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Veltsos P, Kelly JK. The quantitative genetics of gene expression in Mimulus guttatus. PLoS Genet 2024; 20:e1011072. [PMID: 38603726 PMCID: PMC11060551 DOI: 10.1371/journal.pgen.1011072] [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] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2023] [Revised: 04/30/2024] [Accepted: 03/23/2024] [Indexed: 04/13/2024] Open
Abstract
Gene expression can be influenced by genetic variants that are closely linked to the expressed gene (cis eQTLs) and variants in other parts of the genome (trans eQTLs). We created a multiparental mapping population by sampling genotypes from a single natural population of Mimulus guttatus and scored gene expression in the leaves of 1,588 plants. We find that nearly every measured gene exhibits cis regulatory variation (91% have FDR < 0.05). cis eQTLs are usually allelic series with three or more functionally distinct alleles. The cis locus explains about two thirds of the standing genetic variance (on average) but varies among genes and tends to be greatest when there is high indel variation in the upstream regulatory region and high nucleotide diversity in the coding sequence. Despite mapping over 10,000 trans eQTL / affected gene pairs, most of the genetic variance generated by trans acting loci remains unexplained. This implies a large reservoir of trans acting genes with subtle or diffuse effects. Mapped trans eQTLs show lower allelic diversity but much higher genetic dominance than cis eQTLs. Several analyses also indicate that trans eQTLs make a substantial contribution to the genetic correlations in expression among different genes. They may thus be essential determinants of "gene expression modules," which has important implications for the evolution of gene expression and how it is studied by geneticists.
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Affiliation(s)
- Paris Veltsos
- Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, Kansas, United States of America
| | - John K. Kelly
- Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, Kansas, United States of America
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Kelly JK. Rapid adaptation of Viola arvensis to pollinator declines. New Phytol 2024; 242:331-332. [PMID: 38258430 DOI: 10.1111/nph.19547] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/24/2024]
Abstract
This article is a Commentary on Acoca‐Pidolle et al. (2023), 242: 717–726.
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Affiliation(s)
- John K Kelly
- The University of Kansas, 1200 Sunnyside Avenue, Lawrence, KS, 66045, USA
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3
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Veltsos P, Kelly JK. The quantitative genetics of gene expression in Mimulus guttatus. bioRxiv 2023:2023.11.21.568003. [PMID: 38045261 PMCID: PMC10690227 DOI: 10.1101/2023.11.21.568003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/05/2023]
Abstract
Gene expression can be influenced by genetic variants that are closely linked to the expressed gene (cis eQTLs) and variants in other parts of the genome (trans eQTLs). We created a multiparental mapping population by sampling genotypes from a single natural population of Mimulus guttatus and scored gene expression in the leaves of 1,588 plants. We find that nearly every measured gene exhibits cis regulatory variation (91% have FDR < 0.05) and that cis eQTLs are usually allelic series with three or more functionally distinct alleles. The cis locus explains about two thirds of the standing genetic variance (on average) but varies among genes and tends to be greatest when there is high indel variation in the upstream regulatory region and high nucleotide diversity in the coding sequence. Despite mapping over 10,000 trans eQTL / affected gene pairs, most of the genetic variance generated by trans acting loci remains unexplained. This implies a large reservoir of trans acting genes with subtle or diffuse effects. Mapped trans eQTLs show lower allelic diversity but much higher genetic dominance than cis eQTLs. Several analyses also indicate that trans eQTL make a substantial contribution to the genetic correlations in expression among different genes. They may thus be essential determinants of "gene expression modules", which has important implications for the evolution of gene expression and also how it is studied by geneticists.
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Affiliation(s)
- Paris Veltsos
- Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, KS, USA
- Current address: Ecology, Evolution and Genetics Research Group, Biology Department, Vrije Universiteit Brussel, Pleinlaan 2, 1050, Brussels, Belgium
| | - John K. Kelly
- Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, KS, USA
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Wessinger CA, Katzer AM, Hime PM, Rausher MD, Kelly JK, Hileman LC. A few essential genetic loci distinguish Penstemon species with flowers adapted to pollination by bees or hummingbirds. PLoS Biol 2023; 21:e3002294. [PMID: 37769035 PMCID: PMC10538765 DOI: 10.1371/journal.pbio.3002294] [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] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2023] [Accepted: 08/11/2023] [Indexed: 09/30/2023] Open
Abstract
In the formation of species, adaptation by natural selection generates distinct combinations of traits that function well together. The maintenance of adaptive trait combinations in the face of gene flow depends on the strength and nature of selection acting on the underlying genetic loci. Floral pollination syndromes exemplify the evolution of trait combinations adaptive for particular pollinators. The North American wildflower genus Penstemon displays remarkable floral syndrome convergence, with at least 20 separate lineages that have evolved from ancestral bee pollination syndrome (wide blue-purple flowers that present a landing platform for bees and small amounts of nectar) to hummingbird pollination syndrome (bright red narrowly tubular flowers offering copious nectar). Related taxa that differ in floral syndrome offer an attractive opportunity to examine the genomic basis of complex trait divergence. In this study, we characterized genomic divergence among 229 individuals from a Penstemon species complex that includes both bee and hummingbird floral syndromes. Field plants are easily classified into species based on phenotypic differences and hybrids displaying intermediate floral syndromes are rare. Despite unambiguous phenotypic differences, genome-wide differentiation between species is minimal. Hummingbird-adapted populations are more genetically similar to nearby bee-adapted populations than to geographically distant hummingbird-adapted populations, in terms of genome-wide dXY. However, a small number of genetic loci are strongly differentiated between species. These approximately 20 "species-diagnostic loci," which appear to have nearly fixed differences between pollination syndromes, are sprinkled throughout the genome in high recombination regions. Several map closely to previously established floral trait quantitative trait loci (QTLs). The striking difference between the diagnostic loci and the genome as whole suggests strong selection to maintain distinct combinations of traits, but with sufficient gene flow to homogenize the genomic background. A surprisingly small number of alleles confer phenotypic differences that form the basis of species identity in this species complex.
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Affiliation(s)
- Carolyn A. Wessinger
- Department of Biological Sciences, University of South Carolina, Columbia, South Carolina, United States of America
| | - Amanda M. Katzer
- Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, Kansas, United States of America
| | - Paul M. Hime
- Biodiversity Institute and Natural History Museum, University of Kansas, Lawrence, Kansas, United States of America
| | - Mark D. Rausher
- Department of Biology, Duke University, Durham, North Carolina, United States of America
| | - John K. Kelly
- Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, Kansas, United States of America
| | - Lena C. Hileman
- Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, Kansas, United States of America
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Everman ER, Macdonald SJ, Kelly JK. The genetic basis of adaptation to copper pollution in Drosophila melanogaster. Front Genet 2023; 14:1144221. [PMID: 37082199 PMCID: PMC10110907 DOI: 10.3389/fgene.2023.1144221] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2023] [Accepted: 03/21/2023] [Indexed: 04/22/2023] Open
Abstract
Introduction: Heavy metal pollutants can have long lasting negative impacts on ecosystem health and can shape the evolution of species. The persistent and ubiquitous nature of heavy metal pollution provides an opportunity to characterize the genetic mechanisms that contribute to metal resistance in natural populations. Methods: We examined variation in resistance to copper, a common heavy metal contaminant, using wild collections of the model organism Drosophila melanogaster. Flies were collected from multiple sites that varied in copper contamination risk. We characterized phenotypic variation in copper resistance within and among populations using bulked segregant analysis to identify regions of the genome that contribute to copper resistance. Results and Discussion: Copper resistance varied among wild populations with a clear correspondence between resistance level and historical exposure to copper. We identified 288 SNPs distributed across the genome associated with copper resistance. Many SNPs had population-specific effects, but some had consistent effects on copper resistance in all populations. Significant SNPs map to several novel candidate genes involved in refolding disrupted proteins, energy production, and mitochondrial function. We also identified one SNP with consistent effects on copper resistance in all populations near CG11825, a gene involved in copper homeostasis and copper resistance. We compared the genetic signatures of copper resistance in the wild-derived populations to genetic control of copper resistance in the Drosophila Synthetic Population Resource (DSPR) and the Drosophila Genetic Reference Panel (DGRP), two copper-naïve laboratory populations. In addition to CG11825, which was identified as a candidate gene in the wild-derived populations and previously in the DSPR, there was modest overlap of copper-associated SNPs between the wild-derived populations and laboratory populations. Thirty-one SNPs associated with copper resistance in wild-derived populations fell within regions of the genome that were associated with copper resistance in the DSPR in a prior study. Collectively, our results demonstrate that the genetic control of copper resistance is highly polygenic, and that several loci can be clearly linked to genes involved in heavy metal toxicity response. The mixture of parallel and population-specific SNPs points to a complex interplay between genetic background and the selection regime that modifies the effects of genetic variation on copper resistance.
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Affiliation(s)
| | - Stuart J. Macdonald
- Molecular Biosciences, University of Kansas, Lawrence, KS, United States
- Center for Computational Biology, University of Kansas, Lawrence, KS, United States
| | - John K. Kelly
- Ecology and Evolutionary Biology, University of Kansas, Lawrence, KS, United States
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Kelly JK. The genomic scale of fluctuating selection in a natural plant population. Evol Lett 2022; 6:506-521. [PMID: 36579169 PMCID: PMC9783439 DOI: 10.1002/evl3.308] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2022] [Revised: 11/08/2022] [Accepted: 11/13/2022] [Indexed: 12/30/2022] Open
Abstract
This study characterizes evolution at ≈1.86 million Single Nucleotide Polymorphisms (SNPs) within a natural population of yellow monkeyflower (Mimulus guttatus). Most SNPs exhibit minimal change over a span of 23 generations (less than 1% per year), consistent with neutral evolution in a large population. However, several thousand SNPs display strong fluctuations in frequency. Multiple lines of evidence indicate that these 'Fluctuating SNPs' are driven by temporally varying selection. Unlinked loci exhibit synchronous changes with the same allele increasing consistently in certain time intervals but declining in others. This synchrony is sufficiently pronounced that we can roughly classify intervals into two categories, "green" and "yellow," corresponding to conflicting selection regimes. Alleles increasing in green intervals are associated with early life investment in vegetative tissue and delayed flowering. The alternative alleles that increase in yellow intervals are associated with rapid progression to flowering. Selection on the Fluctuating SNPs produces a strong ripple effect on variation across the genome. Accounting for estimation error, we estimate the distribution of allele frequency change per generation in this population. While change is minimal for most SNPs, diffuse hitchhiking effects generated by selected loci may be driving neutral SNPs to a much greater extent than classic genetic drift.
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Affiliation(s)
- John K. Kelly
- Department of Ecology and Evolutionary BiologyUniversity of KansasLawrenceKansasUSA
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Busch JW, Bodbyl‐Roels S, Tusuubira S, Kelly JK. Pollinator loss causes rapid adaptive evolution of selfing and dramatically reduces genome-wide genetic variability. Evolution 2022; 76:2130-2144. [PMID: 35852008 PMCID: PMC9543508 DOI: 10.1111/evo.14572] [Citation(s) in RCA: 2] [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] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2021] [Revised: 03/23/2022] [Accepted: 04/20/2022] [Indexed: 01/22/2023]
Abstract
Although selfing populations harbor little genetic variation limiting evolutionary potential, the causes are unclear. We experimentally evolved large, replicate populations of Mimulus guttatus for nine generations in greenhouses with or without pollinating bees and studied DNA polymorphism in descendants. Populations without bees adapted to produce more selfed seed yet exhibited striking reductions in DNA polymorphism despite large population sizes. Importantly, the genome-wide pattern of variation cannot be explained by a simple reduction in effective population size, but instead reflects the complicated interaction between selection, linkage, and inbreeding. Simulations demonstrate that the spread of favored alleles at few loci depresses neutral variation genome wide in large populations containing fully selfing lineages. It also generates greater heterogeneity among chromosomes than expected with neutral evolution in small populations. Genome-wide deviations from neutrality were documented in populations with bees, suggesting widespread influences of background selection. After applying outlier tests to detect loci under selection, two genome regions were found in populations with bees, yet no adaptive loci were otherwise mapped. Large amounts of stochastic change in selfing populations compromise evolutionary potential and undermine outlier tests for selection. This occurs because genetic draft in highly selfing populations makes even the largest changes in allele frequency unremarkable.
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Affiliation(s)
- Jeremiah W. Busch
- School of Biological SciencesWashington State UniversityPullmanWashington99164
| | - Sarah Bodbyl‐Roels
- Trefny Innovative Instruction CenterColorado School of MinesGoldenColorado80401
| | - Sharif Tusuubira
- Department of Ecology and Evolutionary BiologyUniversity of KansasLawrenceKansas66045
| | - John K. Kelly
- Department of Ecology and Evolutionary BiologyUniversity of KansasLawrenceKansas66045
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Mort ME, Kerbs BR, Kelly JK, Silva LB, Moura M, de Sequeira MM, Santos-Guerra A, Schaefer H, Alfredo Reyes-Betancort J, Caujapé-Castells J, Crawford DJ. Multiplexed shotgun genotyping (MSG) data resolve phylogenetic relationships within and among archipelagos in Macaronesian Tolpis. Am J Bot 2022; 109:952-965. [PMID: 35608078 DOI: 10.1002/ajb2.1866] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/22/2021] [Revised: 04/19/2022] [Accepted: 04/21/2022] [Indexed: 06/15/2023]
Abstract
PREMISE Plants endemic to oceanic archipelagos are suitable for studying evolution, being isolated on substrates of different ages. Evolution has been recent, rendering traditionally employed sequences insufficiently variable for resolving relationships. This study includes sampling in the genus Tolpis (Asteraceae) from the Azores, Madeira, and Cape Verde, and expands upon an earlier study demonstrating the efficacy of multiplexed shotgun genotyping (MSG) for resolving relationships in Canarian Tolpis. METHODS Genomic libraries for 90 accessions of Tolpis and two from the outgroup were generated for genotyping individuals using MSG. Loci were de novo assembled with iPyrad, which clusters MSG loci within and between samples. A maximum likelihood phylogeny was generated with RAxML. Ancestral area reconstruction was inferred using R package BioGeoBEARS. RESULTS MSG data recovered a highly resolved phylogeny from population to inter-archipelago levels. Ancestral area reconstruction provided biogeographic hypotheses for the radiation of Macaronesian Tolpis. CONCLUSIONS Four major clades were resolved. The Madeiran endemic T. macrorhiza is sister to other Tolpis. Species from the Canaries, Cape Verdes, and the continent are sister to T. succulenta from Madeira, which has a sister subclade of Azorean populations composed of T. succulenta and T. azorica. Population-level resolution suggests unrecognized taxa on several archipelagos. Ancestral reconstruction suggests initial dispersal from the continent to Madeira, with dispersal to the Azores, then dispersal from Madeira to the Canary Islands, with both subsequent dispersal to the Cape Verdes and back-dispersal to the continent. Single-island radiations and inter-island dispersal are implicated in divergence in Macaronesian Tolpis.
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Affiliation(s)
- Mark E Mort
- Department of Ecology and Evolutionary Biology, University of Kansas, 1200 Sunnyside Avenue, Lawrence, Kansas, 66045, USA
| | - Benjamin R Kerbs
- Department of Ecology and Evolutionary Biology, University of Kansas, 1200 Sunnyside Avenue, Lawrence, Kansas, 66045, USA
| | - John K Kelly
- Department of Ecology and Evolutionary Biology, University of Kansas, 1200 Sunnyside Avenue, Lawrence, Kansas, 66045, USA
| | - Lurdes Borges Silva
- CIBIO, Centro de Investigação em Biodiversidade e Recursos Genéticos, InBIO Laboratório Associado, Pólo dos Açores, Universidade dos Açores, Rua da Mãe de Deus 13 A, 9501-801, Ponta Delgada, Açores, Portugal
| | - Mónica Moura
- CIBIO, Centro de Investigação em Biodiversidade e Recursos Genéticos, InBIO Laboratório Associado, Pólo dos Açores, Universidade dos Açores, Rua da Mãe de Deus 13 A, 9501-801, Ponta Delgada, Açores, Portugal
| | - Miguel Menezes de Sequeira
- Madeira Botanical Group, Faculty of Life Sciences, Campus Universitário da Penteada, University of Madeira, 9020-105, Funchal, Portugal
- CIBIO, Centro de Investigação em Biodiversidade e Recursos Genéticos, InBIO Laboratório Associado, Pólo dos Açores, 9501-81, Ponta Delgada, Portugal
| | - Arnoldo Santos-Guerra
- Calle Guaidil 16, Urbanización Tamarco, Tegueste, Tenerife, Canary Islands, 38280, Spain
| | - Hanno Schaefer
- Department of Life Science Systems, Plant Biodiversity Research, Technical University of Munich, Emil-Ramann-Str. 2, 85354, Freising, Germany
| | - J Alfredo Reyes-Betancort
- Unidad de Botánica Aplicada, Instituto Canario de Investigaciones Agrarias, Jardín de Aclimatación de La Orotava, Puerto de La Cruz, Santa Cruz de Tenerife, Spain
| | - Juli Caujapé-Castells
- Departamento de Biodiversidad Molecular y Banco de ADN, Jardín Botánico Canario "Viera y Clavijo"-Unidad Asociada CSIC, Cabildo de Gran Canaria, Camino al Palmeral 15, Tafira Alta, 35017, Las Palmas de Gran Canaria, Spain
| | - Daniel J Crawford
- Department of Ecology and Evolutionary Biology, University of Kansas, 1200 Sunnyside Avenue, Lawrence, Kansas, 66045, USA
- Department of Ecology & Evolutionary Biology, and the Biodiversity Institute, University of Kansas, Lawrence, Kansas, 66045-7534, USA
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Delph LF, Brown KE, Ríos LD, Kelly JK. Sex‐specific natural selection on SNPs in
Silene latifolia. Evol Lett 2022; 6:308-318. [PMID: 35937470 PMCID: PMC9346077 DOI: 10.1002/evl3.283] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2021] [Revised: 02/24/2022] [Accepted: 03/13/2022] [Indexed: 01/15/2023] Open
Affiliation(s)
- Lynda F. Delph
- Department of Biology Indiana University Bloomington Indiana USA
| | - Keely E. Brown
- Department of Ecology and Evolutionary Biology University of Kansas Lawrence Kansas USA
| | - Luis Diego Ríos
- Department of Biology Indiana University Bloomington Indiana USA
| | - John K. Kelly
- Department of Ecology and Evolutionary Biology University of Kansas Lawrence Kansas USA
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Brown KE, Kelly JK. Genome-wide association mapping of transcriptome variation in Mimulus guttatus indicates differing patterns of selection on cis- versus trans-acting mutations. Genetics 2021; 220:6427634. [PMID: 34791192 DOI: 10.1093/genetics/iyab189] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [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: 05/11/2021] [Accepted: 09/28/2021] [Indexed: 11/14/2022] Open
Abstract
We measured the floral bud transcriptome of 151 fully sequenced lines of Mimulus guttatus from one natural population. Thousands of single nucleotide polymorphisms (SNPs) are implicated as transcription regulators, but there is a striking difference in the Allele Frequency Spectrum (AFS) of cis-acting and trans-acting mutations. Cis-SNPs have intermediate frequencies (consistent with balancing selection) while trans-SNPs exhibit a rare-alleles model (consistent with purifying selection). This pattern only becomes clear when transcript variation is normalized on a gene-to-gene basis. If a global normalization is applied, as is typically in RNAseq experiments, asymmetric transcript distributions combined with "rarity disequilibrium" produce a super-abundance of false positives for trans-acting SNPs. To explore the cause of purifying selection on trans-acting mutations, we identified gene expression modules as sets of co-expressed genes. The extent to which trans-acting mutations influence modules is a strong predictor of allele frequency. Mutations altering expression of genes with high "connectedness" (those that are highly predictive of the representative module expression value) have the lowest allele frequency. The expression modules can also predict whole-plant traits such as flower size. We find that a substantial portion of the genetic (co)variance among traits can be described as an emergent property of genetic effects on expression modules.
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Affiliation(s)
- Keely E Brown
- Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, Kansas 66045, USA.,Department of Botany and Plant Sciences, University of California Riverside, Riverside, California 92521, USA
| | - John K Kelly
- Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, Kansas 66045, USA
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11
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Kelly JK. The promise and deceit of genomic selection component analyses. Proc Biol Sci 2021; 288:20211812. [PMID: 34702075 PMCID: PMC8548789 DOI: 10.1098/rspb.2021.1812] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2021] [Accepted: 09/30/2021] [Indexed: 11/12/2022] Open
Abstract
Selection component analyses (SCA) relate individual genotype to fitness components such as viability, fecundity and mating success. SCA are based on population genetic models and yield selection estimates directly in terms of predicted allele frequency change. This paper explores the statistical properties of gSCA: experiments that apply SCA to genome-wide scoring of SNPs in field sampled individuals. Computer simulations indicate that gSCA involving a few thousand genotyped samples can detect allele frequency changes of the magnitude that has been documented in field experiments on diverse taxa. To detect selection, imprecise genotyping from low-level sequencing of large samples of individuals provides much greater power than precise genotyping of smaller samples. The simulations also demonstrate the efficacy of 'haplotype matching', a method to combine information from a limited collection of whole genome sequence (the reference panel) with the much larger sample of field individuals that are measured for fitness. Pooled sequencing is demonstrated as another way to increase statistical power. Finally, I discuss the interpretation of selection estimates in relation to the Beavis effect, the overestimation of selection intensities at significant loci.
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Affiliation(s)
- John K. Kelly
- Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, KS, USA
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12
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Monnahan PJ, Colicchio J, Fishman L, Macdonald SJ, Kelly JK. Predicting evolutionary change at the DNA level in a natural Mimulus population. PLoS Genet 2021; 17:e1008945. [PMID: 33439857 PMCID: PMC7837469 DOI: 10.1371/journal.pgen.1008945] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [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: 06/17/2020] [Revised: 01/26/2021] [Accepted: 10/26/2020] [Indexed: 12/03/2022] Open
Abstract
Evolution by natural selection occurs when the frequencies of genetic variants change because individuals differ in Darwinian fitness components such as survival or reproductive success. Differential fitness has been demonstrated in field studies of many organisms, but it remains unclear how well we can quantitatively predict allele frequency changes from fitness measurements. Here, we characterize natural selection on millions of Single Nucleotide Polymorphisms (SNPs) across the genome of the annual plant Mimulus guttatus. We use fitness estimates to calibrate population genetic models that effectively predict allele frequency changes into the next generation. Hundreds of SNPs experienced "male selection" in 2013 with one allele at each SNP elevated in frequency among successful male gametes relative to the entire population of adults. In the following generation, allele frequencies at these SNPs consistently shifted in the predicted direction. A second year of study revealed that SNPs had effects on both viability and reproductive success with pervasive trade-offs between fitness components. SNPs favored by male selection were, on average, detrimental to survival. These trade-offs (antagonistic pleiotropy and temporal fluctuations in fitness) may be essential to the long-term maintenance of alleles. Despite the challenges of measuring selection in the wild, the strong correlation between predicted and observed allele frequency changes suggests that population genetic models have a much greater role to play in forward-time prediction of evolutionary change.
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Affiliation(s)
- Patrick J. Monnahan
- Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, Kansas, United States of America
| | - Jack Colicchio
- Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, Kansas, United States of America
| | - Lila Fishman
- Division of Biological Sciences, University of Montana, Missoula, Minnesota, United States of America
| | - Stuart J. Macdonald
- Department of Molecular Biosciences, University of Kansas, Lawrence, Kansas, United States of America
| | - John K. Kelly
- Department of Molecular Biosciences, University of Kansas, Lawrence, Kansas, United States of America
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13
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Kerbs B, Crawford DJ, White G, Moura M, Borges Silva L, Schaefer H, Brown K, Mort ME, Kelly JK. How rapidly do self-compatible populations evolve selfing? Mating system estimation within recently evolved self-compatible populations of Azorean Tolpis succulenta (Asteraceae). Ecol Evol 2020; 10:13990-13999. [PMID: 33391697 PMCID: PMC7771160 DOI: 10.1002/ece3.6992] [Citation(s) in RCA: 4] [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] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2020] [Revised: 10/08/2020] [Accepted: 10/14/2020] [Indexed: 01/04/2023] Open
Abstract
Genome-wide genotyping and Bayesian inference method (BORICE) were employed to estimate outcrossing rates and paternity in two small plant populations of Tolpis succulenta (Asteraceae) on Graciosa island in the Azores. These two known extant populations of T. succulenta on Graciosa have recently evolved self-compatibility. Despite the expectation that selfing would occur at an appreciable rate (self-incompatible populations of the same species show low but nonzero selfing), high outcrossing was found in progeny arrays from maternal plants in both populations. This is inconsistent with an immediate transition to high selfing following the breakdown of a genetic incompatibility system. This finding is surprising given the small population sizes and the recent colonization of an island from self-incompatible colonists of T. succulenta from another island in the Azores, and a potential paucity of pollinators, all factors selecting for selfing through reproductive assurance. The self-compatible lineage(s) likely have high inbreeding depression (ID) that effectively halts the evolution of increased selfing, but this remains to be determined. Like their progeny, all maternal plants in both populations are fully outbred, which is consistent with but not proof of high ID. High multiple paternity was found in both populations, which may be due in part to the abundant pollinators observed during the flowering season.
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Affiliation(s)
- Benjamin Kerbs
- Department of Ecology & Evolutionary BiologyUniversity of KansasLawrenceKSUSA
| | - Daniel J. Crawford
- Department of Ecology & Evolutionary BiologyUniversity of KansasLawrenceKSUSA
- Biodiversity InstituteUniversity of KansasLawrenceKSUSA
| | - Griffin White
- Department of Ecology & Evolutionary BiologyUniversity of KansasLawrenceKSUSA
- ETH ZurichFunctional Genomics Center ZurichZurichSwitzerland
| | - Mónica Moura
- InBIO Laboratório Associado, Pólo dos AçoresFaculdade de Ciências TecnoclogiaCIBIO, Centro de Investigação em Biodiversidade e Recursos GenéticosUniversidade dos AçoresPonta DelgadaPortugal
| | - Lurdes Borges Silva
- InBIO Laboratório Associado, Pólo dos AçoresFaculdade de Ciências TecnoclogiaCIBIO, Centro de Investigação em Biodiversidade e Recursos GenéticosUniversidade dos AçoresPonta DelgadaPortugal
| | - Hanno Schaefer
- Department of Ecology and Ecosystem ManagementPlant Biodiversity ResearchTechnical University of MunichFreisingGermany
| | - Keely Brown
- Department of Ecology & Evolutionary BiologyUniversity of KansasLawrenceKSUSA
| | - Mark E. Mort
- Department of Ecology & Evolutionary BiologyUniversity of KansasLawrenceKSUSA
| | - John K. Kelly
- Department of Ecology & Evolutionary BiologyUniversity of KansasLawrenceKSUSA
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14
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Gibson MJS, Crawford DJ, Holder MT, Mort ME, Kerbs B, de Sequeira MM, Kelly JK. Genome-wide genotyping estimates mating system parameters and paternity in the island species Tolpis succulenta. Am J Bot 2020; 107:1189-1197. [PMID: 32864742 DOI: 10.1002/ajb2.1515] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/21/2019] [Accepted: 02/22/2020] [Indexed: 06/11/2023]
Abstract
PREMISE The mating system has profound consequences, not only for ecology and evolution, but also for the conservation of threatened or endangered species. Unfortunately, small populations are difficult to study owing to limits on sample size and genetic marker diversity. Here, we estimated mating system parameters in three small populations of an island plant using genomic genotyping. Although self-incompatible (SI) species are known to often set some self-seed, little is known about how "leaky SI" affects selfing rates in nature or the role that multiple paternity plays in small populations. METHODS We generalized the BORICE mating system program to determine the siring pattern within maternal families. We applied this algorithm to maternal families from three populations of Tolpis succulenta from Madeira Island and genotyped the progeny using RADseq. We applied BORICE to estimate each individual offspring as outcrossed or selfed, the paternity of each outcrossed offspring, and the level of inbreeding of each maternal plant. RESULTS Despite a functional self-incompatibility system, these data establish T. succulenta as a pseudo-self-compatible (PSC) species. Two of 75 offspring were strongly indicated as products of self-fertilization. Despite selfing, all adult maternal plants were fully outbred. There was high differentiation among and low variation within populations, consistent with a history of genetic isolation of these small populations. There were generally multiple sires per maternal family. Twenty-two percent of sib contrasts (between outcrossed offspring within maternal families) shared the same sire. CONCLUSIONS Genome-wide genotyping, combined with appropriate analytical methods, enables estimation of mating system and multiple paternity in small populations. These data address questions about the evolution of reproductive traits and the conservation of threatened populations.
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Affiliation(s)
- Matthew J S Gibson
- Department of Ecology & Evolutionary Biology, University of Kansas, Lawrence, KS, 66045-7534, USA
| | - Daniel J Crawford
- Department of Ecology & Evolutionary Biology, University of Kansas, Lawrence, KS, 66045-7534, USA
- Biodiversity Institute, University of Kansas, Lawrence, KS, 66045-7534, USA
| | - Mark T Holder
- Department of Ecology & Evolutionary Biology, University of Kansas, Lawrence, KS, 66045-7534, USA
- Biodiversity Institute, University of Kansas, Lawrence, KS, 66045-7534, USA
| | - Mark E Mort
- Department of Ecology & Evolutionary Biology, University of Kansas, Lawrence, KS, 66045-7534, USA
| | - Benjamin Kerbs
- Department of Ecology & Evolutionary Biology, University of Kansas, Lawrence, KS, 66045-7534, USA
| | - Miguel Menezes de Sequeira
- Madeira Botanical Group, Faculty of Life Sciences, University of Madeira, Campus Universitário da Penteada, 9020-105, Funchal, Portugal
- CIBIO, Centro de Investigação em Biodiversidade e Recursos Genéticos, InBIO Laboratório Associado, Pólo dos Açores, 9501-81, Ponta Delgada, Portugal
| | - John K Kelly
- Department of Ecology & Evolutionary Biology, University of Kansas, Lawrence, KS, 66045-7534, USA
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15
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Brown KE, Kelly JK. Severe inbreeding depression is predicted by the “rare allele load” in
Mimulus guttatus
*. Evolution 2019; 74:587-596. [DOI: 10.1111/evo.13876] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2019] [Revised: 09/30/2019] [Accepted: 10/09/2019] [Indexed: 01/04/2023]
Affiliation(s)
- Keely E. Brown
- Ecology and Evolutionary Biology University of Kansas Lawrence Kansas 66045
| | - John K. Kelly
- Ecology and Evolutionary Biology University of Kansas Lawrence Kansas 66045
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16
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Colicchio J, Monnahan PJ, Wessinger CA, Brown K, Kern JR, Kelly JK. Individualized mating system estimation using genomic data. Mol Ecol Resour 2019; 20:333-347. [DOI: 10.1111/1755-0998.13094] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2019] [Revised: 07/27/2019] [Accepted: 08/19/2019] [Indexed: 11/29/2022]
Affiliation(s)
- Jack Colicchio
- Department of Ecology and Evolutionary Biology University of Kansas Lawrence KS USA
| | - Patrick J. Monnahan
- Department of Ecology and Evolutionary Biology University of Kansas Lawrence KS USA
| | - Carolyn A. Wessinger
- Department of Ecology and Evolutionary Biology University of Kansas Lawrence KS USA
| | - Keely Brown
- Department of Ecology and Evolutionary Biology University of Kansas Lawrence KS USA
| | - James Russell Kern
- Department of Ecology and Evolutionary Biology University of Kansas Lawrence KS USA
| | - John K. Kelly
- Department of Ecology and Evolutionary Biology University of Kansas Lawrence KS USA
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17
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Wessinger CA, Kelly JK. Correction. Am Nat 2019; 194:439. [DOI: 10.1086/704288] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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18
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Flagel LE, Blackman BK, Fishman L, Monnahan PJ, Sweigart A, Kelly JK. GOOGA: A platform to synthesize mapping experiments and identify genomic structural diversity. PLoS Comput Biol 2019; 15:e1006949. [PMID: 30986215 PMCID: PMC6483263 DOI: 10.1371/journal.pcbi.1006949] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [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: 06/07/2018] [Revised: 04/25/2019] [Accepted: 03/15/2019] [Indexed: 11/18/2022] Open
Abstract
Understanding genomic structural variation such as inversions and translocations is a key challenge in evolutionary genetics. We develop a novel statistical approach to comparative genetic mapping to detect large-scale structural mutations from low-level sequencing data. The procedure, called Genome Order Optimization by Genetic Algorithm (GOOGA), couples a Hidden Markov Model with a Genetic Algorithm to analyze data from genetic mapping populations. We demonstrate the method using both simulated data (calibrated from experiments on Drosophila melanogaster) and real data from five distinct crosses within the flowering plant genus Mimulus. Application of GOOGA to the Mimulus data corrects numerous errors (misplaced sequences) in the M. guttatus reference genome and confirms or detects eight large inversions polymorphic within the species complex. Finally, we show how this method can be applied in genomic scans to improve the accuracy and resolution of Quantitative Trait Locus (QTL) mapping.
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Affiliation(s)
- Lex E. Flagel
- Bayer Crop Science, Chesterfield, MO, United States of America
- Department of Plant and Microbial Biology, University of Minnesota, St. Paul, MN, United States of America
- * E-mail: (LEF); (JKK)
| | - Benjamin K. Blackman
- Department of Plant and Microbial Biology, University of California—Berkeley, Berkeley, CA, United States of America
| | - Lila Fishman
- Division of Biological Sciences, University of Montana, Missoula, MT, United States of America
| | - Patrick J. Monnahan
- Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, KS, United States of America
- Department of Ecology, Evolution, and Behavior, University of Minnesota, St. Paul, MN, United States of America
| | - Andrea Sweigart
- Department of Genetics, University of Georgia, Athens, GA, United States of America
| | - John K. Kelly
- Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, KS, United States of America
- * E-mail: (LEF); (JKK)
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19
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Kelly JK, Hughes KA. Pervasive Linked Selection and Intermediate-Frequency Alleles Are Implicated in an Evolve-and-Resequencing Experiment of Drosophila simulans. Genetics 2019; 211:943-961. [PMID: 30593495 PMCID: PMC6404262 DOI: 10.1534/genetics.118.301824] [Citation(s) in RCA: 47] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2018] [Accepted: 12/15/2018] [Indexed: 11/18/2022] Open
Abstract
We develop analytical and simulation tools for evolve-and-resequencing experiments and apply them to a new study of rapid evolution in Drosophila simulans Likelihood test statistics applied to pooled population sequencing data suggest parallel evolution of 138 SNPs across the genome. This number is reduced by orders of magnitude from previous studies (thousands or tens of thousands), owing to differences in both experimental design and statistical analysis. Whole genome simulations calibrated from Drosophila genetic data sets indicate that major features of the genome-wide response could be explained by as few as 30 loci under strong directional selection with a corresponding hitchhiking effect. Smaller effect loci are likely also responding, but are below the detection limit of the experiment. Finally, SNPs showing strong parallel evolution in the experiment are intermediate in frequency in the natural population (usually 30-70%) indicative of balancing selection in nature. These loci also exhibit elevated differentiation among natural populations of D. simulans, suggesting environmental heterogeneity as a potential balancing mechanism.
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Affiliation(s)
- John K Kelly
- Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, Kansas 66045
| | - Kimberly A Hughes
- Department of Biological Science, Florida State University, Tallahassee, Florida 32306
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20
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Nelson TC, Monnahan PJ, McIntosh MK, Anderson K, MacArthur-Waltz E, Finseth FR, Kelly JK, Fishman L. Extreme copy number variation at a tRNA ligase gene affecting phenology and fitness in yellow monkeyflowers. Mol Ecol 2018; 28:1460-1475. [PMID: 30346101 DOI: 10.1111/mec.14904] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [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: 07/20/2018] [Revised: 10/03/2018] [Accepted: 10/08/2018] [Indexed: 12/15/2022]
Abstract
Copy number variation (CNV) is a major part of the genetic diversity segregating within populations, but remains poorly understood relative to single nucleotide variation. Here, we report on a tRNA ligase gene (Migut.N02091; RLG1a) exhibiting unprecedented, and fitness-relevant, CNV within an annual population of the yellow monkeyflower Mimulus guttatus. RLG1a variation was associated with multiple traits in pooled population sequencing (PoolSeq) scans of phenotypic and phenological cohorts. Resequencing of inbred lines revealed intermediate-frequency three-copy variants of RLG1a (trip+; 5/35 = 14%), and trip+ lines exhibited elevated RLG1a expression under multiple conditions. trip+ carriers, in addition to being over-represented in late-flowering and large-flowered PoolSeq populations, flowered later under stressful conditions in a greenhouse experiment (p < 0.05). In wild population samples, we discovered an additional rare RLG1a variant (high+) that carries 250-300 copies of RLG1a totalling ~5.7 Mb (20-40% of a chromosome). In the progeny of a high+ carrier, Mendelian segregation of diagnostic alleles and qPCR-based copy counts indicate that high+ is a single tandem array unlinked to the single-copy RLG1a locus. In the wild, high+ carriers had highest fitness in two particularly dry and/or hot years (2015 and 2017; both p < 0.01), while single-copy individuals were twice as fecund as either CNV type in a lush year (2016: p < 0.005). Our results demonstrate fluctuating selection on CNVs affecting phenological traits in a wild population, suggest that plant tRNA ligases mediate stress-responsive life-history traits, and introduce a novel system for investigating the molecular mechanisms of gene amplification.
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Affiliation(s)
- Thomas C Nelson
- Division of Biological Sciences, University of Montana, Missoula, Montana
| | - Patrick J Monnahan
- Department of Ecology and Evolution, University of Kansas, Lawrence, Kansas
| | - Mariah K McIntosh
- Division of Biological Sciences, University of Montana, Missoula, Montana
| | - Kayli Anderson
- Division of Biological Sciences, University of Montana, Missoula, Montana
| | | | - Findley R Finseth
- Division of Biological Sciences, University of Montana, Missoula, Montana
| | - John K Kelly
- Department of Ecology and Evolution, University of Kansas, Lawrence, Kansas
| | - Lila Fishman
- Division of Biological Sciences, University of Montana, Missoula, Montana
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21
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Abstract
BACKGROUND Transgenerational plasticity occurs when the environmental experience of an organism modifies the growth and development of its progeny. Leaf damage in Mimulus guttatus exhibits transgenerational plasticity mediated through differential expression of hundreds of genes. The epigenetic mechanisms that facilitate this response have yet to be described. RESULTS We performed whole genome bisulfite sequencing in the progeny of genetically identical damaged and control plants and developed a pipeline to compare differences in the mean and variance of methylation between treatment groups. We find that parental damage increases the variability of CG and CHG methylation among progeny, but does not alter the overall mean methylation. Instead it has positive effects in some regions and negative in others. We find 3,396 CHH, 203 CG, and 54 CHG Differentially Methylated Regions (DMRs) ranging from tens to thousands of base pairs scattered across the genome. CHG and CHH DMRs tended to overlap with transposable elements. CG DMRs tended to overlap with gene coding regions, many of which were previously found to be differentially expressed. CONCLUSIONS Genome-wide increases in methylome variation suggest that parental conditions can increase epigenetic diversity in response to stress. Additionally, the potential association between CG DMRs and differentially expressed genes supports the hypothesis that differential methylation is a mechanistic component of transgenerational plasticity in M. guttatus.
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Affiliation(s)
- Jack M Colicchio
- Department of Plant and Microbial Biology, University of California Berkeley, Berkeley, CA 94710 USA
- Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, KS 66045 USA
| | - John K Kelly
- Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, KS 66045 USA
| | - Lena C Hileman
- Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, KS 66045 USA
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22
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Troth A, Puzey JR, Kim RS, Willis JH, Kelly JK. Selective trade-offs maintain alleles underpinning complex trait variation in plants. Science 2018; 361:475-478. [PMID: 30072534 DOI: 10.1126/science.aat5760] [Citation(s) in RCA: 58] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Subscribe] [Scholar Register] [Received: 03/13/2018] [Accepted: 06/22/2018] [Indexed: 11/02/2022]
Abstract
To understand evolutionary factors that maintain complex trait variation, we sequenced genomes from a single population of the plant Mimulus guttatus, identifying hundreds of nucleotide variants associated with morphological and life history traits. Alleles that delayed flowering also increased size at reproduction, which suggests pervasive antagonistic pleiotropy in this annual plant. The "large and slow" alleles, which were less common in small, rapidly flowering populations, became more abundant in populations with greater plant size. Furthermore, natural selection within the field population favored alternative alleles from year to year. Our results suggest that environmental fluctuations and selective trade-offs maintain polygenic trait variation within populations and also contribute to the geographic divergence in this wildflower species.
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Affiliation(s)
- Ashley Troth
- Department of Biology, Duke University, Durham, NC 27708, USA
| | - Joshua R Puzey
- Department of Biology, Duke University, Durham, NC 27708, USA.,Department of Biology, College of William and Mary, Williamsburg, VA 23187, USA
| | - Rebecca S Kim
- Department of Biology, Duke University, Durham, NC 27708, USA.,Department of Environmental Medicine, NYU Langone, New York, NY 10016, USA
| | - John H Willis
- Department of Biology, Duke University, Durham, NC 27708, USA
| | - John K Kelly
- Department of Ecology and Evolution, University of Kansas, Lawrence, KS 27708, USA.
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23
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Wessinger CA, Kelly JK, Jiang P, Rausher MD, Hileman LC. SNP-skimming: A fast approach to map loci generating quantitative variation in natural populations. Mol Ecol Resour 2018; 18:1402-1414. [PMID: 30033616 DOI: 10.1111/1755-0998.12930] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [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: 03/19/2018] [Revised: 06/13/2018] [Accepted: 06/20/2018] [Indexed: 01/20/2023]
Abstract
Genome-wide association mapping (GWAS) is a method to estimate the contribution of segregating genetic loci to trait variation. A major challenge for applying GWAS to nonmodel species has been generating dense genome-wide markers that satisfy the key requirement that marker data are error-free. Here, we present an approach to map loci within natural populations using inexpensive shallow genome sequencing. This "SNP-skimming" approach involves two steps: an initial genome-wide scan to identify putative targets followed by deep sequencing for confirmation of targeted loci. We apply our method to a test data set of floral dimension variation in the plant Penstemon virgatus, a member of a genus that has experienced dynamic floral adaptation that reflects repeated transitions in primary pollinator. The ability to detect SNPs that generate phenotypic variation depends on population genetic factors such as population allele frequency, effect size and epistasis, as well as sampling effects contingent on missing data and genotype uncertainty. However, both simulations and the Penstemon data suggest that the most significant tests from the initial SNP skim are likely to be true positives-loci with subtle but significant quantitative effects on phenotype. We discuss the promise and limitations of this method and consider optimal experimental design for a given sequencing effort. Simulations demonstrate that sampling a larger number of individual at the expense of average read depth per individual maximizes the power to detect loci.
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Affiliation(s)
- Carolyn A Wessinger
- Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, Kansas
| | - John K Kelly
- Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, Kansas
| | - Peng Jiang
- Department of Biology, Duke University, Durham, North Carolina
| | - Mark D Rausher
- Department of Biology, Duke University, Durham, North Carolina
| | - Lena C Hileman
- Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, Kansas
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24
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Abstract
Pollinator-mediated selection on plants can favor transitions to a new pollinator depending on the relative abundances and efficiencies of pollinators present in the community. A frequently observed example is the transition from bee pollination to hummingbird pollination. We present a population genetic model that examines whether the ability to inbreed can influence evolutionary change in traits that underlie pollinator attraction. We find that a transition to a more efficient but less abundant pollinator is favored under a broadened set of ecological conditions if plants are capable of delayed selfing rather than obligately outcrossing. Delayed selfing allows plants carrying an allele that attracts the novel pollinator to reproduce even when this pollinator is rare, providing reproductive assurance. In addition, delayed selfing weakens the effects of Haldane's sieve by increasing the fixation probability for recessive alleles that confer adaptation to the new pollinator. Our model provides novel insight into the paradoxical abundance of recessive mutations in adaptation to hummingbird attraction. It further predicts that transitions to efficient but less abundant pollinators (such as hummingbirds in certain communities) should disproportionately occur in self-compatible lineages. Currently available mating system data sets are consistent with this prediction, and we suggest future areas of research that will enable a rigorous test of this theory.
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25
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Koseva B, Crawford DJ, Brown K, Mort ME, Kelly JK. The genetic breakdown of sporophytic self-incompatibility in Tolpis coronopifolia (Asteraceae). New Phytol 2017; 216:1256-1267. [PMID: 28892151 PMCID: PMC5675808 DOI: 10.1111/nph.14759] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/01/2017] [Accepted: 07/14/2017] [Indexed: 05/31/2023]
Abstract
Angiosperm diversity has been shaped by mating system evolution, with the most common transition from outcrossing to self-fertilizing. To investigate the genetic basis of this transition, we performed crosses between two species endemic to the Canary Islands, the self-compatible (SC) species Tolpis coronopifolia and its self-incompatible (SI) relative Tolpis santosii. We scored self-compatibility as self-seed set of recombinant plants within two F2 populations. To map and genetically characterize the breakdown of SI, we built a draft genome sequence of T. coronopifolia, genotyped F2 plants using multiplexed shotgun genotyping (MSG), and located MSG markers to the genome sequence. We identified a single quantitative trait locus (QTL) that explains nearly all variation in self-seed set in both F2 populations. To identify putative causal genetic variants within the QTL, we performed transcriptome sequencing on mature floral tissue from both SI and SC species, constructed a transcriptome for each species, and then located each predicted transcript to the T. coronopifolia genome sequence. We annotated each predicted gene within the QTL and found two strong candidates for SI breakdown. Each gene has a coding sequence insertion/deletion mutation within the SC species that produces a truncated protein. Homologs of each gene have been implicated in pollen development, pollen germination, and pollen tube growth in other species.
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Affiliation(s)
- Boryana Koseva
- Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, KS 66045-7534, USA
| | - Daniel J. Crawford
- Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, KS 66045-7534, USA
- Biodiversity Institute, University of Kansas, Lawrence, KS 66045-7534, USA
| | - Keely Brown
- Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, KS 66045-7534, USA
| | - Mark E. Mort
- Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, KS 66045-7534, USA
- Biodiversity Institute, University of Kansas, Lawrence, KS 66045-7534, USA
| | - John K. Kelly
- Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, KS 66045-7534, USA
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Kerbs B, Ressler J, Kelly JK, Mort ME, Santos-Guerra A, Gibson MJS, Caujapé-Castells J, Crawford DJ. The potential role of hybridization in diversification and speciation in an insular plant lineage: insights from synthetic interspecific hybrids. AoB Plants 2017; 9:plx043. [PMID: 29225761 PMCID: PMC5714139 DOI: 10.1093/aobpla/plx043] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/18/2016] [Accepted: 08/25/2017] [Indexed: 05/17/2023]
Abstract
Hybridization is recognized as an important process in plant evolution, and this may be particularly true for island plants where several biotic and abiotic factors facilitate interspecific hybridization. Although rarely done, experimental studies could provide insights into the potential of natural hybridization to generate diversity when species come into contact in the dynamic island setting. The potential of hybridization to generate morphological variation was analysed within and among 12 families (inbred lines) of an F4 hybrid generation between two species of Tolpis endemic to the Canary Islands. Combinations of characters not seen in the parents were present in hybrids. Several floral and vegetative characters were transgressive relative to their parents. Morphometric studies of floral, vegetative and fruit characters revealed that several F4 families were phenotypically distinct from other families, and from their parents. The study demonstrates that morphologically distinct pollen-fertile lines, potentially worthy of taxonomic recognition if occurring in nature, can be generated in four generations. The ability of the hybrid lines to set self-seed would reduce gene flow among the lines, and among the hybrids and their parental species. Selfing would also facilitate the fixation of characters within each of the lines. Overall, the results show the considerable potential of hybridization for generating diversity and distinct phenotypes in island lineages.
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Affiliation(s)
- Benjamin Kerbs
- Department of Biological Sciences, Emporia State University, Emporia, KS 66801, USA
| | - Jacob Ressler
- Department of Biology, Indiana University, Bloomington, IN 47405, USA
| | - John K Kelly
- Department of Ecology & Evolutionary Biology, University of Kansas, Lawrence, KS 66045-7534, USA
| | - Mark E Mort
- Department of Ecology & Evolutionary Biology, University of Kansas, Lawrence, KS 66045-7534, USA
| | - Arnoldo Santos-Guerra
- Calle Guaidil 16, Urbanización Tamarco, 38280 Tegueste, Tenerife, Canary Islands, Spain
| | | | - Juli Caujapé-Castells
- Jardín Botánico 13 Canario “Viera y Clavijo”-Unidad Asociada al CSIC (Cabildo de Gran Canaria), Camino del palmeral 14 15 (Tafira Alta), 35017 Las Palmas de Gran Canaria, Spain
| | - Daniel J Crawford
- Department of Ecology & Evolutionary Biology, and the Biodiversity Institute, University of Kansas, Lawrence, KS 66045-7534, USA
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27
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Monnahan PJ, Kelly JK. The Genomic Architecture of Flowering Time Varies Across Space and Time in Mimulus guttatus. Genetics 2017; 206:1621-1635. [PMID: 28455350 PMCID: PMC5500155 DOI: 10.1534/genetics.117.201483] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2017] [Accepted: 04/23/2017] [Indexed: 11/18/2022] Open
Abstract
The degree to which genomic architecture varies across space and time is central to the evolution of genomes in response to natural selection. Bulked-segregant mapping combined with pooled sequencing provides an efficient means to estimate the effect of genetic variants on quantitative traits. We develop a novel likelihood framework to identify segregating variation within multiple populations and generations while accommodating estimation error on a sample- and SNP-specific basis. We use this method to map loci for flowering time within natural populations of Mimulus guttatus, collecting the early- and late-flowering plants from each of three neighboring populations and two consecutive generations. Structural variants, such as inversions, and genes from multiple flowering-time pathways exhibit the strongest associations with flowering time. We find appreciable variation in genetic effects on flowering time across both time and space; the greatest differences evident between populations, where numerous factors (environmental variation, genomic background, and private polymorphisms) likely contribute to heterogeneity. However, the changes across years within populations clearly identify genotype-by-environment interactions as an important influence on flowering time variation.
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Affiliation(s)
- Patrick J Monnahan
- Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, Kansas 66045
| | - John K Kelly
- Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, Kansas 66045
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28
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Affiliation(s)
- John K. Kelly
- Department of Ecology and Evolutionary Biology University of Connecticut Storrs CT 06268 USA
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29
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Kelly JK. FITNESS VARIATION ACROSS A SUBDIVIDED POPULATION OF THE ANNUAL PLANT
IMPATIENS CAPENSIS. Evolution 2017; 51:1100-1111. [DOI: 10.1111/j.1558-5646.1997.tb03957.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/1996] [Accepted: 02/26/1997] [Indexed: 11/28/2022]
Affiliation(s)
- John K. Kelly
- Department of Ecology and Evolution The University of Chicago 1101 East 57th Street Chicago Illinois 60637
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30
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Kelly JK. RESPONSE TO SELECTION IN PARTIALLY SELF-FERTILIZING POPULATIONS. II. SELECTION ON MULTIPLE TRAITS. Evolution 2017; 53:350-357. [DOI: 10.1111/j.1558-5646.1999.tb03771.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/1998] [Accepted: 10/20/1998] [Indexed: 11/28/2022]
Affiliation(s)
- John K. Kelly
- Department of Biology; University of Oregon; Eugene Oregon 97403
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Kelly JK. RESPONSE TO SELECTION IN PARTIALLY SELF-FERTILIZING POPULATIONS. I. SELECTION ON A SINGLE TRAIT. Evolution 2017; 53:336-349. [DOI: 10.1111/j.1558-5646.1999.tb03770.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/1998] [Accepted: 10/20/1998] [Indexed: 11/28/2022]
Affiliation(s)
- John K. Kelly
- Department of Biology; University of Oregon; Eugene Oregon 97403
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Puzey JR, Willis JH, Kelly JK. Population structure and local selection yield high genomic variation in Mimulus guttatus. Mol Ecol 2017; 26:519-535. [PMID: 27859786 PMCID: PMC5274581 DOI: 10.1111/mec.13922] [Citation(s) in RCA: 45] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2015] [Revised: 09/30/2016] [Accepted: 11/07/2016] [Indexed: 12/30/2022]
Abstract
Across western North America, Mimulus guttatus exists as many local populations adapted to site-specific environmental challenges. Gene flow between locally adapted populations will affect genetic diversity both within demes and across the larger metapopulation. Here, we analyse 34 whole-genome sequences from the intensively studied Iron Mountain population (IM) in conjunction with sequences from 22 Mimulus individuals sampled from across western North America. Three striking features of these data address hypotheses about migration and selection in a locally adapted population. First, we find very high levels of intrapopulation polymorphism (synonymous π = 0.033). Variation outside of genes is likely even higher but difficult to estimate because excessive divergence reduces the efficiency of read mapping. Second, IM exhibits a significantly positive genomewide average for Tajima's D. This indicates allele frequencies are typically more intermediate than expected from neutrality, opposite the pattern observed in many other species. Third, IM exhibits a distinctive haplotype structure with a genomewide excess of positive associations between rarer alleles at linked loci. This suggests an important effect of gene flow from other Mimulus populations, although a residual effect of population founding might also contribute. The combination of multiple analyses, including a novel tree-based analytic method, illustrates how the balance of local selection, limited dispersal and metapopulation dynamics manifests across the genome. The overall genomic pattern of sequence diversity suggests successful gene flow of divergent immigrant genotypes into IM. However, many loci show patterns indicative of local adaptation, particularly at SNPs associated with chromosomal inversions.
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Affiliation(s)
- Joshua R. Puzey
- Department of Biology, College of William and Mary, Williamsburg, Virginia, 23187
- Department of Biology, Duke University, Durham, North Carolina, 27708
| | - John H. Willis
- Department of Biology, Duke University, Durham, North Carolina, 27708
| | - John K. Kelly
- Department of Ecology and Evolution, University of Kansas, Lawrence, Kansas, 27708
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Abstract
The extent to which gene interaction or epistasis contributes to fitness variation within populations remains poorly understood, despite its importance to a myriad of evolutionary questions. Here, we report a multi-year field study estimating fitness of Mimulus guttatus genetic lines in which pairs of naturally segregating loci exist in an otherwise uniform background. An allele at QTL x5b-a locus originally mapped for its effect on flower size-positively affects survival if combined with one genotype at quantitative trait locus x10a (aa) but has negative effects when combined with the other genotypes (Aa and AA). The viability differences between genotypes parallel phenotypic differences for the time and node at which a plant flowers. Viability is negatively correlated with fecundity across genotypes, indicating antagonistic pleiotropy for fitness components. This trade-off reduces the genetic variance for total fitness relative to the individual fitness components and thus may serve to maintain variation. Additionally, we find that the effects of each locus and their interaction often vary with the environment.
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Affiliation(s)
- Patrick J Monnahan
- Department of Ecology and Evolutionary Biology, University of Kansas, 1200 Sunnyside Avenue, Lawrence, KS 66045, USA
| | - John K Kelly
- Department of Ecology and Evolutionary Biology, University of Kansas, 1200 Sunnyside Avenue, Lawrence, KS 66045, USA
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Lee YW, Fishman L, Kelly JK, Willis JH. A Segregating Inversion Generates Fitness Variation in Yellow Monkeyflower (Mimulus guttatus). Genetics 2016; 202:1473-84. [PMID: 26868767 PMCID: PMC4905537 DOI: 10.1534/genetics.115.183566] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2015] [Accepted: 02/01/2016] [Indexed: 11/18/2022] Open
Abstract
Polymorphic chromosomal rearrangements can bind hundreds of genes into single genetic loci with diverse effects. Rearrangements are often associated with local adaptation and speciation and may also be an important component of genetic variation within populations. We genetically and phenotypically characterize a segregating inversion (inv6) in the Iron Mountain (IM) population of Mimulus guttatus (yellow monkeyflower). We initially mapped inv6 as a region of recombination suppression in three F2 populations resulting from crosses among IM plants. In each case, the F1 parent was heterozygous for a derived haplotype, homogenous across markers spanning over 5 Mb of chromsome 6. In the three F2 populations, inv6 reduced male and female fitness components. In addition,i nv6 carriers suffered an ∼30% loss of pollen viability in the field. Despite these costs, inv6 exists at moderate frequency (∼8%) in the natural population, suggesting counterbalancing fitness benefits that maintain the polymorphism. Across 4 years of monitoring in the field, inv6 had an overall significant positive effect on seed production (lifetime female fitness) of carriers. This benefit was particularly strong in harsh years and may be mediated (in part) by strong positive effects on flower production. These data suggest that opposing fitness effects maintain an intermediate frequency, and as a consequence, inv6 generates inbreeding depression and high genetic variance. We discuss these findings in relation to the theory of inbreeding depression and the maintenance of fitness variation.
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Affiliation(s)
- Young Wha Lee
- Biology Department, Duke University, Durham, North Carolina 27708
| | - Lila Fishman
- Division of Biological Sciences, University of Montana, Missoula, Montana 59812
| | - John K Kelly
- Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, Kansas 66045
| | - John H Willis
- Biology Department, Duke University, Durham, North Carolina 27708
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Akkerman KC, Sattarin A, Kelly JK, Scoville AG. Transgenerational plasticity is sex-dependent and persistent in yellow monkeyflower ( Mimulus guttatus). Environ Epigenet 2016; 2:dvw003. [PMID: 29492285 PMCID: PMC5804517 DOI: 10.1093/eep/dvw003] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/16/2015] [Revised: 12/16/2015] [Accepted: 01/27/2016] [Indexed: 05/19/2023]
Abstract
Transgenerational phenotypic plasticity, whereby environmental cues experienced by parents alter the phenotype of their progeny, has now been documented in diverse organisms. Transmission of environmentally determined responses is known to occur through both maternal and paternal gametes, but the underlying mechanisms have rarely been compared. In addition, the persistence of induction over multiple generations appears to vary widely, but has been characterized for relatively few systems. Yellow monkeyflower (Mimulus guttatus) is known to exhibit transgenerational induction of increased glandular trichome production in response to simulated insect damage. Here, we test for differences between maternal and paternal transmission of this response and examine its persistence over five generations following damage. Maternal and paternal damage resulted in similar and apparently additive increases in progeny trichome production. Treatment of germinating seeds with the genome-wide demethylating agent 5-azacytidine erased the effect of maternal but not paternal damage. The number of glandular trichomes remained elevated for three generations following damage. These results indicate that transgenerational transmission occurs through both maternal and paternal germ lines, but that they differ in the proximate mechanism of epigenetic inheritance. Our results also indicate that a wounding response can persist for multiple generations in the absence of subsequent damage.
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Affiliation(s)
- Kayla C. Akkerman
- Department of Biology, Central Washington University, Ellensburg, WA 98926, USA
| | - Arash Sattarin
- Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, KS 66045, USA
| | - John K. Kelly
- Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, KS 66045, USA
| | - Alison G. Scoville
- Department of Biology, Central Washington University, Ellensburg, WA 98926, USA
- *Correspondence address. Department of Biology, Central Washington University, Ellensburg, 400 E University Way, Ellensburg, WA, 98926. Tel: 509-963-2802. Fax: 509-963-2730 E-mail:
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Monnahan PJ, Colicchio J, Kelly JK. A genomic selection component analysis characterizes migration-selection balance. Evolution 2015; 69:1713-27. [PMID: 26082096 DOI: 10.1111/evo.12698] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [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: 01/13/2015] [Accepted: 05/22/2015] [Indexed: 12/16/2022]
Abstract
The genetic differentiation of populations in response to local selection pressures has long been studied by evolutionary biologists, but key details about the process remain obscure. How rapidly can local adaptation evolve, how extensive is the process across the genome, and how strong are the opposing forces of natural selection and gene flow? Here, we combine direct measurement of survival and reproduction with whole-genome genotyping of a plant species (Mimulus guttatus) that has recently invaded a novel habitat (the Quarry population). We renovate the classic selection component method to accommodate genomic data and observe selection at SNPs throughout the genome. SNPs showing viability selection in Quarry exhibit elevated divergence from neighboring populations relative to neutral SNPs. We also find that nonsignificant SNPs exhibit a subtle, but still significant, change in allele frequency toward neighboring populations, a predicted effect of gene flow. Given that the Quarry population is most probably only 30-40 generations old, the alleles conferring local advantage are almost certainly older than the population itself. Thus, local adaptation owes to the recruitment of standing genetic variation.
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Affiliation(s)
- Patrick J Monnahan
- Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, Kansas, 66045
| | - Jack Colicchio
- Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, Kansas, 66045
| | - John K Kelly
- Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, Kansas, 66045.
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Colicchio JM, Miura F, Kelly JK, Ito T, Hileman LC. DNA methylation and gene expression in Mimulus guttatus. BMC Genomics 2015; 16:507. [PMID: 26148779 PMCID: PMC4492170 DOI: 10.1186/s12864-015-1668-0] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2015] [Accepted: 05/29/2015] [Indexed: 11/13/2022] Open
Abstract
Background The presence of methyl groups on cytosine nucleotides across an organism’s genome (methylation) is a major regulator of genome stability, crossing over, and gene regulation. The capacity for DNA methylation to be altered by environmental conditions, and potentially passed between generations, makes it a prime candidate for transgenerational epigenetic inheritance. Here we conduct the first analysis of the Mimulus guttatus methylome, with a focus on the relationship between DNA methylation and gene expression. Results We present a whole genome methylome for the inbred line Iron Mountain 62 (IM62). DNA methylation varies across chromosomes, genomic regions, and genes. We develop a model that predicts gene expression based on DNA methylation (R2 = 0.2). Post hoc analysis of this model confirms prior relationships, and identifies novel relationships between methylation and gene expression. Additionally, we find that DNA methylation is significantly depleted near gene transcriptional start sites, which may explain the recently discovered elevated rate of recombination in these same regions. Conclusions The establishment here of a reference methylome will be a useful resource for the continued advancement of M. guttatus as a model system. Using a model-based approach, we demonstrate that methylation patterns are an important predictor of variation in gene expression. This model provides a novel approach for differential methylation analysis that generates distinct and testable hypotheses regarding gene expression. Electronic supplementary material The online version of this article (doi:10.1186/s12864-015-1668-0) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Jack M Colicchio
- Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, KS, 66045, USA.
| | - Fumihito Miura
- Department of Medical Biochemistry, Department of Biochemistry, Fukuoka 812-8581, Fukuoka 812-8582, Japan
| | - John K Kelly
- Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, KS, 66045, USA
| | - Takashi Ito
- Department of Medical Biochemistry, Department of Biochemistry, Fukuoka 812-8581, Fukuoka 812-8582, Japan
| | - Lena C Hileman
- Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, KS, 66045, USA
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Fishman L, Kelly JK. Centromere-associated meiotic drive and female fitness variation in Mimulus. Evolution 2015; 69:1208-18. [PMID: 25873401 DOI: 10.1111/evo.12661] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2015] [Accepted: 04/06/2015] [Indexed: 02/07/2023]
Abstract
Female meiotic drive, in which chromosomal variants preferentially segregate to the egg pole during asymmetric female meiosis, is a theoretically pervasive but still mysterious form of selfish evolution. Like other selfish genetic elements, driving chromosomes may be maintained as balanced polymorphisms by pleiotropic or linked fitness costs. A centromere-associated driver (D) with a ∼58:42 female-specific transmission advantage occurs at intermediate frequency (32-40%) in the Iron Mountain population of the yellow monkeyflower, Mimulus guttatus. Previously determined male fertility costs are sufficient to prevent the fixation of D, but predict a higher equilibrium frequency. To better understand the dynamics and effects of D, we developed a new population genetic model and measured genotype-specific lifetime female fitness in the wild. In three of four years, and across all years, D imposed significant recessive seedset costs, most likely due to hitchhiking by deleterious mutations. With both male and female costs as measured, and 58:42 drive, our model predicts an equilibrium frequency of D (38%) very close to the observed value. Thus, D represents a rare selfish genetic element whose local population genetic dynamics have been fully parameterized, and the observation of equilibrium sets the stage for investigations of coevolution with suppressors.
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Affiliation(s)
- Lila Fishman
- Division of Biological Sciences, University of Montana, Montana, Missoula, 59812.
| | - John K Kelly
- Department of Ecology and Evolutionary Biology, University of Kansas, Kansas, Lawrence, 66045
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Abstract
The influence of genetic interactions (epistasis) on the genetic variance of quantitative traits is a major unresolved problem relevant to medical, agricultural, and evolutionary genetics. The additive genetic component is typically a high proportion of the total genetic variance in quantitative traits, despite that underlying genes must interact to determine phenotype. This study estimates direct and interaction effects for 11 pairs of Quantitative Trait Loci (QTLs) affecting floral traits within a single population of Mimulus guttatus. With estimates of all 9 genotypes for each QTL pair, we are able to map from QTL effects to variance components as a function of population allele frequencies, and thus predict changes in variance components as allele frequencies change. This mapping requires an analytical framework that properly accounts for bias introduced by estimation errors. We find that even with abundant interactions between QTLs, most of the genetic variance is likely to be additive. However, the strong dependency of allelic average effects on genetic background implies that epistasis is a major determinant of the additive genetic variance, and thus, the population’s ability to respond to selection. Complex traits are influenced not only by the effects of individual genes but also by the myriad ways that these genes interact with one another, commonly referred to as epistasis. Theory suggests that epistasis could have important population-level implications in terms of the genetic variance components that govern evolution in response to natural or artificial selection. Unfortunately, empirical examples extending from observed interactions between genes to genetic variances are scant, particularly for natural populations. Here, we characterize epistasis between naturally segregating polymorphisms in M. guttatus and determine the cumulative effect of epistasis on population genetic variance components. To do this, we first elaborate the necessary statistical theory to accommodate estimation error in genetic effects, as failing to do so will upwardly bias variance predictions. We find that gene interactions have a net positive effect on both the total and additive genetic variance for most traits; however, the contribution of individual loci to the additive variance depends heavily on the genotype frequencies at other loci. Therefore, the effect of epistasis extends beyond the individual’s phenotype to influence how both populations and their component alleles respond to selection.
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Affiliation(s)
- Patrick J. Monnahan
- Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, Lawrence, Kansas, United States of America
- * E-mail:
| | - John K. Kelly
- Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, Lawrence, Kansas, United States of America
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40
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Mort ME, Crawford DJ, Kelly JK, Santos-Guerra A, Menezes de Sequeira M, Moura M, Caujapé-Castells J. Multiplexed-shotgun-genotyping data resolve phylogeny within a very recently derived insular lineage. Am J Bot 2015; 102:634-41. [PMID: 25878096 DOI: 10.3732/ajb.1400551] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/17/2014] [Accepted: 03/23/2015] [Indexed: 05/23/2023]
Abstract
PREMISE OF THE STUDY Endemic plants on oceanic islands have long served as model systems for studying patterns and processes of evolution. However, phylogenetic studies of island plants frequently illustrate a decoupling of molecular divergence and ecological/morphological diversity, resulting in phylogenies lacking the resolution required to interpret patterns of evolution in a phylogenetic context. The current study uses the primarily Macaronesian flowering plant genus Tolpis to illustrate the utility of multiplexed shotgun genotyping (MSG) for resolving relationships at relatively deep (among archipelagos) and very shallow (within archipelagos) nodes in this small, yet diverse insular plant lineage that had not been resolved with other molecular markers. METHODS Genomic libraries for 27 accessions of Macaronesian Tolpis were generated for genotyping individuals using MSG, a form of reduced-representation sequencing, similar to restriction-site-associated DNA markers (RADseq). The resulting data files were processed using the program pyRAD, which clusters MSG loci within and between samples. Phylogenetic analyses of the aligned data matrix were conducted using RAxML. KEY RESULTS Analysis of MSG data recovered a highly resolved phylogeny with generally strong support, including the first robust inference of relationships within the highly diverse Canary Island clade of Tolpis. CONCLUSIONS The current study illustrates the utility of MSG data for resolving relationships in lineages that have undergone recent, rapid diversification resulting in extensive ecological and morphological diversity. We suggest that a similar approach may prove generally useful for other rapid plant radiations where resolving phylogeny has been difficult.
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Affiliation(s)
- Mark E Mort
- Department of Ecology and Evolutionary Biology, and Biodiversity Institute; University of Kansas, 1200 Sunnyside Ave, Lawrence, Kansas 66045 USA
| | - Daniel J Crawford
- Department of Ecology and Evolutionary Biology, and Biodiversity Institute; University of Kansas, 1200 Sunnyside Ave, Lawrence, Kansas 66045 USA
| | - John K Kelly
- Department of Ecology and Evolutionary Biology, 1200 Sunnyside Ave, Lawrence, Kansas 66045 USA
| | - Arnoldo Santos-Guerra
- Calle Guaidil 16, Urbanización Tamarco, Tegueste, Tenerife, Canary Islands, Spain 38280
| | | | - Mónica Moura
- Universidade dos Açores, Departamento de Biologia, Rua da Mãe de Deus, Ponta Delgada, Azores, Portugal
| | - Juli Caujapé-Castells
- Jardin Botanico Canario "Viera y Clavijo"-Unidad Asociada CSIC, Cabildo de Gran Canaria; Camino al Palmeral 15, Tafira Alta 35017 Las Palmas de Gran Canaria, Spain
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41
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Colicchio JM, Monnahan PJ, Kelly JK, Hileman LC. Gene expression plasticity resulting from parental leaf damage in Mimulus guttatus. New Phytol 2015; 205:894-906. [PMID: 25297849 DOI: 10.1111/nph.13081] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/26/2014] [Accepted: 08/20/2014] [Indexed: 06/04/2023]
Abstract
Leaf trichome density in Mimulus guttatus can be altered by the parental environment. In this study, we compared global gene expression patterns in progeny of damaged and control plants. Significant differences in gene expression probably explain the observed trichome response, and identify additional responsive pathways. Using whole transcriptome RNA sequencing, we estimated differential gene expression between isogenic seedlings whose parents had, or had not, been subject to leaf damage. We identified over 900 genes that were differentially expressed in response to parental wounding. These genes clustered into groups involved in cell wall and cell membrane development, stress response pathways, and secondary metabolism. Gene expression is modified as a consequence of the parental environment in a targeted way that probably alters multiple developmental pathways, and may increase progeny fitness if they experience environments similar to that of their parents.
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Affiliation(s)
- Jack M Colicchio
- Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, KS 66045, USA
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Abstract
Balancing selection refers to a variety of selective regimes that maintain advantageous genetic diversity within populations. We review the history of the ideas regarding the types of selection that maintain such polymorphism in flowering plants, notably heterozygote advantage, negative frequency-dependent selection, and spatial heterogeneity. One shared feature of these mechanisms is that whether an allele is beneficial or detrimental is conditional on its frequency in the population. We highlight examples of balancing selection on a variety of discrete traits. These include the well-referenced case of self-incompatibility and recent evidence from species with nuclear-cytoplasmic gynodioecy, both of which exhibit trans-specific polymorphism, a hallmark of balancing selection. We also discuss and give examples of how spatial heterogeneity in particular, which is often thought unlikely to allow protected polymorphism, can maintain genetic variation in plants (which are rooted in place) as a result of microhabitat selection. Lastly, we discuss limitations of the protected polymorphism concept for quantitative traits, where selection can inflate the genetic variance without maintaining specific alleles indefinitely. We conclude that while discrete-morph variation provides the most unambiguous cases of protected polymorphism, they represent only a fraction of the balancing selection at work in plants.
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Affiliation(s)
- Lynda F. Delph
- Department of Biology, Indiana University, 1001 East Third Street, Bloomington, IN 47405, USA
| | - John K. Kelly
- Department of Ecology and Evolutionary Biology, University of Kansas, 1200 Sunnyside Avenue, Lawrence, KS 66045, USA
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Abstract
The molecular signature of selection depends strongly on whether new mutations are immediately favorable and sweep to fixation (hard sweeps) as opposed to when selection acts on segregating variation (soft sweeps). The prediction of reduced sequence variation around selected polymorphisms is much stronger for hard than soft sweeps, particularly when considering quantitative traits where sweeps are likely to be incomplete. Here, we directly investigate the genomic signal of soft sweeps within an artificial selection experiment on Mimulus guttatus. We first develop a statistical method based on Fisher’s angular transformation of allele frequencies to identify selected loci. Application of this method identifies about 400 significant windows, but no fixed differences between phenotypically divergent populations. With two notable exceptions, we find a modest average effect of partial sweeps on the amount of molecular variation. The first exception is a polymorphic inversion on chromosome 6. The increase of the derived haplotype has a broad genomic effect due to recombination suppression coupled with substantial initial haplotype structure within the population. Second, we found significant increases in nucleotide variation around selected loci in the population evolving larger flowers. This suggests that “high” alleles for flower size were initially less frequent than “low” alleles. This result is consistent with prior studies of M. guttatus and illustrates how molecular evolution can depend on the allele frequency spectrum at quantitative trait loci.
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Affiliation(s)
- John K Kelly
- Department of Ecology and Evolutionary Biology, University of Kansas.
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Abstract
Background The transition from vegetative to reproductive stages marks a major milestone in plant development. It is clear that global change factors (e.g., increasing [CO2] and temperature) have already had and will continue to have a large impact on plant flowering times in the future. Increasing atmospheric [CO2] has recently been shown to affect flowering time, and may produce even greater responses than increasing temperature. Much is known about the genes influencing flowering time, although their relevance to changing [CO2] is not well understood. Thus, we present the first study to identify QTL (Quantitative Trait Loci) that affect flowering time at elevated [CO2] in Arabidopsis thaliana. Methodology/Principal Findings We developed our mapping population by crossing a genotype previously selected for high fitness at elevated [CO2] (SG, Selection Genotype) to a Cape Verde genotype (Cvi-0). SG exhibits delayed flowering at elevated [CO2], whereas Cvi-0 is non-responsive to elevated [CO2] for flowering time. We mapped one major QTL to the upper portion of chromosome 1 that explains 1/3 of the difference in flowering time between current and elevated [CO2] between the SG and Cvi-0 parents. This QTL also alters the stage at which flowering occurs, as determined from higher rosette leaf number at flowering in RILs (Recombinant Inbred Lines) harboring the SG allele. A follow-up study using Arabidopsis mutants for flowering time genes within the significant QTL suggests MOTHER OF FT AND TFL1 (MFT) as a potential candidate gene for altered flowering time at elevated [CO2]. Conclusion/Significance This work sheds light on the underlying genetic architecture that controls flowering time at elevated [CO2]. Prior to this work, very little to nothing was known about these mechanisms at the genomic level. Such a broader understanding will be key for better predicting shifts in plant phenology and for developing successful crops for future environments.
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Affiliation(s)
- Joy K Ward
- Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, KS, USA.
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Koelling VA, Monnahan PJ, Kelly JK. A Bayesian method for the joint estimation of outcrossing rate and inbreeding depression. Heredity (Edinb) 2012; 109:393-400. [PMID: 22990309 DOI: 10.1038/hdy.2012.58] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
The population outcrossing rate (t) and adult inbreeding coefficient (F) are key parameters in mating system evolution. The magnitude of inbreeding depression as expressed in the field can be estimated given t and F via the method of Ritland (1990). For a given total sample size, the optimal design for the joint estimation of t and F requires sampling large numbers of families (100-400) with fewer offspring (1-4) per family. Unfortunately, the standard inference procedure (MLTR) yields significantly biased estimates for t and F when family sizes are small and maternal genotypes are unknown (a common occurrence when sampling natural populations). Here, we present a Bayesian method implemented in the program BORICE (Bayesian Outcrossing Rate and Inbreeding Coefficient Estimation) that effectively estimates t and F when family sizes are small and maternal genotype information is lacking. BORICE should enable wider use of the Ritland approach for field-based estimates of inbreeding depression. As proof of concept, we estimate t and F in a natural population of Mimulus guttatus. In addition, we describe how individual maternal inbreeding histories inferred by BORICE may prove useful in studies of inbreeding and its consequences.
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Affiliation(s)
- V A Koelling
- Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, KS 66045, USA
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46
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Mojica JP, Lee YW, Willis JH, Kelly JK. Spatially and temporally varying selection on intrapopulation quantitative trait loci for a life history trade-off in Mimulus guttatus. Mol Ecol 2012; 21:3718-28. [PMID: 22686425 DOI: 10.1111/j.1365-294x.2012.05662.x] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Why do populations remain genetically variable despite strong continuous natural selection? Mutation reconstitutes variation eliminated by selection and genetic drift, but theoretical and experimental studies each suggest that mutation-selection balance insufficient to explain extant genetic variation in most complex traits. The alternative hypothesis of balancing selection, wherein selection maintains genetic variation, is an aggregate of multiple mechanisms (spatial and temporal heterogeneity in selection, frequency-dependent selection, antagonistic pleiotropy, etc.). Most of these mechanisms have been demonstrated for Mendelian traits, but there is little comparable data for loci affecting quantitative characters. Here, we report a 3-year field study of selection on intrapopulation quantitative trait loci (QTL) of flower size, a highly polygenic trait in Mimulus guttatus. The QTL exhibit antagonistic pleiotropy: alleles that increase flower size, reduce viability, but increase fecundity. The magnitude and direction of selection fluctuates yearly and on a spatial scale of metres. This study provides direct evidence of balancing selection mechanisms on QTL of an ecologically relevant trait.
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Affiliation(s)
- Julius P Mojica
- Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, KS, USA.
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Abstract
Anthropogenic perturbations including habitat loss and emerging disease are changing pollinator communities and generating novel selection pressures on plant populations. Disruption of plant-pollinator relationships is predicted to cause plant mating system evolution, although this process has not been directly observed. This study demonstrates the immediate evolutionary effects of pollinator loss within experimental populations of a predominately outcrossing wildflower. Initially equivalent populations evolved for five generations within two pollination treatments: abundant bumblebee pollinators versus no pollinators. The populations without pollinators suffered greatly reduced fitness in early generations but rebounded as they evolved an improved ability to self-fertilize. All populations diverged in floral, developmental, and life-history traits, but only a subset of characters showed clear association with pollination treatment. Pronounced treatment effects were noted for anther-stigma separation and autogamous seed set. Dramatic allele frequency changes at two chromosomal polymorphisms occurred in the no pollinator populations, explaining a large fraction of divergence in pollen viability. The pattern of phenotypic and genetic changes in this experiment favors a sequential model for the evolution of the multitrait "selfing syndrome" observed throughout angiosperms.
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Affiliation(s)
- Sarah A Bodbyl Roels
- Department of Ecology and Evolutionary Biology, University of Kansas, 1200 Sunnyside Avenue, Lawrence, Kansas 66046, USA.
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48
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Abstract
We describe a statistical framework for QTL mapping using bulk segregant analysis (BSA) based on high throughput, short-read sequencing. Our proposed approach is based on a smoothed version of the standard G statistic, and takes into account variation in allele frequency estimates due to sampling of segregants to form bulks as well as variation introduced during the sequencing of bulks. Using simulation, we explore the impact of key experimental variables such as bulk size and sequencing coverage on the ability to detect QTLs. Counterintuitively, we find that relatively large bulks maximize the power to detect QTLs even though this implies weaker selection and less extreme allele frequency differences. Our simulation studies suggest that with large bulks and sufficient sequencing depth, the methods we propose can be used to detect even weak effect QTLs and we demonstrate the utility of this framework by application to a BSA experiment in the budding yeast Saccharomyces cerevisiae.
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Affiliation(s)
- Paul M Magwene
- Department of Biology and IGSP Center for Systems Biology, Duke University, Durham, North Carolina, United States of America.
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49
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Scoville AG, Barnett LL, Bodbyl-Roels S, Kelly JK, Hileman LC. Differential regulation of a MYB transcription factor is correlated with transgenerational epigenetic inheritance of trichome density in Mimulus guttatus. New Phytol 2011; 191:251-263. [PMID: 21352232 PMCID: PMC3107365 DOI: 10.1111/j.1469-8137.2011.03656.x] [Citation(s) in RCA: 94] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
• Epigenetic inheritance, transgenerational transmission of traits not proximally determined by DNA sequence, has been linked to transmission of chromatin modifications and gene regulation, which are known to be sensitive to environmental factors. Mimulus guttatus increases trichome (plant hair) density in response to simulated herbivore damage. Increased density is expressed in progeny even if progeny do not experience damage. To better understand epigenetic inheritance of trichome production, we tested the hypothesis that candidate gene expression states are inherited in response to parental damage. • Using M. guttatus recombinant inbred lines, offspring of leaf-damaged and control plants were raised without damage. Relative expression of candidate trichome development genes was measured in offspring. Line and parental damage effects on trichome density were measured. Associations between gene expression, trichome density, and response to parental damage were determined. • We identified M. guttatus MYB MIXTA-like 8 as a possible negative regulator of trichome development. We found that parental leaf damage induces down-regulation of MYB MIXTA-like 8 in progeny, which is associated with epigenetically inherited increased trichome density. • Our results link epigenetic transmission of an ecologically important trait with differential gene expression states - providing insight into a mechanism underlying environmentally induced 'soft inheritance'.
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Affiliation(s)
- Alison G Scoville
- Department of Ecology and Evolutionary Biology, The University of Kansas, Lawrence, KS 66045, USA
| | - Laryssa L Barnett
- Department of Ecology and Evolutionary Biology, The University of Kansas, Lawrence, KS 66045, USA
| | - Sarah Bodbyl-Roels
- Department of Ecology and Evolutionary Biology, The University of Kansas, Lawrence, KS 66045, USA
| | - John K Kelly
- Department of Ecology and Evolutionary Biology, The University of Kansas, Lawrence, KS 66045, USA
| | - Lena C Hileman
- Department of Ecology and Evolutionary Biology, The University of Kansas, Lawrence, KS 66045, USA
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50
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Scoville AG, Lee YW, Willis JH, Kelly JK. Explaining the heritability of an ecologically significant trait in terms of individual quantitative trait loci. Biol Lett 2011; 7:896-8. [PMID: 21653565 DOI: 10.1098/rsbl.2011.0409] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Most natural populations display substantial genetic variation in behaviour, morphology, physiology, life history and the susceptibility to disease. A major challenge is to determine the contributions of individual loci to variation in complex traits. Quantitative trait locus (QTL) mapping has identified genomic regions affecting ecologically significant traits of many species. In nearly all cases, however, the importance of these QTLs to population variation remains unclear. In this paper, we apply a novel experimental method to parse the genetic variance of floral traits of the annual plant Mimulus guttatus into contributions of individual QTLs. We first use QTL-mapping to identify nine loci and then conduct a population-based breeding experiment to estimate V(Q), the genetic variance attributable to each QTL. We find that three QTLs with moderate effects explain up to one-third of the genetic variance in the natural population. Variation at these loci is probably maintained by some form of balancing selection. Notably, the largest effect QTLs were relatively minor in their contribution to heritability.
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Affiliation(s)
- Alison G Scoville
- Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, KS 66045, USA
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