scholarly journals Genomic evidence of globally widespread admixture from polar bears into brown bears during the last ice age

2017 ◽  
Author(s):  
James A. Cahill ◽  
Peter D. Heintzman ◽  
Kelley Harris ◽  
Matthew Teasdale ◽  
Joshua Kapp ◽  
...  
Keyword(s):  
Climate Change ◽  
Polar Bear ◽  
Ursus Arctos ◽  
Brown Bear ◽  
Ice Age ◽  
Evolutionary Significance ◽  
Polar Bears ◽  
Brown Bears ◽  
Last Ice Age ◽  
Genomic Introgression

AbstractRecent genomic analyses have provided substantial evidence for past periods of gene flow from polar bears (Ursus maritimus) into Alaskan brown bears (Ursus arctos), with some analyses suggesting a link between climate change and genomic introgression. However, because it has only been possible to sample bears from the present day, the timing, frequency, and evolutionary significance of this admixture remains unknown. Here, we analyze genomic DNA from three additional and geographically distinct brown bear populations, including two that lived temporally close to the peak of the last ice age. We find evidence of admixture in all three populations, suggesting that admixture between these species has been common in their recent evolutionary history. In addition, analyses of ten fossil bears from the now-extinct Irish population indicate that admixture peaked during the last ice age, when brown bear and polar bear ranges overlapped. Following this peak, the proportion of polar bear ancestry in Irish brown bears declined rapidly until their extinction. Our results support a model in which ice age climate change created geographically widespread conditions conducive to admixture between polar bears and brown bears, as is again occurring today. We postulate that this model will be informative for many admixing species pairs impacted by climate change. Our results highlight the power of paleogenomes to reveal patterns of evolutionary change that are otherwise masked with only contemporary data.

scholarly journals Insights into bear evolution from a Pleistocene polar bear genome

2021 ◽  
Author(s):  
Tianying Lan ◽  
Kalle Leppala ◽  
Crystal Tomlin ◽  
Sandra L Talbot ◽  
George K Sage ◽  
...  
Keyword(s):  
Climate Change ◽  
Polar Bear ◽  
Ursus Arctos ◽  
Genetic Erosion ◽  
Brown Bear ◽  
Population History ◽  
Polar Bears ◽  
Effective Population ◽  
Brown Bears ◽  
Svalbard Archipelago

The polar bear (Ursus maritimus) has become a symbol of the threat to biodiversity from climate change. Understanding polar bear evolutionary history may provide insights into apex carnivore responses and prospects during periods of extreme environmental perturbations. In recent years, genomic studies have examined bear speciation and population history, including evidence for ancient admixture between polar bears and brown bears (Ursus arctos). Here, we extend our earlier studies of a 130,000-115,000-year-old polar bear from the Svalbard Archipelago using 10X coverage genome sequence and ten new genomes of polar and brown bears from contemporary zones of overlap in northern Alaska. We demonstrate a dramatic decline in effective population size for this ancient polar bear's lineage, followed by a modest increase just before its demise. A slightly higher genetic diversity in the ancient polar bear suggests a severe genetic erosion over a prolonged bottleneck in modern polar bears. Statistical fitting of data to alternative admixture graph scenarios favors at least one ancient introgression event from brown bears into the ancestor of polar bears, possibly dating back over 150,000 years. Gene flow was likely bidirectional, but allelic transfer from brown into polar bear is the strongest detected signal, which contrasts with other published works. These findings have implications for our understanding of climate change impacts: polar bears, a specialist Arctic lineage, may not only have undergone severe genetic bottlenecks, but also been the recipient of generalist, boreal genetic variants from brown bear during critical phases of Northern Hemisphere glacial oscillations.

scholarly journals Ancient DNA reveals multiple origins and migration waves of extinct Japanese brown bear lineages

2021 ◽  
Vol 8 (8) ◽  
pp. 210518
Author(s):  
Takahiro Segawa ◽  
Takahiro Yonezawa ◽  
Hiroshi Mori ◽  
Ayumi Akiyoshi ◽  
Morten E. Allentoft ◽  
...  
Keyword(s):  
Sea Level ◽  
Ancient Dna ◽  
Ursus Arctos ◽  
Divergence Time ◽  
Brown Bear ◽  
Ecosystem Dynamics ◽  
Ice Age ◽  
Brown Bears ◽  
Substantial Impact ◽  
Sea Level Fluctuations

Little is known about how mammalian biogeography on islands was affected by sea-level fluctuations. In the Japanese Archipelago, brown bears ( Ursus arctos ) currently inhabit only Hokkaido, the northern island, but Pleistocene fossils indicate a past distribution throughout Honshu, Japan's largest island. However, the difficulty of recovering ancient DNA from fossils in temperate East Asia has limited our understanding of their evolutionary history. Here, we analysed mitochondrial DNA from a 32 500-year-old brown bear fossil from Honshu. Our results show that this individual belonged to a previously unknown lineage that split approximately 160 Ka from its sister lineage, the southern Hokkaido clade. This divergence time and fossil record suggest that brown bears migrated from the Eurasian continent to Honshu at least twice; the first population was an early-diverging lineage (greater than 340 Ka), and the second migrated via Hokkaido after approximately 160 Ka, during the ice age. Thus, glacial-age sea-level falls might have facilitated migrations of large mammals more frequently than previously thought, which may have had a substantial impact on ecosystem dynamics in these isolated islands.

scholarly journals Genomic Evidence of Widespread Admixture from Polar Bears into Brown Bears during the Last Ice Age

2018 ◽  
Vol 35 (5) ◽  
pp. 1120-1129 ◽  
Author(s):  
James A Cahill ◽  
Peter D Heintzman ◽  
Kelley Harris ◽  
Matthew D Teasdale ◽  
Joshua Kapp ◽  
...  
Keyword(s):  
Ice Age ◽  
Polar Bears ◽  
Brown Bears ◽  
Last Ice Age

scholarly journals The smell of success: Reproductive success related to rub behavior in brown bears

PLoS ONE ◽  
2021 ◽  
Vol 16 (3) ◽  
pp. e0247964
Author(s):  
Andrea T. Morehouse ◽  
Anne E. Loosen ◽  
Tabitha A. Graves ◽  
Mark S. Boyce
Keyword(s):  
Reproductive Success ◽  
Ursus Arctos ◽  
Scent Marking ◽  
Brown Bear ◽  
Parentage Analysis ◽  
Fitness Component ◽  
Brown Bears ◽  
Male And Female ◽  
Rubbing Behavior ◽  
Insight Into

Several species of bears are known to rub deliberately against trees and other objects, but little is known about why bears rub. Patterns in rubbing behavior of male and female brown bears (Ursus arctos) suggest that scent marking via rubbing functions to communicate among potential mates or competitors. Using DNA from bear hairs collected from rub objects in southwestern Alberta from 2011–2014 and existing DNA datasets from Montana and southeastern British Columbia, we determined sex and individual identity of each bear detected. Using these data, we completed a parentage analysis. From the parentage analysis and detection data, we determined the number of offspring, mates, unique rub objects where an individual was detected, and sampling occasions during which an individual was detected for each brown bear identified through our sampling methods. Using a Poisson regression, we found a positive relationship between bear rubbing behavior and reproductive success; both male and female bears with a greater number of mates and a greater number of offspring were detected at more rub objects and during more occasions. Our results suggest a fitness component to bear rubbing, indicate that rubbing is adaptive, and provide insight into a poorly understood behaviour.

scholarly journals Heart rate during hyperphagia differs between two bear species

2019 ◽  
Vol 15 (1) ◽  
pp. 20180681 ◽  
Author(s):  
Boris Fuchs ◽  
Koji Yamazaki ◽  
Alina L. Evans ◽  
Toshio Tsubota ◽  
Shinsuke Koike ◽  
...  
Keyword(s):  
Heart Rate ◽  
Ursus Arctos ◽  
Brown Bear ◽  
Black Bear ◽  
Black Bears ◽  
Brown Bears ◽  
Fat Reserves ◽  
Generalized Additive Mixed Models ◽  
Additive Mixed Models ◽  
Increased Activity

Hyperphagia is a critical part of the yearly cycle of bears when they gain fat reserves before entering hibernation. We used heart rate as a proxy to compare the metabolic rate between the Asian black bear ( Ursus thibetanus ) in Japan and the Eurasian brown bear ( Ursus arctos ) in Sweden from summer into hibernation. In the hyperphagic period, black bears feed on fat- and carbohydrate-rich hard masts whereas brown bears feed on sugar-rich berries. Availability of hard masts has quantitative and spatial annual fluctuations, which might require increased activity and result in intraspecific stress. Using generalized additive mixed models we analysed the differences in heart rate between the two species. Black bears had decreased heart rates during summer but had doubled heart rate values throughout the hyperphagic period compared to brown bears. This letter illustrates the different physiological consequences of seasonal differences in food availability in two species of the same genus dealing with the same phenological challenge.

scholarly journals Polar bear evolution is marked by rapid changes in gene copy number in response to dietary shift

2019 ◽  
Vol 116 (27) ◽  
pp. 13446-13451 ◽  
Author(s):  
David C. Rinker ◽  
Natalya K. Specian ◽  
Shu Zhao ◽  
John G. Gibbons
Keyword(s):  
Copy Number ◽  
Polar Bear ◽  
Ursus Arctos ◽  
Gene Copy Number ◽  
Brown Bear ◽  
Principal Component ◽  
Ecological Adaptation ◽  
Gene Copy ◽  
Evolutionary Mechanisms ◽  
Dietary Shift

Polar bear (Ursus maritimus) and brown bear (Ursus arctos) are recently diverged species that inhabit vastly differing habitats. Thus, analysis of the polar bear and brown bear genomes represents a unique opportunity to investigate the evolutionary mechanisms and genetic underpinnings of rapid ecological adaptation in mammals. Copy number (CN) differences in genomic regions between closely related species can underlie adaptive phenotypes and this form of genetic variation has not been explored in the context of polar bear evolution. Here, we analyzed the CN profiles of 17 polar bears, 9 brown bears, and 2 black bears (Ursus americanus). We identified an average of 318 genes per individual that showed evidence of CN variation (CNV). Nearly 200 genes displayed species-specific CN differences between polar bear and brown bear species. Principal component analysis of gene CN provides strong evidence that CNV evolved rapidly in the polar bear lineage and mainly resulted in CN loss. Olfactory receptors composed 47% of CN differentiated genes, with the majority of these genes being at lower CN in the polar bear. Additionally, we found significantly fewer copies of several genes involved in fatty acid metabolism as well asAMY1B, the salivary amylase-encoding gene in the polar bear. These results suggest that natural selection shaped patterns of CNV in response to the transition from an omnivorous to primarily carnivorous diet during polar bear evolution. Our analyses of CNV shed light on the genomic underpinnings of ecological adaptation during polar bear evolution.

scholarly journals Use of salmon (Oncorhynchus spp.) by Brown Bears (Ursus arctos) in an Arctic, interior, montane environment

2019 ◽  
Vol 133 (2) ◽  
pp. 151 ◽  
Author(s):  
Mathew S. Sorum ◽  
Kyle Joly ◽  
Matthew D. Cameron
Keyword(s):  
National Park ◽  
Ursus Arctos ◽  
Brown Bear ◽  
The Arctic ◽  
Brooks Range ◽  
Brown Bears ◽  
Arctic Circle ◽  
Aerial Surveys

Salmon (Oncorhynchus spp.) is a key dietary item for temperate coastal Brown Bears (Ursus arctos) across much of their circumpolar range. Brown Bears living in Arctic, interior, and montane environments without large annual runs of salmon tend to be smaller bodied and occur at much lower densities than coastal populations. We conducted ground and aerial surveys to assess whether Brown Bears fished for salmon above the Arctic Circle, in and around Gates of the Arctic National Park and Preserve. Here, we document the use of salmon by interior Brown Bears in the Arctic mountains of the central Brooks Range of Alaska. We believe our findings could be important for understanding the breadth of the species’ diet across major biomes, as well as visitor safety in the park and Brown Bear conservation in the region.

Brown bear habitat selection in relation to anthropogenic structures in the Bieszczady Mountains, Poland

Biologia ◽  
2014 ◽  
Vol 69 (7) ◽  
Author(s):  
Witold Frąckowiak ◽  
Jörn Theuerkauf ◽  
Bartosz Pirga ◽  
Roman Gula
Keyword(s):  
Habitat Selection ◽  
Human Factors ◽  
Ursus Arctos ◽  
Brown Bear ◽  
Human Settlements ◽  
Brown Bears ◽  
Anthropogenic Structures ◽  
Selection Of

AbstractIn Europe, brown bear Ursus arctos habitats frequently overlap with human settlements and infrastructure. We tested whether anthropogenic structures played an important role in habitat selection by brown bears in the Bieszczady Mountains, Poland. We analysed 668 signs of brown bear presence recorded during 6 counts along 246 km of transects (total 1,476 km) in spring, summer and autumn of 1993 and 1994. Habitat selection of bears was more related to habitat and altitude than to human factors. Avoidance of roads, settlements and forest clearings influenced habitat selection by brown bears in spring but less in summer and autumn.

Trichinella and polar bears: a limited risk for humans

2017 ◽  
Vol 91 (4) ◽  
pp. 440-446 ◽  
Author(s):  
J. Dupouy-Camet ◽  
P. Bourée ◽  
H. Yera
Keyword(s):  
World War Ii ◽  
Polar Bear ◽  
Ursus Maritimus ◽  
The Arctic ◽  
Polar Bears ◽  
World War ◽  
Protected Species ◽  
Brown Bears ◽  
Limited Access ◽  
Human Trichinellosis

AbstractIn this review, we identified 63 cases reported since World War II of human trichinellosis linked to the consumption of parasitized polar bear (Ursus maritimus) meat. This low number contrasts to the numerous cases of human trichinellosis related to consumption of the meat of black (U. americanus) or brown bears (U. arctos). The prevalence of Trichinella infection is high in bears, but larval muscular burden is usually lower in polar bears compared to other bear species. Polar bears, therefore, seem to play a limited role in the transmission of trichinellosis to humans, as native residents living in the Arctic traditionally consume well-cooked bear meat, and travellers and foreign hunters have only limited access to this protected species due to the declining polar bear population.

scholarly journals Do Wild Polar Bears (Ursus maritimus) Use Tools When Hunting Walruses (Odobenus rosmarus)?

ARCTIC ◽  
2021 ◽  
Vol 74 (2) ◽  
pp. 175-187
Author(s):  
Ian Stirling ◽  
Kristin L. Laidre ◽  
Erik W. Born
Keyword(s):  
Food Source ◽  
Ursus Arctos ◽  
Ursus Maritimus ◽  
Ecological Knowledge ◽  
Polar Bears ◽  
Brown Bears ◽  
Direct Observations ◽  
Odobenus Rosmarus ◽  
In Captivity ◽  
In The Wild

Since the late 1700s, reports of polar bears (Ursus maritimus) using tools (i.e., pieces of ice or stones) to kill walruses (Odobenus rosmarus) have been passed on verbally to explorers and naturalists by their Inuit guides, based on local traditional ecological knowledge (TEK) as well as accounts of direct observations or interpretations of tracks in the snow made by the Inuit hunters who reported them. To assess the possibility that polar bears may occasionally use tools to hunt walruses in the wild, we summarize 1) observations described to early explorers and naturalists by Inuit hunters about polar bears using tools, 2) more recent documentation in the literature from Inuit hunters and scientists, and 3) recent observations of a polar bear in a zoo spontaneously using tools to access a novel food source. These observations and previously published experiments on brown bears (Ursus arctos) confirm that, in captivity, polar and brown bears are both capable of conceptualizing the use of a tool to obtain a food source that would otherwise not be accessible. Based on the information from all our sources, this may occasionally also have been the case in the wild. We suggest that possible tool use by polar bears in the wild is infrequent and mainly limited to hunting walruses because of their large size, difficulty to kill, and their possession of potentially lethal weapons for both their own defense and the direct attack of a predator. 

Sign in / Sign up

Export Citation Format

Share Document