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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 atRNAligase gene (Migut.N02091;RLG1a) exhibiting unprecedented, and fitness‐relevant,CNVwithin an annual population of the yellow monkeyflowerMimulus 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 ofRLG1a (trip+;5/35 = 14%), andtrip+lines exhibited elevatedRLG1a 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 rareRLG1a variant (high+) that carries 250–300 copies ofRLG1a totalling ~5.7 Mb (20–40% of a chromosome). In the progeny of ahigh+carrier, Mendelian segregation of diagnostic alleles andqPCR‐based copy counts indicate thathigh+is a single tandem array unlinked to the single‐copyRLG1a locus. In the wild,high+carriers had highest fitness in two particularly dry and/or hot years (2015 and 2017; bothp < 0.01), while single‐copy individuals were twice as fecund as eitherCNVtype in a lush year (2016:p < 0.005). Our results demonstrate fluctuating selection onCNVs affecting phenological traits in a wild population, suggest that planttRNAligases mediate stress‐responsive life‐history traits, and introduce a novel system for investigating the molecular mechanisms of gene amplification.
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Increasing Aridity May Threaten the Maintenance of a Plant Defence Polymorphism
ABSTRACT It is unclear how environmental change influences standing genetic variation in wild populations. Here, we characterised environmental conditions that protect versus erode polymorphic chemical defences inBoechera stricta(Brassicaceae), a short‐lived perennial wildflower. By manipulating drought and herbivory in a 4‐year field experiment, we measured the effects of driver variation on vital rates of genotypes varying in defence chemistry and then assessed interacting driver effects on total fitness (estimated as each genotype's lineage growth rate,λ) using demographic models. Drought and herbivory interacted to shape vital rates, but contrasting defence genotypes had equivalent total fitness in many environments. Defence polymorphism thus may persist under a range of conditions; however, ambient field conditions fall close to the boundary of putatively polymorphic environment space, and increasing aridity may drive populations to monomorphism. Consequently, elevated intensity and/or frequency of drought under climate change may erode genetic variation for defence chemistry inB. stricta.
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- Award ID(s):
- 1753980
- PAR ID:
- 10571450
- Publisher / Repository:
- Wiley-Blackwell
- Date Published:
- Journal Name:
- Ecology Letters
- Volume:
- 28
- Issue:
- 1
- ISSN:
- 1461-023X
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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