Download Plants chapter chapter 9
Download Appendix 9.1 List and distribution of all Arctic vascular plants
Download Appendix 9.2 Endemic Arctic vascular plant distribution
Download Appendix 9.3 "Borderline" Arctic vascular plants
Download Appendix 9.4 Stabilized and casual introductions: vascular plants
Download Appendix 9.5 Liverwort genera of Arctic Russia
Download Appendix 9.6 Species list of liverworts of Svalbard
Download Appendix 9.7 Liverworts of Greenland
Download Appendix 9.8 Moss families of the Canadian Arctic Archipelago
PLANTS (Chapter 9)
Lead Authors: Fred J.A. Daniëls, Lynn Gillespie and Michel Poulin
Contributing Authors: Olga M. Afonina, Inger Greve Alsos, Mora Aronsson, Helga Bültmann, Stefanie Ickert-Bond, Nadya A. Konstantinova, Connie Lovejoy, Henry Väre and Kristine Bakke Westergaard
Based on published scientific literature, the diversity of plants in the Arctic is reviewed. The plants are divided into three main groups according to essential differences in anatomy, morphology and reproduction. These are vascular plants, bryophytes (mosses and liverworts) and algae (micro- and macroalgae). As a whole, these three plant groups have the ability to perform photosynthesis. As primary producers they play a key role in the environment, since photosynthesis provides resources for all other organisms. Vascular plants and bryophytes (together with the lichenized fungi, the lichens) are the main structural components of terrestrial vegetation and ecosystems, while algae are more abundant in fresh water and marine ecosystems.
Our knowledge of the taxonomic diversity of these three main groups is very uneven. Although serious knowledge gaps still exist, our understanding of vascular plant diversity in the Arctic was recently improved considerably by the publication of the Annotated Checklist of the Panarctic Flora (PAF) Vascular plants (Elven 2011), a result of many years of laborious research by taxonomists associated with the Panarctic Flora Project. The Arctic bryoflora is relatively well known, but a circumpolar Arctic checklist of mosses and liverworts has not yet been finalized. Knowledge of the circumpolar Arctic taxonomic diversity of algae is still rather fragmentary. Preliminary biodiversity assessments have been made for Arctic marine algae, but there has been no attempt yet to synthesize knowledge of the diversity of Arctic freshwater algae. Knowledge of the biodiversity of terrestrial algae in the Arctic is also very fragmentary.
Willows grow much faster now on the banks of Kolyma. As well in the summer pasture areas along the Arctic Ocean tundra willows are more plentiful and more now. On River Suharnaya the willow bushes are much bigger. Reindeer herders of the Chukchi community of Nutendli, northeastern Sakha-Yakutia, Siberia; Mustonen 2007
The main difficulties in assessing biological diversity at subgeneric levels are the dissimilarities that exist in the taxonomic species concept and classification between the Arctic countries. Moreover, current species concepts from traditional morphological assessments are challenged by the latest molecular phylogenetic analyses, which sometimes conflict with traditional classification.
The vascular plant flora of the Arctic is relatively poor. Approximately 2,218 vascular plant species (including subspecies, apomictic aggregates and some collective species) are recognized. This is less than 1% of the known vascular plant species in the world (c. 0.85% based on an estimated total of 260,000 species; Raven et al. 2005). Arctic vascular plants belong to 430 genera and 91 families, almost all within the flowering plants (angiosperms). Gymnosperms are rare and species diversity per genus and family is low. Species-rich families with more than 100 species include Asteraceae (composite family), Poaceae (grass family), Cyperaceae (sedge family), Brassicaceae (mustard family), Rosaceae (rose family), Fabaceae (pea family), Ranunculaceae (buttercup family) and Caryophyllaceae (pink family). The genera Carex (sedge), Salix (willow), Oxytropis (oxytrope) and Potentilla (cinquefoil) are well represented, with each having more than 50 species. The majority of the Arctic species have a circumpolar distribution.
The Arctic territory is divided into 21 floristic provinces and five subzones. These strongly differ in species richness and composition. There is a pronounced increase in species numbers from the northernmost high Arctic subzone A (102 species) to the southernmost low Arctic subzone E (2180 species). A comparison of species numbers per floristic province showed a range from approximately 200 species for the rather heavily glaciated and northern floristic province Ellesmere Land-N Greenland to more than 800 species for Beringian W Alaska.
Endemism is well developed. One hundred six species (and subspecies), or around 5% of the Arctic vascular plant flora, are endemic to the Arctic. The genera Papaver (poppy), Puccinellia (salt marsh-grass, goose grass), Oxytropis, Potentilla and Draba (draba, whitlow-grass) are particularly rich in endemic species, and almost all endemic species are forbs and grasses, whereas there are no endemic woody species. Though the absolute number of Arctic endemic species increases from north to south, i.e. from the high Arctic to the low Arctic, the relative percentage of endemic species decreases.
The floras of the northern floristic provinces Ellesmere Land-N Greenland, Svalbard-Franz Joseph Land and Wrangel Island are relatively rich in Arctic endemic species. Ten Arctic endemic species are restricted to Wrangel Island and underline the hotspot character of this high Arctic island. Twenty Arctic endemic species are very rare, and as such are possibly threatened. Polyploidy1 (allopolyploidy) levels are high in Arctic plants.
Borderline species are primarily non-Arctic species just reaching the southernmost extent of the Arctic (subzone E). Taxonomically this is a rather diverse group of 136 vascular plant species in 91 genera and 45 families.
Non-native species that occur as persisting stabilized introductions in the Arctic account for 5% of the flora (101 species). In addition there are 89 species native to the Arctic that also occur as stabilized introductions in other parts of the Arctic. In addition, more than 205 non-native species have been recorded in the Arctic only as casual introductions that do not persist. Non-native species mainly occur in and around settlements and towns, in particular in climatologically favorable parts of the Euro-Siberian Arctic.
No single, predominantly Arctic vascular plant species is known to have gone extinct due to human activities in the last 250 years. There are no species in the Arctic that are considered to be seriously invasive, but some are at risk of becoming it with increasing human traffic combined with climate change. The Arctic flora is considered taxonomically, ecologically, biologically and genetically a coherent and distinctive complex of young and dynamic species that occupies a vast natural area characterized by a cold climate. The present Arctic vegetation shows climate change related changes such as greening, shrub expansion and floristical changes.
Local plants always played an essential role in the lives and cultures of Arctic indigenous peoples. The most useful plants have indigenous names, including not only vascular plants, but bryophytes and algae as well.
There are an estimated 900 species of Arctic bryophytes (mosses and liverworts). Distributional types are similar to those observed for vascular plants. Arctic endemism is not common among bryophyte species, but many widely distributed species in the Arctic show considerable morphological plasticity representing subspecies, variants or forms. The bryoflora is in general rather uniform. Almost 80% of the species have a circumboreal distribution. In rather stable, moist to wet sites, bryophytes contribute substantially to vegetation biomass, and they contribute significantly to species richness of many vegetation types in other habitats. Very few vegetation types in the Arctic occur without bryophytes, and single shoots occur almost everywhere, in particular in the high Arctic. The ecosystem function of bryophytes is poorly studied, and the bryofloras of several Arctic regions are still incompletely known. The most speciesrich families include Bryaceae (threadmoss family), Dicranaceae (forkmoss family), Amblystegiaceae (feathermoss family), Pottiaceae (tuftmoss family), Grimmiaceae (Grimmia family), Sphagnaceae (bogmoss family), Hypnaceae (feathermoss family), Mniaceae (thyme-moss family), Brachytheciaceae (feathermoss family), Polytrichaceae (haircap family) and Splachnaceae (dung moss family), which collectively account for 70% of the total moss flora. Bryum (Bryum moss), Sphagnum (bogmoss), Pohlia (nodding moss) and Dicranum (forkmoss) are among the most species-rich genera. Species-rich liverwort families include the leafy liverworts Scapaniaceae (earwort family), Jungermanniaceae (flapwort family), Gymnomitriaceae (frostwort family), Cephaloziaceae (pincerwort family) and Cephaloziellaceae (threadwort family), whereas Scapania (earthwort) and Lophozia (notchwort) are prominent genera. The use of bryophytes by indigenous people is very limited. There are no known threatened bryophyte species.
Algae are ubiquitous, ecologically important and constitute the first layer of marine and freshwater food webs. They occur either free floating in the upper water column (pelagic), associated with sea ice (sympagic), or attached to bottom substrates (benthic). Phaeophyta (brown algae) range in size from less than 2 μm to more than 100 m long in giant kelps. Pelagic algae, known as phytoplankton, and sea ice algae are autotrophic, singlecelled eukaryotes ranging in size from 0.2 to 200 μm. Benthic algae mainly refer to marine macroalgae characteristic of coastal regions, but also include microalgae attached to various substrates along the seashore. Algae, including the autotrophic prokaryote cyanobacteria (blue-green algae), are classified into different groups or phyla, depending on the classification system used.
The following groups have been recognized in this review: (1) Archaeplastida, including Chlorophyta (green algae), Streptophyta, Glaucophyta, Rhodophyta (red algae), (2) Chromalveolata, with Cryptophyta, Haptophyta, Dinophyta, Stramenopiles (including Dictyochophyceae, Eustigmatophyceae, Pelagophyceae, Bacillariophyta (diatoms), Phaeophyceae (brown algae), Xanthophyceae, Chrysophyceae (yellow-green algae), Rhaphidophyceae), (3) Excavata (Euglenophyta), (4) Opisthokonta (Choanoflagellida), (5) Rhizaria (Chlorarachniophyta) and (6) Cyanophyceae (blue-green algae).
There is a conservative estimate of 4000 algal species reported from the circumpolar Arctic, including both freshwater and marine habitats. The species diversity of microalgae and cyanobacteria for the Arctic is still largely unknown, especially in terrestrial and freshwater environments, but it is assumed to be much lower than in warmer regions of comparable size. In Arctic regions, marine diatoms are very diverse and abundant in annual sea ice, pelagic waters and benthic environments. Recent molecular studies reported a high diversity in the smallest-sized fraction of the phytoplankton in polar regions, frequently contributing to more than 50% of total phytoplankton biomass and production. In the western Canadian Arctic alone, 10,000 species of singlecelled phytoplankton species were documented through molecular analyses, at least half of which are likely autotrophic. There are c. 200-215 seaweed (macroalgae) taxa in the Arctic, with endemism poorly developed. A major challenge facing biodiversity assessments will be matching morphology of a single-celled alga to a given gene sequence, which will require development of better sampling strategies and culture techniques for these small-sized microalgae.
This plant chapter deals with the taxonomical biodiversity of organisms that are able to perform photosynthesis. They use light energy for conversion of carbon dioxide and water into chemical energy in the form of sugar and other organic substances under release of oxygen. Most of them are photoautotrophic, using carbon dioxide as their carbon source.
They include three main groups based on differences in anatomy, morphology, physiology and reproduction, and phylogenetic relationships.
The kingdom Plantae of the eukaryotic life domain comprises the green land plants. These are the vascular plants – Tracheophyta (section 9.2) and the bryophytes – Bryophyta (section 9.3). The vascular plants are subdivided into spore-producing plants (clubmosses – Lycopodiophyta and ferns – Pteridophyta) and seed producing plants (Gymnospermae with uncovered seeds, Angiospermae with covered seeds). The bryophytes are divided into the hornworts (Anthocerophyta), liverworts (Hepatophyta) and mosses sensu stricto (Bryophyta) (Raven et al. 2005).
The photoautotrophic algae (section 9.4) of the kingdom Protista comprise eukaryotic organisms which cannot be attributed to the kingdoms Fungi, Plantae or Animalia. The green algae (Chlorophyta) are ancestral to the algal Streptophyta and hence to the kingdom Plantae, the bryophytes – Bryophyta and vascular plants – Tracheophyta. Some other algae are both autotrophic and heterotrophic (Poulin et al. 2011).
The blue-green algae belong to the prokaryotic life domain Bacteria and are classified as Cyanobacteria (Raven et al. 2005).
As primary producers, all groups play a key role in the environment, since photosynthesis provides resources for all other organisms. Vascular plants and bryophytes (together with the lichenized fungi, the lichens; see Dahlberg & Bültmann, Chapter 10) are the main structural components of terrestrial vegetation and ecosystems, while algae are more abundant in freshwater and marine ecosystems.
The state of knowledge of Arctic vascular plants, bryophytes, and algae differs among countries, regions, and floristic provinces, and there remain many differences in taxonomic opinions among botanists on different continents. The data presented here should be viewed as a preliminary assessment.
Scientific names are used throughout the manuscript since there are no standardized common or vernacular names for plants, and many species (e.g. algae) lack common names altogether. For taxa with common names, these are provided in parentheses following the scientific names the first time a taxon is mentioned. These names are derived from several sources (among others Clapham et al. 1962, Böcher et al. 1968, Hultén 1968, Porsild & Cody 1980, Rønning 1996, Smith 2004 and Edwards 2012).
The total land surface of the Arctic is estimated at 7.11 million km2, with an estimated 5 million km2 covered by vegetation; the remainder is ice-covered (Walker et al. 2005). The Arctic territory has been and still is sparsely populated. While there was almost no impact by human populations on Arctic flora and vegetation prior to the 1960s, human impacts now pose an increasing threat in certain areas. Nevertheless, these impacts are minor compared with human impacts in the adjacent boreal zone.
CONCLUSIONS AND RECOMMENDATIONS
There is a great need for intensifying biodiversity research on Arctic flora with emphasis on molecular phylogenetic taxonomy, vegetation classification, monitoring and modelling. Coordination and cooperation between researchers must be improved. Baseline information on the distribution of Arctic plant species, including population number and size, is essential for accurately determining species status. Given the almost complete lack of population trend data for Arctic plant species, monitoring programs should be established in order to gather trend data. The conservation status of Arctic plant species can only be objectively assessed once information becomes available on the population status and trends of individual species and their plant community types. Due to their small-scale climatic and biotic diversity, Arctic hotspot complexes are strongly recommended as Arctic field laboratories for climate change-related research (see Elvebakk 2005) and for consideration as protected areas. In particular, monitoring of species ranges along altitudinal gradients in Arctic mountains is strongly recommended. Here we might expect above all species response to climate warming due to the relatively steep climate gradient (e.g. Elvebakk 2005, Schwarzenbach 2006, Pauli et al. 2007, Jedrzejek et al. 2012).
The estimated species number of the bryophyte flora of the Arctic is moderate (c. 900) compared with that of lichens (c. 1750) and vascular plants (c. 2,218). But it is likely that this number will increase significantly in the course of future studies. Arctic endemism is not strongly pronounced, and is displayed mainly on an infraspecies level. The Arctic bryoflora is rather uniform. Almost 80% of the species have a broad circumboreal and circumpolar distribution. In rather stable, wet-to-moist sites they strongly contribute to vegetation biomass, and they also contribute to species richness of many vegetation types in other habitats. Their ecosystem function is poorly studied, and overall the bryofloras of most Arctic regions are still incompletely known. Moreover, Arctic material in the majority of taxonomic groups needs revision using modern molecular phylogenetic approaches (cf. Konstantinova & Vilnet 2009, Söderström et al. 2010). Records of localities of rare and recently described species need verification. There are no known threatened species. The use of bryophytes by indigenous people is very restricted. A circumpolar checklist according to uniform taxonomic concepts and nomenclature is urgently needed and will be highly beneficial for vegetation and ecosystem studies, especially for monitoring and interpretation of change in the face of climate change.
The total number of recognized algal species for the Arctic is at present likely around 4000, which represents 10% of the world’s recognized species. There are between 30,000 and 40,000 described species of algae worldwide, which correspond to only a small fraction of the estimated number of about 400,000 species (Poulin & Williams 2002). The total species number of algae and cyanobacteria in the Arctic is still largely unknown, especially in terrestrial and freshwater environments. Regarding their huge ecological importance for all life on earth, both in the sea and on land, better inventories and monitoring of algae are strongly needed, particularly considering that the Arctic regions are and will be severely impacted by global warming.
A major effort should be undertaken to establish a complete baseline of the biodiversity of marine and freshwater phytoplankton and macroalgae and polar sea ice microalgae, especially since these algae will become part of the CAFF Circumpolar Biodiversity Monitoring Program (CBMP). Reaching that goal requires more taxonomic studies in order to elucidate the species concept and harmonize it across the Arctic. The fields of taxonomy and systematics should be considered more than a descriptive exercise and rather as fundamental tools of discovery, conservation and management. Future efforts should focus particularly on the biodiversity of small-celled (< 20 μm) microalgae. Finally, all this research effort should be undertaken through international networks leveraging the costs associated with such pan-Arctic programs.