Explore the vast range of titles available.

A range-wide morphological analysis of the Mexican cottontail (Sylvilagus cunicularius) has never been conducted using modern-day multivariate analyses. We took 26 craniodental measurements from the skulls of 155 adults. A discriminant function analysis identified four distinct morphological types. The four morphological types consist of two primary groups. The reddish-colored group occurs on the Pacific coastal plain from Sinaloa to Colima. The individuals from Sinaloa to northwestern Jalisco share various skull features, and those from southwestern Jalisco and Colima have other skull features in common. The constricted coastal plain in northwestern Jalisco appears to separate these two morphological types. The other primary group has a grayish dorsal pelage and occurs in the highlands (the Transvolcanic Belt and Sierra Madre del Sur) and Pacific coastal lowlands of Guerrero and Oaxaca. Within this group, the individuals from the highlands differ from those on the Pacific coastal plain of Guerrero and Oaxaca. Both morphological types have been collected along the western slopes of the Sierra Madre del Sur, one from sea level to 305 m and the other from 822 to 2,225 m. The red and gray cottontails might be distinct species, but we take a conservative approach, awaiting additional lines of evidence. Four distinct subspecies are recognized: Sylvilagus cunicularius cunicularius, Sylvilagus cunicularius insolitus, Sylvilagus cunicularius pacificus (here recognized), and Sylvilagus cunicularius new subspecies.

Having suitable animal models is crucial to mimic human disease states and for the successful transfer of experimental data into clinical practice. In the field of papillomavirus research, the domestic rabbit (Oryctolagus cuniculus) has served as an indispensable model organism for almost 100 years. The identification and characterization of the first papillomaviruses in rabbits, their carcinogenic potential and their immunogenicity have contributed significantly to the state of knowledge on the genetics and life cycle of papillomaviruses in general, as well as the development of antiviral strategies such as vaccination procedures. Due to the high species specificity of papillomaviruses, only rabbit papillomaviruses (RPVs) can be used for animal studies on papilloma-based tumor diseases in the rabbit. The major focus of this article is on cottontail rabbit papillomavirus (CRPV)-related rabbit squamous cell carcinoma (RSCC). A brief history outlines the discovery and generation of experimentally used RSCC tumors. A comprehensive overview of the current CRPV-associated VX2 carcinoma-based tumor models with a major focus on human head and neck squamous cell carcinoma (HNSCC) tumor models is provided, and their strengths in terms of transferability to human HNSCC are discussed.

Introduced species competing with native species can decrease the density and abundance of native species, causing concern for the persistence of native species populations. The presence of the introduced eastern cottontail (Sylvilagus floridanus—EC) in habitat patches with the imperiled New England cottontail (Sylvilagus transitionalis—NEC) can lead to interspecific competition. However, the degree to which this interspecific competition leads to changes in NEC relative abundance is unknown. We used open 2 species N-mixture models with directional interactions to determine how EC relative abundance at a site influences NEC relative abundance and how covariates affected both species’ relative abundance. We found that EC relative abundance had a strong negative influence on NEC relative abundance, with an estimated effect of − 0.163, providing further evidence of interspecific competition between the 2 species. We found evidence of resource partitioning between the 2 species, where NEC relative abundance was positively influenced and EC relative abundance was negatively influenced by vegetation heights of 0.5 to < 2.5 m. Overall, our results demonstrate the consequences of EC presence in native lagomorph ranges and the utility of N-mixture models for assessing the magnitude of interspecific competition between introduced and imperiled species.

Trophic dynamics can be altered in complex ways as a result of urbanization. Understanding predator diets in these contexts may not only provide insight into these changes, but also in sources of mortality for vulnerable prey species like the New England cottontail ( Sylvilagus transitionalis ). However, studying the diets of mammalian predators such as bobcats ( Lynx rufus ) can be challenging because of their elusive behavior. DNA metabarcoding of stomach contents from roadkill is a method which provides a new opportunity to study predator diets when mortality events occur. We used this technique to examine variation in bobcat diet across a range of urbanized environments in Connecticut, USA, as well as determine whether bobcats consume the declining New England cottontail. DNA metabarcoding identified between two and five species in the majority of bobcat stomachs. Cottontail ( Sylvilagus spp. ) and eastern gray squirrel ( Sciurus carolinensis ) were each found in over 80% of samples, and most remaining taxa were other small mammals. Nearly a third of the bobcats had consumed white-tailed deer ( Odocoileus virginianus ). Stomach contents containing cottontail remains were sequenced at an additional species-specific marker, but no samples containing the New England cottontail were identified. Bobcats in Connecticut consumed a wide variety of natural prey species including a relatively high proportion of semi-aquatic mammals, and we found no evidence of domestic dog or cat consumption. DNA metabarcoding of stomach contents is an effective approach for opportunistically examining predator diet, and our use of this tool may provide a more complete picture of bobcat diet where other techniques have failed to do so.

Occupancy monitoring of the New England cottontail (Sylvilagus transitionalis) relies on collections of fecal pellets made following a snowfall, and subsequent genetic screening to distinguish New England cottontail pellets from those of the eastern cottontail (S. floridanus) and snowshoe hare (Lepus americanus). In years when snowy conditions are not common, less frequent sampling may result in data gaps at long-term monitoring sites, and jeopardize ongoing field research projects that rely on genetic data from fecal pellets. Such conditions occurred in the lower Hudson Valley, New York, USA, in the winter of 2015–2016, during which we collected pellets from the ground to evaluate performance of genetic testing relative to pellet quality. Pellets were categorized on overall appearance of degradation, assigned a pellet quality score, and then genetically analyzed to identify species using mitochondrial DNA. The pellets identified as being from New England cottontail were further evaluated targeting nuclear microsatellite DNA to obtain a multilocus genotype to identify individual rabbits. Species identification was possible for 89% of the highest quality pellets from the ground, and 68% in the most degraded pellets. A complete multilocus genotype was obtained in 79% of the least degraded pellets, but only 14% of the most degraded pellets. Certain genetic loci strongly influenced this success rate, with some performing better than others. Pellets collected from snow were still most reliable with 100% identified to species, and >97% of New England cottontail with a complete multilocus genotype. Thus, if researchers are genotyping rabbit pellets for applications such as abundance estimations, only the higher quality pellets from the ground or those collected from snow will likely be useful. For occupancy monitoring, a wider range of pellets may be acceptable for species identification, with the understanding that there is a tradeoff with pellet quality and successful DNA analysis. These results indicate that sampling from the ground and qualitative assessment of pellet quality using our categorization scheme is a viable method for New England cottontail monitoring in years with less snow.

Using 26 cranial measurements, we conducted a morphometric study on 113 adult skulls of the currently recognized rabbits Sylvilagus brasiliensis and S. sanctaemartae from Colombia, Ecuador, and Peru. Five morphological groups are identified of which 4 warrant species-level recognition. North and west of the Andes, S. gabbi occupies the lowlands of northern Colombia and northwestern Ecuador. Sylvilagus sanctaemartae is morphologically indistinguishable from S. gabbi and is a synonym of it. Two species live in the Andes of Colombia: S. fulvescens in the Western and Central Andes and S. apollinaris in the Eastern Andes. East of the Andes, Sylvilagus brasiliensis defilippi is found in the tropical Orinoco and Amazon basins of Colombia, Ecuador, and Peru, and S. brasiliensis andinus occurs in the Andes of Ecuador. These 2 subspecies intergrade in the Amotape-Huancabamba Zone of extreme southern Ecuador and adjacent west-central Peru. The eastern distributional limit of S. b. defilippi outside the study area in South America is unknown. An additional 50 skulls of S. gabbi and 14 of S. dicei were examined from Costa Rica and Panama to compare with the rabbits from South America. The data show that S. gabbi exhibits no noticeable geographic variation from Central America to northern Colombia and northwestern Ecuador. Sylvilagus dicei from the Cordillera de Talamanca of Costa Rica and Panama is morphologically most similar to S. fulvescens from the Western and Central Andes of Colombia and they are likely closely related. Methods are presented to identify all taxa and the distribution of each taxon is provided. This taxonomic arrangement is based on few specimens. Accordingly, species boundaries and phylogenetic relationships should be tested by focusing future collecting and morphological and molecular research in high-priority areas such as: 1) along the Colombian–Ecuadorian border from the Pacific Coast, across the Andes into the Amazon Basin; 2) Amotape-Huancabamba Zone of Ecuador and Peru; and 3) Eastern Andes of Colombia.

A range-wide morphological analysis of the Mexican cottontail (Sylvilagus cunicularius) has never been conducted using modern-day multivariate analyses. We took 26 craniodental measurements from the skulls of 155 adults. A discriminant function analysis identified four distinct morphological types. The four morphological types consist of two primary groups. The reddish-colored group occurs on the Pacific coastal plain from Sinaloa to Colima. The individuals from Sinaloa to northwestern Jalisco share various skull features, and those from southwestern Jalisco and Colima have other skull features in common. The constricted coastal plain in northwestern Jalisco appears to separate these two morphological types. The other primary group has a grayish dorsal pelage and occurs in the highlands (the Transvolcanic Belt and Sierra Madre del Sur) and Pacific coastal lowlands of Guerrero and Oaxaca. Within this group, the individuals from the highlands differ from those on the Pacific coastal plain of Guerrero and Oaxaca. Both morphological types have been collected along the western slopes of the Sierra Madre del Sur, one from sea level to 305 m and the other from 822 to 2,225 m. The red and gray cottontails might be distinct species, but we take a conservative approach, awaiting additional lines of evidence. Four distinct subspecies are recognized: Sylvilagus cunicularius cunicularius, Sylvilagus cunicularius insolitus, Sylvilagus cunicularius pacificus (here recognized), and Sylvilagus cunicularius new subspecies. Nunca se ha realizado un análisis morfológico de amplio rango en el conejo mexicano de monte, S. cunicularius, utilizando análisis multivariados modernos. Se tomaron veintiséis mediciones craneodentales de 155 adultos. Un Análisis de Función Discriminante (DFA) identificó cuatro tipos morfológicos distintos. De los cuatro tipos morfológicos, existen dos grupos principales. El grupo de color rojizo se encuentra en la llanura costera del Pacífico desde Sinaloa hasta Colima. Los de Sinaloa al noroeste de Jalisco comparten varias características del cráneo y los del suroeste de Jalisco y Colima tienen otras características del cráneo en común. La estrecha llanura costera del noroeste de Jalisco parece separar estos dos tipos morfológicos. El otro grupo principal tiene un pelaje dorsal grisáceo y se encuentra en las tierras altas (Cinturón Transvolcánico y Sierra Madre del Sur) y en llanura baja costera del Pacífico de Guerrero y Oaxaca. Dentro de este grupo, los de las tierras altas se diferencian de los de la llanura costera del Pacífico de Guerrero y Oaxaca. Ambos tipos morfológicos han sido recolectados a lo largo de las vertientes occidentales de la Sierra Madre del Sur, uno desde el nivel del mar hasta los 305 m y el otro desde los 822 m hasta los 2,225 m. Los conejos rojos y grises podrían ser especies separadas, pero aquí se adopta un enfoque conservador en espera de líneas de evidencia adicionales. Se reconocen cuatro subespecies distintas, S. cunicularius cunicularius, S. cunicularius insolitus, S. cunicularius pacificus (aquí reconocida), y S. cunicularius nueva subespecie.

Habitat quality regulates fitness and population density, making it a key driver of population size. Hence, increasing habitat quality is often a primary goal of species conservation. Yet, assessments of fitness and density are difficult and costly to obtain. Therefore, species conservation often uses “best available science,” extending inferences across taxa, space, or time, and inferring habitat quality from studies of habitat selection. However, there are scenarios where habitat selection is not reflective of habitat quality, and this can lead to maladaptive management strategies. The New England cottontail (Sylvilagus transitionalis) is an imperiled shrubland obligate lagomorph whose successful recovery hinges on creation of suitable habitat. Recovery of this species is also negatively impacted by the non‐native eastern cottontail (Sylvilagus floridanus), which can competitively exclude New England cottontails from preferred habitat. Herein, we evaluate habitat quality for adult and juvenile New England and eastern cottontails using survival and density as indicators. Our findings did not support selection following an ideal free distribution by New England cottontails. Instead, selected resources, which are a target of habitat management, were associated with low survival and density and pointed to a complex trade‐off between density, survival, habitat, and the presence of eastern cottontails. Further, movement distance was inversely correlated with survival in both species, suggesting that habitat fragmentation limits the ability of cottontails to freely distribute based on habitat quality. While habitat did not directly regulate survival of juvenile cottontails, tick burden had a strong negative impact on juvenile cottontails in poor body condition. Given the complex interactions among New England cottontails, eastern cottontails, and habitat, directly assessing and accounting for factors that limit New England cottontail habitat quality in management plans is vital to their recovery. Our study demonstrates an example of management for possible ecological trap conditions via the application of incomplete knowledge. Habitat selection studies are frequently used to infer habitat quality and establish management guidelines; however, habitat selection may become decoupled from fitness, resulting in incorrect inferences of habitat quality. We evaluate habitat quality using survival and density as indicators for New England cottontails and non‐native eastern cottontails. Our findings suggest New England cottontails selected resources that were associated with low survival and density, and pointed to a complex trade‐off between density, survival, habitat, and the presence of eastern cottontails.

Sylvilagus obscurus Chapman, Cramer, Dippenaar, and Robinson, 1992, commonly called the Appalachian cottontail, is distinguished from other syntopic leporids by its black spot between the ears, black fur along the anterior edge of the ears, and reddish-gray sides overlaid with a black wash. One of 22 species in the genus, S. obscurus is found across the Appalachian Mountains region, from Pennsylvania to northern Alabama. An inhabitant of habitats with dense woody understory cover such as early successional forests and mature forests with ericaceous shrubs, this rabbit is considered “Near Threatened,” with major threats that include habitat destruction, climate change, and competition with the eastern cottontail, Sylvilagus floridanus.

Many ecosystems face multiple invaders, and interactions among invasive and native species may complicate conservation efforts for imperiled species. Examination of fine‐scale resource selection can be used to detect patterns in habitat selection resulting from species interactions and assess the value of specific resources, including invasive plants, to wildlife. We used animal location data with mixed‐effects resource selection models to examine seasonal competitive interactions and species‐specific selection for forage and cover resources by an imperiled native lagomorph, the New England cottontail Sylvilagus transitionalis and its nonnative competitor, the eastern cottontail S. floridanus in the eastern Hudson Valley, NY. We found evidence that resource selection by New England cottontails depended on the relative prevalence of eastern cottontails to New England cottontails. Where eastern cottontails were less prevalent New England cottontail selected for resources characteristic of early successional shrublands. Where eastern cottontails were more prevalent, New England cottontails selected for resources characteristic of later successional shrublands. New England cottontail use of certain invasive shrubs depended on the prevalence of eastern cottontails relative to New England cottontails, suggesting response to invasive plants is confounded by interactions with a nonnative competitor. Our results further emphasize the need for conservation efforts to consider invasive management within the ecosystem context. We demonstrate the utility of resource selection studies to assist in this regard by exploring competitive interactions in the absence of removal studies, while simultaneously assessing the impact of habitat components such as invasive vegetation on species of conservation concern. Synthesis and applications Resource selection studies can be directly applied to inform ongoing species conservation where multiple invaders are present or where species interactions influence resource selection. Fine‐scale assessments of resource selection, similar to those presented here, can be used to selectively manage habitat to benefit desired species within the ecosystem context. We present strong evidence that the prevalence of a nonnative competitor alters resource selection and promotes use of an invasive shrub by an imperiled native cottontail. We identify seasonal shifts in selection that could facilitate displacement of residents and identify resources to selectively manage to benefit desired over undesired species.