Breeding season of the South American fur seal (Arctocephalus Australis, Otariidae: Carnivora): new data for establishing independent evolutionary histories?

The South American fur seal (SAFS) is distributed from Peru (Pacific Ocean) to Uruguay (Atlantic Ocean). However, there is a section of coastline of about 2,300 km along the Chilean coast where no SAFS are recorded. Based on morphological comparisons 3 geographic forms have been reported (Peruvian, South Chilean, Atlantic), whereas preliminary genetic studies suggest the presence of 3 distinct genetic types (Peruvian, South Chile, Atlantic). However, both of these approaches are support only the existence of 2 independent evolutionary histories for SAFS (Peruvian, Atlantic), in which case, we would also expect to find some differences in the species’ life histories among these locals populations (e.g., in the timing of the breeding season). In this study, we compare the breeding seasons of SAFS at Punta Pichalo (19°36’S-Chile), Isla Guafo (43°33’S-Chile), and Isla de Lobos (35°01’S-Uruguay) with data published for Punta San Juan (15°21’S-Peru). The periods for establishing territories, pupping, and mating took place on similar dates at Isla Guafo and Isla de Lobos, but occurred about a month earlier at Punta Pichalo and Punta San Juan. Pupping peaked at Isla Guafo on 15-December, at Isla de Lobos on 17-December, and at Punta Pichalo on 27-November. These differences in timing were not related to demographic, oceanographic or photoperiod conditions of the breeding sites under study, neither is related with the latitudinal effects on the breeding phenology. Based on results, we suggest that certain characteristics of life history can help identify species with independent evolutionary historie

The role of Pleistocene glaciations in shaping the genetic structure of South American fur seals (Arctocephalus australis)

Analysing a 529 bp segment of the mitochondrial control region, we evaluated the role that Pleistocene glaciations may have had in shaping the genetic structure currently found in the two southernmost breeding areas of the South American fur seal, Arctocephalus australis. Additionally, we analysed if these two breedingareas correspond to different conservation units. We found 26 haplotypes in 54 individuals. Colonies from the Uruguayan breeding area did not show significant differences in haplotype frequencies, which suggest that they are remnants of a single ancient gene pool. The genealogical relationship between haplotypes revealed a pattern of phylogeographic structure with two main haplogroups corresponding to the different breeding areas. The analysis of molecular variance and the estimate of population divergence time also indicated significant genetic differences and a long period of isolation between Atlantic and Pacific colonies, suggesting that these breeding areas would correspond to different conservation units.Fil: Tunez, Juan Ignacio. Universidad Nacional de Luján. Departamento de Ciencias Básicas. Grupo de Estudios en Ecología de Mamíferos; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Cappozzo, Humberto Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; ArgentinaFil: Pavés, H.. Universidad Austral de Chile; ChileFil: Albareda, D. A.. Jardín Zoológico y Acuario de Buenos Aires; ArgentinaFil: Cassini, Marcelo Hernan. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Biología y Medicina Experimental. Fundación de Instituto de Biología y Medicina Experimental. Instituto de Biología y Medicina Experimental; Argentina. Universidad Nacional de Luján. Departamento de Ciencias Básicas. Grupo de Estudios en Ecología de Mamíferos; Argentin

Morphometrical and molecular evidence suggests cryptic diversity among hookworms (Nematoda: Uncinaria) that parasitize pinnipeds from the south-eastern Pacific coasts

Hookworms of the genus Uncinaria parasitize pinniped pups in various locations worldwide. Four species have been described, two of which parasitize pinniped pups in the southern hemisphere: Uncinaria hamiltoni parasitizes Otaria flavescens and Arctocephalus australis from the South American coast, and Uncinaria sanguinis parasitizes Neophoca cinerea from the Australian coast. However, their geographical ranges and host specificity are unknown. Uncinaria spp. are morphologically similar, but molecular analyses have allowed the recognition of new species in the genus Uncinaria. We used nuclear genetic markers (internal transcribed spacer (ITS) and large subunit (LSU) rDNA) and a mitochondrial genetic marker (cytochrome c oxidase subunit I (COI)) to evaluate the phylogenetic relationships of Uncinaria spp. parasitizing A. australis and O. flavescens from South American coasts (Atlantic and Pacific coasts). We compared our sequences with published Uncinaria sequences. A Generalized Mixed Yule Coalescent (GMYC) analysis was also used to delimit species, and principal component analysis was used to compare morphometry among Uncinaria specimens. Parasites were sampled from A. australis from Peru (12 degrees S), southern Chile (42 degrees S), and the Uruguayan coast, and from O. flavescens from northern Chile (24 degrees S) and the Uruguayan coast. Morphometric differences were observed between Uncinaria specimens from both South American coasts and between Uncinaria specimens from A. australis in Peru and southern Chile. Phylogenetic and GMYC analyses suggest that south-eastern Pacific otariid species harbour U. hamiltoni and an undescribed putative species of Uncinaria. However, more samples from A. australis and O. flavescens are necessary to understand the phylogenetic patterns of Uncinaria spp. across the South Pacific.Project "Semillero No 5303-DGI" of "Direccion de Investigacion of the Universidad de Antofagasta

Ancient female philopatry, asymmetric male gene flow, and synchronous population expansion support the influence of climatic oscillations on the evolution of South American sea lion (Otaria flavescens)

The South American sea lion (Otaria flavescens) is widely distributed along the southern Atlantic and Pacific coasts of South America with a history of significant commercial exploitation. We aimed to evaluate the population genetic structure and the evolutionary history of South American sea lion along its distribution by analyses of mitochondrial DNA (mtDNA) and 10 nuclear microsatellites loci. We analyzed 147 sequences of mtDNA control region and genotyped 111 individuals of South American sea lion for 10 microsatellite loci, representing six populations (Peru, Northern Chile, Southern Chile, Uruguay (Brazil), Argentina and Falkland (Malvinas) Islands) and covering the entire distribution of the species. The mtDNA phylogeny shows that haplotypes from the two oceans comprise two very divergent clades as observed in previous studies, suggesting a long period (>1 million years) of low inter-oceanic female gene flow. Bayesian analysis of bi-parental genetic diversity supports significant (but less pronounced than mitochondrial) genetic structure between Pacific and Atlantic populations, although also suggested some inter-oceanic gene flow mediated by males. Higher male migration rates were found in the intra-oceanic population comparisons, supporting very high female philopatry in the species. Demographic analyses showed that populations from both oceans went through a large population expansion ~10,000 years ago, suggesting a very similar influence of historical environmental factors, such as the last glacial cycle, on both regions. Our results support the proposition that the Pacific and Atlantic populations of the South American sea lion should be considered distinct evolutionarily significant units, with at least two managements units in each ocean

Unrooted neighbour-joining tree for South American sea lion populations using D_SW genetic distance on microsatellite data.

<p>Numbers are bootstrap values (%).</p

Mitochondrial genetic and microsatellites diversities in each locality: N number of individuals analyzed (averaged over loci for microsatellites); Hd, haplotype diversity; π, nucleotide diversity; H, number of haplotypes; K, average number of alleles; Ho, observed heterozygosity; He, expected heterozygosity.

<p>Mitochondrial genetic and microsatellites diversities in each locality: N number of individuals analyzed (averaged over loci for microsatellites); Hd, haplotype diversity; π, nucleotide diversity; H, number of haplotypes; K, average number of alleles; Ho, observed heterozygosity; He, expected heterozygosity.</p

Migration rates (%, standard error in parenthesis) between the six sampling areas along the South America based on microsatellite data.

<p>The migration rate is the proportion of individuals in a population that immigrated from a source population per generation. Values in bold are inter-oceanic comparisons.</p

Bayesian phylogenetic tree of South American sea lion and related species <i>cyt b</i> sequences (381 bp).

<p>The two <i>Otaria flavescens</i> clades have a posterior probability of 1 and their median divergence time (in Mya) is indicated, with 95% credibility interval within parentheses.</p

Pairwise microsatellite R_ST (above diagonal) and mtDNA control region Φ_ST distance values (below diagonal) between the six sampling areas. Negative values were adjusted to zero.

<p>Pairwise microsatellite R_ST (above diagonal) and mtDNA control region Φ_ST distance values (below diagonal) between the six sampling areas. Negative values were adjusted to zero.</p

Extended Bayesian skyline plot showing the effective population size fluctuation of three South American sea lions populations throughout time based on the mtDNA control region.

<p>Internal thick lines are median estimates and thin lines and coloured areas are the 95% Central Posterior Density (CPD) intervals. Nef, effective female population size (log scale), ka, thousands of years ago. Time was truncated at 50 ka.</p