Introduced and invasive species make excellent natural experiments for investigating rapid evolution. Here, we describe the effects of genetic drift and rapid genetic adaptation in pink salmon (
Understanding the molecular basis of repeated evolution improves our ability to predict evolution across the tree of life. Only since the last decade has high‐throughput sequencing enabled comparative genome scans to thoroughly examine the repeatability of genetic changes driving repeated phenotypic evolution. The Asian corn borer (ACB),
- NSF-PAR ID:
- 10406195
- Publisher / Repository:
- Wiley-Blackwell
- Date Published:
- Journal Name:
- Molecular Ecology
- Volume:
- 32
- Issue:
- 13
- ISSN:
- 0962-1083
- Format(s):
- Medium: X Size: p. 3419-3439
- Size(s):
- ["p. 3419-3439"]
- Sponsoring Org:
- National Science Foundation
More Like this
-
more » « less
Abstract Oncorhynchus gorbuscha ) that were accidentally introduced to the Great Lakes via a single introduction event 31 generations ago. Using whole‐genome resequencing for 134 fish spanning five sample groups across the native and introduced range, we estimate that the source population's effective population size was 146,886 at the time of introduction, whereas the founding population's effective population size was just 72—a 2040‐fold decrease. As expected with a severe founder event, we show reductions in genome‐wide measures of genetic diversity, specifically a 37.7% reduction in the number of SNPs and an 8.2% reduction in observed heterozygosity. Despite this decline in genetic diversity, we provide evidence for putative selection at 47 loci across multiple chromosomes in the introduced populations, including missense variants in genes associated with circadian rhythm, immunological response and maturation, which match expected or known phenotypic changes in the Great Lakes. For one of these genes, we use a species‐specific agent‐based model to rule out genetic drift and conclude our results support a strong response to selection occurring in a period gene (per2 ) that plays a predominant role in determining an organism's daily clock, matching large day length differences experienced by introduced salmon during important phenological periods. Together, these results inform how populations might evolve rapidly to new environments, even with a small pool of standing genetic variation. -
more » « less
Abstract Patterns of mating for the European corn borer (
Ostrinia nubilalis ) moth depend in part on variation in sex‐pheromone blend. The ratio of (E )‐11‐ and (Z )‐11‐tetradecenyl acetate (E11‐ and Z11‐14:OAc) in the pheromone blend that females produce and males respond to differs between strains ofO. nubilalis . Populations also vary in female oviposition preference for and larval performance on maize (C4) and nonmaize (C3) host plants. The relative contributions of sexual and ecological trait variation to the genetic structure ofO. nubilalis remains unknown. Host‐plant use (13C/14C ratios) and genetic differentiation were estimated among sympatric E and Z pheromone strainO. nubilalis males collected in sex‐pheromone baited traps at 12 locations in Pennsylvania and New York between 2007 and 2010. Among genotypes at 65 single nucleotide polymorphism marker loci, variance at a position in the pheromone gland fatty acyl‐reductase (pgfar ) gene at the locus responsible for determining female pheromone ratio (Pher ) explained 64% of the total genetic differentiation between males attracted to different pheromones (male response,Resp ), providing evidence of sexual inter‐selection at these unlinked loci. Principal coordinate, Bayesian clustering, and distance‐based redundancy analysis (dbRDA) demonstrate that host plant history or geography does not significantly contribute to population variation or differentiation among males. In contrast, these analyses indicate that pheromone response andpgfar ‐defined strain contribute significantly to population genetic differentiation. This study suggests that behavioural divergence probably plays a larger role in driving genetic variation compared to host plant‐defined ecological adaptation. -
more » « less
Abstract Reconstructing a robust phylogenetic framework is key to understanding the ecology and evolution of many economically important taxa. The crambid moth genus
Ostrinia contains multiple agricultural pests, and its classification and phylogeny has remained controversial because of the paucity of characters and the lack of clear morphological boundaries for its species. To address these issues, we inferred a molecular phylogeny ofOstrinia using a phylogenomic dataset containing 498 loci and 115 197 nucleotide sites and examined whether traditional morphological characters corroborate our molecular results. Our results strongly support the monophyly of one of theOstrinia species groups but surprisingly do not support the monophyly of the other two. Based on the extensive morphological examination and broadly representative taxon sampling of the phylogenomic analyses, we propose a revised classification of the genus, defined by three species groups (Ostrinia nubilalis species group,Ostrinia obumbratalis species group, andOstrinia penitalis species group), which differs from the traditional classification of Mutuura & Munroe (1970). Morphological and molecular evidence reveal the presence of a new North American species,Ostrinia multispinosa Yangsp.n. , closely related toO .obumbratalis . Our analyses indicate that theOstrinia ancestral larval host preference was for dicots, and thatO .nubilalis (European corn borer) andOstrinia furnacalis (Asian corn borer) independently evolved a preference for feeding on monocots (i.e., maize). Males of a fewOstrinia species have enlarged, grooved midtibiae with brush organs that are known to attract females to increase mating success during courtship, which may represent a derived condition. Our study provides a strong evolutionary framework for this agriculturally important insect lineage. -
more » « less
Abstract Adaptive radiations are often characterized by the rapid evolution of traits associated with divergent feeding modes. For example, the evolutionary history of African cichlids is marked by repeated and coordinated shifts in skull, trophic, fin and body shape. Here, we seek to explore the molecular basis for fin shape variation in Lake Malawi cichlids. We first described variation within an F2mapping population derived by crossing two cichlid species with divergent morphologies including fin shape. We then used this population to genetically map loci that influence variation in this trait. We found that the genotype–phenotype map for fin shape is largely distinct from other morphological characters including body and craniofacial shape. These data suggest that key aspects of fin, body and jaw shape are genetically modular and that the coordinated evolution of these traits in cichlids is more likely due to common selective pressures than to pleiotropy or linkage. We next combined genetic mapping data with population‐level genome scans to identify
wnt7aa andcol1a1 as candidate genes underlying variation in the number of pectoral fin ray elements. Gene expression patterns across species with different fin morphologies and small molecule manipulation of the Wnt pathway during fin development further support the hypothesis that variation at these loci underlies divergence in fin shape between cichlid species. In all, our data provide additional insights into the genetic and molecular mechanisms associated with morphological divergence in this important adaptive radiation. -
more » « less
Abstract Divergent adaptation to new ecological opportunities can be an important factor initiating speciation. However, as niches are filled during adaptive radiations, trait divergence driving reproductive isolation between sister taxa may also result in trait convergence with more distantly related taxa, increasing the potential for reticulated gene flow across the radiation. Here, we demonstrate such a scenario in a recent adaptive radiation of
Rhagoletis fruit flies, specialized on different host plants. Throughout this radiation, shifts to novel hosts are associated with changes in diapause life history timing, which act as “magic traits” generating allochronic reproductive isolation and facilitating speciation‐with‐gene‐flow. Evidence from laboratory rearing experiments measuring adult emergence timing and genome‐wide DNA‐sequencing surveys supported allochronic speciation between summer‐fruitingVaccinium spp.‐infestingRhagoletis mendax and its hypothesized and undescribed sister taxon infesting autumn‐fruiting sparkleberries. The sparkleberry fly andR .mendax were shown to be genetically discrete sister taxa, exhibiting no detectable gene flow and allochronically isolated by a 2‐month average difference in emergence time corresponding to host availability. At sympatric sites across the southern USA, the later fruiting phenology of sparkleberries overlaps with that of flowering dogwood, the host of another more distantly related and undescribedRhagoletis taxon. Laboratory emergence data confirmed broadly overlapping life history timing and genomic evidence supported on‐going gene flow between sparkleberry and flowering dogwood flies. Thus, divergent phenological adaptation can drive the initiation of reproductive isolation, while also enhancing genetic exchange across broader adaptive radiations, potentially serving as a source of novel genotypic variation and accentuating further diversification.
