Francisco Fonturbel

and 11 more

The arboreal marsupial Monito del Monte (genus Dromiciops, with two recognized species) is a paradigmatic mammal. It is the sole living representative of the order Microbiotheria, the ancestor lineage of Australian marsupials. Also, this marsupial is the unique frugivorous mammal in the temperate rainforest, being the main seed disperser of several endemic plants of this ecosystem, thus acting as keystone species. Dromiciops is also one of the few hibernating mammals in South America, spending half of the year in a physiological dormancy where metabolism is reduced to 10% of normal levels. This capacity to reduce energy expenditure in winter contrasts with the enormous energy turnover rate they experience in spring and summer. The unique life-history strategies of this living Microbiotheria, characterized by an alternation of life in the slow and fast lanes, putatively represent ancestral traits that permitted these cold-adapted mammals to survive in this environment. Here we describe the ecological role of this emblematic marsupial, summarizing the ecophysiology of hibernation and sociality, actualized phylogeographic relationships, reproductive cycle, trophic relationships, mutualisms, conservation and threats. This marsupial shows high densities, despite presenting slow reproductive rates, a paradox that is explained by the unique characteristics of its three-dimensional habitat. We finally suggest immediate actions to protect these locally abundant but globally threatened species.

Grisel Cavieres

and 6 more

Roberto Nespolo

and 5 more

The capacity of some yeasts to extract energy from single sugars, generating CO2 and ethanol (=fermentation), even in the presence of oxygen is known as the Crabtree effect. This phenomenon represents an important adaptation as it allowed the utilization of the ecological niche given by modern fruits, an abundant source of food that emerged in the terrestrial environment in the Cretaceous. However, identifying the evolutionary events that triggered fermentative capacity in Crabtree positive species is challenging, as microorganisms do not leave fossil evidence. Thus, key innovations should be inferred based only on traits measured under culture conditions. Here, we reanalyzed data form a common-garden experiment where several proxies of fermentative capacity were recorded in Crabtree positive and negative species, representing yeast’s phylogenetic diversity. In particular, we applied the “lasso-OU” algorithm which detects points of adaptive shifts, provided trait values representing a given performance measure. We tested whether multiple events or a single event explains the actual fermentative capacity of yeasts. According to the lasso-OU procedure, evolutionary changes in the three proxies of fermentative capacity that we considered (i.e., glycerol production, ethanol yield and respiratory quotient) are consistent with a single evolutionary episode (a whole-genomic duplication, WGD), instead of a series of small genomic rearrangements. Thus, the WGD appears as the key event behind the diversification of fermentative yeasts, which by increasing gene dosage and maximized their capacity of energy extraction for exploiting the new ecological niche provided by single sugars.