Browsing by Author "Franco, Lida M."

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    Body Composition and Energy Savings by Hibernation: Lessons from the South American Marsupial Dromiciops gliroides
    (2022) Mejias, Carlos; Navedo, Juan G.; Sabat, Pablo; Franco, Lida M.; Bozinovic, Francisco; Nespolo, Roberto F.
    Hibernation (i.e., seasonal or multiday torpor) has been described in mammals from five continents and represents an important adaptation for energy economy. However, direct quantifications of energy savings by hibernation are challenging because of the complexities of estimating energy expenditure in the field. Here, we applied quantitative magnetic resonance to determine body fat and body composition in hibernating Dromiciops gliroides (monito del monte). During an experimental period of 31 d in winter, fat was significantly reduced by 5.72 +/- 0.45 g, and lean mass was significantly reduced by 2.05 +/- 0.14 g. This fat and lean mass consumption is equivalent to a daily energy expenditure of hibernation (DEEH) of 8.89 +/- 0.6 kJ d(-1) , representing 13.4% of basal metabolic rate, with a proportional contribution of fat and lean mass consumption to DEEH of 81% and 18%, respectively. During the deep heterothermic bouts of monitos, body temperature remained 0.41 degrees C +/- 0.2 degrees C above ambient temperature, typical of hibernators. Animals shut down metabolism and passively cool down to a critical defended temperature of 5.0 degrees C +/- 0.1 degrees C, where they begin thermoregulation in torpor. Using temperature data loggers, we obtained an empirical estimation of minimum thermal conductance of 3.37 +/- 0.19 J g(-1) h(-1) degrees C-1, which is 107% of the expectation by allometric equations. With this, we parameterized body temperature/ambient temperature time series to calculate torpor parameters and metabolic rates in euthermia and torpor. Whereas the acute metabolic fall in each torpor episode is about 96%, the energy saved by hibernation is 88% (compared with the DEE of active animals), which coincides with values from the literature at similar body mass. Thus, estimating body composition provides a simple method to measure the energy saved by hibernation in mammals.
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    Incomplete lineage sorting and phenotypic evolution in marsupials
    (2022) Feng, Shaohong; Bai, Ming; Rivas-Gonzalez, Iker; Li, Cai; Liu, Shiping; Tong, Yijie; Yang, Haidong; Chen, Guangji; Xie, Duo; Sears, Karen E.; Franco, Lida M.; Gaitan-Espitia, Juan Diego; Nespolo, Roberto F.; Johnson, Warren E.; Yang, Huanming; Brandies, Parice A.; Hogg, Carolyn J.; Belov, Katherine; Renfree, Marilyn B.; Helgen, Kristofer M.; Boomsma, Jacobus J.; Schierup, Mikkel Heide; Zhang, Guojie
    Incomplete lineage sorting (ILS) makes ancestral genetic polymorphisms persist during rapid speciation events, inducing incongruences between gene trees and species trees. ILS has complicated phylogenetic inference in many lineages, including hominids. However, we lack empirical evidence that ILS leads to incongruent phenotypic variation. Here, we performed phylogenomic analyses to show that the South American monito del monte is the sister lineage of all Australian marsupials, although over 31% of its genome is closer to the Diprotodontia than to other Australian groups due to ILS during ancient radiation. Pervasive conflicting phylogenetic signals across the whole genome are consistent with some of the morphological variation among extant marsupials. We detected hundreds of genes that experienced stochastic fixation during ILS, encoding the same amino acids in non-sister species. Using functional experiments, we confirm how ILS may have directly contributed to hemiplasy in morphological traits that were established during rapid marsupial speciation ca. 60 mya.