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1. Genomic Analyses of Phenotypic Differences Between Native and Invasive Populations of Diffuse Knapweed (Centaurea diffusa)

   https://doi.org/10.3389/fevo.2020.577635  

   Turner, Kathryn G. ; Ostevik, Kate L. ; Grassa, Christopher J. ; Rieseberg, Loren H. ( January 2021 , Frontiers in Ecology and Evolution)

   null (Ed.)

   Invasive species represent excellent opportunities to study the evolutionary potential of traits important to success in novel environments. Although some ecologically important traits have been identified in invasive species, little is typically known about the genetic mechanisms that underlie invasion success in non-model species. Here, we use a genome-wide association (GWAS) approach to identify the genetic basis of trait variation in the non-model, invasive, diffuse knapweed [ Centaurea diffusa Lam. (Asteraceae)]. To assist with this analysis, we have assembled the first draft genome reference and fully annotated plastome assembly for this species, and one of the first from this large, weedy, genus, which is of major ecological and economic importance. We collected phenotype data from 372 individuals from four native and four invasive populations of C. diffusa grown in a common environment. Using these individuals, we produced reduced-representation genotype-by-sequencing (GBS) libraries and identified 7,058 SNPs. We identify two SNPs associated with leaf width in these populations, a trait which significantly varies between native and invasive populations. In this rosette forming species, increased leaf width is a major component of increased biomass, a common trait in invasive plants correlated with increased fitness. Finally, we use annotations from Arabidopsis thaliana to identify 98 candidate genes that are near the associated SNPs and highlight several good candidates for leaf width variation. 

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2. Genetic and ecological drivers of molt in a migratory bird

   https://doi.org/10.1038/s41598-022-26973-7  

   Contina, Andrea ; Bossu, Christen M. ; Allen, Daniel ; Wunder, Michael B. ; Ruegg, Kristen C. ( January 2023 , Scientific Reports)

   The ability of animals to sync the timing and location of molting (the replacement of hair, skin, exoskeletons or feathers) with peaks in resource availability has important implications for their ecology and evolution. In migratory birds, the timing and location of pre-migratory feather molting, a period when feathers are shed and replaced with newer, more aerodynamic feathers, can vary within and between species. While hypotheses to explain the evolution of intraspecific variation in the timing and location of molt have been proposed, little is known about the genetic basis of this trait or the specific environmental drivers that may result in natural selection for distinct molting phenotypes. Here we take advantage of intraspecific variation in the timing and location of molt in the iconic songbird, the Painted Bunting (Passerina ciris) to investigate the genetic and ecological drivers of distinct molting phenotypes. Specifically, we use genome-wide genetic sequencing in combination with stable isotope analysis to determine population genetic structure and molting phenotype across thirteen breeding sites. We then use genome-wide association analysis (GWAS) to identify a suite of genes associated with molting and pair this with gene-environment association analysis (GEA) to investigate potential environmental drivers of genetic variation in this trait. Associations between genetic variation in molt-linked genes and the environment are further tested via targeted SNP genotyping in 25 additional breeding populations across the range. Together, our integrative analysis suggests that molting is in part regulated by genes linked to feather development and structure (GLI2andCSPG4) and that genetic variation in these genes is associated with seasonal variation in precipitation and aridity. Overall, this work provides important insights into the genetic basis and potential selective forces behind phenotypic variation in what is arguably one of the most important fitness-linked traits in a migratory bird.

    

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3. Changes in selection pressure can facilitate hybridization during biological invasion in a Cuban lizard

   https://doi.org/10.1073/pnas.2108638118  

   Bock, Dan G. ; Baeckens, Simon ; Pita-Aquino, Jessica N. ; Chejanovski, Zachary A. ; Michaelides, Sozos N. ; Muralidhar, Pavitra ; Lapiedra, Oriol ; Park, Sungdae ; Menke, Douglas B. ; Geneva, Anthony J. ; et al ( October 2021 , Proceedings of the National Academy of Sciences)

   Hybridization is among the evolutionary mechanisms most frequently hypothesized to drive the success of invasive species, in part because hybrids are common in invasive populations. One explanation for this pattern is that biological invasions coincide with a change in selection pressures that limit hybridization in the native range. To investigate this possibility, we studied the introduction of the brown anole (Anolis sagrei) in the southeastern United States. We find that native populations are highly genetically structured. In contrast, all invasive populations show evidence of hybridization among native-range lineages. Temporal sampling in the invasive range spanning 15 y showed that invasive genetic structure has stabilized, indicating that large-scale contemporary gene flow is limited among invasive populations and that hybrid ancestry is maintained. Additionally, our results are consistent with hybrid persistence in invasive populations resulting from changes in natural selection that occurred during invasion. Specifically, we identify a large-effect X chromosome locus associated with variation in limb length, a well-known adaptive trait in anoles, and show that this locus is often under selection in the native range, but rarely so in the invasive range. Moreover, we find that the effect size of alleles at this locus on limb length is much reduced in hybrids among divergent lineages, consistent with epistatic interactions. Thus, in the native range, epistasis manifested in hybrids can strengthen extrinsic postmating isolation. Together, our findings show how a change in natural selection can contribute to an increase in hybridization in invasive populations.

    

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4. Global patterns of genomic and phenotypic variation in the invasive harlequin ladybird

   https://doi.org/10.1186/s12915-023-01638-7  

   Li, Hongran ; Peng, Yan ; Wang, Yansong ; Summerhays, Bryce ; Shu, Xiaohan ; Vasquez, Yumary ; Vansant, Hannah ; Grenier, Christy ; Gonzalez, Nicolette ; Kansagra, Khyati ; et al ( December 2023 , BMC Biology)

   The harlequin ladybirdHarmonia axyridis(Coleoptera: Coccinellidae), native to Asia, has been introduced to other major continents where it has caused serious negative impacts on local biodiversity. Though notable advances to understand its invasion success have been made during the past decade, especially with then newer molecular tools, the conclusions reached remain to be confirmed with more advanced genomic analyses and especially using more samples from larger geographical regions across the native range. Furthermore, althoughH. axyridisis one of the best studied invasive insect species with respect to life history traits (often comparing invasive and native populations), the traits responsible for its colonization success in non-native areas warrant more research.

   Our analyses of genome-wide nuclear population structure indicated that an eastern Chinese population could be the source of all non-native populations and revealed several putatively adaptive candidate genomic loci involved in body color variation, visual perception, and hemolymph synthesis. Our estimates of evolutionary history indicate (1) asymmetric migration with varying population sizes across its native and non-native range, (2) a recent admixture between eastern Chinese and American populations in Europe, (3) signatures of a large progressive, historical bottleneck in the common ancestors of both populations and smaller effective sizes of the non-native population, and (4) the southwest origin and subsequent dispersal routes within its native range in China. In addition, we found that while two mitochondrial haplotypes-Hap1 and Hap2 were dominant in the native range, Hap1 was the only dominant haplotype in the non-native range. Our laboratory observations in both China and USA found statistical yet slight differences between Hap1 and Hap2 in some of life history traits.

   Our study onH.axyridisprovides new insights into its invasion processes into other major continents from its native Asian range, reconstructs a geographic range evolution across its native region China, and tentatively suggests that its invasiveness may differ between mitochondrial haplotypes.

    

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5. Adaptive plasticity and niche expansion in an invasive thistle

   https://doi.org/10.1002/ece3.1599  

   Turner, Kathryn G. ; Fréville, Hélène ; Rieseberg, Loren H. ( July 2015 , Ecology and Evolution)

   Phenotypic differentiation in size and fecundity between native and invasive populations of a species has been suggested as a causal driver of invasion in plants. Local adaptation to novel environmental conditions through a micro‐evolutionary response to natural selection may lead to phenotypic differentiation and fitness advantages in the invaded range. Local adaptation may occur along a stress tolerance trade‐off, favoring individuals that, in benign conditions, shift resource allocation from stress tolerance to increased vigor and fecundity and, therefore, invasiveness. Alternately, the typically disturbed invaded range may select for a plastic, generalist strategy, making phenotypic plasticity the main driver of invasion success. To distinguish between these hypotheses, we performed a field common garden and tested for genetically based phenotypic differentiation, resource allocation shifts in response to water limitation, and local adaptation to the environmental gradient which describes the source locations for native and invasive populations of diffuse knapweed (Centaurea diffusa). Plants were grown in an experimental field in France (naturalized range) under water addition and limitation conditions. After accounting for phenotypic variation arising from environmental differences among collection locations, we found evidence of genetic variation between the invasive and native populations for most morphological and life‐history traits under study. InvasiveC. diffusapopulations produced larger, later maturing, and therefore potentially fitter individuals than native populations. Evidence for local adaptation along a resource allocation trade‐off for water limitation tolerance is equivocal. However, native populations do show evidence of local adaptation to an environmental gradient, a relationship which is typically not observed in the invaded range. Broader analysis of the climatic niche inhabited by the species in both ranges suggests that the physiological tolerances ofC. diffusamay have expanded in the invaded range. This observation could be due to selection for plastic, “general‐purpose” genotypes with broad environmental tolerances.

    

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