1  Introduction

1.1  Aims

The Panarctic Flora Checklist of vascular plants aims to include, to name and to evaluate taxonomically all taxa at ranks of family, genus, species, subspecies, and some varieties and established hybrids, that occur regularly within the Arctic as defined by the Checklist and also to include in two appendices the ones reported, but not accepted, for the Arctic and at least a majority of those that have been found in the Arctic only as casuals. This should be a comparatively simple task as the arctic flora is small and has been studied for a long time, longer than many other floras. The Arctic is among the most species-poor major biomes in the world. In our circumscription it includes a total of somewhere between 2000 and 3000 species and subspecies of vascular plants, that is less that 1% of the vascular plant flora of the world as currently known. The large majority of these taxa also occur outside the Arctic.
            More specific, the aims are:
            (1) To present an authoritative survey of arctic vascular plants applying, as far as possible, the same criteria for circumscription, ranking, and naming of taxa across different plant groups, differences in reproductive modes, and across geographical regions, that is, across different botanical traditions.
            (2) To give a rough survey of the distribution and frequency of all taxa in biogeographical regions and bioclimatic zones (see Yurtsev 1994 and Elvebakk et al. 1999).
            (3) To present a standard list of arctic vascular plants and their scientific names for non-specialists, as far as possible identifying and standardizing the names of plants that have gone under different names in different regions.
            (4) To initiate a process of re-unification of taxonomic views on arctic plants among scientists from different nations and environments.
            (5) To produce a prodromus for a full Panarctic Flora treatment that also should include, e.g., descriptions, keys, reproductional and ecological information, and more detailed distribution data.
            A consensus Checklist has been quite difficult to produce for several reasons, both biological ones and ones connected to differences in scientific approaches. The biological problems are connected to the young age of major parts of the arctic flora. Three million years ago there was no arctic flora as we currently consider it. The plants we find today in the Arctic are either comparatively recent (in a geological time scale) immigrants or recently evolved. Two major processes in this evolution seem to have been hybridization and polyploidization, whereas differentiation due to isolation seems to have been less frequent than in most other biomes. Even if the Arctic is divided by and generally borders on seas, these seas are regularly ice-covered and do not seem to be efficient barriers. The problems of different botanical traditions are mainly due to diverging developments of biological sciences in the so-called 'western' world and in the 'Soviet' world in the 20th century. The political schisma resulted in a scientific schisma with relatively little contact, and where the criteria became somewhat different for what should be considered a species or a subspecies. Even if it now is more than 15 years since the political reasons for this schisma disappeared, its aftermath is still evident in many scientific fields, among them taxonomic botany.
            Taxonomy and nomenclature is not an aim in itself but rather a means of structuring the biological variation – hopefully as an approximation of the 'real' biological situation (whatever that may be) – and of communicating meaningfully and unambiguously about it. Unambiguity is especially necessary for non-taxonomical users of botanical information. In an arctic context these are mainly ecologists and people engaged in nature management and conservation. It is essential when studying variation and processes in species across long distances that one really works on the same species and preferrably applies the same names. It is also important for evaluation and conservation of biological diversity at the taxon level that taxa are identified and circumscribed in essentially the same way everywhere, and that duplicate naming (i.e., different names used for the biologically or evolutionary the same entity in different areas) is avoided.
            A main aim of, and a main problem in, establishing this Checklist has therefore been to try to obliterate as far as possible the differences between NW European, Russian, and North American traditions in how to circumscribe and name taxa. In most groups we feel that we have succeeded, in some not. The editors are aware of the still remaining problems in a unified taxonomy and nomenclature of the arctic vascular plants.

1.2  A condensed history of the Panarctic Flora idea

The first Circumpolar Arctic Flora was published by Polunin (1956). It has been in little use outside North America as it omitted significant parts of the arctic flora in N Asia and N Europe. It exemplifies the problems in producing such an international Flora without taking all arctic regions fully into account.
            Why has it been so difficult to produce or even approach a uniformly approved Panarctic Flora? A main obstacle is that it needs to utilize the expertise in all countries with arctic regions, and that it must be accepted also by the botanists in these countries. Such a unified approach has been attempted several times, as shown by a summary given by Murray & Yurtsev (1999). The idea goes back at least to the International Botanical Congress in Leningrad in 1975 when a project was proposed and a committee formed, with participation of J. Packer (Edmonton, Canada), O. Gjærevoll (Trondheim, Norway), and B.A. Yurtsev (St. Petersburg, Russia). For several reasons, this project never took off.
            A second attempt was initiated in 1988–1990 by D.F. Murray (Fairbanks, USA) and B.A. Yurtsev. There was some bilateral progress in the project in the Gorbachov – Reagan era of the early 1990ies, including combined Russian – American field work to compare plants and align species concepts in Russian NE Asia and NW and N North America. For some years the project had support from the US National Research Foundation and also support at governmental level both in USA and Russia. The two parts involved shared the responsibilities, in USA mainly databasing, in Russia production of drafts (species lists) for the Checklist. The project slowly petered out with little visible progress and the consequent loss of financial support.
            In 1995, during the IOPB Congress in Tromsø (Norway), Murray and Yurtsev contacted Norwegian botanists to extend the project to involve other countries with arctic areas. The Norwegian Polar Institute was approached for support but showed no interest. The Norwegians did, however, not entirely forget the project. It was revived during a study year granted to Dr. I. Nordal and R. Elven at the Centre of Advanced Study (CAS), Norwegian Academy of Sciences. During this year, in 1998–1999, Nordic, North American and Russian botanists collaborated in initiating a new project, with participation of the two main champions of the previous phase (Murray and Yurtsev). The results of this year's and subsequent work are summarized by Nordal & Razzhivin (1999) and also available at a web site: http://www.toyen.uio.no/panarctflora/.
            During the year at CAS, several workshops were held discussing taxonomically difficult groups, mainly in Oslo (Norway) but also in St. Petersburg (Russia). Summaries of these workshops were presented in Nordal & Razzhivin (1999). Two meetings were held to decide how to proceed and to set some taxonomic 'ground rules'. These are referred by Elven (1999). The project was then organized with the primary aim to first produce an annotated Checklist of arctic vascular plants, as a tool for both scientists and non-scientists concerned with arctic environments, and then – if the work with the Checklist succeeded – to discuss continuation into a Flora phase. The Checklist part of the project is hereby presented.

1.3  Procedures

The production of the Checklist has been organized in the following ways, based on decisions during the initial CAS meetings in 1998–1999 (see Elven 1999), partly restricted by decisions made during the previous Panarctic Flora attempts.
            (1) We have, for the time being, abandoned the database approach of the previous Murray – Yurtsev attempt. We have aimed to produce a Checklist before we have the more or less complete data of arctic floristic information available.
            (2) In accordance with the Murray – Yurtsev approach, initial proposals for taxa to be included, their taxonomic status and names (the 'PAF drafts' often referred to below) and draft distributional tables have been supplied mainly by Russian collaborators. This was the main task assigned to the Russian collaborators in the previous attempt, but results came too late to be of use with the dwindling grants. In the meantime, for some families parallel drafts had been produced by Russian and non-Russians. At the end of 1999, numerous drafts were still missing and these have been produced by the Editor-in-Chief (Elven). The authors of initial drafts are listed among the contributors to the Checklist above.
            (3) Editing and supplementing of the drafts has in the main been undertaken by the Editor-in-Chief, supported on the American side mainly by botanists in Ottawa and Montreal ('whipped' into participation by Dr. S.G. Aiken) and by Dr. D.F. Murray, on the Russian side by Dr. B.A. Yurtsev as 'whipper' and by Dr. V.Yu. Razzhivin who has been responsible for databasing the information and for the planned web publication. Initial drafts have been supplied with information on nomenclature, types, chromosome numbers, and additional information of distribution. The Editor-in-Chief has also, in many cases, proposed changes in taxonomic treatment and names and has added notes. The original drafts have in general been so extensively changed that they now ‑ more often than not ‑ reflect views different from those of the initial draft authors. This is a necessary part of the process of reaching as 'Panarctic' a view as possible.
            (4) Edited drafts have been distributed to the original draft authors (except for those now deceased), the Editorial Board, the Steering Committee, and in many cases to some external reviewers, mostly in North America, with invitations to comment and criticize. The drafts have been discussed with the Russian and North American draft authors in several meetings in St. Petersburg, Ottawa and Fairbanks during the period 1999–2007. Comments influencing the present treatments have been received from the initial draft authors (both on their 'own' groups and on other groups), from members of the Editorial Board and the Steering Committee, and from numerous researchers listed above to which the editors are very grateful for comments received and for opportunity to include also many accounts yet unpublished of in print.
            Most comments have been taken into account – in some way or other – in the final editing, but the treatments have been adjusted according to the guidelines decided on for the Checklist project (see Elven 1999). The taxonomy and nomenclature presented in the Checklist is not final in any way. It rather reflects the still very spotty knowledge we have of many plants throughout the huge arctic regions, and it reflects the still prevalent differences in opinions among the scientists in the countries with arctic parts. The notes, including many of these views, are therefore in our opinion the most valuable (and in places perhaps the most entertaining) parts of the Checklist, more useful than the actual taxonomic and nomenclatural solutions chosen.
            (5) An Editorial Board for the PAF Checklist (R. Elven, D.F. Murray, and B.A. Yurtsev) was appointed to be responsible for final decisions as to which taxa to include, their taxonomic ranks and names. The Editorial Board has worked towards consensus or, in cases where the opinions differed to strongly, compromise proposals, but have in some cases taken majority decisions with minority comments where opinions could not meet. The full Editorial Board has not met for final decisions before the conclusion of the Checklist, due to the untimely decise of our dear friend and companion Boris Yurtsev in 2004.
            (6) The final account has therefore been produced mainly by the Editor-in-Chief. This account, as now presented, is not in full accordance with the views of most of the original contributors, or of the commentators, and in some instances not in accordance with the views of the Editor-in-Chief. Such is life. It is, however, the best he is able to do with the present state of knowledge of arctic plants.
            (7) In summary, the original, idealistic aim of reaching a consensus Checklist has not been fully reached. During discussions we have, however, reached a deeper understanding of the reasons behind the different viewpoints, and in many cases also a solution different from and hopefully improving on all the original proposals. In these cases we think the Checklist account might be a step forward compared with previous accounts. In many other cases we have rather reached a compromise that accomodate the differing views, and those views are reflected in the notes.

1.4  Problems in the arctic flora

The Panarctic Flora (PAF) Checklist is a result of a cooperation between botanists in the majority of countries with arctic regions: USA (Alaska), Canada, Iceland, Norway, and Russia. Due to the current lack of professional taxonomists concerned with arctic plants in Greenland (both in Greenland and in Denmark), this very important part of the Arctic is, for the time being, outside the cooperation. We have tried to merge the knowledge available from the North American and Norwegian sides. The 'Greenland gap' is a major problem in current and future arctic botany.
            The current-day Arctic consists of two very different parts palaeo-historically. Most parts of NE Asia and NW North America have a potential continuity in its flora back to the Tertiary due to lack of Quaternary glaciation, whereas the N European and NE North American parts have a very young flora – mostly less than 15,000 years old – due to extensive glaciations (see, e.g., Brochmann et al. 2004). This means that recent immigrations are responsible for a major part of the arctic flora. There have been several phases of disruption of ranges – with some divergence in isolation – and subsequent mergers of ranges. These disruptions have taken place both in the glacial periods for relatively thermophilous taxa and in the warmer interglacial periods for the arctic specialists. The high level of polyploidy, estimates varying between 50–60% and 80% of the flora in different regions, is most probably a result of extensive hybridizations during secondary contacts (Stebbins 1984, Brochmann et al. 2004) with subsequent stabilization and re-aquisition of fertility of hybrid products by polyploidization. It is also probable – and in some cases proven – that polyploidal arctic taxa are polyphyletic at least in the meaning that they have originated several times (polychronically) and/or in several places (polytopically), sometimes probably also taxonomically polyphyletic (originating from different parental combinations). These drastic climatic changes have been going on for at least the past 2 mill. years, and no stabilization is in view. This means that stability in ranges and in competitive environments, as one of the prerequisites for stabilization of species, is and has been a rarity rather than the rule in the Arctic. We should expect an evolutionary 'hot pot' where a large proportion of the 'species' – as a rule – are very young and less than well defined. This has been documented for some groups where the arctic species are so recent that they are not separated in normal phylogenetic analyses based on sequencing (e.g., Scheen et al. 2004 for the arctic Cerastium complexes). It is perhaps surprising that investigators have been able to define, delimit and name as many arctic vascular plants as they have.
            The Arctic also differs from temperate regions in the facilities for investigations. There have been – and still are – few permanent research facilities where the plants can be studied in the field by the same people for extended periods and throughout the season. The most promising such sites fully functional at present are the research stations in W Greenland (Disko) and E Greenland (Sackenberg), in N Alaska (Toolik Lake and Barrow), and the University Studies (UNIS) established with permanent staff, many students, and laboratories in Longyearbyen in the high arctic Svalbard archipelago. Most investigators of the arctic flora have been on expeditions rather than living with the plants throughout the year, as they do in temperate areas. Comparatively little is therefore known about the population biology and, especially, reproduction biology. We are still in an alpha phase in the investigation of many arctic plants and will continue to be so for a long time. We often have to rely on morphology alone, as they did back in the 19th and early 20th centuries.
            A second problem often encountered is the difficulties in drying the collected plant samples and getting them intact back to the 'temperate' institutions where they are permanently stored and studied. The history of potentially important collections lost during shipwrecks or burned during panicky attempts at drying is depressing. Numerous surviving early collections, often important ones for naming and unambiguously characterizing (that is: typifying) the plants, are badly conserved and sometimes without the features needed for safe identification.
            A third and very serious feature, more pronounced after 1900 than before, is that scientists only visit their 'own' arctic areas. During the last 70 years, Greenland has mainly been studied by Danes (except for a short period of unsuccessful Norwegian imperialism in E Greenland in the 1930ies). Svalbard has been visited mainly by Norwegians and Russians (the latter ones due to the Russian mining settlements). Arctic Russia has since c. 1930 almost exclusively been studied by Russians. Arctic Alaska has, after the 'sale', mainly been visited by Americans (and Hultén) and arctic Canada since c. 1910 also almost exclusively by botanists from Canada and USA. This means that the separate parts of the Arctic often have been studied with a viewpoint strongly conditioned by the species content and the taxonomic traditions in their temperate motherlands. Such studies with a temperate – and thereby necessarily provincial – viewpoint have until very recently been paramount in almost all Alaskan, Candian, Greenlandic, Norwegian, and Russian works.
             Efficient comparisons across arctic areas are rare. The last impressive attempt was made by Hultén (1968a) and Hultén & Fries (1986). One example of this lack of knowledge of other arctic regions is the postulating – from the fact of a subglacial find in southern England – that Pedicularis hirsuta could have immigrated to North Scandinavia from a W European refugium, disregarding the fact that it is frequent in much closer areas in N Russia, Svalbard, and NE Greenland. The results of these provincial temperate approaches have partly been duplicate naming, i.e., that one taxonomic and biological entity is named and treated differently in different areas, and partly that the criteria and levels of treatment differ among areas.
            Looking back to the 19th century, we must envy the Victorian scientists their internationality. Publications about arctic and northern plants were almost uniformly written in one of the four languages that every well-educated scientist was familiar with (Latin, French, English, or German). The journals and books were spread efficiently and surprisingly rapidly among the major scientific institutions in each country, apparently without the strong economic restrictions on libraries that we all feel today (and especially so in Russia). Most major western libraries have comparatively good representation of older Russian literature, and vice versa, whereas literature from the last 50 years is much more sparse. And, last but not least, the same approach to botanical taxonomy was prevalent throughout among those concerned with the Arctic. A special 'Russian', 'W European', or 'North American' approach to taxonomy and nomenclature was unthinkable.
            Everything changed with World War I and the October Revolution, or perhaps even somewhat earlier. North Americans did not accept any longer to see their flora from a European (French, German, or British) viewpoint and began an extensive description and naming of species – based on a different Code of Nomenclature – partly duplicating older names and applying a different principle for typification of names. Very narrow species of northern plants were described by some of the most influential North American authors, e.g., Fernald, Rydberg and Greene. The recent effort with a renewed Flora of North America (from 1993 onwards) aims to standardize the treatments but still leaves much amplitude (for splitting or lumping) to the authors. A marked feature that still separates North American treatments from those of Europeans and Russians is their handling of subspecific categories. Americans often consider subspecies and varieties as equivalents, which means that major regional races, local races or ecotypes, and sometimes unique modifications or mutations, are handled at the same taxonomic level.
            After about 1900, N Europeans began to write more extensively in their national languages (Danish, Norwegian, Swedish, Finnish, Icelandic), making their contributions virtually inaccessible outside the Nordic area, and as concerns Finns even outside Finland and possibly Estonia. In taxonomic principles, however, they all followed mainstream European traditions (British, French and German traditions, German ones especially in Norway and Finland). An exception is the Danes working in Greenland and often looking towards Canada, especially relying on Fernald and later on A.E. Porsild. The collective works with Flora Europaea (1964–1993), Atlas florae europaeae (1976 onwards), and Flora Nordica (2000 onwards) have established a common and comparatively consistent view about what constitutes a species and how to apply the ranks of subspecies and variety. In all these floras, there are certain taxonomic and nomenclatorial standards that the authors are told to follow. In principle, subspecies is the rank of major geographical or eco-geographical races. However, in practice, even Flora Europaea accepted numerous very local entities as subspecies and had some treatments (e.g., Festuca) deviating much from the approved standards.
            In Russia, the October Revolution fairly rapidly resulted in a conversion from French and German to Russian as the main scientific language (also evident in some 'Russian' periods in the late 19th century, e.g., during the national revival after the assasination of czar Alexander II), making potentially influential Russian works nearly inaccessible to the rest of the World. This is still the situation. All recent Russian Floras, currently influential journals, and monographs, are in the Russian language, at best with a short and rarely very informative summary in English or German. In addition, a classification tradition applying a very narrow and partly geographically based species circumscription developed during the Komarov era in Russian botany (Flora URSS from 1934 onwards). There were opponents to this 'monotypic' species approach, and luckily for us, the main editor of most of the volumes of Flora Arctica URSS – A.I. Tolmachev – was one of them. However, the authors were given much latitude also in Flora Arctica URSS, from the quite 'lumping' accounts of A.K. Skvortsov to the much more 'splitting' accounts of B.A. Yurtsev (especially in later volumes where he was the editor). There is still a prevalence of species description and generic and subgeneric classification – rather than populational and molecular investigation and associated phylogenetic studies – in much Russian literature, as seen from the last years' issues of, e.g., Botanicheskii Zhurnal and Novosti Sistematiki Vysshich Rastenii. There is also a prevalent view that – irrespective of morphological differences – sympatric (conformity of ranges) or allopatric (disjunct ranges) entities should be treated as species; subspecies should be parapatric (overlapping ranges, preferrably with intergradation). Another difficulty caused by the present economic and political conditions in Russia is that what is considered as modern, experimental work in North America and Europe is nearly impossible to do there. This means that Russian botanists mainly have to rely on methods that now are considered – in critical cases – as insufficient when applied alone in North America and Europe. The 'molecular revolution' will not have a full impact in Russian botanical taxonomy and for Russian plants before they have the economical means to apply these methods on their own plants.

1.5  Summary

A Panarctic Flora Checklist could be compiled in several ways. The simplest way would be just to assemble the names in use in the different parts of the Arctic and the distributions reported regionally of the named entities. Recent lists exist for most regions: For Russia by Sekretareva (1999), for mainland Norway and Jan Mayen by Elven in Lid & Lid (2005), for Svalbard by Elven & Elvebakk (1996), for Iceland by Kristinsson (1987, http://vefsja.ni.is/website/plontuvefsja), for Greenland by Böcher et al. (1978) supplemented by Feilberg (1984), Bay (1992) and Fredskild (1996), and for North America perhaps by Shetler & Skog (1978) or by the Flora of North America compilations.
            Such a compiled list would have some major disadvantages. The same name has often been used in different meanings in different areas, e.g., the names Cerastium alpinum and Papaver radicatum have been used differently in Europe, Greenland, and North America; the names Festuca hyperborea and F. brachyphylla have even recently been used differently in Russia from elsewhere; the name Dryopteris carthusiana is used differently in the Nordic area and in Russia; and the names in Potentilla and Dryas have been used more or less differently everywhere. It would be impossible to make a meaningful distributional table based on these lists. And – even more important – it would be impossible to use the Checklist for, e.g., biodiversity estimates and conservation purposes as the criteria for rare and possibly threathened plants would differ appreciably among regions. Such a list would, in reality, not have any value above that of the primary sources which are fairly easily accessible. To produce such a list is not a very challenging task.
            We have therefore aimed to produce something different, see several accounts in Nordal & Razzhivin (1999) and 'Aims' above. This effort is partly based on the failure of the 2–3 previous attempts to produce a Panarctic Flora (see Murray & Yurtsev 1999, and the summary above). These aims are not entirely fulfilled by the current Checklist. In a few plant groups it has proved difficult to reach a consensus, or even a compromise, among the Panarctic Flora collaborators. The reasons are still connected with different botanical traditions. In spite of the fall of the Soviet Union and the abandonment of the US 'Evil Empire' concept of Russia, efficient cross-comparison of North American, European, and Russian materials is hampered by restrictions in exchange on all sides, not least by recent developments in Putin's Russia. Application of molecular methods on arctic plants is hampered by the expenses and logistics in collecting them. The Checklist is therefore – deplorably – not as uniform and as consensical as we originally aimed it to be. For a few genera it is a compromise between the ideal consensus version and the minimal compilation version. The areas of non-consensus are, however, always marked by notes.
            Another area of surprisingly many botanical conflicts is now between NW Europe and North America. Quite different botanical traditions have emerged on the two continents during the last century. The major cross-tradition arctic botanist in the last century – Eric Hultén – has had a lasting influence on Alaskan and Yukon botany, but his treatments and opinions are often neglected in current North American works which are heavily based in the 'Lower Fortyeights', sometimes very evident in the Flora of North America project where numerous North American names and proposals from Hultén are omitted even from the synonymy.
            The editorial office of the Panarctic Flora Checklist has been located in Norway, politically responsible for only a very small slice of the Arctic: Some square kilometres in mainland Norway, the 'dots' of Jan Mayen and Bear islands, and the somewhat more substantial Svalbard archipelago. In addition, the Norwegian areas are situated in the floristically most depauperate part of the Arctic. During the Checklist work we in Norway have therefore often – by Russians and by North Americans alike – been accused of Eurocentrism and of having a very provincial view of the Arctic. This is probably true. We have a European viewpoint, especially as concerns, e.g., the ranks of species, subspecies, and varieties, and we are ready to defend it. We also have a European view of variation, conditioned by the topographical and glacial history of the continent, a view that may be unsuitable for the more continuous, large areas in Russia – Siberia and in North America – Greenland. However, numerous received comments, especially from North America, have arrested the possible Eurocentrisms and have resulted in changes. At least, the 'Eurocenter' represents a middle road between the fairly extensive splitting of some Russian proposals and the equally extensive lumping of some North American proposals.
            The Checklist is then now presented at its current stage, as a consensus proposal among Russian, North American, and NW European botanists for the major part of the taxa and as a compromise proposal for the remaining taxa.