1
|
Mills KK, Hildebrandt KPB, Everson KM, Horstmann L, Misarti N, Olson LE. Ancient DNA indicates a century of overhunting did not reduce genetic diversity in Pacific Walruses (Odobenus rosmarus divergens). Sci Rep 2024; 14:8257. [PMID: 38589385 PMCID: PMC11001934 DOI: 10.1038/s41598-024-57414-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2023] [Accepted: 03/18/2024] [Indexed: 04/10/2024] Open
Abstract
Pacific Walruses (Odobenus rosmarus divergens [Illiger 1815]) are gregarious marine mammals considered to be sentinels of the Arctic because of their dependence on sea ice for feeding, molting, and parturition. Like many other marine mammal species, their population sizes were decimated by historical overhunting in the nineteenth and twentieth centuries. Although they have since been protected from nearly all commercial hunting pressure, they now face rapidly accelerating habitat loss as global warming reduces the extent of summer sea ice in the Arctic. To investigate how genetic variation was impacted by overhunting, we obtained mitochondrial DNA sequences from historic Pacific Walrus samples in Alaska that predate the period of overhunting, as well as from extant populations. We found that genetic variation was unchanged over this period, suggesting Pacific Walruses are resilient to genetic attrition in response to reduced population size, and that this may be related to their high vagility and lack of population structure. Although Pacific Walruses will almost certainly continue to decline in number as the planet warms and summer sea ice is further reduced, they may be less susceptible to the ratcheting effects of inbreeding that typically accompany shrinking populations.
Collapse
Affiliation(s)
- Kendall K Mills
- Department of Mammalogy, University of Alaska Museum, 1962 Yukon Drive, Fairbanks, AK, 99775, USA.
- Department of Biology and Wildlife, University of Alaska Fairbanks, Fairbanks, AK, 99775, USA.
| | - Kyndall P B Hildebrandt
- Department of Mammalogy, University of Alaska Museum, 1962 Yukon Drive, Fairbanks, AK, 99775, USA
| | - Kathryn M Everson
- Department of Mammalogy, University of Alaska Museum, 1962 Yukon Drive, Fairbanks, AK, 99775, USA
- Department of Integrative Biology, Oregon State University, 2701 SW Campus Way, Corvallis, OR, 97331, USA
| | - Lara Horstmann
- College of Fisheries and Ocean Sciences, University of Alaska Fairbanks, Fairbanks, AK, 99775, USA
| | - Nicole Misarti
- Water and Environmental Research Center, University of Alaska Fairbanks, Fairbanks, AK, 99775, USA
| | - Link E Olson
- Department of Mammalogy, University of Alaska Museum, 1962 Yukon Drive, Fairbanks, AK, 99775, USA
| |
Collapse
|
2
|
Ruiz-Puerta EJ, Keighley X, Desjardins SPA, Gotfredsen AB, Pan SE, Star B, Boessenkool S, Barrett JH, McCarthy ML, Andersen LW, Born EW, Howse LR, Szpak P, Pálsson S, Malmquist HJ, Rufolo S, Jordan PD, Olsen MT. Holocene deglaciation drove rapid genetic diversification of Atlantic walrus. Proc Biol Sci 2023; 290:20231349. [PMID: 37752842 PMCID: PMC10523089 DOI: 10.1098/rspb.2023.1349] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2023] [Accepted: 08/27/2023] [Indexed: 09/28/2023] Open
Abstract
Rapid global warming is severely impacting Arctic ecosystems and is predicted to transform the abundance, distribution and genetic diversity of Arctic species, though these linkages are poorly understood. We address this gap in knowledge using palaeogenomics to examine how earlier periods of global warming influenced the genetic diversity of Atlantic walrus (Odobenus rosmarus rosmarus), a species closely associated with sea ice and shallow-water habitats. We analysed 82 ancient and historical Atlantic walrus mitochondrial genomes (mitogenomes), including now-extinct populations in Iceland and the Canadian Maritimes, to reconstruct the Atlantic walrus' response to Arctic deglaciation. Our results demonstrate that the phylogeography and genetic diversity of Atlantic walrus populations was initially shaped by the last glacial maximum (LGM), surviving in distinct glacial refugia, and subsequently expanding rapidly in multiple migration waves during the late Pleistocene and early Holocene. The timing of diversification and establishment of distinct populations corresponds closely with the chronology of the glacial retreat, pointing to a strong link between walrus phylogeography and sea ice. Our results indicate that accelerated ice loss in the modern Arctic may trigger further dispersal events, likely increasing the connectivity of northern stocks while isolating more southerly stocks putatively caught in small pockets of suitable habitat.
Collapse
Affiliation(s)
- Emily J. Ruiz-Puerta
- Section for Molecular Ecology and Evolution, Globe Institute, Faculty of Health and Medical Sciences, University of Copenhagen, Øster Farimagsgade 5-7, 1353 Copenhagen Kobenhavn, Denmark
- Arctic Centre & Groningen Institute of Archaeology, Faculty of Arts, University of Groningen, PO Box 716, 9700 AS Groningen, The Netherlands
| | - Xénia Keighley
- Section for Molecular Ecology and Evolution, Globe Institute, Faculty of Health and Medical Sciences, University of Copenhagen, Øster Farimagsgade 5-7, 1353 Copenhagen Kobenhavn, Denmark
- The Bureau of Meteorology, The Treasury Building, Parkes Place West, Parkes, Australian Capital Territory 2600, Australia
| | - Sean P. A. Desjardins
- Arctic Centre & Groningen Institute of Archaeology, Faculty of Arts, University of Groningen, PO Box 716, 9700 AS Groningen, The Netherlands
- Palaeobiology Section, Canadian Museum of Nature, PO Box 3443, Station D, Ottawa, Ontario, Canada K1P 6P4
| | - Anne Birgitte Gotfredsen
- Section for GeoGenetics, Globe Institute, University of Copenhagen, Øster Voldgade 5-7, 1350 Copenhagen Kobenhavn, Denmark
| | - Shyong En Pan
- Palaeobiology Section, Canadian Museum of Nature, PO Box 3443, Station D, Ottawa, Ontario, Canada K1P 6P4
| | - Bastiaan Star
- Centre for Ecological and Evolutionary Synthesis, Department of Biosciences, University of Oslo, Blindernveien 31, 0371 Oslo, Norway
| | - Sanne Boessenkool
- Centre for Ecological and Evolutionary Synthesis, Department of Biosciences, University of Oslo, Blindernveien 31, 0371 Oslo, Norway
| | - James H. Barrett
- Department of Archaeology and Cultural History, NTNU University Museum, 7491 Trondheim, Norway
- McDonald Institute for Archaeological Research, Department of Archaeology, University of Cambridge, Downing Street, Cambridge CB2 3ER, UK
| | - Morgan L. McCarthy
- Section for Molecular Ecology and Evolution, Globe Institute, Faculty of Health and Medical Sciences, University of Copenhagen, Øster Farimagsgade 5-7, 1353 Copenhagen Kobenhavn, Denmark
| | - Liselotte W. Andersen
- Department of Ecoscience, Aarhus University, CF Møllers Allé 4-8, build. 1110, 8000 Aarhus C, Denmark
| | - Erik W. Born
- Greenland Institute of Natural Resources, PO Box 570, 3900 Nuuk, Greenland
| | - Lesley R. Howse
- Archaeology Centre, University of Toronto, 19 Ursula Franklin Street, Toronto, Ontario Canada M5S 2S2
| | - Paul Szpak
- Department of Anthropology, Trent University, 1600 West Bank Drive, Peterborough, Ontario, Canada K9L 0G2
| | - Snæbjörn Pálsson
- Faculty of Life and Environmental Sciences, University of Iceland, Askja, Sturlugata 7, 101 Reykjavik, Iceland
| | - Hilmar J. Malmquist
- Icelandic Museum of Natural History, Suðurlandsbraut 24, 108 Reykjavík, Iceland
| | - Scott Rufolo
- Palaeobiology Section, Canadian Museum of Nature, PO Box 3443, Station D, Ottawa, Ontario, Canada K1P 6P4
| | - Peter D. Jordan
- Department of Archaeology and Ancient History, Lund University, Helgonavägen 3, 223 62 Lund, Sweden
- Global Station for Indigenous Studies and Cultural Diversity (GSI), GI-CoRE, HokkaidoUniversity, Japan
| | - Morten Tange Olsen
- Section for Molecular Ecology and Evolution, Globe Institute, Faculty of Health and Medical Sciences, University of Copenhagen, Øster Farimagsgade 5-7, 1353 Copenhagen Kobenhavn, Denmark
- Natural History Museum of Denmark, University of Copenhagen, Denmark
| |
Collapse
|
3
|
Clark CT, Horstmann L, Misarti N. Walrus teeth as biomonitors of trace elements in Arctic marine ecosystems. THE SCIENCE OF THE TOTAL ENVIRONMENT 2021; 772:145500. [PMID: 33571762 DOI: 10.1016/j.scitotenv.2021.145500] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/10/2020] [Revised: 01/24/2021] [Accepted: 01/25/2021] [Indexed: 06/12/2023]
Abstract
Effective biomonitoring requires an understanding of the factors driving concentrations of the substances or compounds of interest in the tissues of studied organisms. Biomonitoring of trace elements, and heavy metals in particular, has been the focus of much research; however, the complex roles many trace elements play in animal and plant tissues can make it difficult to disentangle environmental signals from physiology. This study examined the concentrations of 15 trace elements in the teeth of 122 Pacific walruses (Odobenus rosmarus divergens) to investigate the potential for walrus teeth as biomonitors of trace elements in Arctic ecosystems. Elemental concentrations were measured across cementum growth layer groups (GLGs), thereby reconstructing a lifetime history of element concentrations for each walrus. The locations of GLGs were used to divide trace element time series into individual years, allowing each GLG to be associated with an animal age and a calendar year. The elements studied exhibited a great deal of complexity, reflecting the numerous factors responsible for generating tooth trace element concentrations. Generalized linear mixed models were used to investigate the importance of age and sex in explaining observed variation in trace element concentrations. Some elements exhibited clear physiological signals (particularly zinc, strontium, barium, and lead), and all elements except arsenic varied by age and/or sex. Pearson's correlations revealed that elements were more strongly correlated among calendar years than among individual walruses, and correlations of trace elements within individual walruses were generally inconsistent or weak. Plots of average elemental concentrations through time from 1945 to 2014 further supported the correlation analyses, with many elements exhibiting similar patterns across the ~70-year period. Together, these results indicate the importance of physiology in modulating tooth trace element concentrations in walrus tooth cementum, but suggest that many trace elements reflect a record of environmental exposure and dietary intake/uptake.
Collapse
Affiliation(s)
- Casey T Clark
- Cooperative Institute for Climate, Ocean, and Ecosystem Studies, University of Washington, 3737 Brooklyn Ave NE, Seattle, WA 98105, USA.
| | - Lara Horstmann
- College of Fisheries and Ocean Sciences, University of Alaska Fairbanks, 2150 Koyukuk Drive, Fairbanks, AK 99775-7220, USA.
| | - Nicole Misarti
- Water and Environmental Research Center, University of Alaska Fairbanks, 1764 Tanana Loop, Fairbanks, AK 99775, USA.
| |
Collapse
|
4
|
Clark CT, Horstmann L, Misarti N. Evaluating tooth strontium and barium as indicators of weaning age in Pacific walruses. Methods Ecol Evol 2020; 11:1626-1638. [PMID: 33381293 PMCID: PMC7756818 DOI: 10.1111/2041-210x.13482] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2020] [Accepted: 08/20/2020] [Indexed: 11/30/2022]
Abstract
Lactation length and weaning age provide important information about maternal investment, which can reflect the health and nutritional status of the mother, as well as broader reproductive strategies in mammals. Calcium-normalized strontium (Sr) and barium (Ba) concentrations in the growth layers of mammalian teeth differ for nursing animals and those consuming non-milk foods, thus can be used to estimate age-at-weaning. To date, this approach has been used only for terrestrial animals, and almost exclusively for primates.The goal of this study was to determine whether Sr and Ba concentrations in the cementum of Pacific walrus Odobenus rosmarus divergens teeth can be used to estimate weaning age. Teeth from 107 walruses were analysed using laser ablation inductively coupled plasma mass spectrometry, and calcium-normalized 88Sr and 137Ba concentrations were quantified.For most walruses, both Sr and Ba concentrations exhibited rapid changes in early life. Ba concentrations matched closely with expected patterns in the published literature, rapidly declining from high to low concentrations (typically from ~10 ppm to ~5 ppm). In contrast, Sr exhibited a pattern opposite to that presented in studies of terrestrial mammals, appearing nearly identical to Ba (typically declining from ~400 ppm to ~200 ppm). To explain these findings, we present conceptual models of the factors generating weaning signals in Sr and Ba for terrestrial mammals, as well as a new, hypothetical model for walruses. Both a visual and mathematical approach to weaning age estimation indicated a median weaning age of walruses at the end of the second year of life (in the second dark layer of the tooth cementum), with many walruses estimated to have weaned in their third year of life, and a smaller group weaning in their fourth or fifth year. This is later than expected, given a published estimate of walrus weaning at 18-24 months.These results do not conclusively support the use of tooth Sr and Ba for estimating weaning age in walruses, and further research is warranted to better understand the drivers of the observed patterns of Ba and Sr accumulation in walrus teeth.
Collapse
Affiliation(s)
- Casey T. Clark
- Joint Institute for the Study of Atmosphere and OceanUniversity of WashingtonSeattleWAUSA
- Cooperative Institute for Climate, Ocean, and Ecosystem StudiesUniversity of WashingtonSeattleWAUSA
| | - Lara Horstmann
- College of Fisheries and Ocean SciencesUniversity of Alaska FairbanksFairbanksAKUSA
| | - Nicole Misarti
- Water and Environmental Research CenterUniversity of Alaska FairbanksFairbanksAKUSA
| |
Collapse
|