actually Xanthomendoza hasseana , a very common boreal
species. In fact, Lindblom had identified the specimen correctly but somehow, the
record was mistakenly included with Xanthoria parietina for mapping.
The Agassiz no. 243 collection cited by Hinds (1995) was borrowed from the
Farlow Herbarium and could be confirmed as true X. parietina. The only locality
given on the label, “Lac Supérieur,” is too vague to enable us to determine
whether it was collected in Ontario or in one of the lake states in the United
States. We therefore were unable to map it. Other than that locality, all the
presently known localities of X. parietina in Ontario are indicated in Figure 2,
with the historic Belleville collection marked with a square.
Discussion. The intriguing question is whether Xanthoria parietina has, in
fact, returned to the region or whether it has been there all the time but, for some
reason, was never was noticed, or, at least, recorded, for 140 years. Is the southern
Ontario population physiologically and genetically different from the eastern
coastal populations? Possible explanations for the reappearance or expansion of
X. parietina in southern Ontario include 1) climatic conditions or even climate
change, 2) nutrient enrichment, 3) a salinity effect, and 4) accidental introduction.
There are few climatic similarities between the east coast and southern Ontario.
The climate is “oceanic mid-boreal” to “oceanic low boreal” on the coast (always
humid, with cool to warm summers, frequent fogs and mild winters) and relatively
continental inland: “humid high cool temperate” to “humid high moderate temperate”
(sometimes humid, but with hot summers, infrequent fog, and cold to mild winters)
(Ecoregions Working Group 1989). All the Ontario specimens have been found
growing on bark, never concrete, mortar, or any other “rock” substrate. By contrast,
along the east coast, Xanthoria parietina is often collected on concrete walls or fences
and even on rocky outcrops near the sea. In general, when lichens that are normally
corticolous are found on rock, the conditions surrounding the saxicolous sites are
especially moist, as would occur with frequent coastal fog. On the other hand, the
climate on the Lake Superior shore is quite oceanic and other coastal lichen species
occasionally are found there. For example, Xylographa opegraphella Nyl. ex Rothr.
has recently been reported from coastal localities in Michigan and Wisconsin (Bennett
2006) It is therefore conceivable that the Agassiz collection from the Lake Superior
region is from a humid lakeshore locality having an oceanic climate.
Xanthoria parietina is well known to respond positively to nutrient enrichment,
especially with nitrogen (Brodo 1968, Welch et al. 2006, and references therein).
Lindblom (1997) mentions the affinity of X. parietina for anthropogenous substrates.
Rapid industrial and agricultural development in southern Ontario in the 20th century
has contributed to significant increases in nitrogen deposition. Although leveling off
since 1980, NO3 deposition exceeds 25 kg/ha/yr in areas of southern Ontario (Environment
Canada 2004). McCune (2003) suggests that ammonia pollution (from cattle
urine and manure-saturated soils, and degassing from rivers) in the area around the
lower Wilson River in Oregon, has “created” suitable habitat for this nitrophilous
species (along with a few others), and has permitted it to invade the area where it
never occurred before. The same thing may have occurred in highly agricultural
southern Ontario over the past 60 or 70 years. Ammonia emissions are currently
304 Northeastern Naturalist Vol. 14, No. 2
greater than 500 kg/km2 and are projected to increase over the next decade (Environment
Canada 2004). The abundance of Xanthoria parietina on trees near a drainage
ditch filled with run-off from surrounding fertilized fields lends support to the
possibility of an enrichment effect. The alignment of localities within the calcareous
Silurian dolomite corridor (Fig. 2) suggests that lime-rich dust in the region may also
be involved in the abundance of the species.
Hinds (1995) found that the distribution of Xanthoria parietina on gravestones in
Maine closely parallels the distribution of salt aerosols presumably emanating from the
nearby ocean shore, and he concluded that salt deposition was the deciding factor in
determining the occurrence of the species in that state. The increased use of road salt in
southern Ontario over the last 50–70 years could therefore be another reason for the
expansion of X. parietina in the region since the sites of most of the recent collections
are within close proximity to roadways where the use of salt is evident.
Lichens are occasionally introduced into an area by accident when their substrate,
such as young trees or boulders still supporting viable lichens, are brought into
an area. If this happened in southern Ontario, when might it have occurred?
It may be possible to estimate the time of arrival of these thalli and the direction of
their spread by measuring maximum thallus diameters in the various localities. European
studies cited in Hale (1973) give radial growth rates of up to 2.5 mm per year for
Xanthoria parietina, although measurements of the growth rate of individual thallus
lobes (0.3 mm/month) in Bristol, UK, suggest that a rate of 3.5 mm/year is possible (Hill
2002). Armstrong (1984) and Welch et al. (2006), however, found that moderate levels
of nitrogen enrichment can increase the growth rate of Xanthoria parietina. Based on
the sizes of the Ontario thalli, and assuming an approximate growth rate of 3.0 mm/year,
we can estimate the age of some of the populations.
The largest specimen found in Paisley, the northernmost locality (Fig. 2), was
less than 100 mm in diameter, whereas thalli in Hanover were up to 120 mm. These
thalli were growing on trees that were part of the original sub-division landscaping
done approximately 30 years ago. Of course, these trees would have been nursery
stock (5–10 years old) and not seedlings when they were planted. Assuming thallus
establishment took place after planting (not necessarily the case; see above), combined
with a consideration of thallus size and planting date, the thalli in Hanover are
likely anywhere from 17–20+ years old.
The specimens encountered in Arthur, south of both Hanover and Paisley, were
largest and covered the most area (especially on trees near the drainage ditch), and they
were growing on larger trees. Unfortunately, we could not measure the lichen diameters
since the thalli were growing relatively high up on a multi-stemmed Acer saccharinum
L. (silver maple). The trunks were still relatively smooth, just like Acer
platanoides L. (Norway maple) and Tilia sp. (little leaf linden) trunks and were
probably “suckers,” the result of a home owner cutting the original tree down, leaving a
stump. Cores of this tree could give more exact ages of thalli, but these Arthur
specimens are probably older than the ones found to the north (Hanover, Paisley,
Mount Forest, etc.). The largest thalli in the Hanover/Burlington area were approximately
300–320 mm in diameter. (No systematic observations of thallus diameter were
made in Guelph.) It is tempting to postulate that Xanthoria parietina populations are
therefore spreading from an area centered around Arthur both northward and southward,
but more controlled observations are needed, and this conclusion is very
tentative. Whether their origin in the region is by natural expansion or by introduction
on planted trees such as the nursery stock used in landscaping (see Lindblom 1997)
cannot easily be determined, except perhaps by genetic profiling.
Conclusions. It is now apparent that X. parietina is still very much a part of the
southern Ontario lichen flora and should be considered as potentially present in any
southern Ontario pollution monitoring surveys.
2007 Notes 305
Lichens have a well-deserved reputation for indicating environmental change.
Van Herk (2002) summarized methods for using lichens on roadside trees to assess
eutrophication (especially by ammonia pollution) in the Netherlands. These techniques
could be applied in future studies of the X. parietina populations in Ontario,
considering McCune’s (2003) suggestion that such environmental changes have
created suitable habitat for colonization (by new invasion or range expansion) in
Oregon. Xanthoria parietina seems to have a competitive advantage over other
foliose lichens, especially more acidophilic species, where levels of nitrogen enrichment
are particularly high (Welch et al. 2006). Recent eutrophication may thus
explain why the experienced collectors who visited southern Ontario in the first half
of the 20th century did not find X. parietina.
Although our purpose in this paper was to document the expansion of a rare
Ontario lichen, we must also point out that, if eutrophication is the cause of a range
expansion with respect to a nitrophilous lichen such as Xanthoria parietina, this
same eutrophication can result in the overall loss of lichen species diversity in the
region (Wolseley et al. 2006). Whereas nitrogen enrichment may increase the growth
of many lichens at low levels when nitrogen is a limiting factor, higher level of
nitrates and ammonium in the atmosphere are toxic to lichens, even X. parietina
(Welch et al. 2006).
Xanthoria parietina should be sought in inland localities throughout the region
and, indeed, throughout the northeast, so that we can better understand its distribution,
especially if it is changing.
Acknowledgments. We warmly thank Joan Crowe and Bruce Allen for the historic
information pertaining to Otto and Grace Jennings and their collections in
northwestern Ontario. We also thank Gregory McKee at the Smithsonian Institution
for locating and sending us the specimen from Longulac, and we thank Dr. Chris
Eckert at the Fowler Herbarium, Queens University, for checking the herbarium for
Xanthoria parietina records from Ontario. The manuscript benefited from the comments
and suggestions of Pak Yau Wong, Fenja Brodo, James Hinds, and David
Richardson. The distribution map was kindly produced by Noel Alfonso of the
Canadian Museum of Nature using ArcView GIS software. We are grateful to Donna
Naughton and Michelle LeBlanc, also of the Museum, who helped polish the figures.
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Appendix 1. Specimens seen. Specimens collected by authors B. Craig and C. Lewis were sent
to I.M. Brodo for verification. A variety of habitats along a total of 92 km of road were
surveyed, and 60–70 trees were examined. The specimens were studied using standard stereomicroscopic
techniques, and vouchers were deposited in the National Herbarium of Canada
(CANL) at the Canadian Museum of Nature.
Xanthoria parietina
Canada. Ontario. BRUCE COUNTY: Paisley, (approx. 25 km NW of Hanover), 44°18'N,
81°16'W, C. Lewis 2, 28 Dec. 2005 (CANL); DUFFERIN COUNTY: Orangeville, 43°54'N,
80°9'W, Lewis 120, 28 Jan. 2006 (CANL); County Road 109 between Orangeville and Arthur,
43°51'N, 80°24'W, C. Lewis 121, 28 Jan. 2006 (CANL); Shelburne, 44°04'N, 80°11'W, C.
Lewis 125, 29 Jan. 2006 (CANL); DURHAM COUNTY: Bowmanville (Municipality of
Clarington), Along Soper Creek, East Branch, 43°53'N, 78°40'W, on Acer negundo, C. Lewis,
s.n., 26 July 2006 (CANL); GREY COUNTY: Hanover, 44°9'N, 81°2'W, C. Lewis 1, 18 June
2005 (CANL); HALDIMAND COUNTY: North of Dunnville, on Fraxinus americana,
42°59'30.9"N, 79°40'53.8"W, B. Craig, s.n., August 2002 (CANL); HALTON COUNTY:
Burlington, just outside the Canada Centre for Inland Waters, adjacent to Lake Ontario,
growing on Tilia sp., 43°17'58.6"N, 79°47'58.2"W, B. Craig, 14 March 2004 (CANL);
HASTINGS COUNTY: Belleville, Macoun 533 (42), 1868 (CANL); VICTORIA COUNTY:
Reaboro, 44º19'N, 78º39'W, C.Lewis (photo voucher). WELLINGTON COUNTY: Arthur (405
George St.), 43°50'N, 80°32'W, C. Lewis 122, 123, 28 Jan. 2006 (CANL); Mount Forest,
44°0'N, 80°46'W, C. Lewis 124, 28 Jan. 2006 (CANL); Guelph, University of Guelph Arboretum,
on Salix sp., 43°32' 08.9"N, 80°12' 57.2"W, B. Craig, s.n., 12 July 2002 (CANL).
Locality uncertain: “Lac Supérieur,” L. Agassiz 243, 1868 (FH).
Xanthomendoza hasseana
Canada. Ontario. THUNDER BAY DISTRICT: “On dead Populus balsamifera. H.B. [Hudson
Bay] Post, Longulac [Longlac], Long Lake, Ontario,O.E. and G.K. Jennings, 12 July 1917”
(US). Det. by C.C. Plitt as Xanthoria parietina; annotated by L. Lindblom as X. hasseana.
1Canadian Museum of Nature, PO Box 3443, Station “D,” Ottawa, ON K1P 6P4 Canada.
2Biology Department, Trent University, 1600 West Bank Drive, Peterborough, ON K9J 7B8
Canada. 3Ecological Monitoring and Assessment Network Coordinating Office, Environment
Canada, Canada Centre for Inland Waters, 867 Lakeshore Road, Burlington, ON L7R 4A6
Canada. 4Current address - Southwestern Ontario Field Unit, Parks Canada Agency, 15 Duke
Street East, Kitchener, ON N2H 1A2 Canada. *Corresponding author - ibrodo@mus-nature.ca.