Genetics and Demography of Kelp Gulls in Patagonia

Abstract

The Kelp Gull (Larus dominicanus), a common seabird in coastal Patagonia, has recently increased in overall abundance and distribution, creating some concerns for the protection and conservation of other native, threatened species. We combined genetic and demographic data of four large Kelp Gull colonies distributed along 1800 km of the northern Patagonian coast of Argentina to further understand patterns of population growth and migration of the species. DNA analysis of variable intron sequences of two separate genes (myelin proteolipid protein, β-fibrinogen) revealed similar intra-colony levels of DNA sequence diversity. Pairwise FST comparisons revealed significant differentiation of the northernmost colony, Islote La Pastosa, from the two southern colonies, Punta Tombo and Isla Vernaci Sudoeste (p < 0.05). Indirect estimates of gene flow suggest significant mixing among colonies (Nm > 6). Demographic estimates revealed that Islote La Pastosa showed an increase in the number of breeding individuals over time (λ = 1.075), representing an area of potential population expansion. This is consistent with previous studies that have suggested that the demographic connectivity among Kelp Gull colonies in Patagonia may follow a source-sink dynamics, where growth rates of growing colonies are fuelled by the immigration of individuals from nearby colonies. The observed pattern also reflects the overall expansion of the species in the Patagonian region. This study suggests that proper management strategies for the Kelp Gull should take into account the genetic and demographic dynamics of this species.

Population structure and connectivity among coastal and freshwater Kelp Gull (Larus dominicanus) populations from Patagonia

“…This is the first genetic study to include freshwater Kelp Gull colonies from Patagonia, and we find that those from Nahuel Huapi Lake are genetically differentiated from their closest coastal Atlantic and Pacific counterparts. Previous studies on Kelp Gulls have found genetic structure both at a South American continental scale [ 22 – 24 ] and among populations along the Argentine coast [ 16 ]. Particularly, Lyons et al [ 16 ] found some level of differentiation among the most geographically distant colonies in their study, as expected from a pattern of isolation by distance with gradually diminishing connectivity with distance along the Argentine coast.…”

“…Previous studies on Kelp Gulls have found genetic structure both at a South American continental scale [ 22 – 24 ] and among populations along the Argentine coast [ 16 ]. Particularly, Lyons et al [ 16 ] found some level of differentiation among the most geographically distant colonies in their study, as expected from a pattern of isolation by distance with gradually diminishing connectivity with distance along the Argentine coast. Our findings also indicate closer affinities among colonies within each specific region, as opposed to the relationships observed between colonies situated in distinct geographic regions.…”

“…Studies conducted on gulls belonging to the genus Larus in various parts of the world have revealed genetic structure among populations, often following a pattern of isolation by distance [15][16][17][18]. Moreover, Herring Gull (Larus argentatus) populations from the Laurentian Great Lakes were found to be genetically distinct from their marine counterparts [19,20], supporting the idea that reproductive Herring Gulls from the Great Lakes region constitute a closed and isolated system [21].…”

“…Moreover, Herring Gull ( Larus argentatus ) populations from the Laurentian Great Lakes were found to be genetically distinct from their marine counterparts [ 19 , 20 ], supporting the idea that reproductive Herring Gulls from the Great Lakes region constitute a closed and isolated system [ 21 ]. Genetic studies in the Kelp Gull show different degrees of population structure depending on their geographic scale, over a background of demographic expansion during the Holocene [ 16 , 22 – 24 ]. However, the resolution provided by the genetic tools employed (mitochondrial DNA and microsatellite markers) and the scope of the sampling, particularly in the Patagonian region, may be underpowered to detect fine-scale population differences and adequately understand population connectivity.…”