Browsing by Author "Spotorno, AE"

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    Molecular diversity among domestic guinea-pigs (Cavia porcellus) and their close phylogenetic relationship with the Andean wild species Cavia tschudii
    (2004) Spotorno, AE; Valladares, JP; Marín, JC; Zeballos, H
    To investigate the origin and diversity of domestic guinea-pigs Cavia porcellus (Linnaeus, 1758; Rodentia, Caviidae), we sequenced the mitochondrial cytochrome b gene of 12 domestic and 10 wild specimens from six species, including the two presumed as ancestral to the domestic one: Cavia tschudii and Cavia aperea. All maximum parsimony and maximum likelihood analyses grouped C. porcellus with C. tschudii (mean K2P distance = 3.2%); best trees had 609 steps (CI = 0.796; Bremer support Index (SI) = 28), and a -Ln = 4419.52, with 100% and 97% bootstrap support respectively. This clade, supported by three substitutions and 96% bootstrap, is also obtained in the cladistic analysis of corresponding amino acids. When the C. aperea node was forced to join C. porcellus, these trees were consistently longer, less likely and robust, and with less defining characters than the optimal one. All C. porcellus sequences also clustered in a node defined by 15 substitutions. The sub-node containing animals from city markets, pet shops and laboratories was characterized by four substitutions (one non-silent, SI = 7, and 91% bootstrap). Some South American C. porcellus, called "criollos" (creoles) by local breeders, were more diverse. Probably, a particular clade from southern Peru and Chile may represent a pre-Columbian lineage. Mean K2P distance between C. tschudii and C. aperea was rather large, 7.7%. Cavia appeared as a robust node (100% bootstrap). These results indicate that C. tschudii is the species most closely related to C. porcellus.
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    Molecular systematics of marsupials based on the rRNA 12S mitochondrial gene
    (1999) Palma, RE; Spotorno, AE
    Nucleotide sequence data from the mitochondrial 125 rRNA gene were used to evaluate the phylogenetic relationships among the major groups of didelphimorph and paucituberculatan marsupials from South America, the microbiotheriid Dromiciops gliroides, and representatives of four orders of Australasian marsupials. Based on approximately 800 hp in 18 genera, we conclude that the didelphids constitute a monophyletic group with large-sized forms differentiated from small opossums, while Caluromys constitutes the sister taxon to didelphids. The peramelid Isoodon was recovered as the sister taxon to the paucituberculatans Caenolestes and Rhyncholestes, although it is in an uncertain phylogenetic position within the marsupial tree. Dromiciops was recovered as a well-differentiated lineage from South American opossums within the Australidelphian radiation of metatherians that include dasyurid, diprotodontian, and notoryctemorph marsupials. (C) 1999 Academic Press.
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    Phylogeography of Oligoryzomys longicaudatus (Rodentia: Sigmodontinae) in temperate South America
    (2005) Palma, RE; Rivera-Milla, E; Salazar-Bravo, J; Torres-Pérez, F; Pardiñas, UFJ; Marquet, PA; Spotorno, AE; Meynard, AP; Yates, TL
    Phylogeographic relationships were evaluated at the intraspecific level using nucleotide sequence data from the mitochondrial cytochrome b gene of representative specimens of "colilargo" (Oligoryzomys longicaudatus) from 31 localities, along its distributional range over a large part of the western Andes and southern Argentina. Based on approximately 1,000 base pairs (bp), we recognized a single species on both the Chilean and the Argentinean side as far as at least latitude 51degreesS, rejecting the subspecific distinctiveness of longicaudatus and philippi. We thus placed the latter in full synonymy with O. longicaudatus as earlier studies proposed, and enlarged its range as far as Torres del Paine, about 51degreesS. The occurrence of subspecies in this range is doubtful given the low sequence divergence values and the absence of significant associations between haplotypes and their geography. Additionally, we hypothesized that the entrance of this species into the Chilean side of the Andes mountains occurred through the Patagonian forests of southern Argentina, with further dispersal to the north from the south.