Introduction

There is a growing interest in the distribution of terrestrial organisms in Antarctica because of the potential use of biodiversity as an indicator or predictor of the effects of climate change. For example, the New Zealand Latitudinal Gradient Project (LGP, http://www.lgp.aq) was set up specifically to enhance our understanding of the distribution and diversity of both marine and terrestrial biota, in the Ross Sea region, as well as factors that control present-day distributions (Howard-Williams et al. 2006, 2010). The main biological programme in SCAR, Evolution and Biodiversity in the Antarctic (EBA, http://www.eba.aq), also seeks to understand the properties and dynamics of present-day Antarctic ecosystems and to predict how organisms and communities will respond to current and future environmental changes. As a result of such major collaborative and multidisciplinary programmes, our knowledge of Antarctic biodiversity has been considerably advanced.

In an assessment of the diversity and biogeography of the Antarctic flora, Peat et al. (2007) concluded that a clear diversity gradient for lichens exists along the Antarctic Peninsula, with a strong decline, albeit in steps, in species richness from 62°S to around 70°S. However, they did not find any current evidence for a diversity gradient along the Victoria Land coast and into the Transantarctic Mountains from 72°S to the southernmost records at 86°29′S. They noted, however, that there have been very few collections made at some latitudes. In particular, there have been no recent botanical surveys south of the McMurdo Dry Valleys (77–79°S). Knowledge of the terrestrial biodiversity at high latitude sites in the southern Ross Sea region is a key to understanding distribution patterns along the Ross Sea coast. Such information would confirm the presence or absence of a biodiversity cline and would provide potential indicator species for climate change.

The use of any cline in biodiversity to predict the effects of climate change in polar regions is founded on the premise that the lichens present are in equilibrium with the climate and that any changes in environmental factors would, therefore, lead to consequential alterations in lichen distribution and/or diversity. However, there is growing evidence that the distributions of some organisms in Antarctica (e.g. Collembola) are influenced by historical events and local survival (Stevens et al. 2006; Nolan et al. 2006; Convey and Stevens 2007; Convey et al. 2008; Hawes et al. 2010; Torricelli et al. 2010), a situation that would tend to mask any climatic effects. Peat et al. (2007) also note that the patterns of endemism amongst lichens suggest that a proportion of the lichen flora may have an ancient vicariant distribution. Again, better knowledge of lichen systematics, together with biodiversity of these deep southern sites, particularly in combination with modern molecular techniques, may help clarify the origins of, and the factors controlling, present-day lichen populations.

Here, we present a synthesis of lichen collections taken from near 84°S in the Transantarctic Mountains of the Ross Sea Region. The area is south of the Beardmore Glacier and within 2° latitude of the southernmost known collection of lichens (Broady and Weinstein 1998). The collections were made by New Zealand-led groups in 1959 and 1963 and a more recent visit in 2003.

Methods

The lichen samples considered here were collected by three separate research groups that visited the extreme south of the Ross Sea, Queen Maud Mountains. A list of the sites is given in Table 1, and they are marked on the maps in Figs. 1 and 2.

Table 1 Locations of the collection sites: the sites in the Mt. Kyffin area (A to N) are marked in Fig. 2 and used for lichen distribution analysis in Table 2
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Fig. 1
figure 1

Location of the collection sites at the southern part of the Ross Sea in Antarctica; a the general location of the collection area, numbers are the latitude in degrees south; b more detailed map of the inset box in a. Actual collection sites are shown in Fig. 2. The maps are sourced from the online Atlas of Antarctic Research

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Fig. 2
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Detailed maps of collection sites. a Location of Garden Spur adjacent to the Massam Glacier and near the Shackleton Glacier. b Collection sites in the vicinity of the Beardmore Glacier; right hand panel is an enlargement of the marked area in the more general left hand map. The letters on the maps mark the actual collection sites and are named in Table 1. Maps are modified from New Zealand Alpine Journal (Tyndale-Biscoe 1960a). Map a is sourced from the online US Atlas of Antarctic Research

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The first collections were by an eight-member group from the New Zealand Alpine Club led by R. W. Cawley (Cawley 1960; Tyndale-Biscoe 1960a). The group carried out extensive surveys from 23rd November 1959 to 7th January 1960 in the vicinity of Mt. Kyffin (83°48′S, 171°38′E, 1,670 m) immediately south of the Beardmore Glacier, covering an area measuring approximately 15 by 60 km, 83°45′–84°13′S, 171°30′–172°45′E (Fig. 2). Over 200 samples of lichens were returned to New Zealand and are now archived in the herbarium of the Dominion Museum of New Zealand, Wellington (WELT). During curation activities, the samples were inspected and identified to the lowest taxonomic level possible, by R.D. Seppelt in 2005. In Table 1, the sites visited by this group have been verified using the route map in Cawley (1960) and Tyndale-Biscoe (1960a), together with the narrative of the journey in the same reports, and with the collection date and collectors name marked on each sample. Where necessary, the names of the localities have been changed to conform to those accepted by United States Board on Geographic Names and marked on the appropriate maps.

The second group to visit the area was the southern party from the New Zealand Geological Survey Antarctic Expedition (NZGSAE) 1963–64, who collected near the Shackleton Glacier at Garden Spur (84°33′S 174°45′W, 690 m, which they so named because of the rich flora found there; Figs 1, 2). A small number of samples from the latter site, collected by McGregor VR, around 10, are also archived in WELT.

The third group was a research party led by the University of Waikato who visited a small area near Mt. Kyffin (within the area surveyed by the New Zealand Alpine Club) from 7th to 11th January 2003, when around 200 samples were collected, predominantly from Ebony Ridge and its vicinity (Figs. 2, 3). The samples are at present located in the private herbarium of R. Türk and at MAF herbarium, Madrid (see authors and Table 4). Identification was by standard taxonomic microscopy and by molecular methods for the Lecideaceae (Ruprecht et al. 2010).

Fig. 3
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Photographs of a A ridge site forming part of Ebony Ridge near Mt. Kyffin, 83 46′S, 172 40′E, near to the Beardmore Glacier. The sharp, asymmetric peak of Mt. Kyffin can be seen in the top, left corner of the photograph. The pole on the ridge is a crevasse pole about 1.5 m high. b Large thallus of Pseudephebe minuscula growing on a greywacke boulder; bar is 20 cm

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Results

A total of 410 samples was examined, about 200 collected in 1959/1960 and about 200 in 2003 from the Mt. Kyffin/Beardmore Glacier area, and 10 from Garden Spur in 1963/64. The species found and their locations are provided in Table 2. Five named lichen species were found at Garden Spur and two more identified to genus level. One of the latter is an Acarospora species which is a member of the brown Phaeothallia group [Acarospora sect. Phaeothallia (H.Magn.) Räsänen]; this represents a range extension within the Ross Sea as Phaeothallia group species have only been reported from Botany Bay (Seppelt et al. 2010) and Terra Nova Bay (Castello and Nimis 2000), in both cases Acarospora williamsii. The Lecidea samples are most likely to be all forms of L. cancriformis (Ruprecht et al. 2010). Based on these records, and including the two taxa yet to be identified with certainty, 7 species were found at Garden Spur. Of these, Sarcogyne privigna was not found at the Mt. Kyffin area although it is already known from further south in the La Gorce Mountains, (86°29′S, see Table 3). This number of species makes the site slightly richer than the four sites further south, which have more than one lichen species present (Table 3).

Table 2 Sites at which the different lichen and moss species were found; names of the sites can be found in Table 1 and the geographical locations in Fig. 2
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Table 3 Sites south of 85°S latitude for which more than one lichen species has been reported; modified from Table 6, Øvstedal and Smith (2001)
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The lichen diversity at the Mt. Kyffin site (this includes all sites on the detailed map Fig. 2a) was substantially richer (Table 2). A total of 27 named species were found with another 5 identified only to genus level. As for the Garden Spur records, the samples of Acarospora (all Phaeothallia members), Caloplaca and Lepraria are each expected to represent single species, although their specific identity remains to be determined. The Lecidea samples are all expected to be L. cancriformis, whilst the Buellia samples could be an unknown number of species. Excluding the latter two groups, the total number of species would be 30. This total far exceeds that from any other site at this latitude and is just greater than the 29 lichen species reported for Botany Bay, one of the richer plant sites in the Ross Sea region with a diversity exceeded only by Edmonson Point, Terra Nova Bay (Cannone and Guglielmin 2010; Seppelt et al. 2010). All of these species, with the exception of Caloplaca citrina and Umbilicaria aprina, are found at Ebony Ridge (site C, Fig. 2) and its associated summits (Airdrop Peak, site B; Mt. Kathleen, site D; Mt. Harcourt, site E; Fig. 2, Table 1). This makes the location a hotspot for lichen diversity and a typical view of the ridge is shown in Fig. 3a and a closer view showing the surprising size of some lichen thalli in Fig. 3b.

As a result of these collections, the latitudinal ranges of 15 of the 27 named species have been extended considerably further south (Fig. 4). About half of the species were previously known in Southern Victoria Land. However, the remainder appear to have been reported from, or close to, the Antarctic Peninsula giving range extensions in the order of 14 degrees of latitude. The high lichen diversity in this area reflects the presence of a substantial number of species not previously reported for the Ross Sea region.

Fig. 4
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Increase in range for all lichen and moss species not previously found at 84°S or higher latitudes. Upper panel horizontal arrows indicate the increase in latitude from left to right. Lower panel is a map of Antarctica showing where the main previous southern limits were, around 77°S in the Dry Valleys region and around 69°S in the Antarctic Peninsula

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In addition to the lichens, one lichenicolous fungus, Taeniolella sp., and four moss species were found, all on Ebony Ridge (site C) or Mt. Harcourt, (site E) (Table 2). All three named species represent an extension to their known distribution, from Southern Victoria Land (around 78°S) for B. pseudotriquetrum and Schistidium antarctici, and from the Antarctic Peninsula and from Marie Byrd Land, 78°S (Ochyra et al. 2005), for Schistidium urnulaceum.

Discussion

The collections reported here from Garden Spur and the Mt. Kyffin area have approximately doubled the number of lichen species known from the Queen Maud Mountains, in the southern Ross Sea region. These findings provide little support for a major cline in lichen diversity with increasing latitude within the Ross Sea Region. Specifically, the total number of lichen species found at 84oS exceeds that found in the Dry Valleys (unpublished data) has one more species than at Botany Bay (Seppelt et al. 2010) and represents approximately 60% of the number of lichens reported from Northern Victoria Land (Cannone 2006; Cannone and Seppelt 2008; Cannone and Guglielmin 2010). Around 30 lichen species have also been reported for the continental coastal site Larsemann Hills (Singh et al. 2007). However, there may be some evidence for a relationship between species diversity and increasing altitude. The high species numbers at Ebony Ridge and Garden Spur strongly suggest that the lower altitude sites along the Ross Ice Shelf are the sites of highest diversity. In the vicinity of Mt. Kyffin, the other more inland sites had no more than four lichen species each. This contrasts with the McMurdo Dry Valley where lichen diversity and abundance is greater along ridges of the valley sides above around 800 m altitude because of higher atmospheric humidity and moisture derived from clouds. There is a major decline in the number of moss species from nine at Granite Harbour and in Northern Victoria Land (Cannone and Seppelt 2008) to four species at Mt. Kyffin and none at any site further south, including Garden Spur (note, however, that the naming description for Garden Spur says it was named “because of the rich flora of mosses, algae and lichens found there”).

Ebony Ridge and its summits, Mt. Kathleen, Airdrop Peak and Mt. Harcourt, stands out as an exceptional site with only three of the 31 species now known for the area not being found there, Umbilicaria aprina, Caloplaca citrina and Sarcogyne privigna (Garden Spur only). The majority of the named lichens at this site can be allocated to three main groupings (Table 4). The first group of 9 species (Acarospora gwynnii, Buellia frigida, Lecanora polytropa, Lecidea cancriformis, Pleopsidium chlorophanum, Pseudephebe minuscula. Rhizoplaca melanophthalma, Umbilicaria decussata and Usnea sphacelata) corresponds to a “tolerant” set of lichens proposed by Øvstedal and Smith (2001) that are typical of cold, dry and windy habitats. This appears to be a widespread and relatively consistent grouping. Perhaps, not surprisingly, seven of these species are already known from sites further south (Fig. 4). Four species (Candelariella flava, Caloplaca sp. Lecanora expectans and Xanthomendoza borealis, at Ebony Ridge, plus C. citrina from another site) are often found growing on moss but also occur on rock and gravels. They are usually found on gravel and sandy soil in the 84°S region. Two of the species (C. flava and L. expectans) were not unexpected as they are known from more southern sites (Fig. 4). However, of note is the presence of X. borealis, a nitrophilous species usually associated with nutrient-rich sites, particularly bird colonies.

Table 4 Lichens collected in the Mt. Kyffin (Beardmore Glacier) area and categorised according to their distribution pattern (Cosmopolitan, Bipolar or Endemic) according to Øvstedal and Smith (2001) and to their proposed origin/substrate (moss—typically found on dry moss; tolerant—members of broadly distributed group tolerant of cold, dry, windy conditions, after Øvstedal and Smith (2001); peninsula—only reported from the Antarctic Peninsula region outside this site, after Øvstedal and Smith (2001)
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The most surprising and unexpected grouping is that of the six species categorised as Peninsular in Øvstedal and Smith (2001). None of these species appear to have been previously reported from the Ross Sea region, so their occurrence represents a range extension of over 13 degrees latitude. There are several possible explanations for the occurrence of this Peninsula grouping at Ebony Ridge.

First, previously inadequate collections; this is the most obvious explanation although we suggest it is inappropriate in this case. Peat et al. (2007) analysed all the records for Antarctica and concluded that, overall, it had been well sampled although obviously not so at these extreme southern sites. All the authors of this paper have extensively collected at other sites along the Ross Sea coast including at Botany Bay, the Dry Valleys and Cape Hallett. One author (RDS) has visited and collected extensively along the continental coast and inland from 40°E to the Ross Sea. In Northern Victoria Land and at other sites, Nimis and co-workers have thoroughly analysed herbarium records, in particular for northern Victoria Land (Castello and Nimis 1995, 2000; Castello 2003). Yet none of these authors has reported any of the lichens between Mt. Kyffin and the Antarctic Peninsula. If there were only one or two species that fell into this grouping, then under-collecting might be a strong possibility. However, with 6 species, we consider this to be highly unlikely.

A second possibility is introduction by visiting scientists. We suggest that this is also highly unlikely as the Ebony Ridge site has been rarely visited and any such quarantine breaches would be far more likely to have occurred at more northerly sites.

A third possibility is the long-distance dispersal. The presence of the other lichen species that are more typical of the Ross Sea, especially the tolerant group, shows that this might be a possibility. However, it is highly unlikely that this has occurred for this number of species over 14 degrees of latitude without their occurrence at intermediate sites.

A fourth possibility is that these lichens represent relicts that have survived in situ from preglacial times when the climate was more similar to that presently occurring in the Antarctic Peninsula. This suggestion is supported by similar studies on the unique springtails (Collembola) and mites (Acari) collected from the same area (e.g. Tyndale-Biscoe 1960b; Strandtmann 1967) and including more recent molecular studies (Stevens and Hogg 2003; Demetras et al. 2010). One difficulty with this suggestion for the lichens is not so much the occurrence of the group in the Mt. Kyffin area, but their absence in the rest of continental Antarctica. If they are relict, then it is possible that they were once present along the entire Ross Sea coast during the interglacial periods. The disappearance of these populations from intervening areas whilst they continued to survive at Mt. Kyffin is interesting. However, one possibility is that increased snow fall during the glacial advance may have covered all potential lichen habitats and led to their extinction in the intermediate areas. The negative effect on lichens of extended snow duration is well known (Benedict 1990; Körner 1999; Pomeroy and Brun 2001), and the negative effect on activity under present conditions has been demonstrated (Pannewitz et al. 2003; Schroeter et al. 2010). The site at Mt. Kyffin would have been protected because, as often found in alpine areas, it is a sharp ridge that although receiving substantial snow fall the habitat remains available for lichens because is kept clear of deep snow fall by the wind. Furthermore, with distance from the open sea increasing as the ice sheet advanced, there would have been a concomitant decline in precipitation.

If the lichens do represent a relict group, then how long have they survived at 84°S? Although glaciation of the Antarctic continent started some tens of millions of years ago, there is recent evidence from drilling near Ross Island that the Ross Ice Shelf has disappeared on several occasions, resulting in the Ross Sea becoming a marine embayment (Naish et al. 2009). This is supported by modelling that shows major collapses of the West Antarctic ice sheet, the so-called super-interglacials, as recently as 200 k years ago (Pollard and DeConto 2009), together with more recent estimates of ice extension (Storey et al. 2010), which show that ice-free areas almost certainly existed at these high latitudes even during the last glacial maximum. Accordingly, the relict populations may be as young as 200 k years. Most importantly, there was a period when ice cover was much greater than that presently found. Such extensive glaciations could have contributed to the elimination of the intermediate populations of Peninsular lichens. Future sampling together with the application of modern molecular techniques will be necessary to test this hypothesis.