1
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Kyriazis CC, Beichman AC, Brzeski KE, Hoy SR, Peterson RO, Vucetich JA, Vucetich LM, Lohmueller KE, Wayne RK. Genomic Underpinnings of Population Persistence in Isle Royale Moose. Mol Biol Evol 2023; 40:msad021. [PMID: 36729989 PMCID: PMC9927576 DOI: 10.1093/molbev/msad021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2022] [Revised: 01/20/2023] [Accepted: 01/25/2023] [Indexed: 02/03/2023] Open
Abstract
Island ecosystems provide natural laboratories to assess the impacts of isolation on population persistence. However, most studies of persistence have focused on a single species, without comparisons to other organisms they interact with in the ecosystem. The case study of moose and gray wolves on Isle Royale allows for a direct contrast of genetic variation in isolated populations that have experienced dramatically differing population trajectories over the past decade. Whereas the Isle Royale wolf population recently declined nearly to extinction due to severe inbreeding depression, the moose population has thrived and continues to persist, despite having low genetic diversity and being isolated for ∼120 years. Here, we examine the patterns of genomic variation underlying the continued persistence of the Isle Royale moose population. We document high levels of inbreeding in the population, roughly as high as the wolf population at the time of its decline. However, inbreeding in the moose population manifests in the form of intermediate-length runs of homozygosity suggestive of historical inbreeding and purging, contrasting with the long runs of homozygosity observed in the smaller wolf population. Using simulations, we confirm that substantial purging has likely occurred in the moose population. However, we also document notable increases in genetic load, which could eventually threaten population viability over the long term. Overall, our results demonstrate a complex relationship between inbreeding, genetic diversity, and population viability that highlights the use of genomic datasets and computational simulation tools for understanding the factors enabling persistence in isolated populations.
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Affiliation(s)
- Christopher C Kyriazis
- Department of Ecology and Evolutionary Biology, University of California, Los Angeles, CA
| | | | - Kristin E Brzeski
- College of Forest Resources and Environmental Science, Michigan Technological University, Houghton, MI
| | - Sarah R Hoy
- College of Forest Resources and Environmental Science, Michigan Technological University, Houghton, MI
| | - Rolf O Peterson
- College of Forest Resources and Environmental Science, Michigan Technological University, Houghton, MI
| | - John A Vucetich
- College of Forest Resources and Environmental Science, Michigan Technological University, Houghton, MI
| | - Leah M Vucetich
- College of Forest Resources and Environmental Science, Michigan Technological University, Houghton, MI
| | - Kirk E Lohmueller
- Department of Ecology and Evolutionary Biology, University of California, Los Angeles, CA
- Interdepartmental Program in Bioinformatics, University of California, Los Angeles, CA
- Department of Human Genetics, David Geffen School of Medicine, University of California, Los Angeles, CA
| | - Robert K Wayne
- Department of Ecology and Evolutionary Biology, University of California, Los Angeles, CA
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2
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Abstract
SignificanceThe dynamics of deleterious variation under contrasting demographic scenarios remain poorly understood in spite of their relevance in evolutionary and conservation terms. Here we apply a genomic approach to study differences in the burden of deleterious alleles between the endangered Iberian lynx (Lynx pardinus) and the widespread Eurasian lynx (Lynx lynx). Our analysis unveils a significantly lower deleterious burden in the former species that should be ascribed to genetic purging, that is, to the increased opportunities of selection against recessive homozygotes due to the inbreeding caused by its smaller population size, as illustrated by our analytical predictions. This research provides theoretical and empirical evidence on the evolutionary relevance of genetic purging under certain demographic conditions.
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3
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López-Cortegano E, Moreno E, García-Dorado A. Genetic purging in captive endangered ungulates with extremely low effective population sizes. Heredity (Edinb) 2021; 127:433-442. [PMID: 34584227 PMCID: PMC8551332 DOI: 10.1038/s41437-021-00473-2] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2021] [Revised: 09/09/2021] [Accepted: 09/09/2021] [Indexed: 02/07/2023] Open
Abstract
Inbreeding threatens the survival of small populations by producing inbreeding depression, but also exposes recessive deleterious effects in homozygosis allowing for genetic purging. Using inbreeding-purging theory, we analyze early survival in four pedigreed captive breeding programs of endangered ungulates where population growth was prioritized so that most adult females were allowed to contribute offspring according to their fitness. We find evidence that purging can substantially reduce inbreeding depression in Gazella cuvieri (with effective population size Ne = 14) and Nanger dama (Ne = 11). No purging is detected in Ammotragus lervia (Ne = 4), in agreement with the notion that drift overcomes purging under fast inbreeding, nor in G. dorcas (Ne = 39) where, due to the larger population size, purging is slower and detection is expected to require more generations. Thus, although smaller populations are always expected to show smaller fitness (as well as less adaptive potential) than larger ones due to higher homozygosis and deleterious fixation, our results show that a substantial fraction of their inbreeding load and inbreeding depression can be purged when breeding contributions are governed by natural selection. Since management strategies intended to maximize the ratio from the effective to the actual population size tend to reduce purging, the search for a compromise between these strategies and purging could be beneficial in the long term. This could be achieved either by allowing some level of random mating and some role of natural selection in determining breeding contributions, or by undertaking reintroductions into the wild at the earliest opportunity.
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Affiliation(s)
- Eugenio López-Cortegano
- grid.4305.20000 0004 1936 7988Institute of Evolutionary Biology, University of Edinburgh, EH9 3FL Edinburgh, UK
| | - Eulalia Moreno
- grid.466639.80000 0004 0547 1725Estación Experimental de Zonas Áridas (CSIC), 04120 Almería, Spain
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4
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Abstract
AbstractGenetic rescue is increasingly considered a promising and underused conservation strategy to reduce inbreeding depression and restore genetic diversity in endangered populations, but the empirical evidence supporting its application is limited to a few generations. Here we discuss on the light of theory the role of inbreeding depression arising from partially recessive deleterious mutations and of genetic purging as main determinants of the medium to long-term success of rescue programs. This role depends on two main predictions: (1) The inbreeding load hidden in populations with a long stable demography increases with the effective population size; and (2) After a population shrinks, purging tends to remove its (partially) recessive deleterious alleles, a process that is slower but more efficient for large populations than for small ones. We also carry out computer simulations to investigate the impact of genetic purging on the medium to long term success of genetic rescue programs. For some scenarios, it is found that hybrid vigor followed by purging will lead to sustained successful rescue. However, there may be specific situations where the recipient population is so small that it cannot purge the inbreeding load introduced by migrants, which would lead to increased fitness inbreeding depression and extinction risk in the medium to long term. In such cases, the risk is expected to be higher if migrants came from a large non-purged population with high inbreeding load, particularly after the accumulation of the stochastic effects ascribed to repeated occasional migration events. Therefore, under the specific deleterious recessive mutation model considered, we conclude that additional caution should be taken in rescue programs. Unless the endangered population harbors some distinctive genetic singularity whose conservation is a main concern, restoration by continuous stable gene flow should be considered, whenever feasible, as it reduces the extinction risk compared to repeated occasional migration and can also allow recolonization events.
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5
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Pérez-Pereira N, Pouso R, Rus A, Vilas A, López-Cortegano E, García-Dorado A, Quesada H, Caballero A. Long-term exhaustion of the inbreeding load in Drosophila melanogaster. Heredity (Edinb) 2021; 127:373-383. [PMID: 34400819 PMCID: PMC8478893 DOI: 10.1038/s41437-021-00464-3] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2020] [Revised: 07/29/2021] [Accepted: 07/29/2021] [Indexed: 02/07/2023] Open
Abstract
Inbreeding depression, the decline in fitness of inbred individuals, is a ubiquitous phenomenon of great relevance in evolutionary biology and in the fields of animal and plant breeding and conservation. Inbreeding depression is due to the expression of recessive deleterious alleles that are concealed in heterozygous state in noninbred individuals, the so-called inbreeding load. Genetic purging reduces inbreeding depression by removing these alleles when expressed in homozygosis due to inbreeding. It is generally thought that fast inbreeding (such as that generated by full-sib mating lines) removes only highly deleterious recessive alleles, while slow inbreeding can also remove mildly deleterious ones. However, a question remains regarding which proportion of the inbreeding load can be removed by purging under slow inbreeding in moderately large populations. We report results of two long-term slow inbreeding Drosophila experiments (125-234 generations), each using a large population and a number of derived lines with effective sizes about 1000 and 50, respectively. The inbreeding load was virtually exhausted after more than one hundred generations in large populations and between a few tens and over one hundred generations in the lines. This result is not expected from genetic drift alone, and is in agreement with the theoretical purging predictions. Computer simulations suggest that these results are consistent with a model of relatively few deleterious mutations of large homozygous effects and partially recessive gene action.
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Affiliation(s)
- Noelia Pérez-Pereira
- grid.6312.60000 0001 2097 6738Centro de Investigación Mariña, Universidade de Vigo, Facultade de Bioloxía, Vigo, Spain
| | - Ramón Pouso
- grid.6312.60000 0001 2097 6738Centro de Investigación Mariña, Universidade de Vigo, Facultade de Bioloxía, Vigo, Spain
| | - Ana Rus
- grid.6312.60000 0001 2097 6738Centro de Investigación Mariña, Universidade de Vigo, Facultade de Bioloxía, Vigo, Spain
| | - Ana Vilas
- grid.6312.60000 0001 2097 6738Centro de Investigación Mariña, Universidade de Vigo, Facultade de Bioloxía, Vigo, Spain
| | - Eugenio López-Cortegano
- grid.6312.60000 0001 2097 6738Centro de Investigación Mariña, Universidade de Vigo, Facultade de Bioloxía, Vigo, Spain ,grid.4305.20000 0004 1936 7988Present Address: Institute of Evolutionary Biology, School of Biological Sciences, University of Edinburgh, Edinburgh, United Kingdom
| | - Aurora García-Dorado
- grid.4795.f0000 0001 2157 7667Facultad de Ciencias Biológicas, Departamento de Genética, Universidad Complutense, Madrid, Spain
| | - Humberto Quesada
- grid.6312.60000 0001 2097 6738Centro de Investigación Mariña, Universidade de Vigo, Facultade de Bioloxía, Vigo, Spain
| | - Armando Caballero
- grid.6312.60000 0001 2097 6738Centro de Investigación Mariña, Universidade de Vigo, Facultade de Bioloxía, Vigo, Spain
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Detecting purging of inbreeding depression by a slow rate of inbreeding for various traits: the impact of environmental and experimental conditions. Heredity (Edinb) 2021; 127:10-20. [PMID: 33903740 PMCID: PMC8249611 DOI: 10.1038/s41437-021-00436-7] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2020] [Revised: 04/08/2021] [Accepted: 04/08/2021] [Indexed: 02/02/2023] Open
Abstract
Inbreeding depression (ID) has since long been recognized as a significant factor in evolutionary biology. It is mainly the consequence of (partially) recessive deleterious mutations maintained by mutation-selection balance in large random mating populations. When population size is reduced, recessive alleles are increasingly found in homozygous condition due to drift and inbreeding and become more prone to selection. Particularly at slow rates of drift and inbreeding, selection will be more effective in purging such alleles, thereby reducing the amount of ID. Here we test assumptions of the efficiency of purging in relation to the inbreeding rate and the experimental conditions for four traits in D. melanogaster. We investigated the magnitude of ID for lines that were inbred to a similar level, F ≈ 0.50, reached either by three generations of full-sib mating (fast inbreeding), or by 12 consecutive generations with a small population size (slow inbreeding). This was done on two different food media. We observed significant ID for egg-to-adult viability and heat shock mortality, but only for egg-to-adult viability a significant part of the expressed inbreeding depression was effectively purged under slow inbreeding. For other traits like developmental time and starvation resistance, however, adaptation to the experimental and environmental conditions during inbreeding might affect the likelihood of purging to occur or being detected. We discuss factors that can affect the efficiency of purging and why empirical evidence for purging may be ambiguous.
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Nelson SL, Taylor SA, Reuter JD. An isolated white-tailed deer ( Odocoileus virginianus) population on St. John, US Virgin Islands shows low inbreeding and comparable heterozygosity to other larger populations. Ecol Evol 2021; 11:2775-2781. [PMID: 33767835 PMCID: PMC7981213 DOI: 10.1002/ece3.7230] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2020] [Revised: 11/03/2020] [Accepted: 11/09/2020] [Indexed: 11/13/2022] Open
Abstract
This is the first study to document the genetic diversity of the white-tailed deer population on St. John, US Virgin Islands. The island population was founded by a small number of animals, has very limited hunting or predation, and recently experienced a reduction in size following an extended drought in 2015. DNA samples were collected from hair from 23 anesthetized adult deer (13 males, 10 females) ranging in age from 1 to 8 years (3.36 ± 1.9 years) and also from fecal DNA samples, for a total of 42 individuals analyzed for genetic diversity. The St. John deer data set averaged 4.19 alleles per marker and demonstrates the second lowest number of alleles (A) when compared to other populations of Odocoileus virginianus (4.19). Heterozygosity was similar to the other studies (0.54) with little evidence of inbreeding. To explain the level of heterozygosity and level of inbreeding within the St. John population, three hypotheses are proposed, including the effect of intrinsic biological traits within the population, a recent infusion of highly heterogeneous loci from North American populations, and a consistent level of immigration from a nearby island. Additional work is needed to further understand the genetic history of the St. John and regional deer populations.
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Affiliation(s)
- Suzanne L. Nelson
- Department of Integrative PhysiologyUniversity of Colorado BoulderBoulderCOUSA
| | - Scott A. Taylor
- Department of Ecology and Evolutionary BiologyUniversity of Colorado BoulderBoulderCOUSA
| | - Jon D. Reuter
- Office of Animal ResourcesDepartment of Psychology and NeuroscienceUniversity of Colorado BoulderBoulderCOUSA
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8
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Liu L, Bosse M, Megens H, de Visser M, A. M. Groenen M, Madsen O. Genetic consequences of long-term small effective population size in the critically endangered pygmy hog. Evol Appl 2021; 14:710-720. [PMID: 33767746 PMCID: PMC7980308 DOI: 10.1111/eva.13150] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2020] [Revised: 10/11/2020] [Accepted: 10/13/2020] [Indexed: 12/24/2022] Open
Abstract
Increasing human disturbance and climate change have a major impact on habitat integrity and size, with far-reaching consequences for wild fauna and flora. Specifically, population decline and habitat fragmentation result in small, isolated populations. To what extend different endangered species can cope with small population size is still largely unknown. Studies on the genomic landscape of these species can shed light on past demographic dynamics and current genetic load, thereby also providing guidance for conservation programs. The pygmy hog (Porcula salvania) is the smallest and rarest wild pig in the world, with current estimation of only a few hundred living in the wild. Here, we analyzed whole-genome sequencing data of six pygmy hogs, three from the wild and three from a captive population, along with 30 pigs representing six other Suidae. First, we show that the pygmy hog had a very small population size with low genetic diversity over the course of the past ~1 million years. One indication of historical small effective population size is the absence of mitochondrial variation in the six sequenced individuals. Second, we evaluated the impact of historical demography. Runs of homozygosity (ROH) analysis suggests that the pygmy hog population has gone through past but not recent inbreeding. Also, the long-term, extremely small population size may have led to the accumulation of harmful mutations suggesting that the accumulation of deleterious mutations is exceeding purifying selection in this species. Thus, care has to be taken in the conservation program to avoid or minimize the potential for further inbreeding depression, and guard against environmental changes in the future.
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Affiliation(s)
- Langqing Liu
- Animal Breeding and GenomicsWageningen University & ResearchWageningenthe Netherlands
| | - Mirte Bosse
- Animal Breeding and GenomicsWageningen University & ResearchWageningenthe Netherlands
| | - Hendrik‐Jan Megens
- Animal Breeding and GenomicsWageningen University & ResearchWageningenthe Netherlands
| | - Manon de Visser
- Animal Breeding and GenomicsWageningen University & ResearchWageningenthe Netherlands
| | - Martien A. M. Groenen
- Animal Breeding and GenomicsWageningen University & ResearchWageningenthe Netherlands
| | - Ole Madsen
- Animal Breeding and GenomicsWageningen University & ResearchWageningenthe Netherlands
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9
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Nonaka E, Sirén J, Somervuo P, Ruokolainen L, Ovaskainen O, Hanski I. Scaling up the effects of inbreeding depression from individuals to metapopulations. J Anim Ecol 2019; 88:1202-1214. [PMID: 31077598 DOI: 10.1111/1365-2656.13011] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2018] [Accepted: 03/10/2019] [Indexed: 12/01/2022]
Abstract
Inbreeding is common in nature, and many laboratory studies have documented that inbreeding depression can reduce the fitness of individuals. Demonstrating the consequences of inbreeding depression on the growth and persistence of populations is more challenging because populations are often regulated by density- or frequency-dependent selection and influenced by demographic and environmental stochasticity. A few empirical studies have shown that inbreeding depression can increase extinction risk of local populations. The importance of inbreeding depression at the metapopulation level has been conjectured based on population-level studies but has not been evaluated. We quantified the impact of inbreeding depression affecting the fitness of individuals on metapopulation persistence in heterogeneous habitat networks of different sizes and habitat configuration in a context of natural butterfly metapopulations. We developed a spatial individual-based simulation model of metapopulations with explicit genetics. We used Approximate Bayesian Computation to fit the model to extensive demographic, genetic and life-history data available for the well-studied Glanville fritillary butterfly (Melitaea cinxia) metapopulations in the Åland islands in SW Finland. We compared 18 semi-independent habitat networks differing in size and fragmentation. The results show that inbreeding is more frequent in small habitat networks, and consequently, inbreeding depression elevates extinction risks in small metapopulations. Metapopulation persistence and neutral genetic diversity maintained in the metapopulations increase with the total habitat amount in and mean patch size of habitat networks. Dispersal and mating behaviour interact with landscape structure to determine how likely it is to encounter kin while looking for mates. Inbreeding depression can decrease the viability of small metapopulations even when they are strongly influenced by stochastic extinction-colonization dynamics and density-dependent selection. The findings from this study support that genetic factors, in addition to demographic factors, can contribute to extinctions of small local populations and also of metapopulations.
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Affiliation(s)
- Etsuko Nonaka
- Department of Biosciences, Metapopulation Research Centre, University of Helsinki, Helsinki, Finland.,Department of Ecology, Environment and Plant Sciences, Stockholm University, Stockholm, Sweden
| | - Jukka Sirén
- Department of Biosciences, Metapopulation Research Centre, University of Helsinki, Helsinki, Finland
| | - Panu Somervuo
- Department of Biosciences, Metapopulation Research Centre, University of Helsinki, Helsinki, Finland.,Organismal and Evolutionary Biology Research Programme, University of Helsinki, Helsinki, Finland
| | - Lasse Ruokolainen
- Department of Biosciences, Metapopulation Research Centre, University of Helsinki, Helsinki, Finland.,Organismal and Evolutionary Biology Research Programme, University of Helsinki, Helsinki, Finland
| | - Otso Ovaskainen
- Department of Biosciences, Metapopulation Research Centre, University of Helsinki, Helsinki, Finland.,Organismal and Evolutionary Biology Research Programme, University of Helsinki, Helsinki, Finland.,Department of Biology, Centre for Biodiversity Dynamics, Norwegian University of Science and Technology, Trondheim, Norway
| | - Ilkka Hanski
- Department of Biosciences, Metapopulation Research Centre, University of Helsinki, Helsinki, Finland
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10
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Prokop ZM, Hlebowicz K, Gaczorek TS, Antoł WM, Martin OY, Gage MJG, Michalczyk Ł. No evidence for short‐term purging benefits of sexual selection in inbred red flour beetle populations. J Zool (1987) 2018. [DOI: 10.1111/jzo.12633] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Z. M. Prokop
- Institute of Environmental Sciences Jagiellonian University Kraków Poland
| | - K. Hlebowicz
- Institute of Environmental Sciences Jagiellonian University Kraków Poland
- Institute of Zoology and Biomedical Research Jagiellonian University Kraków Poland
| | - T. S. Gaczorek
- Institute of Environmental Sciences Jagiellonian University Kraków Poland
| | - W. M. Antoł
- Institute of Environmental Sciences Jagiellonian University Kraków Poland
| | - O. Y. Martin
- Department of Biology IBZ Institute of Integrative Biology ETH Zürich Zürich Switzerland
| | - M. J. G. Gage
- School of Biological Sciences Norwich Research Park University of East Anglia Norwich UK
| | - Ł. Michalczyk
- Institute of Zoology and Biomedical Research Jagiellonian University Kraków Poland
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11
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Hollenbeck CM, Johnston IA. Genomic Tools and Selective Breeding in Molluscs. Front Genet 2018; 9:253. [PMID: 30073016 PMCID: PMC6058216 DOI: 10.3389/fgene.2018.00253] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2017] [Accepted: 06/25/2018] [Indexed: 11/13/2022] Open
Abstract
The production of most farmed molluscs, including mussels, oysters, scallops, abalone, and clams, is heavily dependent on natural seed from the plankton. Closing the lifecycle of species in hatcheries can secure independence from wild stocks and enables long-term genetic improvement of broodstock through selective breeding. Genomic techniques have the potential to revolutionize hatchery-based selective breeding by improving our understanding of the characteristics of mollusc genetics that can pose a challenge for intensive aquaculture and by providing a new suite of tools for genetic improvement. Here we review characteristics of the life history and genetics of molluscs including high fecundity, self-fertilization, high genetic diversity, genetic load, high incidence of deleterious mutations and segregation distortion, and critically assess their impact on the design and effectiveness of selective breeding strategies. A survey of the results of current breeding programs in the literature show that selective breeding with inbreeding control is likely the best strategy for genetic improvement of most molluscs, and on average growth rate can be improved by 10% per generation and disease resistance by 15% per generation across the major farmed species by implementing individual or family-based selection. Rapid advances in sequencing technology have resulted in a wealth of genomic resources for key species with the potential to greatly improve hatchery-based selective breeding of molluscs. In this review, we catalog the range of genomic resources currently available for molluscs of aquaculture interest and discuss the bottlenecks, including lack of high-quality reference genomes and the relatively high cost of genotyping, as well as opportunities for applying genomics-based selection.
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Affiliation(s)
- Christopher M Hollenbeck
- School of Biology, Scottish Oceans Institute, University of St Andrews, St Andrews, United Kingdom
| | - Ian A Johnston
- School of Biology, Scottish Oceans Institute, University of St Andrews, St Andrews, United Kingdom.,Xelect Ltd, St Andrews, United Kingdom
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12
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Constandinou S, Nikoloudakis N, Kyratzis AC, Katsiotis A. Genetic diversity of Avena ventricosa populations along an ecogeographical transect in Cyprus is correlated to environmental variables. PLoS One 2018. [PMID: 29529086 PMCID: PMC5846772 DOI: 10.1371/journal.pone.0193885] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Avena ventricosa Balansa ex Coss. is considered the C-genome donor of the cultivated hexaploid oat and is a ‘priority’ species for conservation, since it has limited geographic distribution and the only recorded populations in Europe are present in Cyprus. The current study attempts to characterize the genetic structure and fragmentation of the species via the application of genotypic markers. It was revealed that the genetic variety was mainly allocated among the populations collected, since clustering obtained was according to the geographic origin of the samples and the habitat. Species distribution modeling showed that the most important climatic variable defining A. ventricosa distribution is the mean diurnal temperature. Furthermore, significant association of the genetic structure to environmental variables was detected; overall, a negative association to precipitation was confirmed, while significant correlations of genetic structure and the temperature at the time of anthesis and germination were established. The safeguarding of this valuable genetic resource is discussed.
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Affiliation(s)
- Stella Constandinou
- Department of Agricultural Science, Biotechnology and Food Science, Cyprus University of Technology, Athinon and Anexartisias 57, Limassol, Cyprus
| | - Nikolaos Nikoloudakis
- Department of Agricultural Science, Biotechnology and Food Science, Cyprus University of Technology, Athinon and Anexartisias 57, Limassol, Cyprus
| | - Angelos C. Kyratzis
- Department of Agricultural Science, Biotechnology and Food Science, Cyprus University of Technology, Athinon and Anexartisias 57, Limassol, Cyprus
- Department of Vegetable Crops, Agricultural Research Institute, Nicosia, Cyprus, Nicosia, Cyprus
| | - Andreas Katsiotis
- Department of Agricultural Science, Biotechnology and Food Science, Cyprus University of Technology, Athinon and Anexartisias 57, Limassol, Cyprus
- * E-mail:
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13
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Voillemot M, Rougemont Q, Roux C, Pannell JR. The divergence history of the perennial plant Linaria cavanillesii
confirms a recent loss of self-incompatibility. J Evol Biol 2017; 31:136-147. [DOI: 10.1111/jeb.13209] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2017] [Revised: 11/03/2017] [Accepted: 11/07/2017] [Indexed: 11/30/2022]
Affiliation(s)
- M. Voillemot
- Department of Ecology and Evolution; Biophore/Sorge; University of Lausanne; Lausanne Switzerland
| | - Q. Rougemont
- Institut de Biologie Intégrative et des Systèmes (IBIS); University of Laval; Québec City Québec Canada
| | - C. Roux
- Department of Ecology and Evolution; Biophore/Sorge; University of Lausanne; Lausanne Switzerland
- Unité Evo-Eco-Paléo (EEP) - UMR 8198; CNRS; Université de Lille Sciences et Technologies; Villeneuve d'Ascq Cedex France
| | - J. R. Pannell
- Department of Ecology and Evolution; Biophore/Sorge; University of Lausanne; Lausanne Switzerland
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14
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Anderson C, Cunha L, Sechi P, Kille P, Spurgeon D. Genetic variation in populations of the earthworm, Lumbricus rubellus, across contaminated mine sites. BMC Genet 2017; 18:97. [PMID: 29149838 PMCID: PMC5693503 DOI: 10.1186/s12863-017-0557-8] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2017] [Accepted: 10/03/2017] [Indexed: 12/21/2022] Open
Abstract
BACKGROUND Populations of the earthworm, Lumbricus rubellus, are commonly found across highly contaminated former mine sites and are considered to have under-gone selection for mitigating metal toxicity. Comparison of adapted populations with those found on less contaminated soils can provide insights into ecological processes that demonstrate the long-term effects of soil contamination. Contemporary sequencing methods allow for portrayal of demographic inferences and highlight genetic variation indicative of selection at specific genes. Furthermore, the occurrence of L. rubellus lineages across the UK allows for inferences of mechanisms associated with drivers of speciation and local adaptation. RESULTS Using RADseq, we were able to define population structure between the two lineages through the use of draft genomes for each, demonstrating an absence of admixture between lineages and that populations over extensive geographic distances form discrete populations. Between the two British lineages, we were able to provide evidence for selection near to genes associated with epigenetic and morphological functions, as well as near a gene encoding a pheromone. Earthworms inhabiting highly contaminated soils bare close genomic resemblance to those from proximal control soils. We were able to define a number of SNPs that largely segregate populations and are indicative of genes that are likely under selection for managing metal toxicity. This includes calcium and phosphate-handling mechanisms linked to lead and arsenic contaminants, respectively, while we also observed evidence for glutathione-related mechanisms, including metallothionein, across multiple populations. Population genomic end points demonstrate no consistent reduction in nucleotide diversity, or increase in inbreeding coefficient, relative to history of exposure. CONCLUSIONS Though we can clearly define lineage membership using genomic markers, as well as population structure between geographic localities, it is difficult to resolve markers that segregate entirely between populations in response to soil metal concentrations. This may represent a highly variable series of traits in response to the heterogenous nature of the soil environment, but ultimately demonstrates the maintenance of lineage-specific genetic variation among local populations. L. rubellus appears to provide an exemplary system for exploring drivers for speciation, with a continuum of lineages coexisting across continental Europe, while distinct lineages exist in isolation throughout the UK.
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Affiliation(s)
- Craig Anderson
- Biological and Environmental Sciences, School of Natural Sciences, University of Stirling, Stirling, FK9 4LA UK
- Centre for Ecology and Hydrology, Maclean Building, Benson Lane, Wallingford, OX10 8BB UK
- School of Biosciences, University of Cardiff, Main Building, Museum Avenue, Cardiff, CF10 3AT UK
| | - Luis Cunha
- School of Biosciences, University of Cardiff, Main Building, Museum Avenue, Cardiff, CF10 3AT UK
- Embrapa Florestas, Estrada da Ribeira km. 111, Colombo, PR 83411-000 Brazil
| | - Pierfrancesco Sechi
- School of Biosciences, University of Cardiff, Main Building, Museum Avenue, Cardiff, CF10 3AT UK
| | - Peter Kille
- School of Biosciences, University of Cardiff, Main Building, Museum Avenue, Cardiff, CF10 3AT UK
| | - David Spurgeon
- Centre for Ecology and Hydrology, Maclean Building, Benson Lane, Wallingford, OX10 8BB UK
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15
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Male Infertility Is Responsible for Nearly Half of the Extinction Observed in the Mouse Collaborative Cross. Genetics 2017; 206:557-572. [PMID: 28592496 DOI: 10.1534/genetics.116.199596] [Citation(s) in RCA: 50] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2017] [Accepted: 03/09/2017] [Indexed: 11/18/2022] Open
Abstract
The goal of the Collaborative Cross (CC) project was to generate and distribute over 1000 independent mouse recombinant inbred strains derived from eight inbred founders. With inbreeding nearly complete, we estimated the extinction rate among CC lines at a remarkable 95%, which is substantially higher than in the derivation of other mouse recombinant inbred populations. Here, we report genome-wide allele frequencies in 347 extinct CC lines. Contrary to expectations, autosomes had equal allelic contributions from the eight founders, but chromosome X had significantly lower allelic contributions from the two inbred founders with underrepresented subspecific origins (PWK/PhJ and CAST/EiJ). By comparing extinct CC lines to living CC strains, we conclude that a complex genetic architecture is driving extinction, and selection pressures are different on the autosomes and chromosome X Male infertility played a large role in extinction as 47% of extinct lines had males that were infertile. Males from extinct lines had high variability in reproductive organ size, low sperm counts, low sperm motility, and a high rate of vacuolization of seminiferous tubules. We performed QTL mapping and identified nine genomic regions associated with male fertility and reproductive phenotypes. Many of the allelic effects in the QTL were driven by the two founders with underrepresented subspecific origins, including a QTL on chromosome X for infertility that was driven by the PWK/PhJ haplotype. We also performed the first example of cross validation using complementary CC resources to verify the effect of sperm curvilinear velocity from the PWK/PhJ haplotype on chromosome 2 in an independent population across multiple generations. While selection typically constrains the examination of reproductive traits toward the more fertile alleles, the CC extinct lines provided a unique opportunity to study the genetic architecture of fertility in a widely genetically variable population. We hypothesize that incompatibilities between alleles with different subspecific origins is a key driver of infertility. These results help clarify the factors that drove strain extinction in the CC, reveal the genetic regions associated with poor fertility in the CC, and serve as a resource to further study mammalian infertility.
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16
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Hedrick PW, Garcia-Dorado A. Understanding Inbreeding Depression, Purging, and Genetic Rescue. Trends Ecol Evol 2016; 31:940-952. [DOI: 10.1016/j.tree.2016.09.005] [Citation(s) in RCA: 196] [Impact Index Per Article: 24.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2016] [Revised: 09/13/2016] [Accepted: 09/14/2016] [Indexed: 01/17/2023]
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17
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López-Cortegano E, Vilas A, Caballero A, García-Dorado A. Estimation of genetic purging under competitive conditions. Evolution 2016; 70:1856-70. [PMID: 27302839 DOI: 10.1111/evo.12983] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2015] [Revised: 05/26/2016] [Accepted: 06/01/2016] [Indexed: 11/27/2022]
Abstract
Inbreeding depression for fitness traits is a key issue in evolutionary biology and conservation genetics. The magnitude of inbreeding depression, though, may critically depend on the efficiency of genetic purging, the elimination or recessive deleterious mutations by natural selection after they are exposed by inbreeding. However, the detection and quantification of genetic purging for nonlethal mutations is a rather difficult task. Here, we present two comprehensive sets of experiments with Drosophila aimed at detecting genetic purging in competitive conditions and quantifying its magnitude. We obtain, for the first time in competitive conditions, an estimate for the predictive parameter, the purging coefficient (d), that quantifies the magnitude of genetic purging, either against overall inbreeding depression (d ≈ 0.3), or against the component ascribed to nonlethal alleles (dNL ≈ 0.2). We find that competitive fitness declines at a high rate when inbreeding increases in the absence of purging. However, in moderate size populations under competitive conditions, inbreeding depression need not be too dramatic in the medium to short term, as the efficiency of purging is also very high. Furthermore, we find that purging occurred under competitive conditions also reduced the inbreeding depression that is expressed in the absence of competition.
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Affiliation(s)
- Eugenio López-Cortegano
- Departamento de Genética, Facultad de Biología, Universidad Complutense, 28040, Madrid, España
| | - Ana Vilas
- Departamento de Bioquímica, Genética e Inmunología, Facultad de Biología, Universidad de Vigo, 36310, Vigo (Pontevedra), España
| | - Armando Caballero
- Departamento de Bioquímica, Genética e Inmunología, Facultad de Biología, Universidad de Vigo, 36310, Vigo (Pontevedra), España
| | - Aurora García-Dorado
- Departamento de Genética, Facultad de Biología, Universidad Complutense, 28040, Madrid, España.
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18
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Effect of spatial constraints on Hardy-Weinberg equilibrium. Sci Rep 2016; 6:19297. [PMID: 26771073 PMCID: PMC4725899 DOI: 10.1038/srep19297] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2015] [Accepted: 12/07/2015] [Indexed: 11/18/2022] Open
Abstract
Panmixia is a key issue in maintaining genetic diversity, which facilitates evolutionary potential during environmental changes. Additionally, conservation biologists suggest the importance of avoiding small or subdivided populations, which are prone to losing genetic diversity. In this paper, computer simulations were performed to the genetic drift of neutral alleles in random mating populations with or without spatial constraints by randomly choosing a mate among the closest neighbours. The results demonstrated that the number of generations required for the neutral allele to become homozygous (Th) varied proportionally to the population size and also strongly correlated with spatial constraints. The average Th for populations of the same size with spatial constraints was approximately one-and-a-half times longer than without constraints. With spatial constraints, homozygous population clusters formed, which reduced local diversity but preserved global diversity. Therefore, panmixia might be harmful in preserving the genetic diversity of an entire population. The results also suggested that the gene flow or gene exchange among the subdivided populations must be carefully processed to restrict diseases transmission or death during transportation and to monitor the genetic diversity. The application of this concept to similar systems, such as information transfer among peers, is also discussed.
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19
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Moreno E, Pérez-González J, Carranza J, Moya-Laraño J. Better Fitness in Captive Cuvier's Gazelle despite Inbreeding Increase: Evidence of Purging? PLoS One 2015; 10:e0145111. [PMID: 26679703 PMCID: PMC4682998 DOI: 10.1371/journal.pone.0145111] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2015] [Accepted: 11/27/2015] [Indexed: 11/19/2022] Open
Abstract
Captive breeding of endangered species often aims at preserving genetic diversity and to avoid the harmful effects of inbreeding. However, deleterious alleles causing inbreeding depression can be purged when inbreeding persists over several generations. Despite its great importance both for evolutionary biology and for captive breeding programmes, few studies have addressed whether and to which extent purging may occur. Here we undertake a longitudinal study with the largest captive population of Cuvier's gazelle managed under a European Endangered Species Programme since 1975. Previous results in this population have shown that highly inbred mothers tend to produce more daughters, and this fact was used in 2006 to reach a more appropriate sex-ratio in this polygynous species by changing the pairing strategy (i.e., pairing some inbred females instead of keeping them as surplus individuals in the population). Here, by using studbook data we explore whether purging has occurred in the population by investigating whether after the change in pairing strategy a) inbreeding and homozygosity increased at the population level, b) fitness (survival) increased, and c) the relationship between inbreeding and juvenile survival, was positive. Consistent with the existence of purging, we found an increase in inbreeding coefficients, homozygosity and juvenile survival. In addition, we showed that in the course of the breeding programme the relationship between inbreeding and juvenile survival was not uniform but rather changed over time: it was negative in the early years, flat in the middle years and positive after the change in pairing strategy. We highlight that by allowing inbred individuals to mate in captive stocks we may favour sex-ratio bias towards females, a desirable managing strategy to reduce the surplus of males that force most zoos to use ethical culling and euthanizing management tools. We discuss these possibilities but also acknowledge that many other effects should be considered before implementing inbreeding and purging as elements in management decisions.
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Affiliation(s)
- Eulalia Moreno
- Estación Experimental de Zonas Áridas (CSIC), Dept. Ecología Funcional y Evolutiva, Ctra. de Sacramento s/n, E-04120, La Cañada de San Urbano, Almería, Spain
- * E-mail:
| | - Javier Pérez-González
- Ungulate Research Unit, Cátedra de Recursos Cinegéticos y Piscícolas, Universidad de Córdoba, E-14071, Córdoba, Spain
- Guardería Rural, Mancomunidad Integral de Municipios Centro, E-06810, Calamonte, Badajoz, Spain
| | - Juan Carranza
- Ungulate Research Unit, Cátedra de Recursos Cinegéticos y Piscícolas, Universidad de Córdoba, E-14071, Córdoba, Spain
| | - Jordi Moya-Laraño
- Estación Experimental de Zonas Áridas (CSIC), Dept. Ecología Funcional y Evolutiva, Ctra. de Sacramento s/n, E-04120, La Cañada de San Urbano, Almería, Spain
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20
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Ala-Honkola O, Laine L, Pekkala N, Kotiaho JS, Honkola T, Puurtinen M. Males Benefit from Mating with Outbred Females inDrosophila littoralis: Male Choice for Female Genetic Quality? Ethology 2015. [DOI: 10.1111/eth.12369] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Outi Ala-Honkola
- University of Jyvaskyla; Department of Biological and Environmental Science; P.O. Box 35 FI-40014 University of Jyvaskyla Finland
| | - Lily Laine
- University of Jyvaskyla; Department of Biological and Environmental Science; P.O. Box 35 FI-40014 University of Jyvaskyla Finland
| | - Nina Pekkala
- University of Jyvaskyla; Department of Biological and Environmental Science; P.O. Box 35 FI-40014 University of Jyvaskyla Finland
| | - Janne S. Kotiaho
- University of Jyvaskyla; Department of Biological and Environmental Science; P.O. Box 35 FI-40014 University of Jyvaskyla Finland
| | - Terhi Honkola
- Department of Biology; University of Turku; Turku Finland
| | - Mikael Puurtinen
- University of Jyvaskyla; Department of Biological and Environmental Science; P.O. Box 35 FI-40014 University of Jyvaskyla Finland
- University of Jyvaskyla; Centre of Excellence in Biological Interactions; P.O. Box 35 FI-40014 University of Jyvaskyla Finland
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21
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Plant-species diversity correlates with genetic variation of an oligophagous seed predator. PLoS One 2014; 9:e94105. [PMID: 24728342 PMCID: PMC3984091 DOI: 10.1371/journal.pone.0094105] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2013] [Accepted: 03/11/2014] [Indexed: 11/29/2022] Open
Abstract
Several characteristics of habitats of herbivores and their food-plant communities, such as plant-species composition and plant quality, influence population genetics of both herbivores and their host plants. We investigated how different ecological and geographic factors affect genetic variation in and differentiation of 23 populations of the oligophagous seed predator Lygaeus equestris (Heteroptera) in southwestern Finland and in eastern Sweden. We tested whether genetic differentiation of the L. equestris populations was related to the similarity of vegetation, and whether there was more within-population genetic variation in habitats with a high number of plant species or in those with a large population of the primary food plant, Vincetoxicum hirundinaria. We also tested whether genetic differentiation of the populations was related to the geographic distance, and whether location of the populations on islands or on mainland, island size, or population size affected within-population genetic variation. Pairwise FST ranged from 0 to 0.1 indicating low to moderate genetic differentiation of populations. Differentiation increased with geographic distance between the populations, but was not related to the similarity of vegetation between the habitats. Genetic variation within the L. equestris populations did not increase with the population size of the primary food plant. However, the more diverse the plant community the higher was the level of genetic variation within the L. equestris population. Furthermore, the level of genetic variation did not vary significantly between island and mainland populations. The effect of the population size on within-population genetic variation was related to island size. Usually small populations are susceptible to loss of genetic variation, but small L. equestris populations on large islands seemed to maintain a relatively high level of within-population genetic variation. Our findings suggest that, in addition to geographic and species-specific ecological factors, the plant community affects population genetic structure of oligophagous herbivores.
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22
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Pekkala N, Knott KE, Kotiaho JS, Nissinen K, Puurtinen M. The effect of inbreeding rate on fitness, inbreeding depression and heterosis over a range of inbreeding coefficients. Evol Appl 2014; 7:1107-19. [PMID: 25553071 PMCID: PMC4231599 DOI: 10.1111/eva.12145] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2013] [Accepted: 12/20/2013] [Indexed: 11/28/2022] Open
Abstract
Understanding the effects of inbreeding and genetic drift within populations and hybridization between genetically differentiated populations is important for many basic and applied questions in ecology and evolutionary biology. The magnitudes and even the directions of these effects can be influenced by various factors, especially by the current and historical population size (i.e. inbreeding rate). Using Drosophila littoralis as a model species, we studied the effect of inbreeding rate over a range of inbreeding levels on (i) mean fitness of a population (relative to that of an outbred control population), (ii) within-population inbreeding depression (reduction in fitness of offspring from inbred versus random mating within a population) and (iii) heterosis (increase in fitness of offspring from interpopulation versus within-population random mating). Inbreeding rate was manipulated by using three population sizes (2, 10 and 40), and fitness was measured as offspring survival and fecundity. Fast inbreeding (smaller effective population size) resulted in greater reduction in population mean fitness than slow inbreeding, when populations were compared over similar inbreeding coefficients. Correspondingly, populations with faster inbreeding expressed more heterosis upon interpopulation hybridization. Inbreeding depression within the populations did not have a clear relationship with either the rate or the level of inbreeding.
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Affiliation(s)
- Nina Pekkala
- Department of Biological and Environmental Science, University of Jyväskylä Jyväskylä, Finland
| | - K Emily Knott
- Department of Biological and Environmental Science, University of Jyväskylä Jyväskylä, Finland
| | - Janne S Kotiaho
- Department of Biological and Environmental Science, University of Jyväskylä Jyväskylä, Finland ; Natural History Museum, University of Jyväskylä Jyväskylä, Finland
| | - Kari Nissinen
- Finnish Institute for Educational Research, University of Jyväskylä Jyväskylä, Finland
| | - Mikael Puurtinen
- Department of Biological and Environmental Science, University of Jyväskylä Jyväskylä, Finland ; Centre of Excellence in Biological Interactions, University of Jyväskylä Jyväskylä, Finland
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23
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Kennedy ES, Grueber CE, Duncan RP, Jamieson IG. SEVERE INBREEDING DEPRESSION AND NO EVIDENCE OF PURGING IN AN EXTREMELY INBRED WILD SPECIES-THE CHATHAM ISLAND BLACK ROBIN. Evolution 2013; 68:987-95. [DOI: 10.1111/evo.12315] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2013] [Accepted: 11/01/2013] [Indexed: 11/27/2022]
Affiliation(s)
- Euan S. Kennedy
- Science and Capability; Department of Conservation; PO Box 4715 Christchurch 8140 New Zealand
| | - Catherine E. Grueber
- Department of Zoology and Allan Wilson Centre for Molecular Ecology and Evolution; University of Otago; PO Box 56 Dunedin New Zealand
| | - Richard P. Duncan
- Institute for Applied Ecology; University of Canberra; ACT 2601 Australia
| | - Ian G. Jamieson
- Department of Zoology and Allan Wilson Centre for Molecular Ecology and Evolution; University of Otago; PO Box 56 Dunedin New Zealand
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24
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Haanes H, Markussen SS, Herfindal I, Røed KH, Solberg EJ, Heim M, Midthjell L, Sæther BE. Effects of inbreeding on fitness-related traits in a small isolated moose population. Ecol Evol 2013; 3:4230-42. [PMID: 24324873 PMCID: PMC3853567 DOI: 10.1002/ece3.819] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2013] [Revised: 08/26/2013] [Accepted: 08/29/2013] [Indexed: 11/18/2022] Open
Abstract
Inbreeding can affect fitness-related traits at different life history stages and may interact with environmental variation to induce even larger effects. We used genetic parentage assignment based on 22 microsatellite loci to determine a 25 year long pedigree for a newly established island population of moose with 20–40 reproducing individuals annually. We used the pedigree to calculate individual inbreeding coefficients and examined for effects of individual inbreeding (f) and heterozygosity on fitness-related traits. We found negative effects of f on birth date, calf body mass and twinning rate. The relationship between f and calf body mass and twinning rate were found to be separate but weaker after accounting for birth date. We found no support for an inbreeding effect on the age-specific lifetime reproductive success of females. The influence of f on birth date was related to climatic conditions during the spring prior to birth, indicating that calves with a low f were born earlier after a cold spring than calves with high f. In years with a warm spring, calf f did not affect birth date. The results suggest that severe inbreeding in moose has both indirect effects on fitness through delayed birth and lower juvenile body mass, as well as separate direct effects, as there still was a significant relationship between f and twinning rate after accounting for birth date and body mass as calf. Consequently, severe inbreeding as found in the study population may have consequences for population growth and extinction risk.
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Affiliation(s)
- Hallvard Haanes
- Centre for Biodiversity Dynamics, Department of Biology, Norwegian University of Science and Technology Trondheim, N-7491, Norway ; Departments of Basic Sciences and Aquatic Medicine, Norwegian School of Veterinary Science PO-8146 Dep, Oslo, N-0033, Norway
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25
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Bersabé D, García-Dorado A. On the genetic parameter determining the efficiency of purging: an estimate for Drosophila egg-to-pupae viability. J Evol Biol 2012. [PMID: 23199278 DOI: 10.1111/jeb.12054] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The consequences of inbreeding on fitness can be crucial in evolutionary and conservation grounds and depend upon the efficiency of purging against deleterious recessive alleles. Recently, analytical expressions have been derived to predict the evolution of mean fitness, taking into account both inbreeding and purging, which depend on an 'effective purging coefficient (d(e) )'. Here, we explore the validity of that predictive approach and assay the strength of purging by estimating d(e) for egg-to-pupae viability (EPV) after a drastic reduction in population size in a recently captured base population of Drosophila melanogaster. For this purpose, we first obtained estimates of the inbreeding depression rate (δ) for EPV in the base population, and we found that about 40% was due to segregating recessive lethals. Then, two sets of lines were founded from this base population and were maintained with different effective size throughout the rest of the experiment (N = 6; N = 12), their mean EPV being assayed at different generations. Due to purging, the reductions in mean EPV experienced by these lines were considerably smaller than the corresponding neutral predictions. For the 60% of δ attributable to nonlethal deleterious alleles, our results suggest an effective purging coefficient d(e) > 0.02. Similarly, we obtain that d(e) > 0.09 is required to roughly account for purging against the pooled inbreeding depression from lethal and nonlethal deleterious alleles. This implies that purging should be efficient for population sizes of the order of a few tens and larger, but might be inefficient against nonlethal deleterious alleles in smaller populations.
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Affiliation(s)
- D Bersabé
- Departamento de Genética, Facultad de Biología, Universidad Complutense, Madrid, Spain
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26
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Pekkala N, Knott KE, Kotiaho JS, Nissinen K, Puurtinen M. The benefits of interpopulation hybridization diminish with increasing divergence of small populations. J Evol Biol 2012; 25:2181-3. [PMID: 22947037 DOI: 10.1111/j.1420-9101.2012.02594.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2012] [Revised: 07/04/2012] [Accepted: 07/09/2012] [Indexed: 01/22/2023]
Abstract
Interpopulation hybridization can increase the viability of small populations suffering from inbreeding and genetic drift, but it can also result in outbreeding depression. The outcome of hybridization can depend on various factors, including the level of genetic divergence between the populations, and the number of source populations. Furthermore, the effects of hybridization can change between generations following the hybridization. We studied the effects of population divergence (low vs. high level of divergence) and the number of source populations (two vs. four source populations) on the viability of hybrid populations using experimental Drosophila littoralis populations. Population viability was measured for seven generations after hybridization as proportion of populations facing extinction and as per capita offspring production. Hybrid populations established at the low level of population divergence were more viable than the inbred source populations and had higher offspring production than the large control population. The positive effects of hybridization lasted for the seven generations. In contrast, at the high level of divergence, the viability of the hybrid populations was not significantly different from the inbred source populations, and offspring production in the hybrid populations was lower than in the large control population. The number of source populations did not have a significant effect at either low or high level of population divergence. The study shows that the benefits of interpopulation hybridization may decrease with increasing divergence of the populations, even when the populations share identical environmental conditions. We discuss the possible genetic mechanisms explaining the results and address the implications for conservation of populations.
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Affiliation(s)
- Nina Pekkala
- Department of Biological and Environmental Science, University of Jyväskylä, Jyväskylä, Finland.
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