Genetic connectivity of the South American fur seal (Arctocephalus australis) across Atlantic and Pacific oceans revealed by mitochondrial genes

Abstract

South American fur seals, Arctocephalus australis, were intensively hunted for centuries, leaving the species at the edge of extinction. After the cessation of commercial hunting in the 20th century the overall population has increased to an estimated population of 250 000–300 000 individuals, with Guafo Island being the largest breeding colony in Southern Chile with Guafo Island in Southern Chile being the largest breeding colony. The genetic diversity of the South American fur seal population on Guafo Island and the possible genetic connectivity among populations from the Atlantic and Pacific oceans were studied in order to assess the importance of the Southern Chile Pacific population for the management of the species. Mitochondrial DNA sequences from the Guafo Island population were compared with those from various Atlantic (Brazil, Uruguay, and Argentina) and Pacific (Peru) populations previously studied. The results indicate the occurrence of historical and/or current gene flow among the populations of Guafo Island in the Pacific Ocean and the populations of the Atlantic Ocean, displaying a lack of genetic structure within these areas. In contrast, the Peruvian population is highly divergent compared with the Chilean and Atlantic populations. The lack of genetic structure of Guafo Island fur seals suggests that this group is connected to populations in the Atlantic Ocean. Thus, the significant genetic diversity pool harboured by the Guafo Island population represents the northernmost point of expansion of this species from the Atlantic Ocean to the Pacific Ocean, which could be important for the eventual dispersal of the species to more northern areas of the Pacific and to the future adaptation of the species to changing environmental conditions on the Pacific coasts.

Recovery of South American fur seals from Fuegian Archipelago (Argentina)

“…Bearing in mind that these regions are very close to Fuegian archipelago, we can infer that animals travel throughout the Atlantic and between the Atlantic and Pacific Oceans. Genetic studies support the hypothesis of connectivity between both oceans (i.e., there are no barriers to gene flow; Rodrígues et al, 2018), and also among different areas of the Atlantic (Abreu, 2011;Crespo et al, 2015).…”

“…In contrast, the population in southern Chile (Magallanes Region) has experienced a decline between 1978 and 2001 (Venegas et al, 2002). Different studies (morphometrics, genetics, and foraging behavior) support the connectivity among southern Chile and Atlantic regions (Uruguay, mainland Argentina, and Falkland Islands (Malvinas); (Baylis, Tierney, Orben, Staniland, & Brickle, 2018a;Oliveira, 2004;Rodrígues, Seguel, Gutierrez, Pavés, & Verdugo, 2018;Túnez, Capozzo, Pavés, Albareda, & Cassini, 2013), suggesting that the specimens from these areas belong to the same population. In this context, of a recovering population of SAFS in the southwestern Atlantic and an interconnection between areas with different trends, the aim F I G U R E 1 (a) Current distribution of Arctocephalus australis colonies along the southwestern Atlantic coast.…”

“…Otherwise, it may occur because of a high increase in a particular population (Rodrígues et al, 2018). Southern…”

Sighting patterns and habitat use of marine mammals at Guafo Island, Northern Chilean Patagonia during eleven austral summers

“…However, South American fur seal populations in the eastern South Pacific Ocean experienced a decline close to 60% in the last decade of the 20 th century, being the cause of this decline unknown as well as the current population trends (Venegas et al 2002, Pavés 2008, Cárdenas-Alayza et al 2016a. Guafo Island fur seal population represent the last point of expansion of the western South Atlantic fur seals into the Pacific Ocean, which probably occurred more than 10,000 years ago before the last glaciation (Túnez et al 2013, Crespo et al 2015, Rodrigues et al 2018. However, the genetic structure of Guafo Island fur seals also differs from the western South Atlantic populations (Crespo et al 2015, Rodrigues et al 2018, therefore Guafo Island is a strategic point for management of this subspecies and its conservation, as it represents unique genetic diversity, which has probably been favored by local adaptations to the southern Pacific Ocean conditions (Rodrigues et al 2018).…”

Genetic diversity and kinship relationships in one of the largest South American fur seal (Arctocephalus australis) populations of the Pacific Ocean

“…The South American fur seal (Arctocephalus australis; SAFS) is an amphi-oceanic pinniped that is widely distributed throughout Southern South America (Figure 1), ranging from Foca Island (5°20′S 81°12′W) along the Peruvian coast (Pacific Ocean) to Del Castillo islands off Uruguay (34°21′S 53°44′W) (Atlantic Ocean) (Cárdenas-Alayza & Oliveira, 2016). A large gap of approximately 2,300 km, in the Chilean Pacific coast between Mejillones (23°06′S 70°27′W) and Guafo Island (43°36′S 74°43′W) (Cárcamo et al, 2019;Cárdenas-Alayza & Oliveira, 2016), creates two evolutionarily significant units: the Northern Pacific/Peruvian (hereafter "Northern") population and the Southern Pacific/Atlantic (hereafter "Southern") SAFS population (De Oliveira & Brownell, 2014;Rodrigues et al, 2018). Although historically inhabiting the entire Southern Patagonia cone, SAFS were intensively exploited during the past two centuries for subsistence food supply (Torres et al, 2000), fur trade (Martinic, 1973), or as bait for crab fishing (Cárdenas et al, 1987), bringing the species to near extinction (Bonner, 1982).…”