Distributional ecology of Andes hantavirus: a macroecological approach.

BACKGROUND: Hantavirus pulmonary syndrome (HPS) is an infection endemic in Chile and Argentina, caused by Andes hantavirus (ANDV). The rodent Oligoryzomys longicaudatus is suggested as the main reservoir, although several other species of Sigmodontinae are known hosts of ANDV. Here, we explore potential ANDV transmission risk to humans in southern South America, based on eco-epidemiological associations among: six rodent host species, seropositive rodents, and human HPS cases. METHODS: We used ecological niche modeling and macroecological approaches to determine potential geographic distributions and assess environmental similarity among rodents and human HPS cases. RESULTS: Highest numbers of rodent species (five) were in Chile between 35° and 41°S latitude. Background similarity tests showed niche similarity in 14 of the 56 possible comparisons: similarity between human HPS cases and the background of all species and seropositive rodents was supported (except for Abrothrix sanborni). Of interest among the results is the likely role of O. longicaudatus, Loxodontomys micropus, Abrothrix olivaceus, and Abrothrix longipilis in HPS transmission to humans. CONCLUSIONS: Our results support a role of rodent species' distributions as a risk factor for human HPS at coarse scales, and suggest that the role of the main reservoir (O. longicaudatus) may be supported by the broader rodent host community in some areas.

Insularity and Aridity as Drivers of Mandibular Disparity in Thylamys elegans (Waterhouse, 1839) from Populations of the Atacama Desert, Chile.

Island ecosystems differ in several elements from mainland ecosystems and may induce variations related to natural selection and patterns of adaptation in most aspects of the biology of an organism. Thylamys elegans (Waterhouse, 1839) is a marsupial endemic to Chile, distributed from Loa River to Concepción. Historically, three subspecies have been described: Thylamys elegans elegans, Thylamys elegans coquimbensis and Thylamys elegans soricinus. For this research, two morphometric approaches and a biomechanical model were used to compare the mandible shapes and biomechanics between two Chilean mouse opossum populations belonging to different subspecies: one from the coastal desert of Chile (T. e. coquimbensis) and the other from the central inland region (T. e. elegans). Additionally, mandibles of insular populations found in the Reserva Nacional Pinguino de Humboldt (RNPH)), from which the subspecies association is unknown, were also included. The results showed that insular populations have differences in mandibular shapes, sizes and biomechanical characteristics compared to continental populations, which may be related to environmental variables like aridity and vegetation cover, prey type, insularity effects and/or the founder effect on micromammals, apart from vicariance hypotheses and other selective pressures.

Patterns of the fecal microbiota in the Juan Fernández fur seal (Arctocephalus philippii).

As apex predators, pinnipeds are considered to be useful bioindicators of marine and coastal environments. Endemic to a small archipelago in the South Pacific, the Juan Fernandez fur seal (JFFS) is one of the less-studied members of the pinniped family Otariidae. This study aimed to characterize the fecal microbiome of the JFFS for the first time, to establish a baseline for future studies of host-microbial-environment interactions and monitoring programs. During two consecutive reproductive seasons, 57 fecal samples were collected from seven different JFFS colonies within the Juan Fernandez Archipelago, Chile. Bacterial composition and abundance were characterized by sequencing the V4 region of the 16S rRNA gene. The overall microbiome composition was dominated by five phyla: Firmicutes (40% ±24), Fusobacteria (30% ±17), Bacteroidetes (22% ±10), Proteobacteria (6% ±4), and Actinobacteria (2% ±3). Alpha diversity was higher in Tierras Blancas. However, location was not found to be a dominant driver of microbial composition. Interestingly, the strongest signal in the data was a negative association between the genera Peptoclostridium and Fusobacterium, which explained 29.7% of the total microbial composition variability between samples. The genus Peptoclostridium has not been reported in other pinniped studies, and its role here is unclear, with interpretation challenging due to a lack of information regarding microbiome functionality in marine mammals. As a first insight into the JFFS fecal microbiome, these results contribute towards our understanding of the natural microbial diversity and composition in free-ranging pinnipeds.

Composition and structure of the skin microbiota of rorquals off the Eastern South Pacific.

Recent advances in high-throughput sequencing have enabled the large-scale interrogation of microbiota in the most diverse environments, including host-associated microbiota. This has led to the recognition that the skin microbiota of rorquals is specific and structurally different from that of the ocean. This study reveals the skin microbiome of 85 wild individuals along the Chilean coast belonging to Megaptera novaeangliae, Balaenoptera musculus and Balaenoptera physalus. Alpha diversity analysis revealed significant differences in richness and phylogenetic diversity, particularly among humpback whales from different locations and between blue and humpback whales. Beta diversity was partially explained by host and location but only accounting for up to 17% of microbiota variability (adjusted VPA). Overall, we found that microbiota composition was dominated by bacterial genera such as Cardiobacter, Moraxella, Tenacibaculum, Stenotrophomonas, Flavobacteria and Pseudomonas. We also found that no ASVs were associated with the three rorqual species. Up to four ASVs were specific of a location, indicating a great variability in the microbiota. To the best of our knowledge, this is the first report on the composition and structure of the skin microbiota of whales off the coast of Chile, providing a foundational dataset to understand the microbiota's role in rorquals.

Author Correction: 50 Years of Cetacean Strandings Reveal a Concerning Rise in Chilean Patagonia.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

50 Years of Cetacean Strandings Reveal a Concerning Rise in Chilean Patagonia.

Cetacean strandings (CS) have been reported in increasing numbers in coastal areas worldwide. Although the causes of these strandings are unknown, a number of anthropogenic and environmental factors have been suggested. This paper aims to characterize CS patterns and describe their fine-scale spatiotemporal dynamics. We analysed spatial and spatiotemporal CS patterns in Chile from January 1968 to January 2020. We identified a total of 389 CS events affecting eight cetacean families, 21 genera, and 35 species, which represent more than 85% of the reported species richness for the country. Most CS events (94.1%) were single (i.e., ≤two individuals). There were also 18 mass stranding (three to 24 individuals, 4.1%) and nine unusually large mass stranding events (>25 individuals, 2%). Purely spatial tests showed CS events appearing in random occurrence along the Chilean coast. Local tests for spatio-temporal clusters, however, identified a greater number of hotspots reported in the southernmost part of the country, namely, Chilean Patagonia. Specifically, significant spatio-temporal clusters were identified and defined as containing three or more individuals within a two-month period as a focal coastal event (<1 km radius). It is a cause of concern that CS events in Chile have been increasing consistently over the last decades, and although we were not able to identify their causes, we are able to highlight the importance of changes in climate conditions and of an increase in monitoring activities as primary drivers for such patterns, particularly important in Chilean Patagonia.