Ecological modeling, biogeography, and phenotypic analyses setting the tiger cats' hyperdimensional niches reveal a new species.

Recently, the tiger-cat species complex was split into Leopardus tigrinus and Leopardus guttulus, along with other proposed schemes. We performed a detailed analysis integrating ecological modeling, biogeography, and phenotype of the four originally recognized subspecies-tigrinus, oncilla, pardinoides, guttulus-and presented a new multidimensional niche depiction of the species. Species distribution models used > 1400 records from museums and photographs, all checked for species accuracy. Morphological data were obtained from institutional/personal archives. Spotting patterns were established by integrating museum and photographic/camera-trap records. Principal component analysis showed three clearly distinct groups, with the Central American specimens (oncilla) clustering entirely within those of the Andes, namely the pardinoides group of the cloud forests of the southern Central-American and Andean mountain chains (clouded tiger-cat); the tigrinus group of the savannas of the Guiana Shield and central/northeastern Brazil (savanna tiger-cat); and the guttulus group in the lowland forests of the Atlantic Forest domain (Atlantic Forest tiger-cat). This scheme is supported by recent genetic analyses. All species displayed different spotting patterns, with some significant differences in body measurements/proportions. The new distribution presented alarming reductions from the historic range of - 50.4% to - 68.2%. This multidimensional approach revealed a new species of the elusive and threatened tiger-cat complex.

Edge channels of broken-symmetry quantum Hall states in graphene visualized by atomic force microscopy.

The quantum Hall (QH) effect, a topologically non-trivial quantum phase, expanded the concept of topological order in physics bringing into focus the intimate relation between the "bulk" topology and the edge states. The QH effect in graphene is distinguished by its four-fold degenerate zero energy Landau level (zLL), where the symmetry is broken by electron interactions on top of lattice-scale potentials. However, the broken-symmetry edge states have eluded spatial measurements. In this article, we spatially map the quantum Hall broken-symmetry edge states comprising the graphene zLL at integer filling factors of [Formula: see text] across the quantum Hall edge boundary using high-resolution atomic force microscopy (AFM) and show a gapped ground state proceeding from the bulk through to the QH edge boundary. Measurements of the chemical potential resolve the energies of the four-fold degenerate zLL as a function of magnetic field and show the interplay of the moiré superlattice potential of the graphene/boron nitride system and spin/valley symmetry-breaking effects in large magnetic fields.

Circadian activity patterns of mammalian predators and prey in Costa Rica.

Temporal niche shifts can shape predator-prey interactions by enabling predator avoidance, enhancing feeding success, and reducing competition among predators. Using a community-based conservation approach, we investigated temporal niche partitioning of mammalian predators and prey across 12 long-term camera trap surveys in the Pacific slope and Talamanca Cordillera of Costa Rica. Temporal overlap and segregation were investigated between predator-prey and predator-predator pairs using overlap analysis, circular statistics, and relative abundance after accounting for differences in habitat, season, and human impact among sites. We made the assumption that predators select abundant prey and adjust their activity to maximize their temporal overlap, thus we predicted that abundant prey with high overlap would be preferred prey species for that predator. We also predicted that similar-sized pairs of predator species with the greatest potential for competitive interactions would have the highest temporal segregation. Our results supported the existence of temporal niche separation among the eight species of predators-the smaller Leopardus felids (ocelot, margay, oncilla) were primarily nocturnal, the largest felids (jaguar and puma) and coyote were cathemeral, and the smaller jaguarundi and tayra were mostly diurnal. Most prey species (67%) were primarily nocturnal versus diurnal or cathemeral (33%). Hierarchical clustering identified relationships among species with the most similar activity patterns. We discuss the primary prey and competitor species predicted for each of the eight predators. Contrary to our prediction, the activity pattern of similar-sized intraguild competitors overlapped more than dissimilar-sized competitors, suggesting that similar-sized predators are hunting the same prey at the same time. From this we conclude that prey availability is more important than competition in determining circadian activity patterns of Neotropical predators. Our results indicate the presence of a delicate balance of tropical food webs that may be disrupted by overhunting, leading to a depauperate community consisting of ubiquitous generalists and endangered specialists. With Central America a hotspot for hunting-induced "empty forests," community-based conservation approaches may offer the best road to reduce illegal hunting and maintain the biodiversity and community structure of tropical forest systems.

Los cambios temporales de nicho pueden amoldar las interacciones predador-presa al permitir a la presa evadir los predadores, mejorar la eficacia de la alimentación y reducir la competición entre predadores. Mediante muestreos con cámaras trampa en 12 sitios de la pendiente del Pacífico y la Cordillera de Talamanca de Costa Rica, investigamos la división temporal de los nichos de mamíferos predadores y presas usando un enfoque de conservación basado en la comunidad. Investigamos la superposición y segregación temporal entre pares predador-presa y predador-predador utilizando análisis de superposición, estadísticas circulares y abundancia relativa, teniendo en cuenta diferencias de hábitat, estacionales y de impacto humano entre los sitios. Asumimos que los predadores seleccionan presas abundantes y ajustan su actividad para maximizar su superposición temporal con éstas; por lo tanto, predijimos que una presa abundante con alta superposición sería una especie de presa preferida para ese predador. También predijimos que pares de especies de predadores de tamaño similar con el mayor potencial para interacciones competitivas tendrían la mayor segregación temporal. Nuestros resultados respaldaron la existencia de una separación temporal de nicho entre las ocho especies de predadores­determinamos que los felinos más pequeños del género Leopardus (manigordo, caucel, tigrillo) son principalmente nocturnos, los felinos más grandes (jaguar y puma) y el coyote son catemerales, y los jaguarundi y tayra más pequeños son principalmente diurnos. La mayoría de las especies de presas (67%) son principalmente nocturnas versus diurnas o catemerales (33%). Mediante análisis de agrupación jerárquica, identificamos relaciones entre especies con los patrones de actividad más similares. Para cada uno de los predadores discutimos las presas primarias predichas y las especies competidoras. Contrario a nuestra predicción, el patrón de actividad de los predadores intragremios de tamaño similar se superpone más que el de los competidores de distinto tamaño, lo que indica que los predadores de tamaño similar están cazando la misma presa y están activos al mismo tiempo. De esto concluimos que la disponibilidad de presas es más importante que la competición en cuanto a determinar los patrones de actividad circadiana de los predadores neotropicales. Nuestros resultados revelan que el delicado equilibrio de las redes tróficas tropicales puede ser interferido por la caza excesiva, lo que lleva a una comunidad depauperada compuesta por generalistas ubicuos y especialistas en peligro de extinción. Con América Central como un centro de "bosques vacíos" inducidos por la caza, los enfoques de conservación basados en la comunidad pueden ofrecer el mejor camino para reducir la caza ilegal, y mantener la biodiversidad y estructura ecológica comunitaria de los sistemas forestales tropicales.

Achieving µeV tunneling resolution in an in-operando scanning tunneling microscopy, atomic force microscopy, and magnetotransport system for quantum materials research.

Research in new quantum materials requires multi-mode measurements spanning length scales, correlations of atomic-scale variables with a macroscopic function, and spectroscopic energy resolution obtainable only at millikelvin temperatures, typically in a dilution refrigerator. In this article, we describe a multi-mode instrument achieving a µeV tunneling resolution with in-operando measurement capabilities of scanning tunneling microscopy, atomic force microscopy, and magnetotransport inside a dilution refrigerator operating at 10 mK. We describe the system in detail including a new scanning probe microscope module design and sample and tip transport systems, along with wiring, radio-frequency filtering, and electronics. Extensive benchmarking measurements were performed using superconductor-insulator-superconductor tunnel junctions, with Josephson tunneling as a noise metering detector. After extensive testing and optimization, we have achieved less than 8 µeV instrument resolving capability for tunneling spectroscopy, which is 5-10 times better than previous instrument reports and comparable to the quantum and thermal limits set by the operating temperature at 10 mK.

Invited review article: A 10 mK scanning probe microscopy facility.

We describe the design, development and performance of a scanning probe microscopy (SPM) facility operating at a base temperature of 10 mK in magnetic fields up to 15 T. The microscope is cooled by a custom designed, fully ultra-high vacuum (UHV) compatible dilution refrigerator (DR) and is capable of in situ tip and sample exchange. Subpicometer stability at the tip-sample junction is achieved through three independent vibration isolation stages and careful design of the dilution refrigerator. The system can be connected to, or disconnected from, a network of interconnected auxiliary UHV chambers, which include growth chambers for metal and semiconductor samples, a field-ion microscope for tip characterization, and a fully independent additional quick access low temperature scanning tunneling microscope (STM) and atomic force microscope (AFM) system. To characterize the system, we present the cooling performance of the DR, vibrational, tunneling current, and tip-sample displacement noise measurements. In addition, we show the spectral resolution capabilities with tunneling spectroscopy results obtained on an epitaxial graphene sample resolving the quantum Landau levels in a magnetic field, including the sublevels corresponding to the lifting of the electron spin and valley degeneracies.