Biogeographical survey of Estonian lichen flora, with reference to conservation strategies
Tiina Randlane and A ndres Saag
Institute of Botany and Ecology, University of Tartu, Lai Street 38, 51005 Tartu, Estonia randlane@ut.ee
A bstract
This present revision is based on the recent checklist of lichenized, lichenicolous and allied fungi of Estonia, including 863 taxa from 200 genera. The distribution of taxa in five regions has been indicated and among these the three western regions have been compared to the two eastern regions. A bout one-third of all lichen species are more or less uniformly distributed throughout Estonia. The western areas are clearly more rich in species than the eastern regions: 351 taxa have not been found in the eastern regions, while only 61 species are not known in the western regions.
In the western islands, about 75% of the total lichen flora is present on one-tenth of the area of the country.The important phytogeographic border distinguished in Estonia according to the flora and vegetation of higher plants can also be recognised in the distribution of lichenized fungi.
Conservation strategies concerning lichens should be based more on the distributional patterns of taxa. The species that are found at the limits of their distributional areas should surely be included in the local Red Lists.
Keywords: lichenized fungi, lichenicolous fungi, Estonia, distribution of lichens, phytogeographic zonation, Red Lists
1 Introduction
Floristic studies of the lichens of Estonia were started in the second half of the 18th century.
The earliest paper in which lichen species from the area known as Estonia today were listed was written by J. L. FISCHER(1778) and published in Leipzig under the title “Versuch einer Naturgeschichte von Livland”.The most outstanding early papers concerning the lichen flora of Estonia were produced by BRUTTA N(1870), RÄ SÄ NEN(1931) and TRA SS(1970).The last- mentioned contribution presented the first complete checklist of Estonian lichens, including 677 species, as well as an original analysis of the geographical elements of the lichen flora.The next important study was not published until over twenty years later – a flora of Estonian macrolichens (TRA SS and RA NDLA NE 1994) for 382 species (332 species reported from Estonia and 50 species occurring in the neighbouring territories and considered as potential members of Estonian flora). RA NDLA NEand SA AG(1999) presented a new, second checklist of lichenized, lichenicolous and allied fungi of Estonia. The following review will provide a preliminary biogeographical survey of Estonian lichen flora based on this checklist.
2 Material and methods
A ll the data analysed in this study have been provided by the recent checklist of lichens of Estonia (RA NDLA NEand SA AG 1999), which is mainly based on herbarium material. This means that most of the herbarium specimens available in different herbaria (including six local herbaria – ICEB, IE, TA A , TA L, TBA , TU – as well as H, LD, RIG, S and UPS) have been re-checked. The biggest collection of Estonian lichens is kept in TU, comprising about 26 000 specimens altogether. A ll the other herbaria together include less material. Thus the total number of lichen specimens from Estonia can be estimated to be about 50 000. In the checklist, abbreviations of the names of the herbaria where the material is kept have been added after each taxon as sources of verification. Still, some species (54 altogether), of which no herbarium material exist, were included on the basis of literature data.These taxa are con- sidered doubtful for Estonia (and are marked with a question-mark in the list). Furthermore, 40 species have not been recorded after 1950 and are therefore treated as extinct or probably extinct in Estonia (and are marked with an asterisk in the list). Both doubtful and extinct /probably extinct lichens have been included in the present geographical survey.
In the checklist, the geographic distribution of taxa is indicated in five regions. Four of them are situated in the mainland of Estonia and are based on the four quarters of compass – north- western part of the mainland (NW), north-eastern (NE), south-eastern (SE) and south- western (SW) parts. The fifth region consists of the western islands (WIs). These regions are rather artificially composed, containing two to four administrative divisions (counties), while their borders follow the formal borders of the counties (Fig. 1). With the present level of knowledge it is not possible to indicate the distribution of lichen taxa in the 15 administrative counties of Estonia because no special distributional studies have been carried out until now, and only the usual floristic ones have been undertaken. Therefore the present data are clearly incomplete.In addition,the territories of most of the counties are rather small.Still,the regions used in presenting distributional data of lichens in Estonia are appoximately of the same size as the provinces used for mapping in Nordic Lichen Flora Vol. 1 (1999).
WIs
NW
SW
NE
SE
Fig. 1. Locations of the five regions in Estonia for which there are distributional data for lichens in the recent checklist of lichenized, lichenicolous and allied fungi of Estonia (RA NDLA NEand SA AG1999).
NW: north-western part; NE: north-eastern part; SE: south-eastern part; SW: south-western part; WIs:
western islands. Boundaries of counties are indicated by thin lines.
3 Results and discussion
3.1 General data
The checklist contains 851 species and 12 infraspecific taxa from 200 genera.A mong them 790 species are lichenized, 39 species lichenicolous and 22 species non-lichenized. 42 new species, not on the checklist, have been reported during the last year, and this increases the total number of lichenized and allied taxa in Estonia to 893.The total number is much smaller than that in neighbouring northern countries, where it is 1422 in Finland (VITIKA INENet al.1997), and 2271 in Sweden and Norway (SA NTESSON1993). This evidently has to do with various factors, of which geographical conditions are of primary importance. Estonia is a small country in the southern part of the boreal zone with a territory of 45 000 km2; it is uniformly flat, the highest point being 318 m above the sea level. Lichen floras of some other European countries with limited territories and flat landscape are quite similar to the Estonian flora in the total number of species, e.g. 915 in Denmark (ALSTRUPand SØCHTING1989) and 787 in Netherland (APTROOTet al.1999). Latvia and Lithuania, our closest neighbours in the Baltic region are less rich in lichenized taxa: 503 species are known in Latvia (unpublished data of Piterans 1999) and 511 in Lithuania (MOTIEJUNA ITE1999).A lthough the territories of Latvia and Lithuania are somewhat larger than Estonia (both are approx. 65 000 km2), there are considerably less diverse habitats suitable for lichens (due to e.g.,lack of alvars,poor occurrence of siliceous erratic boulders etc., absence of marine islands).
3.2 Phytogeographic zonation of the region
Climatically, Estonia belongs to the temperate zone, which is characterised by rather warm summers and moderately mild winters. Since there is approximately twice as much annual precipitation as there is evaporation, the climate is excessively damp.The main features of the weather are determined by the location of Estonia in the extreme north-western part of the great Eurasian land mass – in the area which is strongly influenced by the A tlantic ocean.
Local climatic differences are due to the proximity of the Baltic Sea (JÕGIand TA RA ND1995).
Phytogeographically, Estonia is situated in the Euro-Siberian region of the Holarctic kingdom (TA KHTA JA N1978). Subdivisions of Estonia, proposed by local botanists and based either on the distribution (LIPPMA A1935) (Fig. 2) or on the flora and vegetation (LA A SIMER
1958) (Fig. 3) of higher plants, show that there is a phytogeographic border running through Estonia approximately from north-east to south-west, which divides the country into two parts. AHTIet al.(1968) also recognize a distinct border through Estonia in their study of vegetation zones in north-western Europe (Fig. 4). A ccording to these studies, Estonia is a transitional area inside the hemiboreal zone where the south-taiga forest subzone changes into the spruce-hard-wood subzone. However, the exact location of the important phyto- geographic border is still not quite settled. A lthough there is also an essential difference in the age of bedrock in different parts of Estonia – Ordovician and Silurian carbonate rocks occur in the northern and western parts while Devonian sandy-silty and clay deposits prevail in the southern part (VIIDING 1995) – the geological boundary does not coincide with the phytogeographic border.
A B
A B
A B
C
Fig. 2. Subdivision of Estonia according to the distribution of higher plants given in LIPPMA A(1935). A : province of central Europe; B: province of eastern Europe. Boundaries of the five regions for which the distributional data for lichens have been presented are indicated by thin lines.
Fig. 3. Subdivision of Estonia according to the flora and vegetation of higher plants given in LA A SIMER
(1958). A : geobotanical subprovince of western Baltic; B: geobotanical subprovince of eastern Baltic.
Boundaries of the five regions for which the distributional data for lichens have been presented are indi- cated by thin lines.
Fig. 4. Subdivision of Estonia (inside the hemiboreal zone) pursuant to the vegetation zonation in north- western Europe according to AHTIet al.(1968). A : slightly oceanic to indifferent section; B: indifferent to slightly continental section; C: slightly continental section. Boundaries of the five regions for which the distributional data of lichens have been presented are indicated by thin lines.
3.3 D istribution and frequency of lichens in Estonia
The borders between the five regions for which the distribution data of lichens are presented in the checklist follow, as mentioned above, the formal borders of administrative units (counties).They do not trace exactly either the phytogeographic or the geological borderlines discussed above. Still, in the northern part of the country, the border between NW and NE regions almost coincides with that between the geobotanical subprovinces of the western Baltic and eastern Baltic described by LA A SIMER (1958), and it is rather close to the border between the floristic provinces of central and eastern Europe (LIPPMAA1935). In the southern part of the country, the exact location of the phytogeographic border is less clear, it passes through Estonia somewhere in the SW region. To analyse the distributional data of lichens, the three western regions (NW, SW,WIs) have been compared to the two eastern regions (NE, SE).
More than 200 species (out of the 863 taxa listed) are distributed in all five regions, and most of them are frequent or very frequent components of our lichen flora. Furthermore, about 100 species are distributed in four regions and are missing in one of them. We still assume, however, that most of these taxa do not have any special pattern of distribution in Estonia and they may occur all over the country.Thus, today we can suggest that at least one- third of all the lichen species are more or less uniformly distributed throughout entire Estonia.
The western areas (NW, SW,WIs) are clearly richer in species than the eastern regions (NE, SE). 351 taxa (41% ) are listed that are not found in the eastern regions, while only 61 species (7% ) are not found in the western regions (Fig. 5).A ccordingly, only about one half (52% ) of all recorded lichens are present in both eastern and western regions.
The western islands of Estonia (Saaremaa [also known as Oesel], Hiiumaa [Dagö], Muhu, Vormsi and about one thousand smaller islands and islets) are especially suitable for various lichens with different requirements. Today 634 taxa (about 75% of the flora) have been reported from the WIs region, which constitutes less than one-tenth of the area of the country. Erratic granite boulders, calcareous cliffs, old stone hedges, plain alvar territories, deciduous forests and wooded meadows, which are not very widespread on the mainland of Estonia, offer habitats not only for the boreal and nemoral lichens, but also for the species of arctic-alpine, xerocontinental or even submediterranean elements.Caloplaca jungerm anniae, Flavocetraria cucullata, F. nivalis, Fulgensia bracteata, Toninia sedifoliahave been found in Estonia growing only in the alvars of the western islands or the north-western coast of the mainland on soil or mosses and plant debris. Marine and maritime species (e.g.A naptychia runcinata, Caloplaca m arina, C. scopularis, C. thallincola, C. verruculifera) also comprise a considerable part of the western group of lichens.
Eastern regions only (NE and/or SE)
7%
Western regions only (NW and/or SW and/or Wls)
41%
Eastern and western regions both 52%
Fig. 5. Distribution classes of Estonian lichens according to their occurrence in western and eastern regions. For explanation of the abbreviations NW, NE, SE, SW and WIs see Fig. 1.
The eastern group of lichens includes the species that grow on the cliffs of red Devonian sandstone or sandy soil in southern Estonia (Cystocoleus ebeneus, D ibaeis baeom yces, H ypogym nia vittata, Pilophorus cereolus)and also several taxa found only in extensive forest areas (calicioid species, D im erella lutea, L obaria scrobiculata, L opadium disciform e, N ephrom a arcticum , X ylographa trunciseda). Many of them are very rare according to our present data. It is possible that the true distribution pattern of these species might be different.
It seems, then, that the important phytogeographic border distinguished in Estonia accord- ing to the flora and vegetation of higher plants can also be recognised in the distribution of lichenized fungi.
In addition to the distributional data, the frequency of taxa was also estimated in the recent checklist. Lichens reported from Estonia have been divided into the following frequency classes:very rare (1–2 localities) 307 taxa;rare (3–5 localities) 129;rather rare (6–10 localities) 108; rather frequent (11–20 localities) 99; frequent (21-50 localities) 104; very frequent (over 51 localities) 116 (Fig. 6). 64% of all lichen species belong to the group of rare taxa (with 10 or less localities known). The analogous figure for vascular plants in Estonia is 36% (KUKK
1999) and for bryophytes 45% (according to data in INGERPUU et al.1994). The unusually large share of rare taxa in the Estonian lichen flora is partly due to the great diversity of different habitats and substrata suitable for lichenized taxa with various requirements (RA NDLA NEet al.in press). In our present frequency data, however, the subjective impact caused by the unequal recording (collecting and determining) of different species,e.g.between macro- and microlichens, might be misleading. The necessity to find out the true local distribution of those species that are today treated as rare in Estonia is obvious.
Number of taxa
350
300
250
200
150
100
50
0 rr = 1–2 loc. r = 3–5 loc. str = 6–10 loc. stfq = 11–20 loc. fq = 21–50 loc. fqq ≥ 51 loc.
307
129
108 99 104 116
Frequency classes
Fig. 6. Distribution of Estonian lichens according to the frequency classes. loc. = localities.
3.4 References to Red List activities and conservation strategies
The conservation process for threatened species involves several stages. In the first step the systematics, distribution and ecology etc. of taxa are recorded, and in the second extinct and threatened species in Red Lists are listed (THOR1995).
We propose that the listing and categorisation of taxa in national or local Red Lists should be mainly based on their distributional patterns, both world-wide and regional. Intensive mapping, such as that carried out in Great Britain, Germany and Austria (LITTERSKI1999;
SEAWA RD and HITCH 1982; SEAWA RD 1998; TÜRKand OBERMAYER 1998; WIRTH 1995), would provide us with a reasonable basis for compiling lists of species in need of protection.
The availability of earlier herbarium material or literature records makes it possible to estimate the changes in frequency and local distribution of certain taxa, and, thus, to decide on their status. Information about local threat factors should be added to this basic data before cat- egorisation.
The category “Rare”, which has been applied in the Red Lists of many countries (LILLELEHT1998; PISUTet al.1996; RA SSIet al.1992; THORand ARVIDSSON1999), probably often contains species that are poorly investigated and that should actually belong to the category of “Data Deficient” – according to the IUCN Red List categories from 1994 (IUCN 1994). It is reasonable to database all the records of both “Rare” and “Data Deficient” taxa locally, but not all such species are actually threatened and in need of conservation measures.
Consequently, it is not necessary to include all of them in the Red Lists. If all species defined as “rare” at a certain stage of investigation are included in local Red Lists, the red-listed taxa percentage of the total number of recorded species might grow very high. For example, in Estonia this percentage would be, according to our present knowledge of species’ frequency in lichen flora, more than 65% ; in Denmark the percentage of red-listed lichen species is even higher, namely 70% (THOR1995). This means that the next step in the conservation process, proposing practical conservation programmes, may become diffuse and inefficient.
A nalysis of world-wide distributional patterns of taxa would help us to sort out these species which are locally rare because they occur at the periphery of their range. Species found in outposts of their ranges should, in our opinion, certainly be included in the local Red Lists.
It is accepted that a global category of threat may not be the same as a regional or national category for a paticular taxon (IUCN 1994). Furthermore, maintainance of biodiversity is not an indefinite global or regional action but, first of all, activity that should be carried out locally.
Consequently, the species that are locally rare due to the occurrence at the periphery still deserve inclusion and categorisation in national Red Lists, as well as endemic species, species with small areas of distribution, globally red-listed species, etc. A lthough there is no such criterion as “situated at the limit of distribution” for identifying any of the Red List categories and the specific threatening factor cannot usually be identified, for such cases we could probably use the criterion of “population estimated to number less than 50, 250 or 1000 individuals”. This criterion usually applies with taxa inhabiting territories at the very limit of their distribution area.
In Estonia, e.g.A rctoparm elia incurva, Caloplaca jungerm anniae, Flavocetraria cucullata occur at their southern limits while Cladonia convoluta, Flavoparm elia caperata, Phaeophyscia chloanthaare recorded at the northern limits of their distribution.These species mostly belong to the group of very rare or rare lichens in Estonia and are also included in the local Red List (except C. jungerm anniaewhich is omitted as crustose lichens have not yet been evaluated in the Estonian Red List) (RA NDLA NE 1998). The fact that Flavocetraria cucullata is widely distributed in arctic and arctic-alpine areas (Fig. 7), and Flavoparm elia caperata in the deciduous forests of the temperate zone (Fig. 8) does not alter their vulnerable condition in Estonia.
A cknowledgements
We wish to express our gratitude to all the authors of the second checklist of lichenized,lichenicolous and allied fungi of Estonia – Inga Jüriado, Piret Lõhmus, Jüri Martin, Ljudmilla Martin, Eva Nilson, Taimi Piin, Lauri Saag, Mari Sarv, Ave Suija, Marina Temina and Hans Trass – whose contribution to our knowledge of Estonian lichen flora has made it possible to analyse its biogeographical data.
We are also grateful to Triin Randlane for revising the English text. This study has been supported financially by the Estonian Science Foundation (grant no. 3920).
Fig. 7. Distribution of Flavocetraria cucullata:arctic-alpine pattern of distribution in Europe and the only locality in the Baltic region.
Fig. 8. Distribution of Flavoparm elia caperata:temperate pattern of distribution in Europe and recorded localities in the Baltic region.
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