Widespread gene flow between oceans in a pelagic seabird species complex

Abstract

Global-scale gene flow is an important concern in conservation biology as it has the potential to either increase or decrease genetic diversity in species and populations. Although many studies focus on the gene flow between different populations of a single species, the potential for gene flow and introgression between species is understudied, particularly in seabirds. The only well-studied example of a mixed-species, hybridizing population of petrels exists on Round Island, in the Indian Ocean. Previous research assumed that Round Island represents a point of secondary contact between Atlantic (Pterodroma arminjoniana) and Pacific species (Pterodroma neglecta and Pterodroma heraldica). This study uses microsatellite genotyping and tracking data to address the possibility of between-species hybridization occurring outside the Indian Ocean. Dispersal and gene flow spanning three oceans were demonstrated between the species in this complex. Analysis of migration rates estimated using bayesass revealed unidirectional movement of petrels from the Atlantic and Pacific into the Indian Ocean. Conversely, structure analysis revealed gene flow between species of the Atlantic and Pacific oceans, with potential three-way hybrids occurring outside the Indian Ocean. Additionally, geolocation tracking of Round Island petrels revealed two individuals travelling to the Atlantic and Pacific. These results suggest that interspecific hybrids in Pterodroma petrels are more common than was previously assumed. This study is the first of its kind to investigate gene flow between populations of closely related Procellariiform species on a global scale, demonstrating the need for consideration of widespread migration and hybridization in the conservation of threatened seabirds.

Killer whale genomes reveal a complex history of recurrent admixture and vicariance

“…However, periods of admixture leave genomic signatures that can be used to infer the direction, extent and timing of ancestral gene flow (Duranton et al, 2018;Patterson et al, 2012;Racimo et al, 2015;Sousa & Hey, 2013). Divergence-with-gene-flow is often studied at local scales, but could influence global genetic structure and variation through connected networks of populations (Booth Jones et al, 2017;Novembre & Stephens, 2008).…”

Integrating Sequence Capture and Restriction Site-Associated DNA Sequencing to Resolve Recent Radiations of Pelagic Seabirds

“…A recent analysis of the major clades of Procellariiformes using only UCE loci ( Estandia 2019 ) recovered a generally well resolved topology, though maximum likelihood and species tree estimation yielded lower support and conflicting topologies for the split among the shearwaters, suggesting a rapid radiation where ILS and/or historical introgression may have occurred. Hybridization has been documented in several species of Procellariiformes, including shearwaters ( Genovart et al 2012 ; Booth Jones et al 2017 ; Masello et al 2019 ) despite strong philopatry to breeding colonies and, in most cases, a lack of overlap between breeding areas of closely related species. Thus, shearwaters demonstrate the challenges typical of many other taxonomic groups, where rapid diversification and introgression hinder attempts to confidently resolve their evolutionary history, and provide a good case study for how combining genomic data sets can aid in clarifying relationships at recalcitrant nodes.…”

Genetic structuring among colonies of a pantropical seabird: Implication for subspecies validation and conservation

“…Similar gene flow between Atlantic and Indian Oceans was proposed for petrels (Pterodroma spp. ;Booth Jones et al, 2017;Brown et al, 2010) and between Atlantic and Pacific Oceans for magnificent frigatebirds Fregata magnificens (Hailer et al, 2010). (Bourjea et al, 2007).…”

“…Seabirds are an intriguing taxon when their populations are considered in terms of gene flow and genetic diversity and structuring. Despite having wide dispersal potential over entire ocean basins (Booth Jones et al., 2017; Egevang et al., 2010; González‐Solís, Croxall, Oro, & Ruiz, 2007), they often show high levels of population isolation and even endemism. This is the so‐called “seabird paradox” (Friesen, 2015; Lombal, O'dwyer, Friesen, Woehler, & Burridge, 2020; Milot, Weimerskirch, & Bernatchez, 2008; Welch et al., 2012).…”