Biology subjects

Rivera, D. C.

Publications and source records attributed to Rivera, D. C..

3 recordsLinked to original sources

bioRxiv2026

A holistic survey of small mammal diversity across an iconic Madrean Sky Island (Santa Catalina Mountains, Arizona, USA)

The Santa Catalina Mountains are an iconic member of the Madrean Sky Islands, rising above Tucson, Arizona, USA, where the Catalina Highway connects Sonoran desertscrub to stands of conifer forest nearly 2,800 meters in elevation. As one of the [~]54 forested mountain areas in this system, the Santa Catalinas host unique biotic communities relative to the surrounding lowlands. However, most of these sky islands lack the surveys of resident small mammals (either historical or recent) needed for studying biodiversity in the context of changing climate and habitat use. From 2021 to 2023, we surveyed 10 localities on the north and south slopes of the Santa Catalina Mountains using holistic sampling methods to document terrestrial small mammal diversity and preserve multiple tissue types. Here we summarize these new collections relative to previous voucher specimens and human observations, identifying gaps for future work to address. Our survey recorded the presence of 15 species, preserved 150 voucher specimens paired with a suite of flash-frozen tissues, and non-lethally sampled another 219 individuals (ear tissue, feces, ectoparasites, and measurements) to provide populational data from sites where vouchering occurred. Despite the road accessibility and long history of sampling in the Santa Catalina Mountains, our surveys extended the known elevational range for 8 species, including the first known specimen of Reithrodontomys fulvescens from the area. Our use of a transect-based survey design, which maximizes species diversity across biotic communities, paired with holistic specimen preservation techniques, provides a model for surveying patterns of population genetic and parasite sharing relationships across other Madrean Sky Islands, bridging a [~]40 year lull in specimen preservation while adding new data dimensions that promote integrative studies of small mammal biodiversity. With more complete sampling, other mountains will offer promising replicates for studying eco-evolutionary impacts of the regions episodic habitat connectivity. Teaser textSurveying the terrestrial small mammals of the Santa Catalina Mountains, part of the Madrean Sky Islands, we analyze modern occurrences relative to previous records and demonstrate the potential value of holistically surveying sky island small mammals.

zoology↗

bioRxiv2025

Uncovering historical small mammal biodiversity among the Madrean Sky Islands

The Madrean Sky Island Archipelago is a system of 54 mountains with isolated woodland habitat above 1,600 meters, primarily in the Sonoran Desert. These mountains harbor a wide variety of native small mammals spanning 11 families of bats, rodents, and shrews. Improved understanding of Madrean Sky Island biodiversity should advance studies of biogeography, phylogeny, host-symbiont interactions, and community assembly in this ecoregion. However, which species are found in each sky island and how their populations are genetically related remain open questions. To establish the current knowledge baseline, we used georeferenced voucher specimens to summarize the extent and timing of past collecting efforts for small mammals in woodland habitats across the Madrean Sky Islands. In total, at least 88 species (35 bats, 50 rodents, 3 shrews) from 9,540 specimens were collected from 1884-2023. Of these specimens, 79% come from 5 sky islands (Chiricahuas, Pinalenos, Huachucas, Animas, and Santa Catalinas) and at least 23 sky islands in the Madrean system have no recorded specimens. Mexicos 25 sky islands are mostly unsampled (only the San Luis, Sierra dos Ajos, and Sierra La Mariquita have any georeferenced specimens) and several of Arizonas larger sky islands have fewer than 40 specimens (Galiuros, Canelo Hills, Santa Teresas, Mules, and Dragoons). Most small mammal specimens (88%) were collected in 1980 or earlier without prioritizing frozen tissues for DNA/RNA preservation. Including 3,946 non-georeferenced specimens may add sampling for another 6 sky islands and 6 species, but georeferencing confirmation is needed and major patterns are unchanged. This distributional summary is the current basis for all derived biodiversity knowledge of Madrean Sky Island small mammals, illustrating clear gaps regarding most species of woodland-dwelling bats, rodents, and shrews. There is a critical need for future fieldwork and voucher specimen preservation (including of flash-frozen tissues) in this region, both to monitor changes compared to historical sampling and to test biodiversity assumptions on unsampled mountains.

ecology↗

bioRxiv2024

Anti-NMDAR encephalitis alters intrinsic spatiotemporal coding by enhancing neuronal coupling and clustering

Autoimmune anti-NMDA-receptor encephalitis is characterized by severe neuropsychiatric symptoms including memory dysfunction and seizures. However, it remains enigmatic what functional changes at the multi-neuronal level mediate network dysfunction. We used two-photon in vivo recording in a passive-transfer mouse model with patients monoclonal anti-GluN1-autoantibodies during slow-wave sleep-like conditions, a critical phase for memory processing. We find enhanced functional coupling and clustering between hippocampal CA1 pyramidal neurons (PNs), which intrinsically expose the network to hypersynchrony. These connectivity changes are associated with a selective preservation of strong excitatory synapses despite overall reduced excitation, thus enhancing hub-like properties of functionally connected PNs. Furthermore, we find abnormal PN firing characteristics, decreased transmission failure, and increased similarity of spontaneous spatiotemporal activity patterns, all affecting CA1 intrinsic neuronal coding. Collectively, the functional rewiring of hippocampal networks and altered intrinsic information processing provide new mechanistic insights into the NMDAR-hypofunction consequences and pathomechanisms of anti-NMDAR encephalitis symptomatology.

neuroscience↗