The dynamics of introgression across an avian radiation

Abstract

Hybridization and resulting introgression can play both a destructive and a creative role in the evolution of diversity. Thus, characterizing when and where introgression is most likely to occur can help us understand the causes of diversification dynamics. Here, we examine the prevalence of and variation in introgression using phylogenomic data from a large (1300+ species), geographically widespread avian group, the suboscine birds. We first examine patterns of gene tree discordance across the geographic distribution of the entire clade. We then evaluate the signal of introgression in a subset of 206 species triads using Patterson's D-statistic and test for associations between introgression signal and evolutionary, geographic, and environmental variables. We find that gene tree discordance varies across lineages and geographic regions. The signal of introgression is highest in cases where species occur in close geographic proximity and in regions with more dynamic climates since the Pleistocene. Our results highlight the potential of phylogenomic datasets for examining broad patterns of hybridization and suggest that the degree of introgression between diverging lineages might be predictable based on the setting in which they occur.

A need for standardized reporting of introgression: Insights from studies across eukaryotes

“… 2020 ; Singhal et al. 2021 ), this relationship is weak overall in our study. As species diverge, the build‐up of reproductive isolation presents both fewer opportunities for introgression (Jagoda et al.…”

“…First, we find a negative relationship between genetic distance and both the significance and magnitude of Patterson's D (Figure 2). While this result is largely expected from several theoretical perspectives (Hamlin et al 2020;Singhal et al 2021), this relationship is weak overall in our study. As species diverge, the build-up of reproductive isolation presents both fewer opportunities for introgression (Jagoda et al 2018;Petr et al 2019) and increases the selection against introgressed regions (Staubach et al 2012;Jagoda et al 2018;Petr et al 2019).…”

“…To answer the overarching question of "How prevalent is introgression across the tree of life?," researchers could shift their focus from taxa-centric studies of introgression to more clade-centric studies (e.g., Hamlin et al (2020), Malinsky et al (2018), Edelman et al (2019), Suvorov et al (2021), Small et al (2020, Singhal et al (2021)). However, we recognize that this may not always be possible or feasible.…”

“…While care must be applied when evaluating any of the fstatistics, they represent an opportunity to compare the frequency and strength of evidence for introgression across different taxa. Ideally, f-statistics would be computed for a variety of taxa using a single set of approaches, as has been done by Hamlin et al (2020) and Singhal et al (2021), but it is difficult to scale this approach using comparable data across eukaryotic life. Alternatively, published data can be used to investigate differences in introgression across taxa.…”

“…( 2020 ) and Singhal et al. ( 2021 ), but it is difficult to scale this approach using comparable data across eukaryotic life. Alternatively, published data can be used to investigate differences in introgression across taxa.…”