Pushing the boundaries: actual and potential distribution of thrushes expanding their ranges in South America.

The distribution of a species reflects its ecological adaptability and evolutionary history, which is shaped by the environment and represents a dynamic area subject to anthropogenic environmental change. We used the MaxEnt algorithm to construct ecological niche models for four thrush species within the Turdus genus; T. amaurochalinus, T. chiguanco, T. falcklandii and T. rufiventris. These models were used to predict the potential geographic distributions of these species that are expanding their ranges in South America. Using occurrence records, we estimated currently occupied areas for each species. We also identified suitable habitats and projected possible areas to be colonized by the four species at continental scale. Temperature annual range had the highest influence for T. falcklandii, while human modification was the main variable explaining the distribution of the other three species. The potential distribution area ranged from 2.5 million km2 for T. falcklandii to nearly seven million km2 for T. amaurochalinus. Large proportions of suitable area remain unoccupied by all four species, being 50% for T. amaurochalinus and T. rufiventris, and about 70% for T. chiguanco and T. falcklandii. Anthropogenic disturbances, such as habitat loss and ecosystem transformation, lead to non-random species extinction and biotic homogenization, highlighting the importance of predictive models as valuable tools for informing mitigation policies and conservation strategies. Thrushes are progressively expanding their ranges, and the colonization of new habitats could bring new challenges.

The ecology and evolution of the monito del monte, a relict species from the southern South America temperate forests.

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, updated phylogeographic relationships, reproductive cycle, trophic relationships, mutualisms, conservation, and threats. This marsupial shows high densities, despite presenting slow reproductive rates, a paradox explained by the unique characteristics of its three-dimensional habitat. We finally suggest immediate actions to protect these species that may be threatened in the near future due to habitat destruction and climate change.