Arctic Taxa Research Articles

Genome Size in the Arenaria ciliata Species Complex (Caryophyllaceae), with Special Focus on Northern Europe and the Arctic.

The main aim of the present study has been the completion of genome size data for the diverse arctic-alpine A. ciliata species complex, with special focus on the unexplored arctic taxon A. pseudofrigida, the north-European A. norvegica, and A. gothica from Gotland (Sweden). Altogether, 46 individuals of these three Nordic taxa have been sampled from seven different regions and their genome size estimated using flow cytometry. Three other alpine taxa in the A. ciliata complex (A. multicaulis, A. ciliata subsp. ciliata, and A. ciliata subsp. bernensis) were also collected and analyzed for standardization purposes, comprising 20 individuals from six regions. A mean 2c value of 1.65 pg of DNA was recorded for A. pseudofrigida, 2.80 pg for A. norvegica, and 4.14 pg for A. gothica, as against the reconfirmed 2c value of 1.63 pg DNA for the type taxon A. ciliata subsp. ciliata. Our results presenting the first estimations of genome sizes for the newly sampled taxa, corroborate ploidy levels described in the available literature, with A. pseudofrigida being tetraploid (2n = 4x = 40), A. norvegica possessing predominantly 2n = 8x = 80, and A. gothica with 2n = 10x = 100. The present study also reconfirms genome size and ploidy level estimations published previously for the alpine members of this species complex. Reflecting a likely complex recent biogeographic history, the A. ciliata species group comprises a polyploid arctic-alpine species complex characterized by reticulate evolution, polyploidizations and hybridizations, probably associated with rapid latitudinal and altitudinal migrations in the Pleistocene-Holocene period.

First record of the rare boreo-alpine moss Herzogiella striatella (Brid.) Z. Iwats. in the Western Balkans

The rare boreo-alpine moss Herzogiella striatella was found on Mt Snježnik (W Croatia) in 2015 and constitutes the first national record. Two populations were recorded inside an old and hardly accessible spruce forest on steep boulders (Lonicero caerulae-Piceetum) along the Frankopanski Put hiking path. The markedly cool and humid microclimate ensured by small karst dolines within the forest shapes the specific bryophyte species composition with the elements of snowbed and timberline pine krummholz vegetation and the domination of boreal and arctic taxa. Due to its pronounced isolation from other European populations, the species is certainly of relict origin in Croatian Dinaric Alps.

Taxonomy of the Subspecies of Papaver pulvinatum (Papaveraceae)

The taxonomy and geographic distribution of four subspecies of the arctic Siberian taxon Papaver pulvinatum Tolm., viz. subsp. interius, subsp. alexandri V.V. Petrovsky subsp. nova, subsp. tschuktschorum Tolm. subsp. nova, and the autonymous subspecies, are discussed. The name P. pulvinatum subsp. lenaense Tolm. as interpreted in a previous validation proved to be a synonym of P. nudicaule var. riparium V.V. Petrovsky. The plants treated before as subsp. lenaense are described as a new subspecies, P. pulvinatum subsp. alexandri. The name P. pulvinatum subsp. tschuktschorum is validated. The description of P. pulvinatum subsp. interius is augmented and amplified.

Arctic Sensitivity? Suitable Habitat for Benthic Taxa Is Surprisingly Robust to Climate Change

Arctic marine ecosystems are often assumed to be highly vulnerable to ongoing climate change, and are expected to undergo significant shifts in structure and function. Community shifts in benthic fauna are likely to result from changes in key physico-chemical drivers, such as ocean warming, but there is little ecological data on most Arctic species to support any specific predictions as to how vulnerable they are, or how future communities may be structured. We used a species distribution modelling approach (MaxEnt) to project changes over the 21st century in suitable habitat area for different species of benthic fauna by combining presence observations from the OBIS database with environmental data from a coupled climate-ocean model (SINMOD). Projected mean % habitat losses over taxonomic groups were small (0-11%), and no significant differences were found between Arctic, boreal, or Arcto-boreal groups, or between calcifying and non-calcifying groups. However, suitable habitat area for 14 of 78 taxa were projected a change by over 20%, and several of these taxa are characteristic and/or habitat-forming fauna on some Arctic shelves, suggesting a potential for significant ecosystem impacts. These results highlight the weakness of general statements regarding vulnerability of taxa on biogeographic or presumed physiological grounds, and suggest that more basic biological data on Arctic taxa are needed for improved projections of ecosystem responses to climate change.Importantly, however, 14 of 78 taxa exhibited a predicted increase or decrease in suitable habitat of over 20%, and several of these taxa are characteristic and/or habitat-forming fauna on some Arctic shelves, suggesting a potential for significant ecosystem impacts. These results highlight the weakness of general statements regarding vulnerability of taxa on biogeographic or presumed physiological grounds, and suggest that more basic biological data on Arctic taxa are needed for improved projections of ecosystem responses to climate change.

Towards a barnacle tree of life: integrating diverse phylogenetic efforts into a comprehensive hypothesis of thecostracan evolution.

Barnacles and their allies (Thecostraca) are a biologically diverse, monophyletic crustacean group, which includes both intensely studied taxa, such as the acorn and stalked barnacles, as well as cryptic taxa, for example, Facetotecta. Recent efforts have clarified phylogenetic relationships in many different parts of the barnacle tree, but the outcomes of these phylogenetic studies have not yet been combined into a single hypothesis for all barnacles. In the present study, we applied a new “synthesis” tree approach to estimate the first working Barnacle Tree of Life. Using this approach, we integrated phylogenetic hypotheses from 27 studies, which did not necessarily include the same taxa or used the same characters, with hierarchical taxonomic information for all recognized species. This first synthesis tree contains 2,070 barnacle species and subspecies, including 239 barnacle species with phylogenetic information and 198 undescribed or unidentified species. The tree had 442 bifurcating nodes, indicating that 79.3% of all nodes are still unresolved. We found that the acorn and stalked barnacles, the Thoracica, and the parasitic Rhizocephala have the largest amount of published phylogenetic information. About half of the thecostracan families for which phylogenetic information was available were polyphyletic. We queried publicly available geographic occurrence databases for the group, gaining a sense of geographic gaps and hotspots in our phylogenetic knowledge. Phylogenetic information is especially lacking for deep sea and Arctic taxa, but even coastal species are not fully incorporated into phylogenetic studies.

Distribution shifts of marine taxa in the Pacific Arctic under contemporary climate changes

AbstractAimTo investigate the species‐specific exposure and distributional responses of marine fish and invertebrate taxa to rapidly shifting climate in the Pacific Arctic, characterized by warming and cooling episodes, over the last 24 years.LocationPacific Arctic region, eastern Bering Sea and Chukchi Sea.MethodsWe examined the variations in the summer (June–July) habitat patterns of 21 marine fish and invertebrate taxa in the eastern Bering Sea using multimodel ensemble predictions of species distribution between 1993 and 2016. Using ensemble model outputs, we examined the rates of predicted (biotic velocities) and expected (bioclimatic velocities) distribution shifts across taxa under four consecutive time periods of distinct climatic regimes. We then compared these species‐specific velocity metrics to the rates of local climatic shifts (climatic velocities) and quantified the potential lags in distributional responses relative to changes in climate across taxa and transitions.ResultsOur analyses showed that individual taxa responded to climatic fluctuations at different paces and generally exhibited lags in their predicted distributional responses. Subarctic species revealed higher habitat sensitivity and exposure to climatic changes than Arctic taxa, as they expand their habitat ranges into suitable regions emerging in the north under warmer conditions. Importantly, the actual rates of climate shifts (climatic velocities) were poorly correlated with both the expected and observed shifts in species distributions across taxa.Main conclusionsOur findings underpin the importance of incorporating species‐specific climatic sensitivity and exposure to changes in climatic conditions when predicting range shift responses and evaluating species vulnerability. These insights are critical for conservation and management of fisheries resources in the region.

Polyphyly of the traditional family Flabellinidae affects a major group of Nudibranchia: aeolidacean taxonomic reassessment with descriptions of several new families, genera, and species (Mollusca, Gastropoda).

The Flabellinidae, a heterogeneous assembly of supposedly plesiomorphic to very derived sea slug groups, have not yet been addressed by integrative studies. Here novel material of rarely seen Arctic taxa as well as North Atlantic, North and South Pacific, and tropical Indo-West Pacific flabellinid species is investigated morpho-anatomically and with multi-locus markers (partial COI, 16S rDNA, 28S rDNA and H3) which were generated and analysed in a comprehensive aeolid taxon sampling. It was found that the current family Flabellinidae is polyphyletic and its phylogeny and taxonomic patterns cannot be understood without considering members from all the Aeolidacean families and, based on a robust phylogenetic hypothesis, morpho-anatomical evolution of aeolids is more complex than suspected in earlier works and requires reclassification of the taxon. Morphological diversity of Flabellinidae is corroborated by molecular divergence rates and supports establishing three new families (Apataidae fam. n., Flabellinopsidae fam. n., Samlidae fam. n.), 16 new genera, 13 new species, and two new subspecies among the former Flabellinidae. Two families, namely Coryphellidae and Paracoryphellidae, are restored and traditional Flabellinidae is considerably restricted. The distinctness of the recently described family Unidentiidae is confirmed by both morphological and molecular data. Several species complexes among all ex-“Flabellinidae” lineages are recognised using both morphological and molecular data. The present study shows that Facelinidae and Aeolidiidae, together with traditional “Tergipedidae”, deeply divide traditional “Flabellinidae.” Diagnoses for all aeolidacean families are therefore provided and additionally two new non-flabellinid families (Abronicidae fam. n. and Murmaniidae fam. n.) within traditional tergipedids are established to accommodate molecular and morphological disparity. To address relationships and disparity, we propose a new family system for aeolids. Here the aeolidacean species are classified into at least 102 genera and 24 families. Operational rules for integration of morphological and molecular data for taxonomy are suggested.

Living on the edge of a shrinking habitat: the ivory gull, Pagophila eburnea, an endangered sea-ice specialist.

The ongoing decline of sea ice threatens many Arctic taxa, including the ivory gull. Understanding how ice-edges and ice concentrations influence the distribution of the endangered ivory gulls is a prerequisite to the implementation of adequate conservation strategies. From 2007 to 2013, we used satellite transmitters to monitor the movements of 104 ivory gulls originating from Canada, Greenland, Svalbard-Norway and Russia. Although half of the positions were within 41 km of the ice-edge (75% within 100 km), approximately 80% were on relatively highly concentrated sea ice. Ivory gulls used more concentrated sea ice in summer, when close to their high-Arctic breeding ground, than in winter. The best model to explain the distance of the birds from the ice-edge included the ice concentration within approximately 10 km, the month and the distance to the colony. Given the strong links between ivory gull, ice-edge and ice concentration, its conservation status is unlikely to improve in the current context of sea-ice decline which, in turn, will allow anthropogenic activities to develop in regions that are particularly important for the species.

Notes on some new and interesting Greenland lichens with particular emphasis on high arctic taxa

Abstract Hansen E. S., 2013: Notes on some new and interesting Greenland lichens with particular emphasis on high arctic taxa [Pastabos apie retas ir įdomias Grenlandijos kerpes, ypač poliarinių dykumų taksonus]. - Bot. Lith., 19(2): 149-156. The paper lists 73 taxa of Greenland lichens. Immersaria athroocarpa, Melanelixia subaurifera and Polyblastia sakkobanensis are recorded for the first time from Greenland. Melanelia agnata, Melanohalea exasperatula and Peltigera britannica are new to South Greenland, while Miriquidica intrudens and Peltigera ponojensis are new to Central West Greenland. Caloplaca citrina, Cladonia galindezii, Pertusaria bryontha, Protoblastenia rupestris, Sphaerophorus globosus and Staurothele drummondii represent northern range extensions in North East Greenland. New localities north of 80° N are given for 59 lichen taxa from Greenland.

Xanthophyll Cycle Pool Size and Composition in Several Cosmarium Strains (Zygnematophyceae, Streptophyta) are Related to their Geographic Distribution Patterns

The photosynthetic behaviour and composition of photosynthetic pigments of four Cosmarium strains collected from different geographic areas were examined under moderate and photoinhibitory white light by means of PAM fluorometry and high-performance liquid chromatography. Generally, all of the Cosmarium strains displayed the photosynthetic performance and the composition of xanthophyll cycle pigments corresponding to that of high-light adapted plants and algae, when grown under the standard laboratory conditions. However, photoinhibitory treatments provoked several strain- and species-specific characteristics despite the long-term cultivation in laboratory conditions. The typical arctic taxon, C. crenatum var. boldtianum, displayed an incomplete violaxanthin cycle yielding an accumulation of antheraxanthin during high light stress, which is considered as an adaptation to occasional high irradiances in the polar zone due to the albedo. So far, the violaxanthin/antheraxanthin turnover was known only in some prasinophycean algae. Antheraxanthin actively participated in the heat dissipation from PSII centres in C. crenatum, as concluded from a significant positive correlation between non-photochemical quenching (NPQ) and the quantity of antheraxanthin. In contrast, all the other Cosmarium strains displayed a complete violaxanthin de-epoxidase action during the high light treatments, as judged from the relatively high production of zeaxanthin which participated in thermal dissipation of excess energy.

Hybridization among Arctic white‐headed gulls (Larus spp.) obscures the genetic legacy of the Pleistocene

We studied the influence of glacial oscillations on the genetic structure of seven species of white-headed gull that breed at high latitudes (Larus argentatus, L. canus, L. glaucescens, L. glaucoides, L. hyperboreus, L. schistisagus, and L. thayeri). We evaluated localities hypothesized as ice-free areas or glacial refugia in other Arctic vertebrates using molecular data from 11 microsatellite loci, mitochondrial DNA (mtDNA) control region, and six nuclear introns for 32 populations across the Holarctic. Moderate levels of genetic structure were observed for microsatellites (FST= 0.129), introns (ΦST= 0.185), and mtDNA control region (ΦST= 0.461), with among-group variation maximized when populations were grouped based on subspecific classification. Two haplotype and at least two allele groups were observed across all loci. However, no haplotype/allele group was composed solely of individuals of a single species, a pattern consistent with recent divergence. Furthermore, northernmost populations were not well differentiated and among-group variation was maximized when L. argentatus and L. hyberboreus populations were grouped by locality rather than species, indicating recent hybridization. Four populations are located in putative Pleistocene glacial refugia and had larger τ estimates than the other 28 populations. However, we were unable to substantiate these putative refugia using coalescent theory, as all populations had genetic signatures of stability based on mtDNA. The extent of haplotype and allele sharing among Arctic white-headed gull species is noteworthy. Studies of other Arctic taxa have generally revealed species-specific clusters as well as genetic structure within species, usually correlated with geography. Aspects of white-headed gull behavioral biology, such as colonization ability and propensity to hybridize, as well as their recent evolutionary history, have likely played a large role in the limited genetic structure observed.

Cryptic introgression between murre sister species (Uria spp.) in the Pacific low Arctic: frequency, cause, and implications

As southern species undergo northward range expansions, reports of hybridization between temperate and arctic taxa are increasing, which may have important implications for the evolution, conservation, and management of arctic species. The extent of hybridization between temperate common murres (Uria aalge) and arctic thick-billed murres (U. lomvia), seabirds in the family Alcidae, has been the subject of debate. In a previous survey of variation in mitochondrial DNA (mtDNA) in common and thick-billed murres sampled from throughout the North Pacific and low Arctic, 12 of 327 common murres (~4%) were found to possess DNA sequences characteristic of thick-billed murres. In the present study, we surveyed variation in three nuclear introns in 230 common murres and 56 thick-billed murres and report that these putative hybrids carry various combinations of intron alleles from common and thick-billed murres. Analysis using the program STRUCTURE indicated that nine of these individuals possessed high proportions of thick-billed murre intron alleles, two possessed alleles in F1 and F2 proportions, and one individual possessed predominantly common murre intron alleles. We propose that the asymmetric mtDNA introgression we observed is most likely the result of mate choice at mixed colonies based on differences in male mating behaviours. Our results highlight that hybridization between thick-billed and common murres is more prevalent than previously thought, which may have important implications for the conservation and management of arctic-dwelling thick-billed murres as common murres expand northward.

Growth and photosynthetic characteristics of several Cosmarium strains (Zygnematophyceae, Streptophyta) isolated from various geographic regions under a constant light-temperature regime

Numerous detailed studies have been made of climatically and environmentally influenced macroalgal geographic distribution patterns. However, so far, there have been only a few intrinsic investigations of the geographic distributions of microalgae. In order to investigate the physiological differences among geographically different microalgal strains, six Cosmarium strains were collected from various climate areas and studied. They were grown under a constant light-temperature regime (16°C and 30 μmol photons m−2 s−1) and nutrient supply. The arctic representative, C. crenatum var. boldtianum, and the typical tropical desmid, C. beatum, behaved like algae adapted to high light intensities, as judged from the distinctly high values of photosynthetic capacity and saturating irradiance measured, in accordance with the high solar radiation prevailing in their sampling areas. The arctic taxon appeared more optimally suited to the low cultivation temperature, as evidenced by the relatively high values of growth rates, maximum quantum yield and photosynthetic efficiency measured. The cosmopolitan taxa, C. meneghinii and C. punctulatum var. subpunctulatum, exhibited a high maximum quantum yield and photosynthetic efficiency concomitantly during growth, which explained their ubiquitous distribution. Nevertheless, two clones belonging to C. punctulatum var. subpunctulatum, collected from polar and mountainous tropical regions, differed significantly with regard to cell volume, growth rates, surface area to volume ratio and photosynthetic parameters. The physiological differences between the Cosmarium strains were in accordance with their geographic origin; they are discussed in detail in this study. Moreover, these differences were maintained despite the long-term cultivation under identical and constant laboratory conditions.

Fragilariopsis (Bacillariophyceae) of the Northern Hemisphere – morphology, taxonomy, phylogeny and distribution, with a description of F. pacifica sp. nov.

Lundholm N. and Hasle G.R. 2010. Fragilariopsis (Bacillariophyceae) of the Northern Hemisphere – morphology, taxonomy, phylogeny and distribution, with a description of F. pacifica sp. nov. Phycologia 49: 438–460. DOI: 10.2216/09-97.1In polar areas, Fragilariopsis are among the most abundant phytoplankton organisms in plankton and ice. Four Fragilariopsis species, F. oceanica, F. reginae-jahniae, F. atlantica and F. pacifica sp. nov., recorded from and apparently restricted to the Northern Hemisphere have been explored with regard to morphology, distribution and phylogeny. Morphologically the examined species are pair-wise very similar and easily confused. Hence, the numerous records of F. oceanica from sea ice and plankton in Arctic waters most likely include F. reginae-jahniae. Fragilariopsis atlantica and the sibling species F. pacifica were found in the plankton, not in ice. All four species exhibit a pronounced valve variation related to the diminution of the apical length through vegetative reproduction (stadial variation). In F. oceanica and F. reginae-jahniae this is expressed by a variation in valve outline from being more linear to almost elliptical and in F. atlantica and F. pacifica by heteropolarity of the greater specimens. Fragilariopsis oceanica and F. reginae-jahniae differed in cell length and width, valve and girdle structures as did F. atlantica and F. pacifica. In the phylogenetic tree of Fragilariopsis, a biogeographical subdivision appeared with the Antarctic Fragilariopsis taxa forming one clade, the bipolar taxa a second clade and the Arctic taxa were found in a third clade and basal in the tree. The phylogenetic analyses support the morphological data and show F. oceanica and F. reginae-jahniae to be sister taxa. The morphologically defined F. oceanica were found to be paraphyletic, representing two cryptic species.

An isotopic investigation of mercury accumulation in terrestrial food webs adjacent to an Arctic seabird colony

At Cape Vera (Devon Island, Nunavut, Canada), a seabird colony of northern fulmars (Fulmarus glacialis) congregates and releases nutrients through the deposition of guano to the coastal terrestrial environment, thus creating nutrient-fertilized habitats important to insects, birds, and mammals. Here we determined whether mercury was similarly enriched in various terrestrial food web components in this High Arctic coastal ecosystem due to seabird inputs. Stable isotopes (δ15N, δ13C) were used to identify trophic linkages and possible routes of contaminant transfer in the food web. Values of δ15N were significantly higher in lichens and certain plants collected closer to the bird colony, demonstrating a gradient of seabird influence, and were higher at Cape Vera than our reference site at Cape Herschel, on eastern Ellesmere Island, an area relatively unaffected by seabirds. In contrast, δ13C showed little variation among terrestrial species, suggesting minimal influence by seabirds. Concentrations of total mercury (THg) in primary producers and phyto/zooplankton were not significantly correlated with distance from the seabird colony or δ15N values, and were similar to other taxa from the High Arctic. Our results provide novel data on THg in several Arctic taxa where concentrations have not been reported previously. Moreover, the analyses indicate that δ15N is significantly enriched in the adjacent environment by guano fertilization, but our study was unable to show an enrichment of THg and δ13C in the terrestrial food web near the seabird colony.

New evidence from the western Canadian Arctic Archipelago for the resubmergence of Bering Strait

Widespread molluscan samples were collected from raised marine sediments to date the last retreat of the NW Laurentide Ice Sheet from the western Canadian Arctic Archipelago. At the head of Mercy Bay, northern Banks Island, deglacial mud at the modern coast contains Hiatella arctica and Portlandia arctica bivalves, as well as Cyrtodaria kurriana, previously unreported for this area. Multiple H. arctica and C. kurriana valves from this site yield a mean age of 11.5 14C ka BP (with 740 yr marine reservoir correction). The occurrence of C. kurriana, a low Arctic taxon, raises questions concerning its origin, because evidence is currently lacking for a molluscan refugium in the Arctic Ocean during the last glacial maximum. Elsewhere, the oldest late glacial age available on C. kurriana comes from the Laptev Sea where it is < 10.3 14C ka BP and attributed to a North Atlantic source. This is 2000 cal yr younger than the Mercy Bay samples reported here, making the Laptev Sea, ~ 3000 km to the west, an unlikely source. An alternate route from the North Atlantic into the Canadian Arctic Archipelago was precluded by coalescent Laurentide, Innuitian and Greenland ice east of Banks Island until ~ 10 14C ka BP. We conclude that the presence of C. kurriana on northern Banks Island records migration from the North Pacific. This requires the resubmergence of Bering Strait by 11.5 14C ka BP, extending previous age determinations on the reconnection of the Pacific and Arctic oceans by up to 1000 yr. This renewed ingress of Pacific water likely played an important role in re-establishing Arctic Ocean surface currents, including the evacuation of thick multi-year sea ice into the North Atlantic prior to the Younger Dryas geochron.

PARALLEL EVOLUTIONARY PATTERNS IN MULTIPLE LINEAGES OF ARCTIC ARTEMISIA L. (ASTERACEAE)

Early observers of plant evolution in the Arctic have noted a floristic similarity with temperate alpine regions and a predominance of high ploidy levels. The aim of our study was to survey these and other traits in multiple closely related but independently evolved lineages of Artemisia. Our phylogenetic study was based on 133 taxa using 3'-ETS and ITS, and on data on morphology, karyology, distribution, and ecological preferences. We compared Arctic lineages with sister groups and tested whether patterns were significantly different. We found: (1) Artemisia has independently adapted to Arctic habitats 13-18 times; (2) There were no ecological preferences of putative progenitors that might determine the colonization success in the Arctic, although most sister groups were centered in steppe habitats; (3) Plant height was distinctly reduced in Arctic lineages; (4) Arctic lineages contained no more polyploids than their respective sister groups or taxa from other habitats; (5) Enlarged flower heads have evolved repeatedly, probably for better pollinator attraction. This strategy could be a substitute for polyploidy, which is typical in other Arctic taxa. Stronger pollinator attraction should result in better outcrossing and higher heterozygosity in the offspring, which is among the main effects of polyploidy.

Arctic dinoflagellate migrations mark the strongest Oligocene glaciations

Here we report on mid-Oligocene globally synchronous Arctic dinoflagellate migration events, calibrated against chron C9n. We show that sudden appearances and marked abundance increases of the Arctic taxon Svalbardella at lower and middle latitudes coincide with the Oi-2b benthic d 18 O glacial episode, dated as ca. 27.1 Ma. These unprecedented migrations are taken to indicate anomalously strong surface-water cooling during Oi-2b time, in turn associated with strong concomitant Antarctic ice-sheet growth and sea-level lowering. We estimate the duration of these unique Svalbardella migrations and the associated episode of profound cooling as ;500 k.y. Our records suggest a close link between this distinct Oligocene glaciation episode, strong sea-level fall, and the classic lower-upper Oligocene, or Rupelian-Chattian, boundary, dating this boundary as ca. 27.1 Ma.

Complex Biogeographic Patterns in Androsace (Primulaceae) and Related Genera: Evidence from Phylogenetic Analyses of Nuclear Internal Transcribed Spacer and Plastid trnL-F Sequences

We conducted phylogenetic analyses of Androsace and the closely related genera Douglasia, Pomatosace, and Vitaliana using DNA sequences of the nuclear internal transcribed spacer (ITS) and the plastid trnL-F region. Analyses using maximum parsimony and Bayesian inference yield congruent relationships among several major lineages found. These lineages largely disagree with previously recognized taxonomic groups. Most notably, (1) Androsace sect. Andraspis, comprising the short-lived taxa, is highly polyphyletic; (2) Pomatosace constitutes a separate phylogenetic lineage within Androsace; and (3) Douglasia and Vitaliana nest within Androsace sect. Aretia. Our results suggest multiple origins of the short-lived lifeform and a possible reversal from annual or biennial to perennial habit at the base of a group that now contains mostly perennial high mountain or arctic taxa. The group containing Androsace sect. Aretia, Douglasia, and Vitaliana includes predominantly high alpine and arctic taxa with an arctic-alpine distribution, but is not found in the European and northeastern American Arctic or in Central and East Asia. This group probably originated in Europe in the Pliocene, from where it reached the amphi-Beringian region in the Pleistocene or late Pliocene.

Glacial refugia, haplotype distributions, and clonal richness of the Daphnia pulex complex in arctic Canada.

As part of a large international Arctic biodiversity expedition (Tundra Northwest '99), we examined the distribution of members of the arctic Daphnia pulex complex (Cladocera, Anomopoda) from 121 tundra ponds, spread across 16 sites spanning a large portion of arctic Canada (i.e. from 62 degrees 22' N to 79 degrees 01' N; 66 degrees 45' W to 139 degrees 37' W). Using allozyme electrophoresis and mitochondrial (mt)DNA analyses, we examined the population genetic (clonal) structure of these populations. The following taxa were detected in this complex: Daphnia pulicaria, D. middendorffiana and D. tenebrosa. Clear geographical differences in mean clonal richness and diversity were observed, with most western sites exhibiting higher clonal richness and diversity, than sites in the eastern Canadian Arctic. For both the pulicaria group (i.e. D. pulicaria and D. middendorffiana) and D. tenebrosa, the highest mean regional clonal richness was detected from the southern section of Banks Island, an unglaciated site situated on the edge or directly in the eastern fringe of the Beringian glacial refuge. A significant negative correlation was found between geographical distance from the Beringian edge, and overall regional clonal richness (i.e. sites closer to the edge harboured greater clonal richness). These results clearly indicate that more recently deglaciated regions (i.e. eastern Canadian Arctic) harbour lower levels of clonal richness than western regions nearer Beringia. We discuss the role that glacial refugia have played in influencing both biotic and genetic diversity in arctic taxa.