DSpace Angular :: Browsing by Author "Nespolo, Roberto F."

Browsing by Author "Nespolo, Roberto F."

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A Mesocosm Experiment in Ecological Physiology: The Modulation of Energy Budget in a Hibernating Marsupial under Chronic Caloric Restriction
(2022) Nespolo, Roberto F.; Fonturbel, Francisco E.; Mejias, Carlos; Contreras, Rodrigo; Gutierrez, Paulina; Oda, Esteban; Sabat, Pablo; Hambly, Catherine; Speakman, John R.; Bozinovic, Francisco
During the past 60 years, mammalian hibernation (i.e., seasonal torpor) has been interpreted as a physiological adaptation for energy economy. However, direct field comparisons of energy expenditure and torpor use in hibernating and active free-ranging animals are scarce. Here, we followed the complete hibernation cycle of a fat-storing hibernator, the marsupial Dromiciops gliroides, in its natural habitat. Using replicated mesocosms, we experimentally manipulated energy availability and measured torpor use, hibernacula use, and social clustering throughout the entire hibernation season. Also, we measured energy flow using daily food intake, daily energy expenditure (DEE), and basal metabolic rate (BMR) in winter. We hypothesized that when facing chronic caloric restriction (CCR), a hibernator should maximize torpor frequency to compensate for the energetic deficit, compared with individuals fed ad lib. (controls). However, being torpid at low temperatures could increase other burdens (e.g., cost of rewarming, freezing risks). Our results revealed that CCR animals, compared with control animals, did not promote heat conservation strategies (i.e., clustering and hibernacula use). Instead, they gradually increased torpor frequency and reduced DEE and, as a consequence, recovered weight at the end of the season. Also, CCR animals consumed food at a rate of 50.8 kJ d(-1), whereas control animals consumed food at a rate of 98.4 kJ d(-1). Similarly, the DEE of CCR animals in winter was 47.3 & PLUSMN;5.64 kJ d(-1), which was significantly lower than control animals (DEE=88.0 & PLUSMN;5.84 kJ d(-1)). However, BMR and lean mass of CCR and control animals did not vary significantly, suggesting that animals maintained full metabolic capacities. This study shows that the use of torpor can be modulated depending on energy supply, thus optimizing energy budgeting. This plasticity in the use of heterothermy as an energy-saving strategy would explain the occurrence of this marsupial in a broad latitudinal and altitudinal range. Overall, this study suggests that hibernation is a powerful strategy to modulate energy expenditure in mammals from temperate regions.
An integrative taxonomy approach reveals Saccharomyces chiloensis sp. nov. as a newly discovered species from Coastal Patagonia
(2024) Pena, Tomas A.; Villarreal, Pablo; Agier, Nicolas; De Chiara, Matteo; Barria, Tomas; Urbina, Kamila; Villarroel, Carlos A.; Santos, Ana R. O.; Rosa, Carlos A.; Nespolo, Roberto F.; Liti, Gianni; Fischer, Gilles; Cubillos, Francisco A.
Species delineation in microorganisms is challenging due to the limited markers available for accurate species assignment. Here, we applied an integrative taxonomy approach, combining extensive sampling, whole-genome sequence-based classification, phenotypic profiling, and assessment of interspecific reproductive isolation. Our work reveals the presence of a distinct Saccharomyces lineage in Nothofagus forests of coastal Patagonia. This lineage, designated Saccharomyces chiloensis sp. nov., exhibits 7% genetic divergence from its sister species S. uvarum, as revealed by whole-genome sequencing and population analyses. The South America-C (SA-C) coastal Patagonia population forms a unique clade closely related to a previously described divergent S. uvarum population from Oceania (AUS, found in Australia and New Zealand). Our species reclassification is supported by a low Ortho Average Nucleotide Identity (OANI) of 93% in SA-C and AUS relative to S. uvarum, which falls below the suggested species delineation threshold of 95%, indicating an independent evolutionary lineage. Hybrid spore viability assessment provided compelling evidence that SA-C and AUS are reproductively isolated from S. uvarum. In addition, we found unique structural variants between S. chiloensis sp. nov. lineages, including large-scale chromosomal translocations and inversions, together with a distinct phenotypic profile, emphasizing their intraspecies genetic distinctiveness. We suggest that S. chiloensis sp. nov diverged from S. uvarum in allopatry due to glaciation, followed by post-glacial dispersal, resulting in distinct lineages on opposite sides of the Pacific Ocean. The discovery of S. chiloensis sp. nov. illustrates the uniqueness of Patagonia's coastal biodiversity and underscores the importance of adopting an integrative taxonomic approach in species delineation to unveil cryptic microbial species. The holotype of S. chiloensis sp. nov. is CBS 18620(T).
Climate change and population persistence in a hibernating marsupial
(2024) Nespolo, Roberto F.; Quintero-Galvis, Julian F.; Fonturbel, Francisco E.; Cubillos, Francisco A.; Vianna, Juliana; Moreno-Meynard, Paulo; Rezende, Enrico L.; Bozinovic, Francisco
Climate change has physiological consequences on organisms, ecosystems and human societies, surpassing the pace of organismal adaptation. Hibernating mammals are particularly vulnerable as winter survival is determined by short-term physiological changes triggered by temperature. In these animals, winter temperatures cannot surpass a certain threshold, above which hibernators arouse from torpor, increasing several fold their energy needs when food is unavailable. Here, we parameterized a numerical model predicting energy consumption in heterothermic species and modelled winter survival at different climate change scenarios. As a model species, we used the arboreal marsupial monito del monte (genus Dromiciops), which is recognized as one of the few South American hibernators. We modelled four climate change scenarios (from optimistic to pessimistic) based on IPCC projections, predicting that northern and coastal populations (Dromiciops bozinovici) will decline because the minimum number of cold days needed to survive the winter will not be attained. These populations are also the most affected by habitat fragmentation and changes in land use. Conversely, Andean and other highland populations, in cooler environments, are predicted to persist and thrive. Given the widespread presence of hibernating mammals around the world, models based on simple physiological parameters, such as this one, are becoming essential for predicting species responses to warming in the short term.
Differential expression of stress candidate genes for thermal tolerance in the sea urchin Loxechinus albus
(2017) Vergara-Amado, Jonathan; Silva, Andrea X.; Manzi, Catalina; Nespolo, Roberto F.; Cardenas, Leyla
Marine ectotherms inhabiting intertidal and shallow subtidal environments are continuously exposed to diurnal tidal cycles and seasonal variability in temperature. These organisms have adaptive mechanisms to maintain cellular homeostasis, irrespective of thermal environmental variation. In this study, we describe the molecular responses to thermal stress in the edible sea urchin Loxechinus albus. In particular, we determined the differential expression of a set of molecular markers that have been identified as targets of stress-related responses. These include the heat shock proteins (hsp70 and hsp90), cell detoxification proteins (cytochrome P450), and osmorregulatory proteins (a and beta-Na+/K+ ATPase). We exposed individuals to different temperatures; a warm treatment (18 +/- 1.0 degrees C), a cold treatment (10 1.0 degrees C), and a control treatment (average local temperature of 14 +/- 1.0 degrees C) and differential expression was quantified after 2, 6, 12 and 48 h of exposure. Levels of mRNA were quantified by reverse transcription-quantitative polymerase chain reaction, and the relative expression of each gene was calculated using the 18S rRNA gene as a reference, and the control treatment as a calibrator. We found that the expression levels of all studied genes increased during exposure to warmth. The largest increase in expression was observed in cytochrome p450 genes (ca. sixteen-fold); this was followed by increases in the expression of the Na+/K+ ATPase (ca. eight-fold) and by the lisp (ca. six fold) genes. These results indicate that sea urchin thermal stress responses depend on differential gene-regulation, involving heat-shock, membrane potential, and detoxification genes that generate an integrated adaptive response to acute environmental changes.
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.
Identification of new ethanol-tolerant yeast strains with fermentation potential from central Patagonia
(2022) Villarreal, Pablo; Quintrel, Pablo A.; Olivares-Munoz, Sebastian; Ruiz, Jose J.; Nespolo, Roberto F.; Cubillos, Francisco A.
The quest for new wild yeasts has increasingly gained attention because of their potential ability to provide unique organoleptic characters to fermented beverages. In this sense, Patagonia offers a wide diversity of ethanol-tolerant yeasts and stands out as a bioprospecting alternative. This study characterized the genetic and phenotypic diversity of yeast isolates obtained from Central Chilean Patagonia and analyzed their fermentation potential under different fermentative conditions. We recovered 125 colonies from Nothofagus spp. bark samples belonging to five yeast species: Saccharomyces eubayanus, Saccharomyces uvarum, Lachancea cidri, Kregervanrija delftensis, and Hanseniaspora valbyensis. High-throughput microcultivation assays demonstrated the extensive phenotypic diversity among Patagonian isolates, where Saccharomyces spp and L. cidri isolates exhibited the most outstanding fitness scores across the conditions tested. Fermentation performance assays under wine, mead, and beer conditions demonstrated the specific potential of the different species for each particular beverage. Saccharomyces spp. were the only isolates able to ferment beer wort. Interestingly, we found that L. cidri is a novel candidate species to ferment wine and mead, exceeding the fermentation capacity of a commercial strain. Unlike commercial strains, we found that L. cidri does not require nutritional supplements for efficient mead fermentation. In addition, L. cidri produces succinic and acetic acids, providing a distinct profile to the final fermented product. This work demonstrates the importance of bioprospecting efforts in Patagonia to isolate novel wild yeast strains with extraordinary biotechnological potential for the fermentation industry.
Integrative Physiological Responses to Acute Dehydration in the Rufous-Collared Sparrow: Metabolic, Enzymatic, and Oxidative Traits
(2021) Navarrete, Lucas; Bozinovic, Francisco; Pena-Villalobos, Isaac; Contreras-Ramos, Carolina; Sanchez-Hernandez, Juan C.; Newsome, Seth D.; Nespolo, Roberto F.; Sabat, Pablo
Predictions indicate that birds worldwide will be affected by global warming and extreme climatic events which is especially relevant for passerines because the diurnal habits, small body size, and high mass-adjusted metabolic rates of this group make it particularly susceptible to increases in temperature and aridity. Some bird species respond to conditions that stress osmoregulation by increasing their rates of energy expenditure, nevertheless, the effect of dehydration on metabolic rates in birds has produced contrasting results. It also remains unknown whether hydration state may cause shifts in tissue-specific metabolic rates or modify tissue oxidative status. We used the rufous-collared sparrow (Zonotrichia capensis), to experimentally test the effect of dehydration on metabolic enzymes in erythrocytes, tissue oxidative status, basal metabolic rate (BMR), and total evaporative water loss. We found a significant increase in mass-adjusted BMR in water restricted (WR) birds compared to control birds (CT). Activity of cytochrome-c-oxidase (COX) in red blood cells (RBCs) was also significantly higher in the WR group relative to the CT group and this activity was positively correlated with mass-adjusted BMR. We found a moderate effect of water restriction on membrane damage of skeletal muscle. In a second set of individuals subjected to the same experimental conditions, lean mass and total water were tightly correlated and decreased by 10 and 12%, respectively, in birds in the WR group relative to the CT group. Decreases in total water and lean mass leads to an increase in mass-adjusted BMR in WR Z. capensis, suggesting that birds may simultaneously increase protein catabolism and production of metabolic water through oxidation. The significant positive relationship between BMR and COX in RBCs is a finding that requires additional research to determine whether erythrocyte metabolism is affected by dehydration per se and or it more generally reflects rates of energy expenditure in birds.
Modeling heterothermic fitness landscapes in a marsupial hibernator using changes in body composition
(2023) Abarzua, Tamara; Camus, Isidora; Ortiz, Felipe; Nunque, Abel; Cubillos, Francisco A.; Sabat, Pablo; Nespolo, Roberto F.
Hibernation is an adaptive strategy that allows animals to enter a hypometabolic state, conserving energy and enhancing their fitness by surviving harsh environmental conditions. However, addressing the adaptive value of hibernation, at the individual level and in natural populations, has been challenging. Here, we applied a non-invasive technique, body composition analysis by quantitative magnetic resonance (qMR), to calculate energy savings by hibernation in a population of hibernating marsupials (Dromiciops gliroides). Using outdoor enclosures installed in a temperate rainforest, and measuring qMR periodically, we determined the amount of fat and lean mass consumed during a whole hibernation cycle. With this information, we estimated the daily energy expenditure of hibernation (DEEH) at the individual level and related to previous fat accumulation. Using model selection approaches and phenotypic selection analysis, we calculated linear (directional, beta), quadratic (stabilizing or disruptive, gamma) and correlational (p) coefficients for DEEH and fat accumulation. We found significant, negative directional selection for DEEH (beta(DEEH) = - 0.58 +/- 0.09), a positive value for fat accumulation (beta(FAT) = 0.34 +/- 0.07), and positive correlational selection between both traits (p(DEEH x FAT) = 0.24 +/- 0.07). Then, individuals maximizing previous fat accumulation and minimizing DEEH were promoted by selection, which is visualized by a bi-variate selection surface estimated by generalized additive models. At the comparative level, results fall within the isometric allometry known for hibernation metabolic rate in mammals. Thus, by a combination of a non-invasive technique for body composition analysis and semi-natural enclosures, we were characterized the heterothermic fitness landscape in a semi-natural population of hibernators.
Rapid selection response to ethanol in Saccharomyces eubayanus emulates the domestication process under brewing conditions
(2022) Mardones, Wladimir; Villarroel, Carlos A.; Abarca, Valentina; Urbina, Kamila; Pena, Tomas A.; Molinet, Jennifer; Nespolo, Roberto F.; Cubillos, Francisco A.
Although the typical genomic and phenotypic changes that characterize the evolution of organisms under the human domestication syndrome represent textbook examples of rapid evolution, the molecular processes that underpin such changes are still poorly understood. Domesticated yeasts for brewing, where short generation times and large phenotypic and genomic plasticity were attained in a few generations under selection, are prime examples. To experimentally emulate the lager yeast domestication process, we created a genetically complex (panmictic) artificial population of multiple Saccharomyces eubayanus genotypes, one of the parents of lager yeast. Then, we imposed a constant selection regime under a high ethanol concentration in 10 replicated populations during 260 generations (6 months) and compared them with propagated controls exposed solely to glucose. Propagated populations exhibited a selection differential of 60% in growth rate in ethanol, mostly explained by the proliferation of a single lineage (CL248.1) that competitively displaced all other clones. Interestingly, the outcome does not require the entire time-course of adaptation, as four lineages monopolized the culture at generation 120. Sequencing demonstrated that de novo genetic variants were produced in all propagated lines, including SNPs, aneuploidies, INDELs and translocations. In addition, the different propagated populations showed correlated responses resembling the domestication syndrome: genomic rearrangements, faster fermentation rates, lower production of phenolic off-flavours and lower volatile compound complexity. Expression profiling in beer wort revealed altered expression levels of genes related to methionine metabolism, flocculation, stress tolerance and diauxic shift, likely contributing to higher ethanol and fermentation stress tolerance in the evolved populations. Our study shows that experimental evolution can rebuild the brewing domestication process in 'fast motion' in wild yeast, and also provides a powerful tool for studying the genetics of the adaptation process in complex populations.
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.

Browsing by Author "Nespolo, Roberto F."

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