Browsing by Author "Marin, Juan Carlos"

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    Genomic Introgression and Adaptation of Southern Seabird Species Facilitate Recent Polar Colonization
    (2025) Jorquera Faundez, Maria Josefina; Morales, Lucina; Ng, Elize Y.X.; Noll, Daly; Pertierra, Luis R.; Pliscoff, Patricio; Balza, Ulises; Boulinier, Thierry; Gamble, Amandine; Kasinsky, Tatiana; McInnes, Julie C.; Marin, Juan Carlos; Olmastroni, Silvia; Pistorius, Pierre; Phillips, Richard A.; Gonzalez-Solis, Jacob; Emmerson, Louise; Poulin, Elie; Bowie, Rauri C.K.; Burridge, Christopher P.; Vianna, Juliana
    Genomic adaptation and introgression can occur during the speciation process, enabling species to diverge in their frequencies of adaptive alleles or acquire new alleles that may promote adaptation to environmental changes. There is limited information on introgression in organisms from extreme environments and their responses to climate change. To address these questions, we focused on the 3 southern skua species, selected for their widespread distribution across the Southern Hemisphere and their complex history of speciation and introgression events. Our genomic data reveal that these skuas underwent diversification around the Penultimate Glacial Period, followed by subsequent demographic expansion. We identified a geographic region of introgression among species that followed a directional pattern sourced from the Antarctic continent, South America, and east to west in subantarctic islands, all converging towards the Antarctic Peninsula. The 3 skua species and admixed individuals exhibited a unique pattern of putative genes under selection, allowing adaptation to extreme conditions. Individuals with a higher proportion of Brown Skua ancestry showed signs of selection on genes related to reproductive isolation, while admixed individuals with a higher proportion of South Polar Skua ancestry displayed patterns resembling those of the South Polar Skua. Introgression may be a key mechanism of adaptation for many species that may help buffer against the ongoing climate change.
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    History of Diversification and Adaptation from North to South Revealed by Genomic Data: Guanacos from the Desert to Sub-Antarctica
    (2024) Leon, Fabiola; Pizarro, Eduardo J.; Noll, Daly; Pertierra, Luis R.; Gonzalez, Benito A.; Johnson, Warren E.; Marin, Juan Carlos; Vianna, Juliana A.
    The increased availability of quality genomic data has greatly improved the scope and resolution of our understanding of the recent evolutionary history of wild species adapted to extreme environments and their susceptibility to anthropogenic impacts. The guanaco (Lama guanicoe), the largest wild ungulate in South America, is a good example. The guanaco is well adapted to a wide range of habitats, including the Sechura Desert, the high Andes Mountains to the north, and the extreme temperatures and conditions of Navarino Island to the south. Guanacos also have a long history of overexploitation by humans. To assess the evolutionary impact of these challenging habitats on the genomic diversity, we analyzed 38 genomes (similar to 10 to 16x) throughout their extensive latitudinal distribution from the Sechura and Atacama Desert to southward into Tierra del Fuego Island. These included analyses of patterns of unique differentiation in the north and geographic region further south with admixture among L. g. cacsilensis and L. g. guanicoe. Our findings provide new insights on the divergence of the subspecies similar to 800,000 yr BP and document two divergent demographic trajectories and to the initial expansion of guanaco into the more southern portions of the Atacama Desert. Patagonian guanacos have experienced contemporary reductions in effective population sizes, likely the consequence of anthropogenic impacts. The lowest levels of genetic diversity corresponded to their northern and western limits of distribution and some varying degrees of genetic differentiation. Adaptive genomic diversity was strongly linked with environmental variables and was linked with colonization toward the south followed by adaptation.
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    Species delimitation and intraspecific diversification in recently diverged South American foxes
    (2024) Pizarro, Eduardo J.; Julio-Kalajzic, Bernardita; Sallaberry-Pincheira, Nicole; Munoz, Valentina; Gonzalez-Acuna, Daniel; Cabello, Javier; Acosta-Jamett, Gerardo; Bonacic, Cristian; Iriarte, Agustin; Rodriguez, Alejandro; Travaini, Alejandro; Cevidanes, Aitor; Brito, Jose Luis; Millan, Javier; Marin, Juan Carlos; Vianna, Juliana A.
    The divergence between the Andean fox (Lycalopex culpaeus) and the South American gray fox (L. griseus) represents a recent speciation event in South America. These taxa are partially sympatric and share biological, morphological, and ecological traits. Previous studies failed to recover reciprocal monophyly, suggesting the occurrence of introgression or incomplete lineage sorting (ILS). Here, we obtained mitochondrial and nuclear markers for 140 L. culpaeus and 134 L. griseus from the Southern Cone of South America to assess their inter and intraspecific divergence. We recovered reciprocal monophyly of L. culpaeus and L. griseus, with mild signatures of introgression or ILS. Therefore, taxonomic misidentification and the use of a limited number of markers may be the main reason behind the past debate about the delimitation of both species. Two main divergent clades were found in L. culpaeus with a phylogeographical boundary in the High Plateau of northeastern Chile. The southern clade along with three northern sub-clades corresponded to four morphological subspecies. Less genetic differentiation was found in L. griseus with a spatial population structure that does not support the occurrence of distinct subspecies. The results found in this study suggest the extant evolutionary significant units that need to be considered for biological conservation management of these species.