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Abstract
The distribution and movement of species, broadly known as biogeography, is one of the fundamental subfields of ecology and evolutionary biology. However, significant mysteries remain about the processes that gave rise to the modern distribution of biodiversity across the globe. Over the last several decades, the genetic study of ancient and subfossil specimens has started to shed light on past migrations of some species, with a particular focus on humans and megafauna. In this issue of Molecular Ecology, Salis et al. (2021) use ancient mitogenomes and a new phylogeographic method to add an important new piece of evidence to the mystery of megafaunal migrations into North America during the Pleistocene. They found a striking synchronicity of brown bear (Ursus arctos) and lion (Panthera spp.) migrations across the Bering Land Bridge at several time points during the late Pleistocene, which highlights the lasting impact of sea level change on the prehistoric and modern dispersal of terrestrial carnivores across continents.
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Affiliation(s)
- Stephen J Gaughran
- Department of Ecology & Evolutionary Biology, Princeton University, Princeton, New Jersey, USA
| | - Bridgett vonHoldt
- Department of Ecology & Evolutionary Biology, Princeton University, Princeton, New Jersey, USA
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Mohr DW, Gaughran SJ, Paschall J, Naguib A, Pang AWC, Dudchenko O, Aiden EL, Church DM, Scott AF. A Chromosome-Length Assembly of the Hawaiian Monk Seal (Neomonachus schauinslandi): A History of “Genetic Purging” and Genomic Stability. Genes (Basel) 2022; 13:genes13071270. [PMID: 35886053 PMCID: PMC9323584 DOI: 10.3390/genes13071270] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2022] [Revised: 06/29/2022] [Accepted: 07/07/2022] [Indexed: 12/04/2022] Open
Abstract
The Hawaiian monk seal (HMS) is the single extant species of tropical earless seals of the genus Neomonachus. The species survived a severe bottleneck in the late 19th century and experienced subsequent population declines until becoming the subject of a NOAA-led species recovery effort beginning in 1976 when the population was fewer than 1000 animals. Like other recovering species, the Hawaiian monk seal has been reported to have reduced genetic heterogeneity due to the bottleneck and subsequent inbreeding. Here, we report a chromosomal reference assembly for a male animal produced using a variety of methods. The final assembly consisted of 16 autosomes, an X, and portions of the Y chromosomes. We compared variants in this animal to other HMS and to a frequently sequenced human sample, confirming about 12% of the variation seen in man. To confirm that the reference animal was representative of the HMS, we compared his sequence to that of 10 other individuals and noted similarly low variation in all. Variation in the major histocompatibility (MHC) genes was nearly absent compared to the orthologous human loci. Demographic analysis predicts that Hawaiian monk seals have had a long history of small populations preceding the bottleneck, and their current low levels of heterozygosity may indicate specialization to a stable environment. When we compared our reference assembly to that of other species, we observed significant conservation of chromosomal architecture with other pinnipeds, especially other phocids. This reference should be a useful tool for future evolutionary studies as well as the long-term management of this species.
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Affiliation(s)
- David W. Mohr
- Department of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA; (D.W.M.); (J.P.)
| | - Stephen J. Gaughran
- Department of Ecology & Evolutionary Biology, Princeton University, Princeton, NJ 08544, USA;
| | - Justin Paschall
- Department of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA; (D.W.M.); (J.P.)
| | - Ahmed Naguib
- Bionano Genomics, Inc., 9640 Towne Centre Dr., Suite 100, San Diego, CA 92121, USA; (A.N.); (A.W.C.P.)
| | - Andy Wing Chun Pang
- Bionano Genomics, Inc., 9640 Towne Centre Dr., Suite 100, San Diego, CA 92121, USA; (A.N.); (A.W.C.P.)
| | - Olga Dudchenko
- The Center for Genome Architecture, Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA; (O.D.); (E.L.A.)
- Center for Theoretical Biological Physics, Rice University, Houston, TX 77030, USA
| | - Erez Lieberman Aiden
- The Center for Genome Architecture, Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA; (O.D.); (E.L.A.)
- Center for Theoretical Biological Physics, Rice University, Houston, TX 77030, USA
- UWA School of Agriculture and Environment, The University of Western Australia, Crawley, WA 6009, Australia
- Broad Institute of MIT and Harvard, Cambridge, MA 02139, USA
- Shanghai Institute for Advanced Immunochemical Studies, ShanghaiTech University, Shanghai 201210, China
| | | | - Alan F. Scott
- Department of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA; (D.W.M.); (J.P.)
- Correspondence:
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Jensen EL, Gaughran SJ, Fusco NA, Poulakakis N, Tapia W, Sevilla C, Málaga J, Mariani C, Gibbs JP, Caccone A. The Galapagos giant tortoise Chelonoidis phantasticus is not extinct. Commun Biol 2022; 5:546. [PMID: 35681083 PMCID: PMC9184544 DOI: 10.1038/s42003-022-03483-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2021] [Accepted: 05/11/2022] [Indexed: 11/25/2022] Open
Abstract
The status of the Fernandina Island Galapagos giant tortoise (Chelonoidis phantasticus) has been a mystery, with the species known from a single specimen collected in 1906. The discovery in 2019 of a female tortoise living on the island provided the opportunity to determine if the species lives on. By sequencing the genomes of both individuals and comparing them to all living species of Galapagos giant tortoises, here we show that the two known Fernandina tortoises are from the same lineage and distinct from all others. The whole genome phylogeny groups the Fernandina individuals within a monophyletic group containing all species with a saddleback carapace morphology and one semi-saddleback species. This grouping of the saddleback species is contrary to mitochondrial DNA phylogenies, which place the saddleback species across several clades. These results imply the continued existence of lineage long considered extinct, with a current known population size of a single individual. Based on genomic data, the Galapagos giant tortoise species native to Fernandina Island appears to be alive and well, survived by at least one female after being considered extinct since 1906.
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Affiliation(s)
- Evelyn L Jensen
- School of Natural and Environmental Sciences, Newcastle University, Newcastle Upon Tyne, UK.
| | - Stephen J Gaughran
- Department of Ecology & Evolutionary Biology, Princeton University, Princeton, NJ, USA.,Department of Ecology and Evolutionary Biology, Yale University, New Haven, CT, USA
| | - Nicole A Fusco
- Department of Ecology and Evolutionary Biology, Yale University, New Haven, CT, USA
| | - Nikos Poulakakis
- Department of Biology, School of Sciences and Engineering, University of Crete, Irakleio, Greece.,The Natural History Museum of Crete, School of Sciences and Engineering, University of Crete, Heraklion, Greece.,Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology-Hellas, Heraklion, Greece
| | - Washington Tapia
- Galapagos Conservancy, Fairfax, VA, USA.,University of Málaga, Campus Teatinos, Apdo, 59.29080, Málaga, Spain
| | - Christian Sevilla
- Conservation and Restoration of Insular Ecosystems Department, Galapagos National Park Directorate, Puerto Ayora, Galapagos, Ecuador
| | - Jeffreys Málaga
- Conservation and Restoration of Insular Ecosystems Department, Galapagos National Park Directorate, Puerto Ayora, Galapagos, Ecuador
| | - Carol Mariani
- Department of Ecology and Evolutionary Biology, Yale University, New Haven, CT, USA.,Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, CT, USA
| | - James P Gibbs
- Galapagos Conservancy, Fairfax, VA, USA.,Department of Environmental Biology, College of Environmental Science and Forestry, State University of New York, Syracuse, NY, USA
| | - Adalgisa Caccone
- Department of Ecology and Evolutionary Biology, Yale University, New Haven, CT, USA
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Jensen EL, Gaughran SJ, Garrick RC, Russello MA, Caccone A. Demographic history and patterns of molecular evolution from whole genome sequencing in the radiation of Galapagos giant tortoises. Mol Ecol 2021; 30:6325-6339. [PMID: 34510620 DOI: 10.1111/mec.16176] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2021] [Revised: 08/19/2021] [Accepted: 08/23/2021] [Indexed: 12/23/2022]
Abstract
Whole genome sequencing provides deep insights into the evolutionary history of a species, including patterns of diversity, signals of selection, and historical demography. When applied to closely related taxa with a wealth of background knowledge, population genomics provides a comparative context for interpreting population genetic summary statistics and comparing empirical results with the expectations of population genetic theory. The Galapagos giant tortoises (Chelonoidis spp.), an iconic rapid and recent radiation, offer such an opportunity. Here, we sequenced whole genomes from three individuals of the 12 extant lineages of Galapagos giant tortoise and estimate diversity measures and reconstruct changes in coalescent rate over time. We also compare the number of derived alleles in each lineage to infer how synonymous and nonsynonymous mutation accumulation rates correlate with population size and life history traits. Remarkably, we find that patterns of molecular evolution are similar within individuals of the same lineage, but can differ significantly among lineages, reinforcing the evolutionary distinctiveness of the Galapagos giant tortoise species. Notably, differences in mutation accumulation among lineages do not align with simple population genetic predictions, suggesting that the drivers of purifying selection are more complex than is currently appreciated. By integrating results from earlier population genetic and phylogeographic studies with new findings from the analysis of whole genomes, we provide the most in-depth insights to date on the evolution of Galapagos giant tortoises, and identify discrepancies between expectation from population genetic theory and empirical data that warrant further scrutiny.
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Affiliation(s)
- Evelyn L Jensen
- Department of Ecology and Evolutionary Biology, Yale University, New Haven, Connecticut, USA
| | - Stephen J Gaughran
- Department of Ecology and Evolutionary Biology, Yale University, New Haven, Connecticut, USA
| | - Ryan C Garrick
- Department of Biology, University of Mississippi, Oxford, Mississippi, USA
| | - Michael A Russello
- Department of Biology, University of British Columbia, Okanagan Campus, Kelowna, British Columbia, Canada
| | - Adalgisa Caccone
- Department of Ecology and Evolutionary Biology, Yale University, New Haven, Connecticut, USA
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Gaughran SJ, Quinzin MC, Miller JM, Garrick RC, Edwards DL, Russello MA, Poulakakis N, Ciofi C, Beheregaray LB, Caccone A. Theory, practice, and conservation in the age of genomics: The Galápagos giant tortoise as a case study. Evol Appl 2018; 11:1084-1093. [PMID: 30026799 PMCID: PMC6050186 DOI: 10.1111/eva.12551] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2017] [Accepted: 08/31/2017] [Indexed: 12/25/2022] Open
Abstract
High-throughput DNA sequencing allows efficient discovery of thousands of single nucleotide polymorphisms (SNPs) in nonmodel species. Population genetic theory predicts that this large number of independent markers should provide detailed insights into population structure, even when only a few individuals are sampled. Still, sampling design can have a strong impact on such inferences. Here, we use simulations and empirical SNP data to investigate the impacts of sampling design on estimating genetic differentiation among populations that represent three species of Galápagos giant tortoises (Chelonoidis spp.). Though microsatellite and mitochondrial DNA analyses have supported the distinctiveness of these species, a recent study called into question how well these markers matched with data from genomic SNPs, thereby questioning decades of studies in nonmodel organisms. Using >20,000 genomewide SNPs from 30 individuals from three Galápagos giant tortoise species, we find distinct structure that matches the relationships described by the traditional genetic markers. Furthermore, we confirm that accurate estimates of genetic differentiation in highly structured natural populations can be obtained using thousands of SNPs and 2-5 individuals, or hundreds of SNPs and 10 individuals, but only if the units of analysis are delineated in a way that is consistent with evolutionary history. We show that the lack of structure in the recent SNP-based study was likely due to unnatural grouping of individuals and erroneous genotype filtering. Our study demonstrates that genomic data enable patterns of genetic differentiation among populations to be elucidated even with few samples per population, and underscores the importance of sampling design. These results have specific implications for studies of population structure in endangered species and subsequent management decisions.
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Affiliation(s)
| | - Maud C. Quinzin
- Department of Ecology and Evolutionary BiologyYale UniversityNew HavenCTUSA
| | - Joshua M. Miller
- Department of Ecology and Evolutionary BiologyYale UniversityNew HavenCTUSA
| | | | | | - Michael A. Russello
- Department of BiologyUniversity of British Columbia, Okanagan CampusKelownaBCCanada
| | - Nikos Poulakakis
- Department of BiologySchool of Sciences and EngineeringUniversity of CreteHeraklion, CreteGreece
- Natural History Museum of CreteSchool of Sciences and EngineeringUniversity of CreteHeraklion, CreteGreece
| | - Claudio Ciofi
- Department of BiologyUniversity of FlorenceSesto Fiorentino (FI)Italy
| | - Luciano B. Beheregaray
- Molecular Ecology LabSchool of Biological SciencesFlinders UniversityAdelaideSAAustralia
| | - Adalgisa Caccone
- Department of Ecology and Evolutionary BiologyYale UniversityNew HavenCTUSA
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Abstract
Elephants have significantly reduced their risk of cancer by duplicating an important
gene called TP53.
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Affiliation(s)
- Stephen J Gaughran
- Department of Ecology and Evolutionary Biology, Yale University, New Haven, United States
| | - Evlyn Pless
- Department of Ecology and Evolutionary Biology, Yale University, New Haven, United States
| | - Stephen C Stearns
- Department of Ecology and Evolutionary Biology, Yale University, New Haven, United States
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Naro-Maciel E, Gaughran SJ, Putman NF, Amato G, Arengo F, Dutton PH, McFadden KW, Vintinner EC, Sterling EJ. Predicting connectivity of green turtles at Palmyra Atoll, central Pacific: a focus on mtDNA and dispersal modelling. J R Soc Interface 2014; 11:20130888. [PMID: 24451389 DOI: 10.1098/rsif.2013.0888] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Population connectivity and spatial distribution are fundamentally related to ecology, evolution and behaviour. Here, we combined powerful genetic analysis with simulations of particle dispersal in a high-resolution ocean circulation model to investigate the distribution of green turtles foraging at the remote Palmyra Atoll National Wildlife Refuge, central Pacific. We analysed mitochondrial sequences from turtles (n = 349) collected there over 5 years (2008-2012). Genetic analysis assigned natal origins almost exclusively (approx. 97%) to the West Central and South Central Pacific combined Regional Management Units. Further, our modelling results indicated that turtles could potentially drift from rookeries to Palmyra Atoll via surface currents along a near-Equatorial swathe traversing the Pacific. Comparing findings from genetics and modelling highlighted the complex impacts of ocean currents and behaviour on natal origins. Although the Palmyra feeding ground was highly differentiated genetically from others in the Indo-Pacific, there was no significant differentiation among years, sexes or stage-classes at the Refuge. Understanding the distribution of this foraging population advances knowledge of green turtles and contributes to effective conservation planning for this threatened species.
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Affiliation(s)
- Eugenia Naro-Maciel
- Biology Department, City University of New York, College of Staten Island, , 2800 Victory Boulevard, Staten Island, NY 10314, USA
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