Browsing by Author "Amico, Guillermo C."

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    Genomic diversity and demographic history of the Dromiciops genus (Marsupialia: Microbiotheriidae)
    (2022) Quintero-Galvis, Julian F.; Saenz-Agudelo, Pablo; Amico, Guillermo C.; Vazquez, Soledad; Shafer, Aaron B. A.; Nespolo, Roberto F.
    Three orders represent the South American fauna of marsupials. Of these, Microbiotheria was until recently known as a monotypic genus with the only surviving species Dromiciops gliroides (monito del monte). The recent proposal of a new Dromiciops species (Dromiciops bozinovici), together with new information on the origin and diversification of living microbioterians has changed the prevailing paradigm around the evolutionary history of these emblematic marsupials. Here, we used a RADseq approach to test for evidence of admixture and past or current gene flow among both species of Dromiciops and evaluate the genetic structure within D. gliroides. We analyzed 127 samples of Dromiciops distributed across the known distribution range of both species. We also inferred the joint demographic history of these lineages, thus corroborating the status of D. bozinovici as a distinct species. Demographic history reconstruction indicated that D. bozinovici diverged from D. gliroides around 4my ago and has remained isolated and demographically stable ever since. In contrast, D. gliroides is subdivided into three subclades that experienced recent expansions and moderate gene flow among them (mostly from north to south). Furthermore, genetic distances among populations within D. gliroides were significantly correlated with geographic distances. These results suggest that some of the D. gliroides populations would have survived in glacial refuges, with posterior expansions after ice retreat. Our results have important implications for the sys-tematics of the genus and have profound conservation consequences for the new species, especially considering the fragmentation level of the temperate rainforest.
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    The biogeography of Dromiciops in southern South America: Middle Miocene transgressions, speciation and associations with Nothofagus
    (2021) Quintero-Galvis, Julian F.; Saenz-Agudelo, Pablo; Celis-Diez, Juan L.; Amico, Guillermo C.; Vazquez, Soledad; Shafer, Aaron B. A.; Nespolo, Roberto F.
    The current distribution of the flora and fauna of southern South America is the result of drastic geological events that occurred during the last 20 million years, including marine transgressions, glaciations and active vulcanism. All these have been associated with fragmentation, isolation and subsequent expansion of the biota, south of 35 degrees S, such as the temperate rainforest. This forest is mostly dominated by Nothofagus trees and is the habitat of the relict marsupial monito del monte, genus Dromiciops, sole survivor of the order Microbiotheria. Preliminary analyses using mtDNA proposed the existence of three main Dromiciops lineages, distributed latitudinally, whose divergence was initially attributed to recent Pleistocene glaciations. Using fossil-calibrated dating on nuclear and mitochondrial genes, here we reevaluate this hypothesis and report an older (Miocene) biogeographic history for the genus. We performed phylogenetic reconstructions using sequences from two mitochondrial DNA and four nuclear DNA genes in 159 specimens from 31 sites across Chile and Argentina. Our phylogenetic analysis resolved three main clades with discrete geographic distributions. The oldest and most differentiated clade corresponds to that of the northern distribution (35.2 degrees S to 39.3 degrees S), which should be considered a distinct species (D. bozinovici, sensu D'Elia et al. 2016). According to our estimations, this species shared a common ancestor with D. gliroides (southern clades) about similar to 13 million years ago. Divergence time estimates for the southern clades (39.6 degrees S to 42.0 degrees S) ranged from 9.57 to 6.5 Mya. A strong genetic structure was also detected within and between clades. Demographic analyses suggest population size stability for the northern clade (D. bozinovici), and recent demographic expansions for the central and southern clades. All together, our results suggest that the diversification of Dromiciops were initiated by the Middle Miocene transgression (MMT), the massive marine flooding that covered several lowlands of the western face of Los Andes between 37 and 48 degrees S. The MMT resulted from an increase in global sea levels at the Miocene climatic optimum, which shaped the biogeographic origin of several species, including Nothofagus forests, the habitat of Dromiciops.