Global warming and the Arctic: a new world beyond the reach of the Grinnellian niche?

MacDonald, Glen M.

doi:10.1242/jeb.039511

Cited by 46 publications

(29 citation statements)

References 33 publications

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“…However, the current trend toward an increasingly warmer climate in the Arctic has caused sea ice to retreat dramatically and possibly at a pace never experienced before (51). If this trend continues, it is possible that future PBs throughout most of their range may be forced to spend increasingly more time on land, perhaps even during the breeding season, and therefore come into contact with brown bears more frequently.…”

Section: Discussionmentioning

confidence: 99%

Polar and brown bear genomes reveal ancient admixture and demographic footprints of past climate change

Miller

Schuster

Welch

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

322

375

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Polar bears (PBs) are superbly adapted to the extreme Arctic environment and have become emblematic of the threat to biodiversity from global climate change. Their divergence from the lower-latitude brown bear provides a textbook example of rapid evolution of distinct phenotypes. However, limited mitochondrial and nuclear DNA evidence conflicts in the timing of PB origin as well as placement of the species within versus sister to the brown bear lineage. We gathered extensive genomic sequence data from contemporary polar, brown, and American black bear samples, in addition to a 130,000-to 110,000-y old PB, to examine this problem from a genome-wide perspective. Nuclear DNA markers reflect a species tree consistent with expectation, showing polar and brown bears to be sister species. However, for the enigmatic brown bears native to Alaska's Alexander Archipelago, we estimate that not only their mitochondrial genome, but also 5-10% of their nuclear genome, is most closely related to PBs, indicating ancient admixture between the two species. Explicit admixture analyses are consistent with ancient splits among PBs, brown bears and black bears that were later followed by occasional admixture. We also provide paleodemographic estimates that suggest bear evolution has tracked key climate events, and that PB in particular experienced a prolonged and dramatic decline in its effective population size during the last ca. 500,000 years. We demonstrate that brown bears and PBs have had sufficiently independent evolutionary histories over the last 4-5 million years to leave imprints in the PB nuclear genome that likely are associated with ecological adaptation to the Arctic environment.demographic history | hybridization | mammalian genomics | phylogenetics G enome-scale studies of speciation and admixture have become essential tools in evolutionary analyses of recently diverged lineages. For example, paradigm-shifting genomic research on archaic and anatomically modern humans has identified critical gene flow events during hominin history (1, 2). However, aside from several analyses of domesticated species and their wild relatives (e.g., ref.3), studies that use whole-genome sequencing to investigate admixture in wildlife populations are only now beginning to emerge.The bear family (Ursidae, Mammalia) represents an excellent, largely untapped model for investigating complex speciation and rapid evolution of distinct phenotypes. Although polar bears (PBs; Ursus maritimus) and brown bears (Ursus arctos) are considered separate species, analyses of fossil evidence and mitochondrial sequence data have indicated a recent divergence of PBs from within brown bears (surveyed in ref. 4). For example, phylogenetic analyses of complete mitochondrial genomes, including from a unique 130,000-to 110,000-y-old PB jawbone from Svalbard, Norway, confirmed a particularly close relationship between PB and a genetically isolated population of brown bears from the Admiralty, Baranof, and Chichagof islands in Alaska's Alexander Archipelago (hereaf...

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Section: Discussionmentioning

confidence: 99%

Polar and brown bear genomes reveal ancient admixture and demographic footprints of past climate change

Miller

Schuster

Welch

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

322

375

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“…(3) Whilst current temperatures, and those predicted to occur over the next 50-100 years are within the range that organisms have experienced in previous climate cycles, both the rate of temperature change and the predicted future levels of CO 2 are unprecedented (MacDonald, 2010).…”

Section: Global Climate Change -The Thermal Contextmentioning

confidence: 99%

Insect overwintering in a changing climate

Bale

Hayward

2010

Journal of Experimental Biology

653

542

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SummaryInsects are highly successful animals inhabiting marine, freshwater and terrestrial habitats from the equator to the poles. As a group, insects have limited ability to regulate their body temperature and have thus required a range of strategies to support life in thermally stressful environments, including behavioural avoidance through migration and seasonal changes in cold tolerance. With respect to overwintering strategies, insects have traditionally been divided into two main groups: freeze tolerant and freeze avoiding, although this simple classification is underpinned by a complex of interacting processes, i.e. synthesis of ice nucleating agents, cryoprotectants, antifreeze proteins and changes in membrane lipid composition. Also, in temperate and colder climates, the overwintering ability of many species is closely linked to the diapause state, which often increases cold tolerance ahead of temperature-induced seasonal acclimatisation. Importantly, even though most species can invoke one or both of these responses, the majority of insects die from the effects of cold rather than freezing. Most studies on the effects of a changing climate on insects have focused on processes that occur predominantly in summer (development, reproduction) and on changes in distributions rather than winter survival per se. For species that routinely experience cold stress, a general hypothesis would be that predicted temperature increases of 1°C to 5°C over the next 50-100 years would increase winter survival in some climatic zones. However, this is unlikely to be a universal effect. Negative impacts may occur if climate warming leads to a reduction or loss of winter snow cover in polar and sub-polar areas, resulting in exposure to more severe air temperatures, increasing frequency of freeze-thaw cycles and risks of ice encasement. Likewise, whilst the dominant diapause-inducing cue (photoperiod) will be unaffected by global climate change, higher temperatures may modify normal rates of development, leading to a decoupling of synchrony between diapause-sensitive life-cycle stages and critical photoperiods for diapause induction. In terms of climate warming and potential heat stress, the most recent predictions of summer temperatures in Europe of 40°C or higher in 50-75 years, are close to the current upper lethal limit of some insects. Long-term data sets on insect distributions and the timing of annual migrations provide strong evidence for 'positive' responses to higher winter temperatures over timescales of the past 20-50 years in North America, Europe and Asia.

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“…Predictions of future surface air temperature increases prognosticate that particularly winter temperatures will increase much more markedly than summer temperatures. By the end of this century, winter air temperatures in the Arctic may increase by even up to 7 °C, while summer air temperatures might only increase by 2-4 °C (IPCC 2007;MacDonald 2010). Over the period 1971-2010, the ocean absorbed 90% of the climate change induced heat of the climate system, leading to averaged ocean warming of 0.11 °C per decade of the upper 75 m (IPCC 2014).…”

Section: Introductionmentioning

confidence: 99%

Effects of prolonged darkness and temperature on the lipid metabolism in the benthic diatom Navicula perminuta from the Arctic Adventfjorden, Svalbard

et al. 2017

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which could consequently lead to a depletion of this energy reserves before the end of the polar night. On the other hand, the membrane building phospho-and glycolipids remained unchanged during the 8 weeks darkness, indicating still intact thylakoid membranes. These results explain the shorter survival times of polar diatoms with increasing water temperatures during prolonged dark periods. Abstract The Arctic represents an extreme habitat for phototrophic algae due to long periods of darkness caused by the polar night (~4 months darkness). Benthic diatoms, which dominate microphytobenthic communities in shallow water regions, can survive this dark period, but the underlying physiological and biochemical mechanisms are not well understood. One of the potential mechanisms for long-term dark survival is the utilisation of stored energy products in combination with a reduced basic metabolism. In recent years, water temperatures in the Arctic increased due to an ongoing global warming. Higher temperatures could enhance the cellular energy requirements for the maintenance metabolism during darkness and, therefore, accelerate the consumption of lipid reserves. In this study, we investigated the macromolecular ratios and the lipid content and composition of Navicula cf. perminuta Grunow, an Arctic benthic diatom isolated from the microphytobenthos of Adventfjorden (Svalbard, Norway), over a dark period of 8 weeks at two different temperatures (0 and 7 °C). The results demonstrate that N. perminuta uses the stored lipid compound triacylglycerol (TAG) during prolonged dark periods, but also the pool of free fatty acids (FFA). Under the enhanced temperature of 7 °C, the lipid resources were used significantly faster than at 0 °C, Keywords

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Global warming and the Arctic: a new world beyond the reach of the Grinnellian niche?

Cited by 46 publications

References 33 publications

Polar and brown bear genomes reveal ancient admixture and demographic footprints of past climate change

Polar and brown bear genomes reveal ancient admixture and demographic footprints of past climate change

Insect overwintering in a changing climate

Effects of prolonged darkness and temperature on the lipid metabolism in the benthic diatom Navicula perminuta from the Arctic Adventfjorden, Svalbard

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