2,239 research outputs found
The Mammals of the Animas Mountains and Adjacent Areas, Hidalgo County, New Mexico
Get PDFA study of the mammals of the Animas Mountains and adjacent areas of Hidalgo County, New Mexico, was conducted from February 1981 to March 1982. Some 745 specimens were collected along with data concerning the habitat affinities, natural history, and relative abundance of the mammalian fauna. Examination of an additional947 specimens and reporting of specimens in museums supplemented the fieldwork. The recent mammals of the Animas Mountains include 76 species in 21 families. Didelphis virginiana, Lasionycteris noctivagans, Lasiurus ega, Ammospermophilus harrisii, and Reithrodontomys fulvescens are reported for the first time from the study area. The most abundant mammal in the area is Peromyscus boylii; while Didelphis virginiana, Choeronycteris mexicana, Leptonycteris sanborni, Lasionycteris noctivagans, and Tadarida macrotis may be present only at irregular intervals. Within historic time, two species, Mus musculus and Sus scrofa, have been introduced and three species, Cynomys ludovicianus, Canis lupus, and Ursus arctos, have been extirpated. The subspecies Thomomys umbrinus emotus is the only mammal endemic to the Animas Mountains. Other montane relicts include Sorex arizonae, Sylvilagus floridanus, Eutamias dorsalis, and Neotoma mexicana. Sorex arizonae and Lepus callotis are the most restricted species, occuring in only one habitat type. Myotis leibii, Neotoma albigula, and Canis latrans are the most euryecious, being found in 9 of the 10 habitat types. Riparian habitats exhibit the greatest species richness and coniferous forest the least. A general trend of decreasing number of species with increasing elevation is evident among the various habitat types. A Jaccard\u27s index of similarity matrix indicates a decreasing faunal resemblance with increasing elevational separation of habitats
First-principles study of field emission from carbon nanotubes and graphene nanoribbons
Get PDFA real-space, real-time implementation of time-dependent density functional theory is used to study
electron field emission from nanostructures. Carbon nanotubes and graphene nanoribbons are used as
model systems. The calculations show that carbon nanotubes with iron adsorbates have spin-polarized
emission currents. Graphene nanoribbons are shown to be good field emitters with spatial variation of
the emission current influenced by the presence of passivating hydroge
Historic hybridization and persistence of a novel mito-nuclear combination in red-backed voles (genus Myodes)
Get PDF<p>Abstract</p> <p>Background</p> <p>The role of hybridization in generating diversity in animals is an active area of discovery and debate. We assess hybridization across a contact zone of northern (<it>Myodes rutilus</it>) and southern (<it>M. gapperi</it>) red-backed voles using variation in skeletal features and both mitochondrial and nuclear loci. This transect extends approximately 550 km along the North Pacific Coast of North America and encompasses 26 populations (n = 485). We establish the history, geographic extent and directionality of hybridization, determine whether hybridization is ongoing, and assess the evolutionary stability of novel genomic combinations.</p> <p>Results</p> <p>Identification of <it>M. rutilus </it>and <it>M. gapperi </it>based on the degree of closure of the post-palatal bridge was concordant with the distribution of diagnostic nuclear MYH6 alleles; however, an 80 km zone of introgressed populations was identified. The introgressant form is characterized by having mitochondrial haplotypes closely related to the northern <it>M. rutilus </it>on a nuclear background and morphological characteristics of southern <it>M. gapperi</it>.</p> <p>Conclusion</p> <p>Introgression appears to have been historic as pure populations of <it>M. rutilus </it>are now isolated to the north from introgressants or pure <it>M. gapperi </it>by the LeConte Glacier. As we do not find pure <it>M. rutilus </it>or <it>M. gapperi </it>individuals throughout the distribution of the introgressant form, it appears that the introgressants are a self-sustaining entity not requiring continued hybridization between pure parental forms to generate this novel combination of characters.</p
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