There are few detailed surveys of lichens in the Canadian Arctic Archipelago (CAA) and only one from Victoria Island, which previously recorded 108 species. We surveyed a further 31 sites near Cambridge Bay and another eight sites from the Wellington Inlier, an area of Precambrian Era rocks, about 70 km to the northwest of Cambridge Bay. Based on these surveys and existing records, a total of 237 species are now reported that include 186 from our sampling sites and another 51 from various previous collections. Thirty-five species were previously unreported from the Archipelago. The 39 surveyed sites surveyed were from six geographic locations and 40% of 237 the lichen species occurred at only one location. Only three species occurred at all six locations. To date, no endemic species have been recorded for Victoria Island and only one is known for the CAA; likely a consequence of the recently deglaciated landscape (ca. 5000 years).
Introduction
Lichens are key components of arctic ecosystems and provide an important food source for biota such as muskox and caribou (Thomas and Hervieux 1986). During the winter months, caribou forage primarily on lichen mats which are readily digested by caribou and are high in energy relative to other available forage (Thomas and Hervieux 1986; Webber et al. 2022). For these large herbivores, a good understanding of lichen cover and distribution is essential particularly when considering management of biologically relevant protected areas (Jenkins et al. 2020).
This study presents the results of detailed lichen surveys for southern Victoria Island (also known as Kitlineq), near the Canadian High Arctic Research Station (CHARS), Nunavut, Canada. The surveys were undertaken in summers of 2018 and 2019 to enhance knowledge of the terrestrial flora within the CHARS Environmental Research Area (ERA) which includes watersheds that flow into the Dolphin and Union Strait to Bellot Strait and McClintock Channel. The land area of the ERA covers the south and eastern portion of Victoria Island and a strip of land approximately 1000 km wide and 200 km deep on the main continent to the south of the strait. The ERA exhibits a strong climatic gradient that includes four of the five Terrestrial Bioclimatic Subzones that occur in the circumpolar Arctic (CAVM Team 2024). Owing to the steep climatic gradient, the region was identified as a ‘hemispheric hot spot’ (Lawler et al. 2009), where major climate-driven biodiversity shifts are predicted (e.g. Wrona et al. 2016). There are already indications of both warming and increased precipitation (Łupikasza and Cielecka-Nowak 2020) with a consequent vegetation change in the Canadian Arctic (Pearson et al. 2013; Myers-Smith, et al. 2019).
The aim of our study was to obtain a comprehensive inventory of the lichen species present in southern Victoria Island and to provide catalogued herbarium specimens as a baseline for ongoing morphological and molecular-based research including DNA barcoding (e.g. Pentinsaari et al. 2020). The work contributes to the Science and Technology Framework as outlined in Polar Knowledge Canada (2020) which focuses on detecting and predicting change based on an adequate baseline knowledge of existing vegetation. Specifically, the aim is to “Improve knowledge of dynamic northern terrestrial, freshwater and marine ecosystems in the context of rapid climate change” (Polar Knowledge Canada 2020). Our study also assesses “the status, distribution, and conditions of terrestrial species, populations, communities, landscapes/ecosystems as well as the key processes/functions occurring in the Arctic” as outlined in the Canadian Arctic Archipelago Arctic Terrestrial Monitoring Plan (Christensen et al. 2013).
Study Area - Victoria Island ( Inuinnaqtun: Kitlineq) forms part of the Canadian Arctic Archipelago (CAA) which is composed of 94 major islands with an individual area greater than 130 km2 ( https://en.wikipedia.org/wiki/Arctic_Archipelago) and 36,469 smaller islands (Adams & Dunbar, 2007) lying predominantly to the north of the main continent and of the Arctic Circle. The Island has an area of 217,291 km2 (83,897 mi2) making it the second largest island in Canada and the eighth-largest island in the world. It is separated from continental northern Canada by Dease Strait and Coronation Gulf (part of the Northwest Passage) and averaging 70 km in width. Politically, Victoria Island is divided between Northwest Territories (west) and Nunavut (east). The total population is 2168 with about 1760 living in Cambridge Bay (69° 07′ N, 105° 03′ W) and the remainder; around 408, in Ulukhaktok (70° 44′ N, 117° 46′ W) (Canadian census, 2021).
Geology - Victoria Island is underlain by dolomite, limestone, sandstone and shales so that lichen substrata across the island are mainly calcareous (Fyles et al. 1963; Rainbird et al. 2013; Harrison et al. 2013; 2015). The northwest of the Island has a belt of Precambrian rocks that form the Shaler Mountains (maximum elevation 655 m), and there is an inlier of similar composition (The Wellington Inlier) about 80 km to the west of Cambridge Bay. Victoria Island was covered by the Laurentide ice sheet during the Wisconsin glaciation from 75000 to 11000 years BP and the landscape is made up of numerous glacial landforms including extensive moraines and numerous lakes (Dyke 2005; Storrar and Stokes 2007). The only protected site in Victoria Island is Ovayok Territorial Park about 15 km east of Cambridge Bay. The reserve is centred on Mount Pelly (Ovayok/Uvajuq) which is an esker with an elevation of more than 200 m.
Climate - Cambridge Bay has a polar climate with no month having a mean temperature of 10°C or higher (ECCC 2022). The sun is continuously below the horizon from 30th November to 11th January, and above the horizon from 19th May to 22nd July. Only four months (June to September, inclusive) have mean temperatures above 0°C. July is the warmest month with daily mean temperature of 9.4°C, mean highest daily temperature of 13.3°C with the absolute highest temperature recorded of 28.9°C on July 1st, 1930. Winter months are very cold with daily mean temperatures lower than -20°C from November to April, inclusive. The lowest recorded temperature is -52.8°C on January 3rd, 1935. Average annual precipitation is low at 150.4 mm with 72.1 mm falling as rain and highest falls of 23.9 mm in July and August. Annual snowfall averages 80.2 cm, averaging around 7 cm per month from November to May, with the highest fall,15.9 cm, in October. Perennially frozen ground, permafrost, lies beneath the entire ecozone and can reach a thickness of 1 km. In summer, a thin (<1m) surface layer can thaw (active layer) and, because the ground below is frozen, the poor drainage, together with low evapotranspiration, means that, despite the low annual precipitation, there can be extensive surface water with lakes and streams. The constant freezing and thawing create unstable soils that can form patterned ground.
Climate change - Over the last 100 years, the Arctic has seen an average warming of 1.5°C and it is expected to increase at least another 2°C before the end of this century (IPCC 2023). This has resulted in a noticeable “greening” for many local areas (Angohiatok et al. 2023; Schaefer 2023). Climate data indicate that between 1948 and 2016 average temperatures increased by 2°C in Cambridge Bay causing widespread ecological shifts (Sim et al. 2019). It is, therefore, urgent to understand and document current plant biodiversity such that ecosystem change can be both detected and monitored.
Vegetation - Victoria Island has a Köppen Climate classification of ET (Polar Tundra). Botanically, it lies entirely within the Canadian Arctic ecozone and, together with most of the archipelago, the subzone Northern Arctic (Wiken 1986) which covers 1.5 million square kilometres, or about one seventh of Canada and is one of the largest arctic ecosystems in the world. Victoria Island spans bioclimate subzones D and C, reflecting the climatic gradient across the island (Walker et al. 2005). Subzone C covers the northern and eastern portion of the island and has a mean July temperature of 5–7°C, a summer warmth index (i.e., sum of mean monthly temperatures greater than 0 °C) of 9–12, 5–50% cover of vascular plants, herbaceous layer 5–10 cm tall, prostrate and hemi-prostrate dwarf shrubs less than 15 cm tall, and 75–150 species in local floras. Subzone D (southern and west) has a mean July temperature of 7–9°C, a summer warmth index of 12–20, 50–80% cover of vascular plants, herbaceous and dwarf shrub layers 10–40 cm tall, and 125–250 species in local floras. The Canadian High Arctic Research Station (CHARS) is leading bioclimatic mapping of Victoria Island to improve resolution of the boundaries between subzones C and D on the island based on results of fieldwork and aerial surveys and to establish detailed monitoring sites around Cambridge Bay (McLennan et al. 2017). Saarela et al. (2020) report that the vascular plant flora of Victoria Island comprises 38 families, 108 genera, and 272 species and provide an extensive description of the terrain of Victoria Island. Many plants are herbaceous with a few low/prostrate woody species such as the arctic willow.
In addition to the vascular plants there are many species of bryophytes and lichens (Hogg et al. 2018; E.R. Cox, et al. unpubl. data). The bryophytes are more abundant in wetter areas while the lichens are more prevalent in drier habitats such as on rocks, organic soil and on woody plants stems.
Previous lichen collections - There is a single published lichen survey for Cambridge Bay which is Thomson and Weber (1992). Lichens were collected during an excursion following 9th International Botanical Congress held in 1959 in Montreal. Seven sites were visited in western and northern Canada and a total of 372 species collected. Cambridge Bay was visited only briefly for two days (12th - 13th August 1959) during which just over 118 species were collected of which 105 are listed in the publication and in Table S.1 (Table_S.1_Triple_Lists_of_sample_sources.xlsx). The collection site was at Old Town (near Sites 11a - 14; Fig. 2D), which was the original location of Cambridge Bay on the east side of the inlet.
A second resource of collected lichens are the samples held in herbaria, many of which can now be accessed online through the Consortium of Lichen Herbaria ( https://lichenportal.org). A search resulted in a total of 289 collected samples of which 138 species were from Cambridge Bay with the vast majority collected by Thomson (122 samples of 78 taxa) and Weber (82 samples and 69 taxa). In addition, 158 samples, representing 56 taxa, were collected throughout Victoria Island by Margaret E. Oldenburg, a librarian from Minnesota, during extensive visits between 1942 and 1954 (see a full list of the lichen species she collected at Cambridge Bay; Table S.2 (Table_S.2_Oldenburg_collections_for_Victoria_Island_(2).xlsx)). Together, Thompson and Weber (1992) and the herbarium collections, comprise a total of 492 samples, representing 167 taxa, for the whole of Victoria Island.
Only four other published intensive collections exist from the Canadian Arctic Archipelago in addition to that by Thomson and Weber (1992) at Cambridge Bay. These are by Thomson and Scotter (1985) for Axel Heiberg Island, 80°N, 149 species, Barrett and Thomson (1975) for Devon Island, 75° 41′N, 182 species, Thomson and Scotter (1985) for Bylot Island, 73°N, 165 species, and Northern Baffin Island, 72°30′N, 145 species (see Fig. 1 for numbers and citations). In addition, there have been several major collections on the continent immediately south of the Archipelago and these are also shown in Fig. 1 together with all references.
Figure 1.
Reported number of lichen species at locations across the Canadian Arctic Archipelago (CAA) which were collected in detail and published as follows: a, Thomson & Scotter (1985); b, Barrett & Thomson (1975); c, Thomson & Scotter (1985); d, Ahti et al. (1973); e, Gould (1994); f, Thomson & Weber (1992); g, Thomson & Scotter (1992); h, Thomson & Scotter (1983); i, Scotter & Thomson (1966), j, Thomson & Scotter (1969).
Materials and Methods
Collected lichens were primarily identified using keys of Thomson (1984, 1997) and Brodo (2016). The microscopic examinations of the thalli and apothecia were undertaken using light microscopes (Wild M3B and Zeiss Axiophot) at 40-400X magnification (400X is usually sufficient except when looking at spores). The hand cut sections of the apothecia and the perithecia were examined through a Zeiss Axiophot microscope at 40-1000X magnification. Some specimens were sent to other experts for confirmation (Othmar Breuss, Vienna; Helmut Mayrhofer, Graz). Nomenclature conforms almost entirely to that of the Consortium of Lichen Herbaria (CNALH) website. All samples have been lodged at the Canadian High Arctic Research Station Herbarium, Polar Knowledge Canada, Cambridge Bay, Herbarium Code: CHARS.
Surveyed locations - Detailed lichen collections were made at six geographic locations in the vicinity of Cambridge Bay, Nunavut, during two visits on 20th July 2018 to 2nd August 2018, and 18th July to 30th July 2019. A total of 39 sites were surveyed (Fig. 2) with the actual area covered being determined by available time. Sites were allocated to six geographic Groups ( Table S.3 (Table_S.3_Groups_and_39_sites_16_04.xlsx)) which varied in area and were established because of different geology and formed a visible grouping when mapped (Fig. 2). Group 1 contains eight sites (Sites 5, 6, 7, 8, 31, 32, 33a, 33b; Fig. 2B) at the Wellington Inlier, an area that lies about 60-80 km northwest of Cambridge Bay. The remaining geographical groups are all in the neighbourhood of Cambridge Bay (Fig. 2). Group 2 contains 21 sites (Fig. 2D) in the area directly north of Cambridge Bay. Group 3 contains four sites (Sites, 9, 10, 35, 37; Fig. 2D) on the east side of the inlet to the east of Cambridge Bay, Group 4 contains four sites (Sites 11a, 12, 13, 14; Fig. 2D) on the west side of the inlet, Groups 5 has only two sites (Sites 34a, 34b) which are coastal at Long Point. Group 6 is the list of species from Thomson and Weber (1992) whose survey was located at, and around, the Old Town site on the east side of the inlet (near Sites 11a, 12, 13, 14; Fig. 2D). Territorial Park, and Cambridge Bay (inset dashed box d); Panel D, collection sites at Cambridge Bay. Symbols: dark blue circles - Group 1 & 2, light blue squares - Group 3, green triangles - Group 4, and purple rhomboids - Group 5. Yellow diamond shown in Panels A and C indicates the location of Cambridge Bay. Geology overlay derived from Harrison et al. 2013. Map with projected coordinate system WGS 72/UTM zone 12N.
Figure 2.
Locations of surveyed sites in Groups 1 to 5: Panel A, overview of surveyed locations on Victoria Island; inset, location of Victoria Island (green) in the CAA; inset dashed box b, Wellington Inlier sites; inset dashed box c, Cambridge Bay sites. Panel B, collection sites for Groups 1 & 2 (dark blue circles) at Wellington Inlier. Panel C, collection sites at Long Point, near Ovayok
Surface geology of Groups - The majority (31) of sites and groups (Groups 2 to 6) were near Cambridge Bay in the vicinity of the hamlet. The landscape is covered with Laurentide moraines which are derived from rock that is Cambrian to Silurian, Late Cambrian to Ludlow, Arctic Platform: dolostone, dolomitic limestone, limestone, minor sandstone, shale, intraclast conglomerate (Harrison et al. 2013). The surfaces are covered with a mixed moraine debris which has a high limestone content and is basic (Fig. 2B). The locations of Groups 2 to 5 are marked as blue circles, light blue squares, green triangles, and purple rhomboids in Fig. 2C.
The remaining sites (n = 8) were 70 - 100 km northwest of Cambridge Bay in the Wellington Inlier. The Inlier is an intrusion of older rocks and there is a mixture of rock types. Sites 5, 6, 7, 33a and 33b are the youngest and are Mesoproterozoic, Neoproterozoic, Stenion to Cryogenian (1033 to 723 Ma), dolostone, dolosilitite, quartz arenite, minor lithic arenite, intraclast conglomerate; (Rae group), blue locations in Fig. 2 (Harrison et al. 2013).
Site 32 is Mesoproterozoic, Ectasian (1270 Ma), Mackenzie plutonic assemblage: diabase, mostly high titanium tholeiite, olivine-bearing, brown to black, subophitic; plagioclase often saussuratized, olivine replaced by carbonate (Mackenzie swarm): pink location (Fig. 2; Harrison et al. 2013). Sites 8 and 31 are Paleoproterozoic, Orosirian (2050 to 1810 Ma), Burnside: quartz arenite, pink to purple and maroon weathering, paraconglomerate; (Burnside River, lower part), yellow locations (Fig. 2; Harrison et al. 2013).
Lichen vegetation analysis - In addition to the collections made at the 39 sites described above, a total of 48 quadrats were assessed at five locations (5 at Wellington Inlier, Group 1; 10 at Long Point, Group 5; 3 at Old Town; 17 at Group 2; 13 in front of CHARS building). Each quadrat was 20 cm x 20 cm and lichen species presence was recorded as intercept frequency, and cover estimates of lichens, mosses and higher plants were made visually. Previous experience has shown that field estimations of cover values using visual assessment or point quadrats maintained an accuracy of ± 1%. The lichen substrates were recorded as saxicolous, terricolous or muscicolous within each quadrat.
Data analysis - Maps showing the locations of the survey sites were prepared using standard GIS systems. Five raster tiles of the 2 m spatial resolution Arctic Digital Elevation Model (DEM) that covered the southern Victoria Island study site were downloaded from https://arcticdem.apps.pgc.umn.edu/. The DEM was projected in the WGS 84 (EPGS:7030) ellipsoid and displayed in a Pseudo-Mercator co-ordinate system. QGIS 3.28.0 desktop was used to calculate slope and aspect from the DEM. The Arctic DEM has a vertical reference which is height above the WGS 84 ellipsoid, therefore, the Arctic DEM values can differ significantly from Geoidal and Mean Sea Level heights. Cartesian distance between point and both ocean coast and nearest water body was measured on screen, due to the lack of accurate open water maps for the entire study area. Base imagery for measurement was the Google Satellite Base Imagery which is provided standard in QGIS 3.28.0 at a substantially higher spatial resolution than the Arctic DEM.
The data set containing lichen information as presence/absence for the species and the habitat features listed above were analysed using standard Principal Component Analysis (PCA) provided in XLSTAT (Lumivero, https://xlstat.com).
Similarity indices (SI) were calculated between the lichen flora at Cambridge Bay and other locations, both north and south, for which there were substantial published lists from detailed surveys. The SI were calculated for each location pair as SI = (2Σnc)/(Σn1 + Σn2) in which nc is the number of species in common between the locations and Σn1 and Σn2 are the total number of species at each location.
Results
Lichen diversity - The list of lichen species presently known from around Cambridge Bay and local area is provided in Table 1 (Total List). The Total List, which contains 237 species, has been compiled from three sources which are shown separately, but aligned, in Table S.1 (Table_S.2_Oldenburg_collections_for_Victoria_Island_(2).xlsx) (Triple List). The first source is the published list from Thomson & Weber (1992) with 105 species. The second source is the present investigation, 186 species, and the third source was a list of species generated from a search of existing herbarium specimens in the Consortium of Lichen Herbaria database, 121 species (lichenportal.org). Many of the specimens obtained from the herbaria search were also from the work of Thomson & Weber although not included in their publication (Thomson & Weber 1992). The herbaria search also revealed samples from other collectors, in particular, Margaret E. Oldenburg 1940s collections from sites on Victoria Island including Cambridge Bay ( Table S.2 (Table_S.2_Oldenburg_collections_for_Victoria_Island_(2).xlsx)). The three sources are aligned in Table S.1 (Table_S.1_Triple_Lists_of_sample_sources.xlsx); taking the present collections as the base list, 186 species, the paper by Thomson & Weber (1992) added another 32 species and the herbaria search, an additional 19 species, giving a grand total of 237 species (Total List, Table 1). Of this total, 106 species from the present survey were new to the Cambridge Bay area. Three species appear to be new records for North America (Atla praetermissa Savić & Tibell, Phaeophyscia kairamoi (Vainio) Moberg, Thalloidima rosulatum Anzi), six species new to Canada, 31 species new to the CAA and 84 new to Victoria Island (Table 1).
The Total List provides the full lichen biodiversity known to date and is suitable for analyses such as occurrence of morphological type. However, it is less useful for more detailed analyses because of uncertainty as to exact location and conditions for the samples from Thomson & Weber (1992) and for most of the previously collected herbarium specimens.
Table 1.
Total List of lichen species found at Cambridge Bay and vicinity
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Lichen diversity by geographic location (Group) - The 39 sampling sites we surveyed were allocated to five Groups (Groups 1 to 5) based on their geographic location and as described in the Methods ( Table S.3 (Table_S.3_Groups_and_39_sites_16_04.xlsx), Fig. 2). A sixth group (Group 6) contained the species found by Thomson & Weber (1992). Analysis of the occurrence of species across these six geographic Groups (Table 2) showed that only three species (1.4%) were found in all six Groups (Lecanora epibryon (Ach.) Ach., Physconia muscigena (Ach.) Poelt, and Xanthoria elegans (Link) Th. Fr.) (Table 3, Species distribution). Nearly 40% of the species (83 species, 38.4%) were found in only a single group, 15.3% (33 species) in three groups, 12.5% (27 species) in four groups and 6.88% (15 species) in five groups (Table 2).
Table 2.
Distribution of species across the landscape shown by the number of geographic Groups (1, 2, 3, 4, 5 or all 6) in which each species occurred.
Cambridge Bay and Wellington Inlier lichen diversity - Group 1 contained eight sites at the Wellington Inlier and had a SI (Similarity Index) of 0.34 with Groups 2 - 6 which were all in the vicinity of Cambridge Bay. Of the total 237 species in the Total List, 82 species occur at both Wellington Inlier and around Cambridge Bay, 91 species were found only at Groups 2 - 6 around Cambridge Bay and 64 species only at Group 1, Wellington Inlier ( Table S.4 (Table_S.4_Species_at_both_CB_and_WI,only_at_CB_and_WI_16_04.xlsx)). Given the large 70 -100 km separation between Group 1 and Groups 2 - 6 as well as the low SI value, we calculated separate totals for Cambridge Bay (CB), 173 species (82 + 91) and Wellington Inlier (WI), 146 species (82 + 64). There appear to have been no past collections from the Wellington Inlier region, so it is very likely that it is under-collected at present.
Species Gross morphology - Details of the gross morphology of the species were obtained from personal knowledge and from descriptions of different species in the Consortium of Lichen Herbaria. In the Total List (237 species), crustose species made up 54.8% of the total, foliose 21.8%, fruticose 13.4%, squamulose 5.9% of the fruticose genera, Cladonia was the most common with 4.2% (Table 3).
Table 3.
Thallus morphologies for all species in the Total List for Cambridge Bay and vicinity. Species = number of species; Percentage (%) is the contribution of each morphology type to the total number of species.
Comparison of the lichen lists for the two locations (Cambridge Bay and Wellington Inlier) showed crustose species were higher at Cambridge Bay (57.7 vs. 47.9%), whilst foliose and Cladonia species were lower (Table 4). The differences were more pronounced when the thallus morphologies of the species that occurred only at Cambridge Bay or Wellington Inlier were compared (Table 4). Species found only at Cambridge Bay had a much higher proportion of crustose lichens than Wellington Inlier (67.0% vs 45.3%), and a lower proportion of foliose species (16.5% vs 28.1%). The proportions of fruticose species were also higher at Cambridge Bay relative to Wellington Inlier (9.9% vs 6.3%). The numbers of squamulose species were slightly higher at Wellington Inlier (8 vs 7 species; 5.5% vs 4.0%). However, only one species occurred at both locations so the squamulose lichens at Cambridge Bay and Wellington Inlier were, therefore, different species and this suggests that they are very much determined by their habitat. Six species of Cladonia (9.4%) were found only at the Wellington Inlier, none were unique to Cambridge Bay, and 4.9% (n = 4) occurred at both locations.
Table 4.
Thallus morphologies for lichen species found at both Cambridge Bay (CB) and Wellington Inlier (WI), and those found only at one of the locations. No - number for each morphology for lichen species present; % - percentage of total species for each morphology present at each site.
Similarity across the Canadian Arctic Archipelago - Table 5 provides a comparison of the species found at Cambridge Bay, with those found at other locations in the Canadian Arctic Archipelago. The total number of recorded species at the seven locations across the CAA ranged from a high of 176 (Devon Island, Axel Heiberg) to 145 at Baffin Island with a mean value of 164.6 ± 5.13. The mean number of shared species between Cambridge Bay and the other locations was 49.2 ±1.82 (29.9%). Both the totals and number of shared species are, therefore, similar among locations. However, 70.1% (115 species) were different, indicating a discontinuous lichen flora. Similarity Indices were between 0.264 (Cambridge Bay with Axel Heiberg Island) and 0.531 (between Bylot and Baffin Islands). The latter two locations are closer to each other than the former. There is a significant (p = 0.01) negative relationship between the Similarity Index, calculated between Cambridge Bay and the other locations, and the distance (km) between the locations (Fig. 3). The further the locations were apart, the more dissimilar they were.
Figure 3.
Relationship (non-linear regression) between Similarity Index (Y-axis) calculated for comparisons between Cambridge Bay and the other 6 locations in Fig.1 versus distance from Cambridge Bay (km, X-axis). The relationship is highly significant (p = 0.01).
Table 5.
Comparison (Similarity Indices) of the lichen species present at Cambridge Bay (CB, not including Wellington Inlier sites) and six additional sites in the Canadian Arctic Archipelago: Axel Heiberg (Axel), Bylot Island (Bylot), northern Baffin Island, (Baffin), and Devon Island (Devon), as well as two sites on the northern coast of the main continent, Melville Hills (Melville) and Cape Parry (Parry).The second column provides the total number of reported species for each site. Number of shared species (blue numbers) for each site comparison are displayed in the lower left of the matrix and Similarity Indices (black numbers) in the upper right. Similarity Indices are calculated as given in the Methods and a map showing site locations are in Fig. 1
PCA (Principal Component Analyses) - PCA analyses were carried out on two data sets. The first is the list ( Table S.3 (Table_S.3_Groups_and_39_sites_16_04.xlsx)) which contains 218 species recorded from 39 sites in this investigation. Species reported only from Thomson and Weber (1992) and from web surveys are not included because of the lack of accurate site information. The second data set, Quadrat List, contains information from 35 quadrats surveyed at four locations: the coast south of the Old Town site (OT, 3 quadrats), around the research site north of Cambridge Bay (R, 17 quadrats) north part of Wellington Inler (W, 5 quadrats) and Long Point (LP, 10 quadrats), The key difference between the two data sets is that the first represents a non-quantitative, best search of a defined area whilst the Quadrat List has quantitative data. However, because visits were often opportunistic and time-limited, only a small number of quadrats were completed at each location and would likely miss some species. Analyses of the first dataset used only present/absence data whilst, for the Quadrat List, both presence/absence and cover (quadrat point analysis) could be used. Some habitat information was available: dW (distance from nearest water, lake or stream), dC, distance from coast, H, altitude, A, site aspect and correlation coefficients were calculated between the environmental data and Factor values. The gross morphology for each lichen species is included in the biplot of the species PCA.
Figure 4.
PCA Sites. Biplots for Factors 1 and 2 from PCA analysis of collection/quadrat sites. Panels A, C and E utilized the Collection List while Panels B and D are from the quadrat data. Panels A and B use the full data sets whilst C and D do not include the sites from Wellington Inlier. Panel E is the expanded main group of C. Symbols: in A, C, and E, R – Research site (Group 2); W – Wellington Inlier (Group 1); Cw – CB inlet west side (Group 3); OT – Old Town site; LP – Long Point (Group 5); in B and D, W – Wellington Inlier (Group 1); R – Research site (Group 2); C – coast south of Old Town (Group 4); L – Long Point (Group 5).
The PCA results are presented as biplots with the horizonal axis being Factor 1 and the vertical axis being Factor 2. The PCA analyses returned two main forms of results, one looking at the relationships between locations (collection sites or quadrat location), and the other the relationships between the species.
The biplots in Fig. 4 (A to E) show the relationship between the surveyed sites. Figures 4A, C and E utilized the survey information from the 39 sites while Figures 4B and D are from the quadrat data. The two upper biplots are from the complete data sets and, in both, the sites from the Wellington Inlier are outliers and not included in the main group which contains all sites from the Cambridge Bay region. Factor 1 for the Wellington Inlier and Cambridge Bay sites are significantly different (p = 0.001, t = 3.594, df = 33). Biplots in Figures 4C and D were calculated using only data from the Cambridge Bay region and the Biplot in Figure 4E shows an expanded version of the main group in Figure 4C. Although some locations seem to form groups, for example OT sites (Fig. 4E) and L sites in the quadrat data (Fig. 4D), these are nested within the other data and are not significantly different.
Figure 5 was calculated using the data for species; Figs. 5A and B for all data from our survey and quadrat survey, Figs. 5C and D for information from sites at Cambridge Bay (Wellington Inlier sites removed). In all four figures, the points are color-coded for gross morphology (green symbol – foliose; red – fruticose; black – crustose; pink – Cladonia). In 5B the bryophyte and higher plants data are labelled by name in blue (Bryo and HP, respectively). In 5A, fruticose and crustose species are significantly different (p = 0.195 t = 2.478 df = 28). However, this was the only statistically significant difference found between lichen gross morphologies. All environmental parameters were positively related to Factor 1. However, whereas dW, A and S are almost directly aligned with the F1 axis, H and C have a positive link to Factor 2. Almost all species lie on the positive side of Factor 1 indicating a strong relationship with water as well as avoidance of wet environments (left part of Factor 1). In Fig. 5B, quadrat survey, both higher plants and bryophytes, showed an avoidance of habitats close to water. When only Cambridge Bay sites are considered (Figs. 5C and D) the data show a similar pattern to the full data set whereas the quadrat survey shows a greater spread of species with higher plants negatively related to distance from water whilst bryophytes are the opposite and seem to inhabit drier sites.
Fig. 5E is identical to Fig. 5A although the individual species are colour coded according to whether they occur only at Wellington Inlier (red), only at Cambridge Bay (black) or at both locations (blue). Cambridge Bay species form a very tight grouping at the center of the Biplot whereas species found at both sites or only Wellinton Inlier, are spread out on the right-hand part of the graph (positive Factor 1) and are positively related to all the environmental factors.
Figure 5.
PCA Species. Biplots for presence/absence for A and C - Collection Sites; and cover (count-point intercept) for B and D. Panels A and B use the entire data set with information from all locations whilst data from Wellington Inlier were removed when calculating panels C and D. Data points are color-coded according to gross morphology: blue – bryophytes or higher plants (labelled by name, Bryo or HP in panel B); black – crustose, green – foliose, red – fruticose, pink – Cladonia. Panel E is identical to Panel A but the points are color coded as black – only at Cambridge Bay (CB); red – only at Wellington Inlier (WI); blue – present at both locations. Habitat information in panels A, B and D are: dW - distance from nearest water, lake or stream; dC - distance from coast; H – altitude; A - aspect; S – substrate.
Discussion
Species numbers - Despite the large overall size (1,424,500 km2) of the Canadian Arctic Archipelago (CAA) there have been only four detailed surveys of lichens (Barrett & Thomson, 1975; Thomson & Scotter, 1984; Thomson & Scotter, 1985) and only one (Thomson & Weber 1992) for Victoria Island (217,291 km2). We report 173 species from Cambridge Bay and 146 from Wellington Inlier. These numbers are very much in line with the previously reported 176 species from Axel Heiberg Island (Thomson & Scotter, 1985), 182 from Devon Island (Barrett & Thomson, 1975), 165 from Bylot Island and 145 from northern Baffin Island (Thomson & Scotter, 1984) with a mean of 164.6 species. This suggests that there might be a carrying capacity for lichen species in the CAA of around 170 species. This is almost certainly a consequence of the low precipitation (approx. 90mm pa), low temperature and short, around 3 months, growing season.
Surprisingly, the three most common lichen species from our survey, which occurred in all six geographic groups (Lecanora epibryon, Physconia muscigena, Xanthoria elegans), were not found in a detailed survey at Glacier Bay, Alaska which yielded a total of 831 lichen taxa (Spribille et al. 2020). Collectively, our data suggest considerable spatial, and possibly temporal, variability of lichen taxa within and among Arctic habitats.
Species distribution - Several environmental factors appear to be important in controlling lichen species distribution at the surveyed sites: Water availability - Water appears to be the major factor determining local lichen distribution. The PCA analysis of the species present at each site shows that distance from water is aligned with Factor 1 and with a high factor loading. Precipitation is low and so that uptake of water vapor from the soil by lichens is most probably an important additional process for activating lichens. This would be important even for crustose species because, although some species grow on rock surfaces and need snow melt from actual precipitation, the remainder occurred on surfaces such as soil and are linked to surface water availability (e.g., Psora decipiens: Colesie et al. 2017).
Substrate - Comparison of the collections from Cambridge Bay and Wellington Inlier strongly suggests that underlying substrate geology is also important. Several lichen species were found only at Cambridge Bay (91) or Wellington Inlier (64) with 82 species occurring at both locations. The PCA analysis also shows strong differences between these three groups. Species found only at Cambridge Bay are tightly clustered whereas species found only at Wellington Inlier or at both sites show a broad and similar spread across the biplot (Fig. 5E).
The vast majority of south-eastern Victoria Island is underlain by Cambrian rocks that are predominantly dolomite and the moraine cover around Cambridge Bay left by the Laurentine ice sheet is composed of a high component of calcareous rock and is basic. In contrast, the rocks of the Wellington Inlier are much older, 1,200 to 2,000 million years, often granitic or similar rocks and they tend to produce an acidic moraine. The rocks of the Inlier are generally deficient in essential plant nutrients, such as nitrogen (N), phosphorus (P), potassium (K), and sulphur (S); and can have a calcium (Ca) to magnesium (Mg) molar ratio (Ca:Mg) of less than 1 (Rajakaruna et al. 2012). Combined with elevated levels of heavy metals such as nickel (Ni) and chromium (Cr), it is probable that the acidity of the rocks is a likely explanation for differences in lichen species occurrence (Rajakaruna et al. 2012). Typically, lichen populations on acidic rocks are limited and based on our data, this is supported at the Wellington Inlier. Considering species that were found only at Cambridge Bay or Wellington Inlier, crustose lichens were much more abundant at Cambridge Bay, 61 spp. (67.0%), compared to 29 spp. (45.3%) at Wellington Inlier. Squamulose species had only one species which occurred at both sites while six were found at Cambridge Bay and eight (different) species at Wellington Inlier, again suggesting high substrate selection. Underlying geology is obviously an important factor on Victoria Island. The majority of the north-west of the Island (Shaler Mountains) is composed of these very old rocks and is very under-reported for lichens.
Habitat age and endemism - Another landscape feature is that suitable habitats have only been exposed for a relatively short time. Victoria Island was completely covered in glacier ice (Laurentide icesheet) until 12,000 years ago followed by a retreat from the north-west to the south-east until the entire island was ice-free about 8500 years ago (Stokes 2017; Ullman et al. 2016; Dalton et al. 2020). The isostatic response to the weight of the ice also meant that much of Victoria island was below present sea levels as shown by raised beaches throughout the area (Washburn 1947; Dyke et al. 2005).
A key 14C date is 8020 ±80 years for a raised beach on Mount Pelly at an elevation of 157 m above present sea level (GSC-4313; McNeeley & McCuaig 1991, Fig. 6). This means that, immediately after the retreat of the ice cap, the land surface was well below sea level and Washburn (1947) suggests that Mount Pelly may have been completely submerged. Isostatic rebound then occurred and other 14C dates suggest that the landscape immediately around Cambridge Bay was first above sea level around 4000–5000 years ago (GSC-4331, 2710 ± 60, 30m asl; GSC-4254, 4920 ± 100, 30m asl, 7 km west of Cambridge Bay). The lichen populations are, therefore, also relatively young with all species being new arrivals. It is no surprise, therefore, that there are no endemic lichen species on Victoria Island and only one for the CAA, Seirophora aurantiaco (R. Br.) Frödén (Conservation of arctic flora and fauna; CAFF Technical Report No. 20, July 2010). In contrast to Alaska and Antarctica, it is a young landscape. In the case of Antarctica, with almost complete ice cover and geographic isolation for 20 million years, a high proportion of the present lichen flora (e.g. 49% along the Ross Sea coast) are endemics owing to survival on ice-free nunataks (Singh et al 2015; Ruprecht et al. 2020).
Figure 6.
Marine strand lines on the northeast side of the northwest nose of Mount Pelly; the circles mark the same strand line around the mountain and are at identical heights for each strand line; picture duplicated from Plate 16, Washburn (1947). Mount Pelly has a height of 204 m and the 14C date site is 157 m above sea level.
Stochastic colonization - Owing to the relatively young landscape, it is possible that actual species assemblages might be in part dictated by random events. There is high variability in the occurrence of species within the six different geographic locations (Groups). Only three species occur in all six groups and one additional species in five groups. The largest grouping is of species that only occur once at a single location (38.45%). A similar situation is also found along coast of the Ross Sea coast, Antarctica, with similar total numbers of lichen species occurring at sites along the coastline but Similarity Indices between the sites are low (Colesie et al. 2014). One possible explanation is that this is a consequence of the colonization process. Colonization of a newly exposed site proceeds in a sequence. The first species to arrive can be expected to take the best position and later arrivals must endure less suitable conditions (Vanoverbeke et al. 2016). This process continues until the habitable area is full. A similar process could well have occurred in the CAA. Populations have their location mainly dictated by water and substrate but their composition by random events.
Arctic greening: friend or foe? - Arctic greening is probably one of the most important large-scale ecological responses to global climate change, particularly warming temperatures (Angohiatok et al. 2023; Myers-Smith, et al. 2020). This implies the development over the forthcoming decades of an imbalance towards higher plants in the Arctic tundra. In the western Canadian Arctic strong evidence for a close relationship between shrub expansion and lichen decline have been reported (Fraser et al. 2014). In a survey of several arctic tundra sites and ecosystem manipulation experiments, Cornelissen et al. (2001) concluded that an increase in higher plants with warming would lead to a decline in macrolichen species, particularly those preferred by biota such as caribou (Mitchell et al. 2022). However, greening and warming underpins improved higher plant performance as well as that of cryptogams. In Antarctica, there is a strong positive relationship between lichen species numbers and increasing mean temperatures (Peat et al. 2007). In Canada, when moving south of the CAA into the forested zone of the main continent there is an increase in the number of recorded lichen species; about a doubling in the first 500 km (Fig. 1). Accordingly, increased habitat complexity (e.g. trees) is likely to outweigh any local negative effects of greening on species numbers.
Lichens as a food source for caribou - It is now well accepted that lichens are an important food source for caribou especially in winter (Kennedy et al. 2020: Webber et al. 2022). Knowledge about the extent and resilience of lichens as a food source is important if some form of protection program is to be established. Victoria Island is home to a unique herd of caribou, the Dolphin and Union herd. The numbers in this herd have fallen dramatically with an 89% decline in the total population over a 23-year period from 1997 to 2020 and, as a result, there has been a substantial investigation into possible causes (Species at Risk Committee. 2023).
Caribou are most common near Cambridge Bay in the early winter. The Dolphin and Union herd travels from inland Victoria Island sites to gather on the shore of the Queen Maud Gulf and Dease Strait. The herd waits until the sea is frozen and then crosses to the Canadian mainland where they remain and graze before returning to Victoria Island before the sea ice disappears. This behaviour becomes understandable when one considers the lichen resource available to the animals on Victoria Island. The main lichens used for food by caribou are fruticose species in the genus Cladonia especially the reindeer lichens, Cladonia rangiferina (L.) Weber and Cladonia stellaris (Opiz) Pouzar & Vĕzda (Webber et al. 2022). These two species are abundant on the Canadian mainland where they can form extensive mats on the ground in the boreal forest zone (Kershaw 1978). In contrast, neither species was found in our study and a check using the Consortium of Lichen Herbaria (lichenportal.org) found that no herbarium samples exist for Victoria Island. Cladonia stellaris is also absent from almost all the CAA being only reported in Baffin Island (8 sites). Even Cladonia rangiferia has only 16 records in the CAA and, again, mainly on Baffin Island (10 sites). Both species are common on the Canadia mainland and reach the northern coastline ( Fig. S.1 (Figure_S.1_Distribution_of_Caladonia_species.docx)). Our study reports 10 species of Cladonia with seven being new records (one new to Canada). All the new species were found at Group 1, Wellington Inlier, where they occured on siliceous stones or organic material (Table 1); here the substrate is also more acidic in contrast to the mainly alkaline moraine at Cambridge Bay. The two species are easy to recognise so it is unlikely that under-collecting is the reason for their apparent absence. Webber et al. (2022) reviewed the published literature about grazing activity of caribou and reported 37 named lichen species ( Table S.5 (Table_S.S_Grazed_lichens.docx)) grazed by caribou. Fourteen of these species have been found at Cambridge Bay and/or at the Wellington Inlier, nearby. All fourteen species were collected at Wellington Inlier and eight of these fourteen species were found only at Wellington Inler ( Table S.5 (Table_S.S_Grazed_lichens.docx)) providing further support that substrate conditions impact lichen distribution.
The lack of these species must cause food problems for caribou especially in winter, hence the migration, and is a relevant factor when considering the future of the herd. If climate warming continues then the winter crossing of the strait will become impossible due to either thin or lack of sea ice and this potential problem is aggravated by an increase in shipping (icebreaker) activity through the strait which breaks the ice (Species at Risk Committee. 2023). In this situation the herd will become confined to Victoria Island with a greatly diminished food source in winter. The results of our survey suggest that some form of support will certainly be required if the herd is to survive the winters. Monitoring of vegetation is also necessary to establish whether an alternative food source will appear under warmer conditions with the anticipated increase in higher plant productivity being a possible saving event. It is known that caribou will use higher plants throughout the year if easily available (Webber et al. 2022). DNA analyses of faecal pellets would produce a reference database of what is grazed and when, and also help detect any changes in diet that might occur over time (Mitchell et al. 2022). The lichen species (Cladonia spp.) can be expected to colonise Victoria Island but only substantially when trees occur as found on the mainland and the correct ground conditions develop (acid, organic, boreal forest).
Conclusion
The total lichen species recorded from Cambridge Bay and vicinity has increased from 105 to 237 which confirms that the area was previously under sampled. Of the 237 species, 173 occurred around Cambridge Bay, a total similar to the mean value of 163 species calculated for six other previously surveyed locations across the CAA. This suggests a limited diversity of local lichen floras due to very low precipitation in these areas. Our six geographic locations exhibited very high variability in species composition with Similarity Indices around 0.4 or lower and 38.4% of species occurring at only one site. The relatively young landscape (<8500 years) is the likely responsible for only one endemic lichen species reported for the CAA compared with 40% of the lichen species in Antarctica. Crustose lichens were the most common growth form on Victoria Island and made up 54.2% of species. “Greening” of the arctic tundra will most likely lead to an increased number of lichen species. These conclusions are tentative as the Canadian Arctic Archipelago is a very large area and still seriously under-studied. A better understanding of the spatial and temporal dynamics of lichens will also provide critical insights into food availability and changing migratory pathways for key arctic biota such as caribou and muskox.
Acknowledgements
We are grateful to Dr Alain Leclair, Director, Science and Technology, Polar Knowledge Canada for his support of this work, and to George Angohiatok, Samantha McBeth and Simona Wagner for assistance in the field and/or laboratory. Donald McLennan, Johann Wagner and Sergei Ponomarenko provided input on sampling locations. LGS thanks the Spanish Ministry of Science, project POLAR ROCKS (PID2019-105469RB-C21), for financial support. We also acknowledge Professor David H.S Richardson of Saint Mary's University, Halifax, Nova Scotia for help and for making available information about status reports on caribou prepared for the Committee on the Status of Endangered Wildlife in Canada. Until recently, he was Lichen Co-chair of the Mosses and Lichens Species Specialist Committee.
