Genetic insights into the range expansion of the cattle egret (Pelecaniformes: Ardeidae) in Brazil and population differentiation between the native and colonized areas

Gnotypes of Cattle Egrets (Bubulcus ibis) at 14 microsatellite loci amplified using the primers in Table S1 of the article. The protocols are described in Appendix S1 of the Supplementary Material of Miño et al. 2022.

Bubulcus ibis ibis naturally expanded its range by flying over the Atlantic Ocean from Africa or Europe (native range) to South America, being first reported in Suriname towards the end of the 19th century. However, the source populations of the birds colonising South America still remains unclear. Here, to o gain insights into the possible source and routes of colonisation, we characterize the levels of diversity at nuclear microsatellites and assessed the genetic structure of populations from central and southern Africa (n = 129, 13 sites, five countries) and from different latitudes along Brazil (n = 166, six sites). We found overall high levels of genetic diversity in the colonised range, which fit the expectations for organisms with long-distance dispersal potential, rapid growth rates and feeding plasticity. Noteworthy, the results from population-genetic analyses based on different assumptions concurrently agree in indicating that cattle egrets from Brazil harbour a genetic pool distinct from populations from Africa, suggesting restricted contemporary gene flow between these ranges. The lack of genetic differentiation among the African populations did not enable us to identify the source of Brazilian cattle egrets. Fernando de Noronha Archipelago, off the Brazilian northeastern coast, had the highest proportion of the African allelic ancestry. Approximate Bayesian computation analyses supported a scenario of population growth in Africa with subsequent expansion to Brazil and migration from Africa to Brazil at the time of colonisation. We discuss our findings in light of the anthropogenic changes that may have promoted the range expansion of this egret into Brazil.