Mammals are excellent biomonitors for pollutants such as trace elements; however, there is a lack of studies on this subject in wild mammals across Latin America. This review provides a comprehensive and updated overview of the current state and trends in mammalian toxicology, offering an integrative regional perspective. A systematic literature review was conducted, identifying and synthesizing data on date of publication, country of study, analyzed pollutants, taxonomic group and trophic guild involved, biological matrix used, analytical techniques, and sample origin. Publications show a constant increase in their number and diversity. However, research remains concentrated in high-biodiversity or polluted areas within large countries such as Brazil, Mexico, and Argentina, leading to significant geographical biases. At present, the most frequently analyzed elements have been Hg, Pb, and Cd, reflecting their relevance as environmental pollutants generated from extractive industries and fossil fuel combustion. Aquatic carnivores are highly susceptible to bioaccumulation, making the order Cetacea and the piscivorous trophic guild the most studied groups, underscoring their well-documented issue of mercury contamination in aquatic ecosystems. On the other hand, terrestrial mammals remain comparatively understudied. Due to their central role in metabolic pathways and detoxification of contaminants, liver and kidney have been the most analyzed matrices. Atomic absorption spectrometry has been the most frequent quantification technique, favored for its suitable cost-benefit balance. Future research should incorporate non-invasive techniques and reevaluate the importance of scientific collections, as they offer valuable historical baselines for ecotoxicological studies. We strongly recommend prioritizing further research in mammal species populations living in urban areas and mining regions, to better understand and mitigate the ecological impacts of metal pollution in these threatened ecosystems.
Phenotypic variation in bats reflects the combined influence of environmental and evolutionary factors. Body size often responds to thermal gradients (Bergmann’s rule), whereas cranial and mandibular morphology are often associated with evolutionary history and diet, which are further shaped by resource seasonality. Corynorhinus mexicanus, an endemic bat of Mexico’s temperate forests, was analyzed to assess if environmental factors, evolutionary history, and their interaction influence forearm size and cranial and mandibular shape. Linear mixed models were fitted using forearm measurements and principal components derived from environmental variables, incorporating previously documented intraspecific lineages. Models were compared under annual and monthly temperature variation, accounting for reproductive timing and sex-specific energetic investment. Cranial and mandibular variation were examined using a two-dimensional geometric morphometric protocol to assess the influence of lineage and environmental seasonality as a proxy for dietary composition. Forearm length did not differ between lineages in females but did in males, with those from the Sierra Madre Occidental lineage being smaller. In both sexes, body size followed Bergmann’s rule. Cranial differences between lineages were restricted to the lateral view of the braincase and the ventral view of the rostrum. Overall, cranial variation appeared to be primarily driven by evolutionary history, whereas forearm size reflected a combined influence of evolutionary and environmental factors. Maximum temperatures during the reproductive period influenced forearm length in males, while minimum temperatures affected females. Finally, we highlighted the importance of considering temporal extent and environmental resolution in eco-evolutionary studies.
Recent studies have demonstrated that the Andean sigmodontine rodent Abrothrix andina (Sigmodontinae, Abrotrichini) is neither widespread nor a senior synonym of several nominal taxa (i.e., dolichonyx, cinnamomea, jucundus, gossei, and polius) described from Argentina, Chile, and Peru since the 19th century. However, a comprehensive taxonomic and nomenclatural reassessment requires the examination of type material. Here, we address this by analyzing topotypic specimens collected from three Andean localities near Santiago de Chile (Chile), the type locality of A. andina. Cytochrome b sequences from these specimens cluster within Abrothrix olivacea. These results support treating Abrothrix andina (Philippi in Philippi & Landbeck, 1858) as a junior synonym of Abrothrix olivacea (Waterhouse, 1837). Additionally, the nominal form Abrothrix gossei (Thomas, 1920) warrants recognition as a distinct species of Abrothrix, sister to A. olivacea. Although this study appears to complete the taxonomic reassessment of A. andina, a remote possibility remains that its holotype, currently lost, represents a still-unsampled Andean highland population, now extinct or extremely rare due to climate change.
The Trypanosoma cruzi clade represents one of the most complex and ecologically diverse assemblages of mammalian trypanosomes. Although the group’s human pathogenic member T. cruzi is best known as the etiological agent of Chagas disease, its evolutionary origins remain debated. Two main hypotheses attempt to explain the diversification of the T. cruzi clade: the supercontinent hypothesis, which proposes an ancient co-diversification with South American marsupials, and the bat-seeding hypothesis, which suggests a more recent origin through host-switching from bat trypanosomes. Here, we combined parasite and host phylogenies with global-fit cophylogenetic analyses to evaluate whether mammalian diversification has influenced the evolutionary history of the T. cruzi clade. Using PACo and ParaFit, we detected a weak but statistically significant global correspondence between mammal and trypanosome phylogenies. This correspondence was primarily associated with bat-trypanosome relationships, whereas associations involving non-bat mammals showed limited phylogenetic concordance. Together, these findings suggest that mammalian diversification may have influenced trypanosome evolution across multiple evolutionary contexts and timescales.
Global biodiversity loss is accelerating, driven by multiple factors, including climate change. Protected areas are a cornerstone of conservation strategies; however, their effectiveness is often constrained by limited climate-resilience planning and taxonomic biases that often overlook ecologically important but non-charismatic groups, such as rodents. We analyzed rodent species richness in the Sierra Madre Oriental, Mexico, evaluating conservation effectiveness within protected areas (which cover 29% of the region) under climate change scenarios. Potential species richness for 85 rodent species was estimated using ensemble species distribution models under current conditions and future climate scenarios (RCP4.5 and RCP8.5) for projections to 2030, 2050, and 2070. Temporal trends in potential species richness were evaluated by Mann-Kendall trend test. Additional comparisons included bioclimatic corridors and functional groups (generalists and specialists). Results suggest that protected areas currently encompass all modeled rodent species in the Sierra Madre Oriental (excluding Dipodomys spectabilis, Geomys personatus and Sigmodon mascotensis), however, they do not fully overlap with areas of highest species richness, which are located in the southern Sierra Madre Oriental. Also, an overall decline in high-richness areas by 2070, particularly under the RCP8.5 scenario, where species losses in some protected areas could reach up to 35 species. Although generalist species exhibit relative stability, an overall decreasing trend in species richness is expected in most protected areas, with significant compositional changes projected for specialist species. Notably, bioclimatic corridors were found to host species currently absent from protected areas and to support the same proportion of species classified as at risk. Implementing climate-smart strategies, such as establishing and reinforcing bioclimatic corridors to improve connectivity, is recommended to mitigate biodiversity loss and enhance conservation resilience in the Sierra Madre Oriental.
