Allelic diversity and patterns of selection at the major histocompatibility complex class I and II loci in a threatened shorebird, the Snowy Plover (Charadrius nivosus)

Abstract

Background Understanding the structure and variability of adaptive loci such as the major histocompatibility complex (MHC) genes is a primary research goal for evolutionary and conservation genetics. Typically, classical MHC genes show high polymorphism and are under strong balancing selection, as their products trigger the adaptive immune response in vertebrates. Here, we assess the allelic diversity and patterns of selection for MHC class I and class II loci in a threatened shorebird with highly flexible mating and parental care behaviour, the Snowy Plover (Charadrius nivosus) across its broad geographic range. Results We determined the allelic and nucleotide diversity for MHC class I and class II genes using samples of 250 individuals from eight breeding population of Snowy Plovers. We found 40 alleles at MHC class I and six alleles at MHC class II, with individuals carrying two to seven different alleles (mean 3.70) at MHC class I and up to two alleles (mean 1.45) at MHC class II. Diversity was higher in the peptide-binding region, which suggests balancing selection. The MHC class I locus showed stronger signatures of both positive and negative selection than the MHC class II locus. Most alleles were present in more than one population. If present, private alleles generally occurred at very low frequencies in each population, except for the private alleles of MHC class I in one island population (Puerto Rico, lineage tenuirostris). Conclusion Snowy Plovers exhibited an intermediate level of diversity at the MHC, similar to that reported in other Charadriiformes. The differences found in the patterns of selection between the class I and II loci are consistent with the hypothesis that different mechanisms shape the sequence evolution of MHC class I and class II genes. The rarity of private alleles across populations is consistent with high natal and breeding dispersal and the low genetic structure previously observed at neutral genetic markers in this species.

Development of a Panel of Genotyping-in-Thousands by Sequencing in Capsicum

“…As the cost in GT-seq decreases with increasing pooling, this method is suitable for genotyping many samples at once ( Bootsma et al, 2020 ). The GT-seq method has been widely applied to fish, marine, animal, insect and plant species ( Baetscher et al, 2018 ; Coster et al, 2018 ; Curran et al, 2018 ; Förster et al, 2018 ; Bhattacharyya et al, 2019 ; Natesh et al, 2019 ; Yang et al, 2019 ; Zhao et al, 2019 ; Batz et al, 2020 ; Cruz-López et al, 2020 ; Eriksson et al, 2020 ; Lukindu et al, 2020 ; Nakayama et al, 2020 ; Samuk et al, 2020 ; Schmidt et al, 2020 ; Sjodin et al, 2020 ; Sriboon et al, 2020 ; Nasti et al, 2021 ; Srivathsa et al, 2021 ). In the case of plant, however, there has been no report of optimization GT-seq for thousand samples, and GT-seq was applied for only limited number of samples and mutation detection.…”