Environmental correlates of genetic variation in the invasive and largely panmictic European starling in North America

Abstract

Populations of invasive species that colonize and spread in novel environments may differentiate both through demographic processes and local selection. European starlings (Sturnus vulgaris) were introduced to New York in 1890 and subsequently spread throughout North America, becoming one of the most widespread and numerous bird species on the continent. Genome-wide comparisons across starling individuals and populations can identify demographic and/or selective factors that facilitated this rapid and successful expansion. We investigated patterns of genomic diversity and differentiation using reduced-representation genome sequencing (ddRADseq) of 17 winter-season starling populations. Consistent with this species' high dispersal rate and rapid expansion history, we found low geographic differentiation and few FST outliers even at a continental scale. Despite starting from a founding population of approximately 180 individuals, North American starlings show only a moderate genetic bottleneck, and models suggest a dramatic increase in effective population size since introduction. In genotype-environment associations we found that~200 single-nucleotide polymorphisms are correlated with temperature and/or precipitation against a background of negligible genome-and range-wide divergence. Local adaptation in North American starlings may have evolved rapidly even in this wide-ranging and evolutionarily young population. This survey of genomic signatures of expansion in North American starlings is the most comprehensive to date and complements ongoing studies of worldwide local adaptation in these highly dispersive and invasive birds.

Is a handful of genes responsible for the common starling invasion success?

“…Genetic diversity decreased with distance from the introduction sites in SE Australia, and genetic differentiation between populations increased with geographic distance (Figure 1A, B). These patterns contrast with those observed at other regions of the world where starlings have been introduced, namely in North America (Hofmeister et al, 2019). The starling invasion of North America showed a genetic pattern not consistent with IBD, but rather with isolation‐by‐environment.…”

“…Hofmeister et al . (2019) also detected associations between population structure and environmental variables, particularly mean annual temperature. Associations with the other environmental regimes (‘semi‐arid’ and ‘nonarid’) were not as clear and did not match the structure observed for either the neutral or outlier genetic structure.…”

“…In accordance with the rapid continent‐wide expansion, Hofmeister et al . (2019) also found very low differentiation between sampling localities, indicating not only high dispersal ability but also more so a panmictic population across the entire subcontinent. Studies on invasion genetics clearly indicate that multiple introductions lead to increased genetic diversity, which in turn provide increased chances of expansion into more diverse areas (more genomic targets of selection) (Blackburn et al, 2017; Dlugosch & Parker, 2008).…”

Widespread genetic connectivity of feral pigeons across the Northeastern megacity

“…Similarly, Hofmeister et al. (2019) found low migration rates among European Starlings in the United States, with higher‐than‐expected migration found mostly in areas where the researchers had not sampled starlings. European Starlings are extremely common in urban and suburban areas (Fischl & Caccamise, 1985), and their preference for anthropogenic habitat may explain the observed pattern of low migration between cities.…”

“…Hofmeister et al. (2019) found that European starlings ( Sturnus vulgaris ), another common urban species, showed low genetic structure across 17 populations spanning the entire United States, suggesting that the patterns observed in starlings and pigeons may be common across non‐native birds.…”