Reduced hybrid survival in a migratory divide between songbirds

Abstract

Migratory divides, hybrid zones between populations that use different seasonal migration routes, are hypothesised to contribute to speciation. Specifically, relative to parental species, hybrids at divides are predicted to exhibit (1) intermediate migratory behaviour and (2) reduced fitness as a result. We provide the first direct test of the second prediction here with one of the largest existing avian tracking datasets, leveraging a divide between Swainson's thrushes where the first prediction is supported. Using detection rates as a proxy for survival, our results supported the migratory divide hypothesis with lower survival rates for hybrids than parental forms. This finding was juvenile‐specific (vs. adults), suggesting selection against hybrids is stronger earlier in life. Reduced hybrid survival was not explained by selection against intermediate phenotypes or negative interactions among phenotypes. Additional work connecting specific features of migration is needed, but these patterns provide strong support for migration as an ecological driver of speciation.

Genotype imputation in F2 crosses of inbred lines

“…This optimization can be performed either by relying on quality metrics that are internal to the model (info score) or on external validation (correlation of imputed and known genotypes). Although STITCH has been used successfully in a number of diverse populations ( Nicod et al 2016 , Zan et al 2019 , Scott et al 2021 , Zha et al 2023 , Blain et al 2024 , Li et al 2024 ), often the parameterization and the assessment of the required level of coverage are presented as a single best choice and with little exploration of alternative parameters and experimental designs. Previous work explored some of the parameters that influence STITCH accuracy in an Angora rabbit population ( Wang et al 2022 ), but this work did not explore the complex interplay between sequencing depth, population size, and cross structure.…”