1
|
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.
Collapse
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
| |
Collapse
|
2
|
Sagonas K, Runemark A, Antoniou A, Lymberakis P, Pafilis P, Valakos ED, Poulakakis N, Hansson B. Selection, drift, and introgression shape MHC polymorphism in lizards. Heredity (Edinb) 2019; 122:468-484. [PMID: 30258107 PMCID: PMC6460769 DOI: 10.1038/s41437-018-0146-2] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2018] [Revised: 07/27/2018] [Accepted: 08/09/2018] [Indexed: 01/12/2023] Open
Abstract
The major histocompatibility complex (MHC) has long served as a model for the evolution of adaptive genetic diversity in wild populations. Pathogen-mediated selection is thought to be a main driver of MHC diversity, but it remains elusive to what degree selection shapes MHC diversity in complex biogeographical scenarios where other evolutionary processes (e.g. genetic drift and introgression) may also be acting. Here we focus on two closely related green lizard species, Lacerta trilineata and L. viridis, to address the evolutionary forces acting on MHC diversity in populations with different biogeographic structure. We characterized MHC class I exon 2 and exon 3, and neutral diversity (microsatellites), to study the relative importance of selection, drift, and introgression in shaping MHC diversity. As expected, positive selection was a significant force shaping the high diversity of MHC genes in both species. Moreover, introgression significantly increased MHC diversity in mainland populations, with a primary direction of gene flow from L. viridis to L. trilineata. Finally, we found significantly fewer MHC alleles in island populations, but maintained MHC sequence and functional diversity, suggesting that positive selection counteracted the effect of drift. Overall, our data support that different evolutionary processes govern MHC diversity in different biogeographical scenarios: positive selection occurs broadly while introgression acts in sympatry and drift when the population sizes decrease.
Collapse
Affiliation(s)
- K Sagonas
- School of Biological and Chemical Sciences, Queen Mary University of London, London, E1 4NS, UK.
- Department of Human and Animal Physiology, Faculty of Biology, National and Kapodistrian University of Athens, Panepistimioupoli Zografou, 15784, Athens, Greece.
| | - A Runemark
- Department of Biology, Lund University, Ecology Building, SE-223 62, Lund, Sweden
- Centre for Ecological and Evolutionary Synthesis (CEES), Department of Biosciences, University of Oslo, Oslo, Norway
| | - A Antoniou
- Institute of Marine Biology, Biotechnology and Aquaculture, Hellenic Centre for Marine Research, Gournes Pediados, 71003, Heraklion, Crete, Greece
| | - P Lymberakis
- Natural History Museum of Crete, School of Sciences and Engineering, University of Crete, 71409, Heraklion, Crete, Greece
| | - P Pafilis
- Department of Zoology and Marine Biology, Faculty of Biology, National and Kapodistrian University of Athens, Panepistimioupoli Zografou, 15784, Athens, Greece
| | - E D Valakos
- Department of Human and Animal Physiology, Faculty of Biology, National and Kapodistrian University of Athens, Panepistimioupoli Zografou, 15784, Athens, Greece
| | - N Poulakakis
- Natural History Museum of Crete, School of Sciences and Engineering, University of Crete, 71409, Heraklion, Crete, Greece
- Department of Biology, School of Sciences and Engineering, University of Crete, Vasilika Vouton, 71003, Heraklion, Crete, Greece
| | - B Hansson
- Department of Biology, Lund University, Ecology Building, SE-223 62, Lund, Sweden
| |
Collapse
|
3
|
Runemark A, Sagonas K, Svensson EI. Ecological explanations to island gigantism: dietary niche divergence, predation, and size in an endemic lizard. Ecology 2015; 96:2077-92. [DOI: 10.1890/14-1996.1] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
|
4
|
Runemark A, Brydegaard M, Svensson EI. Does relaxed predation drive phenotypic divergence among insular populations? J Evol Biol 2014; 27:1676-90. [PMID: 24890841 DOI: 10.1111/jeb.12421] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2013] [Revised: 04/21/2014] [Accepted: 04/28/2014] [Indexed: 11/28/2022]
Abstract
The evolution of striking phenotypes on islands is a well-known phenomenon, and there has been a long-standing debate on the patterns of body size evolution on islands. The ecological causes driving divergence in insular populations are, however, poorly understood. Reduced predator fauna is expected to lower escape propensity, increase body size and relax selection for crypsis in small-bodied, insular prey species. Here, we investigated whether escape behaviour, body size and dorsal coloration have diverged as predicted under predation release in spatially replicated islet and mainland populations of the lizard species Podarcis gaigeae. We show that islet lizards escape approaching observers at shorter distances and are larger than mainland lizards. Additionally, we found evidence for larger between-population variation in body size among the islet populations than mainland populations. Moreover, islet populations are significantly more divergent in dorsal coloration and match their respective habitats poorer than mainland lizards. These results strongly suggest that predation release on islets has driven population divergence in phenotypic and behavioural traits and that selective release has affected both trait means and variances. Relaxed predation pressure is therefore likely to be one of the major ecological factors driving body size divergence on these islands.
Collapse
Affiliation(s)
- A Runemark
- Evolutionary Ecology Unit, Department of Biology, Lund University, Lund, Sweden
| | | | | |
Collapse
|