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704 results for “Holarctic”
Environmental drivers of Sphagnum growth in peatlands across the Holarctic region
<p>The relative importance of global versus local environmental factors for growth and thus carbon uptake of the bryophyte genus <i>Sphagnum </i>– the main peat-former and ecosystem engineer in northern peatlands – remains unclear. 2) We measured length growth and net primary production (NPP) of two abundant <i>Sphagnum</i> species across 99 Holarctic peatlands. We tested the importance of previously proposed abiotic and biotic drivers for peatland carbon uptake (climate, N deposition, water table depth, and vascular plant cover) on these two responses. Employing structural equation models, we explored both indirect and direct effects of drivers on <i>Sphagnum</i> growth. 3) Variation in growth was large, but similar within and between peatlands. Length growth showed a stronger response to predictors than NPP. Moreover, the smaller and denser <i>Sphagnum fuscum</i> growing on hummocks had weaker responses to climatic variation than the larger and looser<i> S. magellanicum</i> growing in the wetter conditions. Growth decreased with increasing vascular plant cover within a site. Between sites, precipitation and temperature increased growth for <i>S. magellanicum</i>. The structural equation models indicated that indirect effects are important. For example, vascular plant cover increased with a deeper water table, increased nitrogen deposition, precipitation and temperature. These factors also influenced <i>Sphagnum</i> growth indirectly by affecting moss shoot density. 4) Synthesis Our results imply that in a warmer climate, <i>S. magellanicum</i> will increase length growth as long as precipitation is not reduced, while<i> S. fuscum</i> is more resistant to decreased precipitation, but also less able to take advantage of increased precipitation and temperature. Such species-specific sensitivity to climate may affect competitive outcomes in a changing environment, and potentially the future carbon sink function of peatlands.</p>
FIGURE 39 in Revisionary notes on Chonocephalus Wandolleck (Diptera: Phoridae) with keys to species of the Holarctic Region
FIGURE 39. Chonocephalus heymonsi females, vestiture of abdominal tergites.
FIGURE 25 in Revisionary notes on Chonocephalus Wandolleck (Diptera: Phoridae) with keys to species of the Holarctic Region
FIGURE 25. Chonocephalus heymonsi male, hypopygium from two different angles.
FIGURE 38 in Revisionary notes on Chonocephalus Wandolleck (Diptera: Phoridae) with keys to species of the Holarctic Region
FIGURE 38. Chonocephalus depressus. females, vestiture of abdominal tergites.
Fig. 26 in Contribution To The Taxonomy And Phylogeny Of The Genus Polia Ochsenheimer, 1816 (Noctuidae, Noctuinae, Hadenini): Species Groups And Pairs In The Holarctic Subgenus Polia S. Str.
Fig. 26. Consensus tree based on discrete character data of male genitalia
Map 2 in A revision of Amarochara THOMSON of the Holarctic region V. A new species from China, a new combination, the male of A. caeca ASSING, and additional records (Coleoptera: Staphylinidae: Aleocharinae: Aleocharini)
Map 2: Distribution of Amarochara megalops in the East Palaearctic region.
Fig. 12 in A revision of Amarochara THOMSON of the Holarctic region V. A new species from China, a new combination, the male of A. caeca ASSING, and additional records (Coleoptera: Staphylinidae: Aleocharinae: Aleocharini)
Fig. 12: Type locality of Amarochara daweiana nov.sp.
Environmental drivers of Sphagnum growth in peatlands across the Holarctic region
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Systematics and biogeography of the Holarctic dragonfly genus Somatochlora (Anisoptera: Corduliidae)
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Taxon pulse dynamics, episodic dispersal, and host colonization across Beringia drive diversification of a holarctic tapeworm assemblage
Aim: We test the predictions of the Stockholm Paradigm, a synthesis of eco-evolutionary theory explaining the nature of faunal assembly, host range and parasite diversification. Faunal diversification and assembly, manifested in patterns of host colonization, co-adaptation and parasite speciation, is predicted to emerge as a consequence of alternating episodes of ecological disruption and stability. Specifically, for a diverse cestode genus (Arostrilepis), we evaluate the number and direction of Pleistocene dispersal events across Beringia, the number and relative timing of host colonization events, and the relationship between host and parasite biogeographic histories and associations through time. Location: Beringia and adjacent temperate to arctic biomes in North America and Eurasia. Taxon: Arostrilepis (Cyclophyllidea: Hymenolepididae) and its rodent hosts. Methods: Multi-locus phylogenetic reconstruction and biogeographic ancestral range estimation. Results: Arostrilepis lineages crossed Beringia eastward into North America a minimum of four times and westward into Asia twice in association with temporally disjunct geographic expansions of three major tribes of cricetid rodents (Arvicolini, Myodini, Lemmini). Inferences of ancestral host associations support at least nine instances of host-colonization involving shifts from one rodent tribe or family to another. Several previously unrecognized lineages of Arostrilepis are revealed. Main conclusions: Consistent with expectations of the Stockholm Paradigm, episodes of intercontinental dispersal were both frequent in the history of Arostrilepis and preceded a majority of inferred host-colonization events. Events of historical geographic expansion created numerous opportunities for development of novel host-parasite associations through ecological fitting, as parasites tracked historically conserved resources available across diverse host taxa. Beringia played a major role in shaping rodent/parasite assemblages by mediating dispersal between the northern continents during glacial episodes of the Pleistocene, rather than by serving as a zone of refugial isolation.
- Gonostylus apically rounded; superior volsella with 2 subapical and 2 apical setae.............................................................................................. C. pseudotener (Goetghebuer, 1922) (Holarctic) in A new species of the genus Cryptotendipes Beck et Beck, 1969 (Diptera Chironomidae) from India, with a world key to the males and tentative phylogenetic relationship
- Gonostylus apically rounded; superior volsella with 2 subapical and 2 apical setae.............................................................................................. C. pseudotener (Goetghebuer, 1922) (Holarctic)
Data from: Genetic structure, admixture, and invasion success in a Holarctic defoliator, the gypsy moth (Lymantria dispar, Lepidoptera: Erebidae)
Characterizing the current population structure of potentially invasive species provides a critical context for identifying source populations and for understanding why invasions are successful. Non-native populations inevitably lose genetic diversity during initial colonization events, but subsequent admixture among independently introduced lineages may increase both genetic variation and adaptive potential. Here we characterize the population structure of the gypsy moth (Lymantria dispar Linnaeus), one of the world's most destructive forest pests. Native to Eurasia and recently introduced to North America, the current distribution of gypsy moth includes forests throughout the temperate region of the northern hemisphere. Analyses of microsatellite loci and mitochondrial DNA sequences for 1738 individuals identified four genetic clusters within L. dispar. Three of these clusters correspond to the three named subspecies; North American populations represent a distinct fourth cluster, presumably a consequence of the population bottleneck and allele frequency change that accompanied introduction. We find no evidence that admixture has been an important catalyst of the successful invasion and range expansion in North America. However, we do find evidence of ongoing hybridization between subspecies and increased genetic variation in gypsy moth populations from Eastern Asia, populations that now pose a threat of further human-mediated introductions. Finally, we show that current patterns of variation can be explained in terms of climate and habitat changes during the Pleistocene, a time when temperate forests expanded and contracted. Deeply diverged matrilines in Europe imply that gypsy moths have been there for a long time and are not recent arrivals from Asia.
Data from: Mito-nuclear discord in six congeneric lineages of Holarctic ducks (genus Anas)
Many species have Holarctic distributions that extend across Europe, Asia, and North America. Most genetics research on these species has examined only mitochondrial (mt) DNA, which has revealed wide variance in divergence between Old World (OW) and New World (NW) populations, ranging from shallow, unstructured genealogies to deeply divergent lineages. In this study, we sequenced 20 nuclear introns to test for concordant patterns of OW-NW differentiation between mtDNA and nuclear (nu) DNA for six lineages of Holarctic ducks (genus Anas). Genetic differentiation for both marker types varied widely among these lineages (idiosyncratic population histories), but mtDNA and nuDNA divergence within lineages was not significantly correlated. Moreover, compared to the association between mtDNA and nuDNA divergence observed among different species, OW-NW nuDNA differentiation was generally lower than mtDNA divergence, at least for lineages with deeply divergent mtDNA. Furthermore, coalescent estimates indicated significantly higher rates of gene flow for nuDNA than mtDNA for four of the six lineages. Thus, Holarctic ducks show prominent mito-nuclear discord between OW and NW populations, and we reject differences in sorting rates as the sole cause of the within-species discord. Male-mediated intercontinental gene flow is likely a leading contributor to this discord, although selection could also cause elevated mtDNA divergence relative to weak nuDNA differentiation. The population genetics of these ducks contribute to growing evidence that mtDNA can be an unreliable indicator of stage of speciation, and that more holistic approaches are needed for species delimitation.
Data from: Behavioral vs. molecular sources of conflict between nuclear and mitochondrial DNA: the role of male-biased dispersal in a Holarctic sea duck
Genetic studies of waterfowl (Anatidae) have observed the full spectrum of mitochondrial (mt) DNA population divergence, from panmixia to deep, reciprocally monophyletic lineages. Yet these studies generally found weak or no nuclear (nu) DNA structure which was often attributed to sex-biased gene flow (i.e., male dispersal and female philopatry), a common behavior within this family. An alternative explanation for this "conflict" is that the smaller effective population size and faster sorting rate of mtDNA relative to nuDNA leads to different signals of population structure. To test these alternatives, we simulated expected nuDNA differentiation based on mtDNA patterns of effective population sizes, gene flow, and divergence times in a Holarctic pair of waterfowl subspecies, the goosander (Mergus merganser merganser) and common merganser (M. m. americanus). We compared simulated results to empirical data from 12 nuDNA introns sampled from the species' global range. Between Europe and North America, nuDNA ФST was 3.4-fold lower than mtDNA ФST, a result consistent with differences in sorting rates. However, despite geographically structured and monophyletic mtDNA lineages within continents, nuDNA ФST values were generally < 0 and significantly lower than predicted. This between- and within-continent contrast held when comparing mtDNA and nuDNA among published studies of ducks. Thus, male-mediated gene flow is a better explanation than slower sorting rates for limited nuDNA differentiation within continents, which is also supported by non-molecular data. This study illustrates the value of quantitatively testing discrepancies between mtDNA and nuDNA to reject the null hypothesis that conflict simply reflects different sorting rates.
FIGURES 2224 in Revisionary notes on Chonocephalus Wandolleck (Diptera: Phoridae) with keys to species of the Holarctic Region
FIGURES 2224. Chonocephalus heymonsi male, (22) hypopygium from below; (23) hypopygium, left face. Scale bar = 0.1 mm.
FIGURE 43. Chonocephalus aduncus female, tergite 8 in Revisionary notes on Chonocephalus Wandolleck (Diptera: Phoridae) with keys to species of the Holarctic Region
FIGURE 43. Chonocephalus aduncus female, tergite 8 (to left) and sternite 8, furca and spermatheca. Scale bar = 0.1 mm.
FIGURES 1316 in Revisionary notes on Chonocephalus Wandolleck (Diptera: Phoridae) with keys to species of the Holarctic Region
FIGURES 1316. Chonocephalus collini male, details of hypopygium from below: (13) left side of epandrium and surstylus; (14) right gonopod; (15) right gonopod and hypandrial process; (16) left gonopod and hypandrial process. Scale bar = 0.1 mm.
FIGURES 2630 in Revisionary notes on Chonocephalus Wandolleck (Diptera: Phoridae) with keys to species of the Holarctic Region
FIGURES 2630. Chonocephalus marginatus male, hypopygium from below: (26) left anterior process of epandrium; (27) right anterior process of epandrium; (28) left gonopod and hypandrial lobe; (29) right gonopod; (30) right gonopod from another angle. Scale bars = 0.1 mm.
FIGURE 1 in Revisionary notes on Chonocephalus Wandolleck (Diptera: Phoridae) with keys to species of the Holarctic Region
FIGURE 1. Chonocephalus male hypopygium, diagrammatic ventral view of a generalised species. A = anal tube (with median hypoproct and paired cerci); E = epandrium; H = hypandrium; X = penis complex (simplified). a, p = anterior and posterior processes (probably = subepandrial sclerites) of epandrium; l = lobe(s) of hypandrium; g = gonopod; b = bridge (probably = sternite 10); c = left surstylus clasper; s = spine (modified bristle) of epandrium.
FIGURE 37. Chonocephalus fletcheri female, tergite 8 in Revisionary notes on Chonocephalus Wandolleck (Diptera: Phoridae) with keys to species of the Holarctic Region
FIGURE 37. Chonocephalus fletcheri female, tergite 8 (to left) and sternite 8, furca and spermatheca. Scale bar = 0.1 mm.
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