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Origin of freshwater fauna in Iceland: Cryptic glacial refugia or postglacial founder events?

Goal: The biogeography of Iceland is controversial. Some authors believe that all Icelandic life originated after postglacial dispersal events (tabula rasa hypothesis), but others assume that some organisms survived the last glaciation in ice-free refugia. To extend existing knowledge of the freshwater biogeography of Iceland, we are applying a variety of available methods, including an approximate Bayesian computation, to certain invertebrate taxa as model systems.

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Ivan N. Bolotov
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Origins of the fauna in Iceland is controversial, although the majority of modern research supports the postglacial colonization of this island by terrestrial invertebrates rather than their long-term survival in glacial refugia. In this study, we use three bumblebee species as a model to test the hypothesis regarding possible cryptic refugia in Iceland and to evaluate a putative origin of recently introduced taxa. Bombus jonellus is thought to be a possible native Icelandic lineage, whereas B. lucorum and B. hortorum were evidently introduced in the second half of the 20 th century. These phylogeographic analyses reveal that the Icelandic Bombus jonellus shares two COI lineages, one of which also occurs in populations on the British Isles and in mainland Europe, but a second lineage (BJ-02) has not been recorded anywhere. These results indicate that this species may have colonized Iceland two times and that the lineage BJ-02 may reflect a more ancient Late Pleistocene or Early Holocene founder event (e.g., from the British Isles). The Icelandic populations of both Bombus lucorum and B. hortorum share the COI lineages that were recorded as widespread throughout Eurasia, from the European countries across Russia to China and Japan. The findings presented here highlight that the bumblebee fauna of Iceland comprises mainly widespread ubiquitous lineages that arrived via natural or human-mediated dispersal events from the British Isles or the mainland.
Andri Stefansson
added 2 research items
The interaction of magnesium with bicarbonate and carbonate ions in aqueous solutions was studied using infrared spectroscopy and quantum chemical calculations. Using the infrared vibrational bands for and at 1200-1450 cm⁻¹ (δC-OH, vS and v3) together with their molar absorptivity (ε), the concentrations of the and ions and the corresponding Mg ion pairs have been determined. In the absence of Mg²⁺, measured spectra were accurately reproduced assuming that only and were present in solution. Upon addition of Mg²⁺ at fixed pH, infrared spectra were observed to shift indicating presence of the and ion pairs. From measurements, the second ionization constant of carbonic acid and the and ion pair formation constants have been obtained, these being logK2 = -10.34±0.04, = 1.12±0.11 and = 2.98±0.06, respectively. To support our experimental infrared measurements and to gain further insight into the molecular nature of the ion pair formation, density functional theory (DFT) calculations with VPT2 anharmonic correction were conducted. The most stable geometries predicted for the and ion pairs were a bi-dentate [MgHCO3]⁺(H2O)n and a mono-dentate [MgHCO3]⁺(OH)(H2O)n complexes, respectively. The predicted frequencies for , and were found to shift towards those experimentally measured with an increasing H2O solvation number where possible band shifts were predicted for relative to , this being dependent on the exact structure and hydration of the bulk ion pair. Experimentally, the ion pair formations were found to have insignificant effects on the δC-OH, vS and v3 vibrational frequencies. The speciation of dissolved inorganic carbon may be significantly influenced by ion pair formation, particularly in alkaline solutions where they may be the predominant species.
The Holuhraun eruption in 2014–2015 was the largest in Iceland for more than 200 years. It resulted in emissions of large quantities of volcanic gases into the atmosphere (11 megaton (Mt) SO2, 0.1 Mt HCl, and 0.05 Mt HF). During the eruption the volcanic gases had major effects on F, SO4 and to a lesser extent Cl concentrations in precipitaxtion throughout Iceland, effects not observed in recent decades. The concentrations of F, Cl, and SO4 (n = 705) reached values of 444 µm 12,270 µm, and 17,324 µm during the eruption and were on average ~20 times higher for F and SO4 and much lower for Cl compared to preeruption times. The concentrations of major cations (Si, Na, K, Ca, Mg, Al, and Fe) (n = 151) in the precipitation were taken as having originated from seawater spray and dissolution of rock dust and aerosol. Based on the mixing model developed here, it is demonstrated that the source of the enrichment of F and SO4 was indeed the volcanic gas emissions with >60–100 mol % of SO4 and F in the precipitation originated from volcanic gas, whereas the Cl originated mostly from seawater spray, making the volcanic gas input of Cl relatively less important than for F and SO4. The results showed that large volcanic eruptions can have major effects on atmospheric chemistry and impact the composition of precipitation.
Maxim Vinarski
added a research item
The biogeography of Iceland is controversial. Some authors believe that all Icelandic life originated after postglacial dispersal events (tabula rasa hypothesis), but others assume that some organisms survived the last glaciation in ice-free refugia. To extend existing knowledge of the freshwater biogeography of Iceland, we used a snail species, Radix balthica, as a model system. Based on a sample of 1,070 sequences of the cytochrome c oxidase subunit I gene from Iceland and from islands of the British Isles and continental Europe, a distinct Icelandic lineage was discovered. To explain the origin of the Icelandic lineage, two alternative scenarios were proposed: (i) postglacial colonization followed by rapid divergence under an elevated mutation rate and (ii) ancient preglacial colonization with survival during multiple glacial events in geothermal refugia and slow divergence under a ‘standard’ mutation rate. The results of neutrality tests and mismatch analyses and the star-like shape of the network indicated a recent population expansion of this species in Iceland. The modeling results within an approximate Bayesian computation framework supported the tabula rasa scenario. Based on our findings, a Holocene origin for the Icelandic lineage of R. balthica was suggested, which evolved under a mean rate of 7.95 × 10−7 substitutions/site/year.
Ivan N. Bolotov
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Bolotov, I.N., Aksenova, O.V., Bespalaya, Y.V. et al. Origin of a divergent mtDNA lineage of a freshwater snail species, Radix balthica, in Iceland: cryptic glacial refugia or a postglacial founder event? Hydrobiologia (2016). doi:10.1007/s10750-016-2946-9
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Ivan N. Bolotov
added an update
Based on a sample of 1,070 sequences of the cytochrome c oxidase subunit I (COI) gene of Radix balthica from Iceland and from islands of the British Isles and continental Europe, a distinct Icelandic lineage was discovered. To explain the origin of the Icelandic lineage, two alternative scenarios were proposed: (i) postglacial colonization followed by rapid divergence under an elevated mutation rate and (ii) ancient pre-glacial colonization with survival during multiple glacial events in geothermal refugia and slow divergence under a ‘standard’ mutation rate. The results of neutrality tests and mismatch analyses and the star-like shape of the network indicated a recent population expansion of this species in Iceland. The modeling results within an approximate Bayesian computation framework supported the tabula rasa scenario. Based on our findings, a Holocene origin for the Icelandic lineage of Radix balthica was suggested, which evolved under a mean rate of 7.95E-7 substitutions/site/year.
Keywords: Island Biogeography; Elevated Mutation Rate; Postglacial Environment; Mitochondrial DNA; Lymnaeidae; North Atlantic Islands; Approximate Bayesian Computation
Reference
Bolotov, I.N., Aksenova, O.V., Bespalaya, Y.V., Gofarov, M.Y., Kondakov, A.V., Paltser, I.S., Stefansson, A., Travina, O.V., Vinarski, M.V. (2016) Origin of a divergent mtDNA lineage of a freshwater snail species, Radix balthica, in Iceland: Cryptic glacial refugia or a postglacial founder event? Hydrobiologia, doi: 10.1007/s10750-016-2946-9 [the early online release of the article will be published in mid-August 2016]
 
Ivan N. Bolotov
added a project goal
The biogeography of Iceland is controversial. Some authors believe that all Icelandic life originated after postglacial dispersal events (tabula rasa hypothesis), but others assume that some organisms survived the last glaciation in ice-free refugia. To extend existing knowledge of the freshwater biogeography of Iceland, we are applying a variety of available methods, including an approximate Bayesian computation, to certain invertebrate taxa as model systems.