Rudd, J. L. | Search bioRxiv

bioRxiv2024

Postmortem findings of free-ranging North American beavers (Castor canadensis) reveal potential threats to California freshwater ecosystems

North American beavers (Castor canadensis) are semi-aquatic rodents recognized as keystone species that increase the diversity of freshwater ecosystems. This study aimed to characterize the mortality and pathological findings of free-ranging beavers in California and, based on these results, establish the potential threats to freshwater ecosystems. This study included eighteen beavers submitted for postmortem examination between 2008 and 2024 at the California Animal Health and Food Safety Laboratory, UC Davis. Gross and microscopic examination, bacteriological, parasitological, immunohistochemical, and molecular techniques were used as tools to diagnose the cause of death/reason for euthanasia and comorbidities in the beavers. Encephalitis caused by the larva migrans of Baylisascaris spp. was the most prevalent (9/18) cause of mortality/reason for euthanasia followed by bacterial infections in 6 individuals. In these 6 animals, bacterial bronchopneumonia was diagnosed in two (Staphylococcus aureus and a mix of gram-negative and -positive bacterial infection) and Listeria monocytogenes encephalitis, bacterial myofascitis (Aeromonas bestiarum and Pasteurella multocida), bacterial encephalitis (Acinetobacter towneri), and tularemia (Francisella tularensis) were diagnosed in one beaver each. Three animals died or were euthanized due to non-infectious causes including motor vehicle trauma, squamous cell carcinoma, and capture cardiomyopathy. Endoparasitism was the main comorbidity including granulomatous hepatitis by a suspected capillarid species, cerebral toxoplasmosis, Giardia infection, gastric nematodiasis, and cecal trematodiasis. In California, beavers are exposed to various pathogens that represent threats to humans, domestic animals, and wildlife. Since the interspecies transmission of these pathogens occurs in rivers, streams, lakes, and ponds, we suggest that studying beaver health can reflect freshwater ecosystem health. This study also indicates that the translocation of beavers into new areas without consideration and/or mitigation represents a potential risk for pathogen introduction.

pathology↗

bioRxiv2021

Broad-scale puma connectivity could restore genomic diversity to fine-scale coastal populations

Urbanization is decreasing wildlife habitat and connectivity worldwide, including for apex predators, such as the puma (Puma concolor). Puma populations along Californias central and southern coastal habitats have experienced rapid fragmentation from development, leading to calls for demographic and genetic management. To address urgent conservation genomic concerns, we used double-digest restriction-site associated DNA (ddRAD) sequencing to analyze 16,285 genome-wide single-nucleotide polymorphisms (SNPs) from 401 broadly sampled pumas. Our analyses indicated support for 4-10 geographically nested, broad- to fine-scale genetic clusters. At the broadest scale, the 4 genetic clusters had high genetic diversity and exhibited low linkage disequilibrium, indicating pumas have retained statewide genomic diversity. However, multiple lines of evidence indicated substructure, including 10 fine-scale genetic clusters, some of which exhibited allelic fixation and linkage disequilibrium. Fragmented populations along the Southern Coast and Central Coast had particularly low genetic diversity and strong linkage disequilibrium, indicating genetic drift and close inbreeding. Our results demonstrate that genetically at-risk populations are typically nested within a broader-scale group of interconnected populations that collectively retains high genetic diversity and heterogeneous fixations. Thus, extant variation at the broader scale has potential to restore diversity to local populations if management actions can enhance vital gene flow and recombine locally sequestered genetic diversity. These state- and genome-wide results are critically important for science-based conservation and management practices. Our broad- and fine-scale population genomic analysis highlights the information that can be gained from population genomic studies aiming to provide guidance for fragmented population conservation management.

zoology↗