CITES regulates international trade with the goal of preventing over-exploitation, thus the survi... more CITES regulates international trade with the goal of preventing over-exploitation, thus the survival of species are not jeopardized from trade practices; however it has been used recently in nontrade conservation measures. As an example, the US proposed to uplist polar bears under CITES Appendix I, despite that the species did not conform to the biological criteria. Polar bears were listed as 'threatened' under US ESA in 2008, in response to loss of sea-ice and warming temperatures. In Nunavut, where most of Canada's polar bears are harvested, the resulting trade ban did not decrease total harvest after the ESA listing but reduced US hunter participation and the proportion of quotas taken by sport hunters from specific populations. Consequently, the import ban impacted livelihoods of Arctic indigenous communities with negative conservation-reduced tolerance for dangerous fauna and affected local participation in shared management initiatives. The polar bear may be the exemplar of an emerging problem: the use of trade bans in place of action for non-trade threats, e.g., climate change. Conservation prospects for this species and other climate-sensitive wildlife will likely diminish if the increasing use of trade bans to combat non-trade issues cause stakeholders to lose faith in participatory management.
Global viral diversity is substantial, but viruses that contribute little to the public health bu... more Global viral diversity is substantial, but viruses that contribute little to the public health burden or to agricultural damage receive minimal attention until a seemingly unimportant virus becomes a threat. The Zika virus (ZIKV) illustrated this, as there was limited information and awareness of the virus when it was identified as a public health emergency in February 2016. Predicting which virus may pose a future threat is difficult. This is in part because significant knowledge gaps in the basic biology and ecology of an emerging virus can impede policy development, delay decision making, and hinder public health action. We suggest using a phylogenetic framework of pathogens and their infected host species for insight into which animals may serve as reservoirs. For example, examining flaviviruses closely related to ZIKV, the phylogenetic framework indicates New World monkeys are the most likely candidates to be potential reservoirs for ZIKV. Secondarily, mammals that are in close proximity to humans should be considered because of the increased opportunity for pathogen exchange. The increase in human-mediated environmental change is accelerating the probability of another previously overlooked virus becoming a significant concern. By investing in basic science research and organizing our knowledge into an evolutionary framework, we will be better prepared to respond to the next emerging infectious disease.
We thank J. Heyning and D. Janiger for access to archaeological bone samples from the collection ... more We thank J. Heyning and D. Janiger for access to archaeological bone samples from the collection at the Los Angeles County Museum of Natural History, G. Bernardi for providing DNA sequences from modern Guadalupe fur seals, A. Jacklet, R. Osuna, and D. McKeon for providing facilities for analysis of ancient DNA, and
Sea ice is believed to be a major factor shaping gene flow for polar marine organisms, but it rem... more Sea ice is believed to be a major factor shaping gene flow for polar marine organisms, but it remains unclear to what extent it represents a true barrier to dispersal for arctic cetaceans. Bowhead whales are highly adapted to polar sea ice and were targeted by commercial whalers throughout Arctic and subarctic seas for at least four centuries, resulting in severe reductions in most areas. Both changing ice conditions and reductions due to whaling may have affected geographic distribution and genetic diversity throughout their range, but little is known about range-wide genetic structure or whether it differed in the past. This study represents the first examination of genetic diversity and differentiation across all five putative stocks, including Baffin Bay-Davis Strait, Hudson Bay-Foxe Basin, Bering-Beaufort-Chukchi, Okhotsk, and Spitsbergen. We also utilized ancient specimens from Prince Regent Inlet (PRI) in the Canadian Arctic and compared them with modern stocks. Results from analysis of molecular variance and demographic simulations are consistent with recent and high gene flow between Atlantic and Pacific stocks in the recent past. Significant genetic differences between ancient and modern populations suggest PRI harbored unique maternal lineages in the past that have been recently lost, possibly due to loss of habitat during the Little Ice Age and/or whaling. Unexpectedly, samples from this location show a closer genetic relationship with modern Pacific stocks than Atlantic, supporting high gene flow between the central Canadian Arctic and Beaufort Sea over the past millennium despite extremely heavy ice cover over much of this period.
A bottleneck in population size of a species is often correlated with a sharp reduction in geneti... more A bottleneck in population size of a species is often correlated with a sharp reduction in genetic variation. The northern elephant seal (Mirounga angustirostris) has undergone at least one extreme bottleneck, having rebounded from 20-100 individuals a century ago to over 175,000 individuals today. The relative lack of molecular-genetic variation in contemporary populations has been documented, but the extent of variation before the late 19th century remains unknown. We have determined the nucleotide sequence of a 179 base-pair segment of the mitochondrial DNA (mtDNA) control region from seals that lived before, during and after a bottleneck low in 1892. A 'primerless' PCR was used to improve the recovery of information from older samples. Only two mtDNA genotypes were present in all 150+ seals from the 1892 bottleneck on, but we discovered four genotypes in five pre-bottleneck seals. This suggests a much greater amount of mtDNA genotypic variation before this bottleneck, and that the persistence of two genotypes today is a consequence of random lineage sampling. We cannot correlate the loss of mtDNA genotypes with a lowered mean fitness of individuals in the species today. However, we show that the species historically possessed additional genotypes to those present now, and that sampling of ancient DNA could elucidate the genetic consequences of severe reductions in population size.
ABSTRACT Animals in the Arctic have low pathogen diversity but with rapid climate warming, this i... more ABSTRACT Animals in the Arctic have low pathogen diversity but with rapid climate warming, this is expected to change. One insidious consequence of climate change is exposure of Arctic species to new pathogens derived from more southern species expanding their range northward. To assess potential vulnerability of polar bears to disease exposure, we examined genetic variation in major histocompatibility complex (MHC) loci (part of immune system) in Canadian polar bears and found low genetic diversity, consistent with long-standing exposure to low pathogen/ parasite loads. All polar bears surveyed showed maximum linkage disequilibrium between DRB/DQB loci and 12% of individuals had a duplicated DQB gene haplotype. These results may reflect balancing selection at these loci, a response to an earlier immune-challenge and/or be artifacts of polar bear-brown bear divergence. Consistent with the latter, we found one DQA allele in polar bears that was also a brown bear DQA allele. The reported low MHC diversity and high linkage disequilibrium may have serious implications for polar bear resistance to new pathogens, which would be maladaptive to species in an environment undergoing rapid climate change, such as the Arctic.
As global warming accelerates the melting of Arctic sea ice, polar bears (Ursus maritimus) must a... more As global warming accelerates the melting of Arctic sea ice, polar bears (Ursus maritimus) must adapt to a rapidly changing landscape. This process will necessarily alter the species distribution together with population dynamics and structure. Detailed knowledge of these changes is crucial to delineating conservation priorities. Here, we sampled 361 polar bears from across the center of the Canadian Arctic Archipelago spanning the Gulf of Boothia (GB) and M'Clintock Channel (MC). We use DNA microsatellites and mitochondrial control region sequences to quantify genetic differentiation, estimate gene flow, and infer population history. Two populations, roughly coincident with GB and MC, are significantly differentiated at both nuclear (F ST = 0.01) and mitochondrial (Φ ST = 0.47; F ST = 0.29) loci, allowing Bayesian clustering analyses to assign individuals to either group. Our data imply that the causes of the mitochondrial and nuclear genetic patterns differ. Analysis of mtDNA reveals the matrilineal structure dates at least to the Holocene, and is common to individuals throughout the species' range. These mtDNA differences probably reflect both genetic drift and historical colonization dynamics. In contrast, the differentiation inferred from microsatellites is only on the scale of hundreds of years, possibly reflecting contemporary impediments to gene flow. Taken together, our data suggest that gene flow is insufficient to homogenize the GB and MC populations and support the designation of GB and MC as separate polar bear conservation units. Our study also provide a striking example of how nuclear DNA and mtDNA capture different aspects of a species demographic history.
CITES regulates international trade with the goal of preventing over-exploitation, thus the survi... more CITES regulates international trade with the goal of preventing over-exploitation, thus the survival of species are not jeopardized from trade practices; however it has been used recently in nontrade conservation measures. As an example, the US proposed to up-list polar bears under CITES Appendix I, despite that the species did not conform to the biological criteria. Polar bears were listed as ‘threatened’ under US ESA in 2008, in response to loss of sea-ice and warming temperatures. In Nunavut, where most of Canada’s polar bears are harvested, the resulting trade ban did not decrease total harvest after the ESA listing but reduced US hunter participation and the proportion of quotas taken by sport hunters from specific populations. Consequently, the import ban impacted livelihoods of Arctic indigenous communities with negative conservation — reduced tolerance for dangerous fauna and affected local participation in shared management initiatives. The polar bear may be the exemplar of an emerging problem: the use of trade bans in place of action for non-trade threats, e.g., climate change. Conservation prospects for this species and other climate-sensitive wildlife will likely diminish if the increasing use of trade bans to combat non-trade issues cause stakeholders to lose faith in participatory management.
CITES regulates international trade with the goal of preventing over-exploitation, thus the survi... more CITES regulates international trade with the goal of preventing over-exploitation, thus the survival of species are not jeopardized from trade practices; however it has been used recently in nontrade conservation measures. As an example, the US proposed to uplist polar bears under CITES Appendix I, despite that the species did not conform to the biological criteria. Polar bears were listed as 'threatened' under US ESA in 2008, in response to loss of sea-ice and warming temperatures. In Nunavut, where most of Canada's polar bears are harvested, the resulting trade ban did not decrease total harvest after the ESA listing but reduced US hunter participation and the proportion of quotas taken by sport hunters from specific populations. Consequently, the import ban impacted livelihoods of Arctic indigenous communities with negative conservation-reduced tolerance for dangerous fauna and affected local participation in shared management initiatives. The polar bear may be the exemplar of an emerging problem: the use of trade bans in place of action for non-trade threats, e.g., climate change. Conservation prospects for this species and other climate-sensitive wildlife will likely diminish if the increasing use of trade bans to combat non-trade issues cause stakeholders to lose faith in participatory management.
Global viral diversity is substantial, but viruses that contribute little to the public health bu... more Global viral diversity is substantial, but viruses that contribute little to the public health burden or to agricultural damage receive minimal attention until a seemingly unimportant virus becomes a threat. The Zika virus (ZIKV) illustrated this, as there was limited information and awareness of the virus when it was identified as a public health emergency in February 2016. Predicting which virus may pose a future threat is difficult. This is in part because significant knowledge gaps in the basic biology and ecology of an emerging virus can impede policy development, delay decision making, and hinder public health action. We suggest using a phylogenetic framework of pathogens and their infected host species for insight into which animals may serve as reservoirs. For example, examining flaviviruses closely related to ZIKV, the phylogenetic framework indicates New World monkeys are the most likely candidates to be potential reservoirs for ZIKV. Secondarily, mammals that are in close proximity to humans should be considered because of the increased opportunity for pathogen exchange. The increase in human-mediated environmental change is accelerating the probability of another previously overlooked virus becoming a significant concern. By investing in basic science research and organizing our knowledge into an evolutionary framework, we will be better prepared to respond to the next emerging infectious disease.
We thank J. Heyning and D. Janiger for access to archaeological bone samples from the collection ... more We thank J. Heyning and D. Janiger for access to archaeological bone samples from the collection at the Los Angeles County Museum of Natural History, G. Bernardi for providing DNA sequences from modern Guadalupe fur seals, A. Jacklet, R. Osuna, and D. McKeon for providing facilities for analysis of ancient DNA, and
Sea ice is believed to be a major factor shaping gene flow for polar marine organisms, but it rem... more Sea ice is believed to be a major factor shaping gene flow for polar marine organisms, but it remains unclear to what extent it represents a true barrier to dispersal for arctic cetaceans. Bowhead whales are highly adapted to polar sea ice and were targeted by commercial whalers throughout Arctic and subarctic seas for at least four centuries, resulting in severe reductions in most areas. Both changing ice conditions and reductions due to whaling may have affected geographic distribution and genetic diversity throughout their range, but little is known about range-wide genetic structure or whether it differed in the past. This study represents the first examination of genetic diversity and differentiation across all five putative stocks, including Baffin Bay-Davis Strait, Hudson Bay-Foxe Basin, Bering-Beaufort-Chukchi, Okhotsk, and Spitsbergen. We also utilized ancient specimens from Prince Regent Inlet (PRI) in the Canadian Arctic and compared them with modern stocks. Results from analysis of molecular variance and demographic simulations are consistent with recent and high gene flow between Atlantic and Pacific stocks in the recent past. Significant genetic differences between ancient and modern populations suggest PRI harbored unique maternal lineages in the past that have been recently lost, possibly due to loss of habitat during the Little Ice Age and/or whaling. Unexpectedly, samples from this location show a closer genetic relationship with modern Pacific stocks than Atlantic, supporting high gene flow between the central Canadian Arctic and Beaufort Sea over the past millennium despite extremely heavy ice cover over much of this period.
A bottleneck in population size of a species is often correlated with a sharp reduction in geneti... more A bottleneck in population size of a species is often correlated with a sharp reduction in genetic variation. The northern elephant seal (Mirounga angustirostris) has undergone at least one extreme bottleneck, having rebounded from 20-100 individuals a century ago to over 175,000 individuals today. The relative lack of molecular-genetic variation in contemporary populations has been documented, but the extent of variation before the late 19th century remains unknown. We have determined the nucleotide sequence of a 179 base-pair segment of the mitochondrial DNA (mtDNA) control region from seals that lived before, during and after a bottleneck low in 1892. A 'primerless' PCR was used to improve the recovery of information from older samples. Only two mtDNA genotypes were present in all 150+ seals from the 1892 bottleneck on, but we discovered four genotypes in five pre-bottleneck seals. This suggests a much greater amount of mtDNA genotypic variation before this bottleneck, and that the persistence of two genotypes today is a consequence of random lineage sampling. We cannot correlate the loss of mtDNA genotypes with a lowered mean fitness of individuals in the species today. However, we show that the species historically possessed additional genotypes to those present now, and that sampling of ancient DNA could elucidate the genetic consequences of severe reductions in population size.
ABSTRACT Animals in the Arctic have low pathogen diversity but with rapid climate warming, this i... more ABSTRACT Animals in the Arctic have low pathogen diversity but with rapid climate warming, this is expected to change. One insidious consequence of climate change is exposure of Arctic species to new pathogens derived from more southern species expanding their range northward. To assess potential vulnerability of polar bears to disease exposure, we examined genetic variation in major histocompatibility complex (MHC) loci (part of immune system) in Canadian polar bears and found low genetic diversity, consistent with long-standing exposure to low pathogen/ parasite loads. All polar bears surveyed showed maximum linkage disequilibrium between DRB/DQB loci and 12% of individuals had a duplicated DQB gene haplotype. These results may reflect balancing selection at these loci, a response to an earlier immune-challenge and/or be artifacts of polar bear-brown bear divergence. Consistent with the latter, we found one DQA allele in polar bears that was also a brown bear DQA allele. The reported low MHC diversity and high linkage disequilibrium may have serious implications for polar bear resistance to new pathogens, which would be maladaptive to species in an environment undergoing rapid climate change, such as the Arctic.
As global warming accelerates the melting of Arctic sea ice, polar bears (Ursus maritimus) must a... more As global warming accelerates the melting of Arctic sea ice, polar bears (Ursus maritimus) must adapt to a rapidly changing landscape. This process will necessarily alter the species distribution together with population dynamics and structure. Detailed knowledge of these changes is crucial to delineating conservation priorities. Here, we sampled 361 polar bears from across the center of the Canadian Arctic Archipelago spanning the Gulf of Boothia (GB) and M'Clintock Channel (MC). We use DNA microsatellites and mitochondrial control region sequences to quantify genetic differentiation, estimate gene flow, and infer population history. Two populations, roughly coincident with GB and MC, are significantly differentiated at both nuclear (F ST = 0.01) and mitochondrial (Φ ST = 0.47; F ST = 0.29) loci, allowing Bayesian clustering analyses to assign individuals to either group. Our data imply that the causes of the mitochondrial and nuclear genetic patterns differ. Analysis of mtDNA reveals the matrilineal structure dates at least to the Holocene, and is common to individuals throughout the species' range. These mtDNA differences probably reflect both genetic drift and historical colonization dynamics. In contrast, the differentiation inferred from microsatellites is only on the scale of hundreds of years, possibly reflecting contemporary impediments to gene flow. Taken together, our data suggest that gene flow is insufficient to homogenize the GB and MC populations and support the designation of GB and MC as separate polar bear conservation units. Our study also provide a striking example of how nuclear DNA and mtDNA capture different aspects of a species demographic history.
CITES regulates international trade with the goal of preventing over-exploitation, thus the survi... more CITES regulates international trade with the goal of preventing over-exploitation, thus the survival of species are not jeopardized from trade practices; however it has been used recently in nontrade conservation measures. As an example, the US proposed to up-list polar bears under CITES Appendix I, despite that the species did not conform to the biological criteria. Polar bears were listed as ‘threatened’ under US ESA in 2008, in response to loss of sea-ice and warming temperatures. In Nunavut, where most of Canada’s polar bears are harvested, the resulting trade ban did not decrease total harvest after the ESA listing but reduced US hunter participation and the proportion of quotas taken by sport hunters from specific populations. Consequently, the import ban impacted livelihoods of Arctic indigenous communities with negative conservation — reduced tolerance for dangerous fauna and affected local participation in shared management initiatives. The polar bear may be the exemplar of an emerging problem: the use of trade bans in place of action for non-trade threats, e.g., climate change. Conservation prospects for this species and other climate-sensitive wildlife will likely diminish if the increasing use of trade bans to combat non-trade issues cause stakeholders to lose faith in participatory management.
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Papers by Diana Weber