| 1. |
- Ersmark, Erik, et al.
(författare)
-
From the Past to the Present : Wolf Phylogeography and Demographic History Based on the Mitochondrial Control Region
- 2016
-
Ingår i: Frontiers in Ecology and Evolution. - : FRONTIERS MEDIA SA. - 2296-701X. ; 4
-
Tidskriftsartikel (refereegranskat)abstract
- The global distribution of the gray wolf (Canis lupus) is a complex assembly consisting of a large number of populations and described subspecies. How these lineages are related to one another is still not fully resolved, largely due to the fact that large geographical regions remain poorly sampled both at the core and periphery of the species' range. Analyses of ancient wolves have also suffered from uneven sampling, but have shown indications of a major turnover at some point during the Pleistocene-Holocene boundary in northern North America. Here we analyze variation in the mitochondrial control region in 122 contemporary wolves from some of the less studied populations, as well as six samples from the previously unstudied Greenland subspecies (Canis I. orlon) and two Late Pleistocene samples from Siberia. Together with the publicly available control region sequences of both modern and ancient wolves, this study examines genetic diversity on a wide geographical and temporal scale that includes both Eurasia and North America. We identify 13 new haplotypes, of which the majority is found in northern and eastern Asia. The results show that the Greenland samples are all represented by one haplotype, previously identified in North American wolves, among which this population seems to trace its maternal lineage. The phylogeny and network analyses show a wide spatial distribution of several lineages, but also some clusters with more distinct geographical affiliation. In North America, we find support for an end-Pleistocene population bottleneck through coalescent simulations under an approximate Bayesian framework in contrast to previous studies that suggested an extinction-replacement event. However, we find no support for a similar bottleneck in Eurasia. Overall, this global analysis helps to clarify our understanding of the complex history for wolves in Eurasia and North America.
|
|
| 2. |
- Ersmark, Erik, 1977-
(författare)
-
Large carnivore population turnover and ecological change during the Late Quaternary
- 2016
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The cave lion (Panthera spelaea), the grey wolf (Canis lupus) and the brown bear (Ursus arctos) all shared an intercontinental distribution across the northern hemisphere during most of the Late Quaternary, and experienced repeated events of climate change. The cave lion went extinct at the end of the Pleistocene and although the wolf and the bear have survived until present day, recent human persecution has caused demographic bottlenecks and local extinctions. In this thesis, mitochondrial and nuclear DNA was analyzed from ancient and modern samples in order to study spatiotemporal changes in genetic diversity in the three species. Mitochondrial sequences analyzed from 48 radiocarbon dated cave lion remains revealed two haplogroups, of which the more genetically diverse seemingly disappeared around 41,000 years BP. Serial coalescent simulations on the data supported a population bottleneck in Beringia between roughly 47-18,000 years BP. Its long duration prevents a specific causal factor to be singled out, but the early onset and overlapping declines of other large mammals in the region suggests that major environmental changes greatly impacted the fauna of Beringia during this time. Using a similar genetic marker, a set of 126 modern wolves and two Siberian wolf remains of Late Pleistocene age were analyzed. The sequences yielded from the latter samples pertained to a basal haplogroup, which contained all Late Pleistocene wolves from previous studies. As data from both modern and ancient wolves were combined, a pattern of decreasing genetic diversity was identified around the Pleistocene-Holocene transition. This decrease was further tested by serial coalescent simulations, which supported a bottleneck in northern North America around this time. Further analyses were applied to one of the ancient wolf remains from Siberia, producing a draft genome sequence and a complete mitochondrial genome. Given the radiocarbon date of the Siberian wolf, a slower mutation rate could be inferred, which pushed back the split between the lineages leading to modern wolves and dogs to at least 27,000 years BP. The Siberian wolf was positioned close to the split but basal to these lineages. A global comparison with modern dogs indicated a closer genetic affiliation between the Siberian wolf and some arctic breeds. For the brown bear, phylogeographic changes in Europe were studied over the last 50,000 years, using radiocarbon dating and mitochondrial sequences. When concatenated and compared with published data, the mtDNA revealed a turnover event just before the LGM, while the dating confirmed a presence of brown bears at relatively high latitudes during this period. Marked shifts in population size were also inferred. Furthermore, data of stable isotope levels confirmed a dietary shift to increasing herbivory around the LGM. Finally, a recent anthropogenic bottleneck among Scandinavian brown bears was studied. While no change in genetic structure could be detected, mitochondrial and microsatellite markers showed a decline in genetic diversity, especially pronounced in the southern subpopulation. ABC simulations supported a bottleneck taking place across all of Scandinavia. Taken together, this thesis have identified and elucidated several impacts on genetic diversity in the past populations of large carnivores. The use of different genetic markers has enabled comparisons with published data, but also revealed their comparatively different benefits and limitations. Overall, the presented studies compose a synthesis of past population dynamics in large carnivores, uniquely revealed by ancient DNA.
|
|
| 3. |
- Palkopoulou, Eleftheria, et al.
(författare)
-
Synchronous genetic turnovers across Western Eurasia in Late Pleistocene collared lemmings
- 2016
-
Ingår i: Global Change Biology. - : Wiley. - 1354-1013 .- 1365-2486. ; 22:5, s. 1710-1721
-
Tidskriftsartikel (refereegranskat)abstract
- Recent palaeogenetic studies indicate a highly dynamic history in collared lemmings (Dicrostonyx spp.), with several demographical changes linked to climatic fluctuations that took place during the last glaciation. At the western range margin of D.torquatus, these changes were characterized by a series of local extinctions and recolonizations. However, it is unclear whether this pattern represents a local phenomenon, possibly driven by ecological edge effects, or a global phenomenon that took place across large geographical scales. To address this, we explored the palaeogenetic history of the collared lemming using a next-generation sequencing approach for pooled mitochondrial DNA amplicons. Sequences were obtained from over 300 fossil remains sampled across Eurasia and two sites in North America. We identified five mitochondrial lineages of D.torquatus that succeeded each other through time across Europe and western Russia, indicating a history of repeated population extinctions and recolonizations, most likely from eastern Russia, during the last 50000years. The observation of repeated extinctions across such a vast geographical range indicates large-scale changes in the steppe-tundra environment in western Eurasia during the last glaciation. AllHolocene samples, from across the species' entire range, belonged to only one of the five mitochondrial lineages. Thus, extant D.torquatus populations only harbour a small fraction of the total genetic diversity that existed across different stages of the Late Pleistocene. In North American samples, haplotypes belonging to both D.groenlandicus and D.richardsoni were recovered from a Late Pleistocene site in south-western Canada. This suggests that D.groenlandicus had a more southern and D.richardsoni a more northern glacial distribution than previously thought. This study provides significant insights into the population dynamics of a small mammal at a large geographical scale and reveals a rather complex demographical history, which could have had bottom-up effects in the Late Pleistocene steppe-tundra ecosystem.
|
|
| 4. |
|
|
