Drift, not selection, shapes toll‐like receptor variation among oceanic island populations

González-Quevedo, Catalina; Spurgin, Lewis G.; Illera, Juan Carlos; Richardson, David S.

doi:10.1111/mec.13437

Cited by 54 publications

(69 citation statements)

References 82 publications

(198 reference statements)

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“…Sanger sequencing of TLR4 in the 2016 Porto Santo samples only detected SNPs which have been previously documented in Berthelot's pipits (González‐Quevedo et al, ). SNP allele frequencies differed between the two islands, with different minor alleles found at TLR4_3 and TLR4_4 (Figure a).…”

Section: Resultsmentioning

confidence: 64%

“…A previous TLR4 study genotyped 23–30 individuals from all 13 Berthelot's pipit populations, including Tenerife and Porto Santo (González‐Quevedo et al, ). The primers PauTLR4F , PauTLR4R (Grueber, Wallis, King, & Jamieson, ) were used to amplify a 660‐bp region located within the leucine‐rich repeat domain of TLR4.…”

Section: Methodsmentioning

confidence: 99%

“…Despite a sharp decline in overall genetic diversity associated with the initial colonization of Madeira (Armstrong et al, ), higher levels of TLR4 allelic and amino acid richness exist in Madeira compared to the Canary Islands (González‐Quevedo, Spurgin, Illera, & Richardson, ). Furthermore, evidence of positive selection at TLR4 in Berthelot's pipits suggests it may be an evolutionarily important locus (González‐Quevedo et al, ). In this study, we (a) test for associations between Plasmodium infection status (the only Haemosporidian genus commonly detected; >1% prevalence) in this species (Spurgin et al, ), and variation at TLR4 and two SNPs previously identified in a GWAS of malaria infection across Berthelot's pipit populations (Armstrong et al, ); (b) determine the environmental predictors of malaria risk on Porto Santo; (c) compare genetic associations with malaria risk in Porto Santo and Tenerife, utilizing the above measures of malaria risk for Porto Santo, and those previously calculated for Tenerife (González‐Quevedo et al, , ).…”

Section: Introductionmentioning

confidence: 99%

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Adaptive landscape genetics and malaria across divergent island bird populations

Armstrong

Davies

González-Quevedo

et al. 2019

Ecology and Evolution

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Environmental conditions play a major role in shaping the spatial distributions of pathogens, which in turn can drive local adaptation and divergence in host genetic diversity. Haemosporidians, such as Plasmodium (malaria), are a strong selective force, impacting survival and fitness of hosts, with geographic distributions largely determined by habitat suitability for their insect vectors. Here, we have tested whether patterns of fine‐scale local adaptation to malaria are replicated across discrete, ecologically differing island populations of Berthelot's pipits Anthus berthelotii. We sequenced TLR4, an innate immunity gene that is potentially under positive selection in Berthelot's pipits, and two SNPs previously identified as being associated with malaria infection in a genome‐wide association study (GWAS) in Berthelot's pipits in the Canary Islands. We determined the environmental predictors of malaria infection, using these to estimate variation in malaria risk on Porto Santo, and found some congruence with previously identified environmental risk factors on Tenerife. We also found a negative association between malaria infection and a TLR4 variant in Tenerife. In contrast, one of the GWAS SNPs showed an association with malaria risk in Porto Santo, but in the opposite direction to that found in the Canary Islands GWAS. Together, these findings suggest that disease‐driven local adaptation may be an important factor in shaping variation among island populations.

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Section: Resultsmentioning

confidence: 64%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Adaptive landscape genetics and malaria across divergent island bird populations

Armstrong

Davies

González-Quevedo

et al. 2019

Ecology and Evolution

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“…; Gonzalez‐Quevedo et al . ). On the other hand, several studies have shown that PMBS may counteract the effect of random genetic drift and maintain MHC diversity in spite of small population size (Aguilar et al .…”

Section: Introductionmentioning

confidence: 97%

Balancing selection and genetic drift create unusual patterns of MHCIIβ variation in Galápagos mockingbirds

et al. 2016

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The extracellular subunit of the major histocompatibility complex MHCIIβ plays an important role in the recognition of pathogens and the initiation of the adaptive immune response of vertebrates. It is widely accepted that pathogen-mediated selection in combination with neutral micro-evolutionary forces (e.g. genetic drift) shape the diversity of MHCIIβ, but it has proved difficult to determine the relative effects of these forces. We evaluated the effect of genetic drift and balancing selection on MHCIIβ diversity in 12 small populations of Galápagos mockingbirds belonging to four different species, and one larger population of the Northern mockingbird from the continental USA. After genotyping MHCIIβ loci by high-throughput sequencing, we applied a correlational approach to explore the relationships between MHCIIβ diversity and population size by proxy of island size. As expected when drift predominates, we found a positive effect of population size on the number of MHCIIβ alleles present in a population. However, the number of MHCIIβ alleles per individual and number of supertypes were not correlated with population size. This discrepancy points to an interesting feature of MHCIIβ diversity dynamics: some levels of diversity might be shaped by genetic drift while others are independent and possibly maintained by balancing selection.

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“…; González‐Quevedo et al. ). This nested pattern of population structure enables comparisons of genetic and phenotypic divergence at a range of spatial scales (Spurgin et al.…”

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confidence: 98%

Genomic associations with bill length and disease reveal drift and selection across island bird populations

et al. 2018

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Island species provide excellent models for investigating how selection and drift operate in wild populations, and for determining how these processes act to influence local adaptation and speciation. Here, we examine the role of selection and drift in shaping genomic and phenotypic variation across recently separated populations of Berthelot's pipit (Anthus berthelotii), a passerine bird endemic to three archipelagos in the Atlantic. We first characterized genetic diversity and population structuring that supported previous inferences of a history of recent colonizations and bottlenecks. We then tested for regions of the genome associated with the ecologically important traits of bill length and malaria infection, both of which vary substantially across populations in this species. We identified a SNP associated with variation in bill length among individuals, islands, and archipelagos; patterns of variation at this SNP suggest that both phenotypic and genotypic variation in bill length is largely shaped by founder effects. Malaria was associated with SNPs near/within genes involved in the immune response, but this relationship was not consistent among archipelagos, supporting the view that disease resistance is complex and rapidly evolving. Although we found little evidence for divergent selection at candidate loci for bill length and malaria resistance, genome scan analyses pointed to several genes related to immunity and metabolism as having important roles in divergence and adaptation. Our findings highlight the utility and challenges involved with combining association mapping and population genetic analysis in nonequilibrium populations, to disentangle the effects of drift and selection on shaping genotypes and phenotypes.

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Drift, not selection, shapes toll‐like receptor variation among oceanic island populations

Cited by 54 publications

References 82 publications

Adaptive landscape genetics and malaria across divergent island bird populations

Adaptive landscape genetics and malaria across divergent island bird populations

Balancing selection and genetic drift create unusual patterns of MHCIIβ variation in Galápagos mockingbirds

Genomic associations with bill length and disease reveal drift and selection across island bird populations

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