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PreprintHome site advantage in two long-lived arctic plant species : results from two 30-year reciprocal transplant studies( 2012-03-30) Bennington, Cynthia C. ; Fetcher, Ned ; Vavrek, Milan C. ; Shaver, Gaius R. ; Cummings, Kelli J. ; McGraw, James B.Reciprocal transplant experiments designed to quantify genetic and environmental effects on phenotype are powerful tools for the study of local adaptation. For long-lived species, especially those in habitats with short growing seasons, however, the cumulative effects of many years in novel environments may be required for fitness differences and phenotypic changes to accrue. We returned to two separate reciprocal transplant experiments thirty years after their initial establishment in interior Alaska to ask whether patterns of differentiation observed in the years immediately following transplant have persisted. We also asked whether earlier hypotheses about the role of plasticity in buffering against the effects of selection on foreign genotypes were supported. We censused survival and flowering in three transplant gardens created along a snowbank gradient for a dwarf shrub (Dryas octopetala) and six gardens created along a latitudinal gradient for a tussock-forming sedge (Eriophorum vaginatum). For both species, we used an analysis of variance to detect fitness advantages for plants transplanted back into their home site relative to those transplanted into foreign sites. For D. octopetala, the original patterns of local adaptation observed in the decade following transplant appeared even stronger after three decades, with the complete elimination of foreign ecotypes in both fellfield and snowbed environments. For E. vaginatum, differential survival of populations was not evident 13 years after transplant, but was clearly evident 17 years later. There was no evidence that plasticity was associated with increased survival of foreign populations in novel sites for either D. octopetala or E. vaginatum. Synthesis. We conclude that local adaptation can be strong, but nevertheless remain undetected or underestimated in short-term experiments. Such genetically-based population differences limit the ability of plant populations to respond to a changing climate.
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ArticleLandscape genomics provides evidence of ecotypic adaptation and a barrier to gene flow at treeline for the arctic foundation species Eriophorum vaginatum0(Frontiers Media, 2022-03-24) Stunz, Elizabeth ; Fetcher, Ned ; Lavretsky, Philip ; Mohl, Jonathon E. ; Tang, Jianwu ; Moody, Michael L.Global climate change has resulted in geographic range shifts of flora and fauna at a global scale. Extreme environments, like the Arctic, are seeing some of the most pronounced changes. This region covers 14% of the Earth’s land area, and while many arctic species are widespread, understanding ecotypic variation at the genomic level will be important for elucidating how range shifts will affect ecological processes. Tussock cottongrass (Eriophorum vaginatum L.) is a foundation species of the moist acidic tundra, whose potential decline due to competition from shrubs may affect ecosystem stability in the Arctic. We used double-digest Restriction Site-Associated DNA sequencing to identify genomic variation in 273 individuals of E. vaginatum from 17 sites along a latitudinal gradient in north central Alaska. These sites have been part of 30 + years of ecological research and are inclusive of a region that was part of the Beringian refugium. The data analyses included genomic population structure, demographic models, and genotype by environment association. Genome-wide SNP investigation revealed environmentally associated variation and population structure across the sampled range of E. vaginatum, including a genetic break between populations north and south of treeline. This structure is likely the result of subrefugial isolation, contemporary isolation by resistance, and adaptation. Forty-five candidate loci were identified with genotype-environment association (GEA) analyses, with most identified genes related to abiotic stress. Our results support a hypothesis of limited gene flow based on spatial and environmental factors for E. vaginatum, which in combination with life history traits could limit range expansion of southern ecotypes northward as the tundra warms. This has implications for lower competitive attributes of northern plants of this foundation species likely resulting in changes in ecosystem productivity.
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ArticleEffect of growth temperature on photosynthetic capacity and respiration in three ecotypes of Eriophorum vaginatum(John Wiley & Sons, 2018-03-06) Schedlbauer, Jessica L. ; Fetcher, Ned ; Hood, Katherine ; Moody, Michael L. ; Tang, JianwuEcotypic differentiation in the tussock‐forming sedge Eriophorum vaginatum has led to the development of populations that are locally adapted to climate in Alaska's moist tussock tundra. As a foundation species, E. vaginatum plays a central role in providing topographic and microclimatic variation essential to these ecosystems, but a changing climate could diminish the importance of this species. As Arctic temperatures have increased, there is evidence of adaptational lag in E. vaginatum, as locally adapted ecotypes now exhibit reduced population growth rates. Whether there is a physiological underpinning to adaptational lag is unknown. Accordingly, this possibility was investigated in reciprocal transplant gardens. Tussocks of E. vaginatum from sites separated by ~1° latitude (Coldfoot: 67°15′N, Toolik Lake: 68°37′, Sagwon: 69°25′) were transplanted into the Toolik Lake and Sagwon sites and exposed to either an ambient or an experimental warming treatment. Five tussocks pertreatment combination were measured at each garden to determine photosynthetic capacity (i.e., Vcmax and Jmax) and dark respiration rate (Rd) at measurement temperatures of 15, 20, and 25°C. Photosynthetic enhancements or homeostasis were observed for all ecotypes at both gardens under increased growth temperature, indicating no negative effect of elevated temperature on photosynthetic capacity. Further, no evidence of thermal acclimation in Rd was observed for any ecotype, and there was little evidence of ecotypic variation in Rd. As such, no physiological contribution to adaptational lag was observed given the increase in growth temperature (up to ~2°C) provided by this study. Despite neutral to positive effects of increased growth temperature on photosynthesis in E. vaginatum, it appears to confer no lasting advantage to the species.
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ArticleComparative transcriptomics of an arctic foundation species, tussock cottongrass (Eriophorum vaginatum), during an extreme heat event(Nature Research, 2020-06-02) Mohl, Jonathon E. ; Fetcher, Ned ; Stunz, Elizabeth ; Tang, Jianwu ; Moody, Michael L.Tussock cottongrass (Eriophorum vaginatum) is a foundation species for much of the arctic moist acidic tundra, which is currently experiencing extreme effects of climate change. The Arctic is facing higher summer temperatures and extreme weather events are becoming more common. We used Illumina RNA-Seq to analyse cDNA libraries for differential expression of genes from leaves of ecologically well-characterized ecotypes of tussock cottongrass found along a latitudinal gradient in the Alaskan Arctic and transplanted into a common garden. Plant sampling was performed on a typical summer day and during an extreme heat event. We obtained a de novo assembly that contained 423,353 unigenes. There were 363 unigenes up-regulated and 1,117 down-regulated among all ecotypes examined during the extreme heat event. Of these, 26 HSP unigenes had >log2-fold up-regulation. Several TFs associated with heat stress in previous studies were identified that had >log2-fold up- or down-regulation during the extreme heat event (e.g., DREB, NAC). There was consistent variation in DEGs among ecotypes, but not specifically related to whether plants originated from taiga or tundra ecosystems. As the climate changes it is essential to determine ecotypic diversity at the genomic level, especially for widespread species that impact ecosystem function.
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ArticleBiomass offsets little or none of permafrost carbon release from soils, streams, and wildfire : an expert assessment(IOPScience, 2016-03-07) Abbott, Benjamin W. ; Jones, Jeremy B. ; Schuur, Edward A. G. ; Chapin, F. Stuart ; Bowden, William B. ; Bret-Harte, M. Syndonia ; Epstein, Howard E. ; Flannigan, Michael ; Harms, Tamara K. ; Hollingsworth, Teresa N. ; Mack, Michelle C. ; McGuire, A. David ; Natali, Susan M. ; Rocha, Adrian V. ; Tank, Suzanne E. ; Turetsky, Merritt R. ; Vonk, Jorien E. ; Wickland, Kimberly ; Aiken, George R. ; Alexander, Heather D. ; Amon, Rainer M. W. ; Benscoter, Brian ; Bergeron, Yves ; Bishop, Kevin ; Blarquez, Olivier ; Bond-Lamberty, Benjamin ; Breen, Amy L. ; Buffam, Ishi ; Cai, Yihua ; Carcaillet, Christopher ; Carey, Sean K. ; Chen, Jing M. ; Chen, Han Y. H. ; Christensen, Torben R. ; Cooper, Lee W. ; Cornelissen, Johannes H. C. ; de Groot, William J. ; DeLuca, Thomas Henry ; Dorrepaal, Ellen ; Fetcher, Ned ; Finlay, Jacques C. ; Forbes, Bruce C. ; French, Nancy H. F. ; Gauthier, Sylvie ; Girardin, Martin ; Goetz, Scott J. ; Goldammer, Johann G. ; Gough, Laura ; Grogan, Paul ; Guo, Laodong ; Higuera, Philip E. ; Hinzman, Larry ; Hu, Feng Sheng ; Hugelius, Gustaf ; JAFAROV, ELCHIN ; Jandt, Randi ; Johnstone, Jill F. ; Karlsson, Jan ; Kasischke, Eric S. ; Kattner, Gerhard ; Kelly, Ryan ; Keuper, Frida ; Kling, George W. ; Kortelainen, Pirkko ; Kouki, Jari ; Kuhry, Peter ; Laudon, Hjalmar ; Laurion, Isabelle ; Macdonald, Robie W. ; Mann, Paul J. ; Martikainen, Pertti ; McClelland, James W. ; Molau, Ulf ; Oberbauer, Steven F. ; Olefeldt, David ; Paré, David ; Parisien, Marc-André ; Payette, Serge ; Peng, Changhui ; Pokrovsky, Oleg ; Rastetter, Edward B. ; Raymond, Peter A. ; Raynolds, Martha K. ; Rein, Guillermo ; Reynolds, James F. ; Robards, Martin ; Rogers, Brendan ; Schädel, Christina ; Schaefer, Kevin ; Schmidt, Inger K. ; Shvidenko, Anatoly ; Sky, Jasper ; Spencer, Robert G. M. ; Starr, Gregory ; Striegl, Robert ; Teisserenc, Roman ; Tranvik, Lars J. ; Virtanen, Tarmo ; Welker, Jeffrey M. ; Zimov, Sergey A.As the permafrost region warms, its large organic carbon pool will be increasingly vulnerable to decomposition, combustion, and hydrologic export. Models predict that some portion of this release will be offset by increased production of Arctic and boreal biomass; however, the lack of robust estimates of net carbon balance increases the risk of further overshooting international emissions targets. Precise empirical or model-based assessments of the critical factors driving carbon balance are unlikely in the near future, so to address this gap, we present estimates from 98 permafrost-region experts of the response of biomass, wildfire, and hydrologic carbon flux to climate change. Results suggest that contrary to model projections, total permafrost-region biomass could decrease due to water stress and disturbance, factors that are not adequately incorporated in current models. Assessments indicate that end-of-the-century organic carbon release from Arctic rivers and collapsing coastlines could increase by 75% while carbon loss via burning could increase four-fold. Experts identified water balance, shifts in vegetation community, and permafrost degradation as the key sources of uncertainty in predicting future system response. In combination with previous findings, results suggest the permafrost region will become a carbon source to the atmosphere by 2100 regardless of warming scenario but that 65%–85% of permafrost carbon release can still be avoided if human emissions are actively reduced.
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PreprintResponse of dark respiration to temperature in Eriophorum vaginatum from a 30-year-old transplant experiment in Alaska( 2012-09) van de Weg, Martine J. ; Fetcher, Ned ; Shaver, Gaius R.Background: In the Arctic region, temperature increases are expected to be greater under anticipated climate change than the global average. Understanding how dark respiration (Rd) of common Arctic plant species acclimates to changes in the environment is therefore important for predicting changes to the Arctic carbon balance. Aims: The aim of this study is to investigate the influence of genotype and growing environment on Rd, the temperature response (Q10) of Rd, and foliar N (Nleaf) of the Arctic sedge Eriophorum vaginatum. Methods: We measured Rd, and determined its Q10 and Nleaf of E. vaginatum populations that were reciprocally transplanted 30 years previously along a latitudinal transect of 370 km in northern Alaska. Results: Rd and Q10 did not differ among populations (ecotypes) of E. vaginatum, but the local environment had a significant effect on both variables. Rd as well as Nleaf was higher in northern, colder sites, while Q10 was lower there. Conclusions: Rd in the different populations of E. vaginatum is a very plastic trait and controlled by growing environment, as is Nleaf. The lower Q10 values in the northern sites were most likely a consequence of substrate inhibition of Rd at higher temperatures.
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ArticleEcotypic differences in the phenology of the tundra species Eriophorum vaginatum reflect sites of origin(John Wiley & Sons, 2017-10-19) Parker, Thomas C. ; Tang, Jianwu ; Clark, Mahalia B. ; Moody, Michael L. ; Fetcher, NedEriophorum vaginatum is a tussock-forming sedge that contributes significantly to the structure and primary productivity of moist acidic tussock tundra. Locally adapted populations (ecotypes) have been identified across the geographical distribution of E. vaginatum; however, little is known about how their growth and phenology differ over the course of a growing season. The growing season is short in the Arctic and therefore exerts a strong selection pressure on tundra species. This raises the hypothesis that the phenology of arctic species may be poorly adapted if the timing and length of the growing season change. Mature E. vaginatum tussocks from across a latitudinal gradient (65–70°N) were transplanted into a common garden at a central location (Toolik Lake, 68°38′N, 149°36′W) where half were warmed using open-top chambers. Over two growing seasons (2015 and 2016), leaf length was measured weekly to track growth rates, timing of senescence, and biomass accumulation. Growth rates were similar across ecotypes and between years and were not affected by warming. However, southern populations accumulated significantly more biomass, largely because they started to senesce later. In 2016, peak biomass and senescence of most populations occurred later than in 2015, probably induced by colder weather at the beginning of the growing season in 2016, which caused a delayed start to growth. The finish was delayed as well. Differences in phenology between populations were largely retained between years, suggesting that the amount of time that these ecotypes grow has been selected by the length of the growing seasons at their respective home sites. As potential growing seasons lengthen, E. vaginatum may be unable to respond appropriately as a result of genetic control and may have reduced fitness in the rapidly warming Arctic tundra.
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ArticleIntraspecific variation in phenology offers resilience to climate change for Eriophorum vaginatum(Canadian Science Publishing, 2021-05-19) Parker, Thomas C. ; Unger, Steven L. ; Moody, Michael L. ; Tang, Jianwu ; Fetcher, NedThe phenology of Arctic plants is an important determinant of the pattern of carbon uptake and may be highly sensitive to continued rapid climate change. Eriophorum vaginatum L. (Cyperaceae) has a disproportionate influence over ecosystem processes in moist acidic tundra, but it is unclear whether its growth and phenology will remain competitive in the future. We investigated whether northern tundra ecotypes of E. vaginatum could extend their growing season in response to direct warming and transplanting into southern ecosystems. At the same time, we examined whether southern ecotypes could adjust their growth patterns in order to thrive further north, should they disperse quickly enough. Detailed phenology measurements across three reciprocal transplant gardens over a 2-year period showed that some northern ecotypes were capable of growing for longer when conditions were favourable, but their biomass and growing season length was still shorter than those of the southern ecotype. Southern ecotypes retained large leaf length when transplanted north and mirrored the growing season length better than the others, mainly owing to immediate green-up after snowmelt. All ecotypes retained the same senescence timing, regardless of environment, indicating a strong genetic control. Eriophorum vaginatum may remain competitive in a warming world if southern ecotypes can migrate north.