Mechanistic Evidence of a Ni(0/II/III) Cycle for Nickel Photoredox Amide Arylation.

This work demonstrates the dominance of a Ni(0/II/III) cycle for Ni-photoredox amide arylation, which contrasts with other Ni-photoredox C-heteroatom couplings that operate via Ni(I/III) self-sustained cycles. The kinetic data gathered when using different Ni precatalysts supports an initial Ni(0)-mediated oxidative addition into the aryl bromide. Using NiCl2 as the precatalyst resulted in an observable induction period, which was found to arise from a photochemical activation event to generate Ni(0) and to be prolonged by unproductive comproportionation between the Ni(II) precatalyst and the in situ generated Ni(0) active species. Ligand exchange after oxidative addition yields a Ni(II) aryl amido complex, which was identified as the catalyst resting state for the reaction. Stoichiometric experiments showed that oxidation of this Ni(II) aryl amido intermediate was required to yield functionalized amide products. The kinetic data presented supports a rate-limiting photochemically-mediated Ni(II/III) oxidation to enable C-N reductive elimination. An alternative Ni(I/III) self-sustained manifold was discarded based on EPR and kinetic measurements. The mechanistic insights uncovered herein will inform the community on how subtle changes in Ni-photoredox reaction conditions may impact the reaction pathway, and have enabled us to include aryl chlorides as coupling partners and to reduce the Ni loading by 20-fold without any reactivity loss.

Prospecting for Zoonotic Pathogens by Using Targeted DNA Enrichment.

More than 60 zoonoses are linked to small mammals, including some of the most devastating pathogens in human history. Millions of museum-archived tissues are available to understand natural history of those pathogens. Our goal was to maximize the value of museum collections for pathogen-based research by using targeted sequence capture. We generated a probe panel that includes 39,916 80-bp RNA probes targeting 32 pathogen groups, including bacteria, helminths, fungi, and protozoans. Laboratory-generated, mock-control samples showed that we are capable of enriching targeted loci from pathogen DNA 2,882‒6,746-fold. We identified bacterial species in museum-archived samples, including Bartonella, a known human zoonosis. These results showed that probe-based enrichment of pathogens is a highly customizable and efficient method for identifying pathogens from museum-archived tissues.

Solution and Solid-State Behavior of Amphiphilic ABA Triblock Copolymers of Poly(acrylic acid-stat-styrene)-block-poly(butyl acrylate)-block-poly(acrylic acid-stat-styrene).

A combination of statistical and triblock copolymer properties is explored to produce stable aqueous polymer dispersions suitable for the film formation. In order to perform an extensive structural characterization of the products in the dissolved, dispersed, and solid states, a wide range of symmetrical poly(acrylic acid-stat-styrene) x -block-poly(butyl acrylate) y -block-poly(acrylic acid-stat-styrene) x , poly(AA-st-St) x -b-PBA y -b-poly(AA-st-St) x , (x = 56, 108 and 140, y = 100-750; the AA:St molar ratio is 42:58) triblock copolymers were synthesized by reversible addition-fragmentation chain transfer (RAFT) solution polymerization using a bifunctional symmetrical RAFT agent. It is demonstrated that the amphiphilic statistical outer blocks can provide sufficient stabilization to largely hydrophobic particles in aqueous dispersions. Such a molecular design provides an advantage over copolymers composed only of homoblocks, as a simple variation of the statistical block component ratio provides an efficient way to control the hydrophilicity of the stabilizer block, which ultimately affects the copolymer morphology in solutions and solid films. It was found by small-angle X-ray scattering (SAXS) that the copolymers behaved as dissolved chains in methylethylketone (MEK) but self-assembled in water into stable and well-defined spherical particles that increased in size with the length of the hydrophobic PBA block. These particles possessed an additional particulate surface structure formed by the statistical copolymer stabilizer block, which self-folded through the hydrophobic interactions between the styrene units. SAXS and atomic force microscopy showed that the copolymer films cast from the MEK solutions formed structures predicted by self-consistent field theory for symmetrical triblock copolymers, while the aqueous dispersions formed structural morphologies similar to a close-packed spheres, as would be expected for copolymer particles trapped kinetically due to the restricted movement of the blocks in the initial aqueous dispersion. A strong correlation between the structural morphology and mechanical properties of the films was observed. It was found that the properties of the solvent cast films were highly dependent on the ratios of the hard [poly(AA-st-St)] and soft (PBA) blocks, while the aqueous cast films did not show such a dependence. The continuous phase of hard blocks, always formed in the case of the aqueous cast films, produced films with a higher elastic modulus and a lower extension-to-break in a comparison with the solvent-cast films.

Reevaluation of the phylogenetic relationships among Neotomini rodents (Hodomys, Neotoma, and Xenomys) and comments on the woodrat classification.

The woodrats or packrats of the genus Neotoma have been the subject of a wide array of research including paleoecology, physiology, morphological evolution, systematics, speciation, and hybridization. In recent years, much work has been done to elucidate evolutionary relationships within and between closely related species of the genus; in particular the addition of newly collected specimens from critical geographic regions has provided new opportunities for taxonomic assessment. Given these new data and their potential, parsimony (PARS), maximum likelihood (ML), and Bayesian inference (BI) analyses were conducted on DNA sequences obtained from nine individual genes (four mitochondrial loci: 12S, 16S, CoII, and Cytb; five nuclear loci: AdhI2, BfibI7, En2, Mlr, and Myh6) to estimate the phylogenetic relationships among 23 species of Neotoma. Results of these analyses depicted a wide array of phylogenetic relationships among taxa; with substantial nodal support recovered in both the ML and PARS analyses at some mid-level and terminal positions. Several individual genes, particularly 12S, AdhI2, BfibI7, CoII, and Cytb, provided support at several basal positions; however, phylogenetic resolution was limited in the other genes. A final BI analysis where the nine genes were concatenated into a single data set produced several supported clades that corresponded to previously recognized species groups (floridana, micropus, mexicana, and lepida) and the subgenus Homodontomys. Levels of genetic divergence for within-species comparisons (estimated from the Cytb data set) ranged from 0.88% (N. magister) to 6.82% (N. fuscipes); for between sister species comparisons ranged from 4.68% (N. devia and N. lepida) to 12.70% (N. angustapalata and N. nelsoni); and for members within closely related clades ranged from 8.70% (N. bryanti and N. lepida) to 12.57% (N. goldmani and N. magister). Evaluations of generic, subgeneric, and species group boundaries were explored using phylogenetic principles on the DNA sequence data presented herein, as well as morphological findings from previous studies. Results obtained suggest that the most conservative taxonomic interpretation involves the abandonment of subgeneric delineations and relies on the recognition of eight species groups (cinerea, floridana, fuscipes, lepida, mexicana, micropus, phenax, and stephensi) as the backbone of the woodrat classification.

Las ratas cambalacheras del género Neotoma han sido estudiadas en varios tipos de investigaciones incluyendo paleoecología, fisiología, evolución morfológica, sistemática, especiación e hibridación. Recientemente, se han realizado numerosos estudios para elucidar las relaciones evolutivas dentro del género y entre especies cercanamente relacionadas al mismo; en particular la inclusión de nuevos especímenes provenientes de regiones geográficas críticas han brindado nuevas oportunidades para evaluaciones taxonómicas. A partir de estos nuevos datos se realizaron análisis de parsimonia (PARS), Máxima Verosimilitud (MV), e Inferencia Bayesiana (IB) en secuencias de ADN provenientes de nueve genes individuales (cuatro loci mitocondriales: 12S, 16S, CoII, y Cytb; cinco loci nucleares: Adh-I2, Bfib-I7, En2, Mlr, and Myh6) para determinar la relación filogenética de 23 especies de Neotoma. Los resultados de estos análisis presentan una amplia gama de relaciones filogenéticas entre taxa con un soporte nodal importante en los análisis de MV y PARS en algunas posiciones terminales de nivel medio. Varios genes individuales, en particular 12S, Adh-I2, Bfib-I7, CoII, and Cytb, ofrecieron soporte en varias posiciones basales; sin embargo, la resolución filogenética fue reducida en los demás genes. El último análisis de IB, en donde nueve genes se concatenaron en un solo conjunto de datos, produjo soporte en varios clados que correspondieron a especies de grupos previamente reconocidos (floridana, micropus, mexicana, y lepida) y el sub-género Homodontomys. Los niveles de divergencia genética para comparaciones intraespecíficas fluctuaron entre 0.88% (N. magister) y 6.82% (N. fuscipes); para especies hermanas (4.68%­N. devia y N. lepida hasta 12.70%­N. angustapalata y N. nelsoni); y para los miembros de clados cercanos (8.70%­N. bryanti y N. lepida hasta 12.57%­N. goldmani y N. magister). Las evaluaciones de los limites genéricos, subgenéricos y de grupos de especies fueron explorados usando principios filogenéticos en las secuencias de ADN de este trabajo, y también se basaron en las conclusiones morfológicas de estudios previos. Los resultados obtenidos sugieren que la interpretación taxonómica más conservadora incluye el abandono de las delineaciones subgenéricas y se depende en el reconocimiento de ocho grupos de especies (cinerea, floridana, fuscipes, lepida, mexicana, micropus, phenax, y stephensi) como el pilar central de la clasificación de las ratas cambalacheras.

Comparison of genetic variation between rare and common congeners of Dipodomys with estimates of contemporary and historical effective population size.

Species with low effective population sizes are at greater risk of extinction because of reduced genetic diversity. Such species are more vulnerable to chance events that decrease population sizes (e.g. demographic stochasticity). Dipodomys elator, (Texas kangaroo rat) is a kangaroo rat that is classified as threatened in Texas and field surveys from the past 50 years indicate that the distribution of this species has decreased. This suggests geographic range reductions that could have caused population fluctuations, potentially impacting effective population size. Conversely, the more common and widespread D. ordii (Ord's kangaroo rat) is thought to exhibit relative geographic and demographic stability. We assessed the genetic variation of D. elator and D. ordii samples using 3RAD, a modified restriction site associated sequencing approach. We hypothesized that D. elator would show lower levels of nucleotide diversity, observed heterozygosity, and effective population size when compared to D. ordii. We were also interested in identifying population structure within contemporary samples of D. elator and detecting genetic variation between temporal samples to understand demographic dynamics. We analyzed up to 61,000 single nucleotide polymorphisms. We found that genetic variability and effective population size in contemporary D. elator populations is lower than that of D. ordii. There is slight, if any, population structure within contemporary D. elator samples, and we found low genetic differentiation between spatial or temporal historical samples. This indicates little change in nuclear genetic diversity over 30 years. Results suggest that genetic diversity of D. elator has remained stable despite reduced population size and/or abundance, which may indicate a metapopulation-like system, whose fluctuations might counteract species extinction.

Mild Amide N-Arylation Enabled by Nickel-Photoredox Catalysis.

This paper describes a mild strategy to promote amide arylations. Photoinduced oxidation of a Ni(II) aryl amido intermediate is proposed to facilitate the challenging C-N reductive elimination step at moderate temperatures. Notably, the mildly basic conditions employed facilitate access to a broad scope including protected amino acids, heterocycles, phenols, and sterically hindered substituents. Hence, this work presents an attractive strategy to enable late-stage functionalization of pre-existing amide moieties in commercial drugs and natural products.

Rapid divergence of a gamete recognition gene promoted macroevolution of Eutheria.

BACKGROUND: Speciation genes contribute disproportionately to species divergence, but few examples exist, especially in vertebrates. Here we test whether Zan, which encodes the sperm acrosomal protein zonadhesin that mediates species-specific adhesion to the egg's zona pellucida, is a speciation gene in placental mammals. RESULTS: Genomic ontogeny reveals that Zan arose by repurposing of a stem vertebrate gene that was lost in multiple lineages but retained in Eutheria on acquiring a function in egg recognition. A 112-species Zan sequence phylogeny, representing 17 of 19 placental Orders, resolves all species into monophyletic groups corresponding to recognized Orders and Suborders, with <5% unsupported nodes. Three other rapidly evolving germ cell genes (Adam2, Zp2, and Prm1), a paralogous somatic cell gene (TectA), and a mitochondrial gene commonly used for phylogenetic analyses (Cytb) all yield trees with poorer resolution than the Zan tree and inferior topologies relative to a widely accepted mammalian supertree. Zan divergence by intense positive selection produces dramatic species differences in the protein's properties, with ordinal divergence rates generally reflecting species richness of placental Orders consistent with expectations for a speciation gene that acts across a wide range of taxa. Furthermore, Zan's combined phylogenetic utility and divergence exceeds those of all other genes known to have evolved in Eutheria by positive selection, including the only other mammalian speciation gene, Prdm9. CONCLUSIONS: Species-specific egg recognition conferred by Zan's functional divergence served as a mode of prezygotic reproductive isolation that promoted the extraordinary adaptive radiation and success of Eutheria.

Distinct mtDNA lineages in free-ranging Ammotragus(aoudad) from the United States indicate multiple introductions from northern Africa.

Translocation records indicate aoudad (Ammotragus lervia) populations in the United States are a product of multiple human-mediated introductions. Two mitochondrial markers (cytochrome b, cytb; displacement loop, D loop) and one nuclear gene (prion protein gene exon 3, PRNP) were used to determine: (1) genetic variation, (2) if genetic units correspond to taxonomic designations, (3) the number and geographic origin of translocations, and (4) divergence times. Three phylogenetic analyses (Bayesian inference, maximum likelihood, and parsimony) produced similar topologies with two clades (I and II). Clade I contained progeny of individuals resulting from introductions to Texas and Spain, and individuals from Algeria. Individuals in Clade II were progeny of past introductions to the United States and Europe, and northern Algeria. Clade II was subdivided into two subclades (A and B) representing two haplogroups. No genetic variation was detected in the PRNP sequences. Three haplogroups appeared to correspond to the subspecies A. l. lervia and A. l. sahariensis whose native distribution includes northwestern Africa. Network analyses assigned haplogroups to two major groups similar to those depicted in the phylogenetic analyses. Genetic distances ranged from 0.80% to 5.17% and 2.99% to 15.42% for cytb and D loop, respectively; and were higher than normally recovered for caprids, warranting a reexamination of subspecific status. Divergence dates indicated a major split between A. l. lervia and A. l. sahariensis circa 2.38 mya. Together, the high level of genetic divergences among US populations and apparent presence of two subspecies of aoudad in the United States support the hypothesis of multiple introductions from multiple sources.

Two new species of Peromyscus (Cricetidae: Neotominae) from the Transverse Volcanic Belt of Mexico.

Specimens of the Peromyscus boylii species group distributed in the western and northeastern montane regions of Michoacán, México, historically have been assigned to P. levipes. Previous studies indicated that these specimens possessed mitochondrial DNA haplotypes that were distinct from both P. levipes and P. kilpatricki, a recently named species in the P. boylii species group from northeastern Michoacán and western Morelos. Herein karyotypic, DNA sequence, and morphological data were analyzed from those populations to evaluate their taxonomic affinity. Karyotypic data indicated that individuals from western Michoacán (Dos Aguas and Aguililla) and from a newly discovered population in northeastern Michoacán (Zinapécuaro) were chromosomally similar to P. carletoni (FN = 68) but distinct from other taxa assigned to the P. boylii species group. Analyses of cranial characteristics indicated that, relative to other species in the P. boylii species group, two morphologically distinct groups were present that corresponded to the Dos Aguas/Aguililla and Zinapécuaro populations, respectively. The latter population, although represented by a small sample size (n = 5 specimens), appeared to exhibit some trenchant morphological distinctions compared with other cryptic species in the P. boylii group. Phylogenetic analyses (parsimony, Bayesian, and likelihood) of DNA sequences obtained from the mitochondrial cytochrome-b gene indicated that although the individuals from Dos Aguas/Aguililla and Zinapécuaro formed a sister group relationship, they formed monophyletic clades that differed genetically (2.54%)-a level approaching that seen between other sister species of Peromyscus. Further, the Dos Aguas/Aguililla and Zinapécuaro clade was more closely aligned with a clade containing representatives of P. carletoni and P. levipes instead of with those from closer geographic proximities (P. kilpatricki) located in eastern Michoacán. Together, these results indicated that these two populations seemingly represent two undescribed species in the P. boylii species group for which we propose the names Peromyscus greenbaumi for populations in western Michoacán (circa Dos Aguas and Aguililla) and Peromyscus ensinki for populations in northeastern Michoacán (circa Zinapécuaro).

Los especímenes del grupo de especies de Peromyscus boylii distribuidos en las regiones montañosas occidentales y el noreste de Michoacán, México, históricamente fueron asignados a P. levipes. Sin embargo, estudios previos han indicado que estos especímenes poseen haplotipos de ADN mitocondrial que son distintos de P. levipes y P. kilpatricki, una especie recientemente nombrada en el grupo de especies P. boylii del noreste de Michoacán y el oeste de Morelos. Los datos cariotípicos indicaron que los individuos del oeste de Michoacán (Dos Aguas y Aguililla) y de una población recién descubierta en el noreste de Michoacán (Zinapécuaro) eran cromosómicamente similares a P. carletoni (FN = 68), pero distintos de otros taxones asignados al grupo de especies P. boylii. Los análisis de las características craneales indicaron que en relación con otras especies del grupo de especies P. boylii, dos grupos morfológicamente distintos estaban presentes, y que correspondían a las poblaciones de Dos Aguas/Aguililla y Zinapécuaro, respectivamente. Aunque representada por un tamaño de muestra pequeño (n = 5 especímenes), esta última población pareció exhibir algunas diferencias morfológicas en comparación con las otras especies crípticas en el grupo P. boylii. Los análisis filogenéticos (parsimonia, inferencia bayesiana y verosimilitud) de secuencias de ADN obtenidas del gen mitocondrial citocromo-b, indicaron que, aunque los individuos de Dos Aguas/Aguililla y Zinapécuaro tienen una relación de grupo hermano, estos forman clados monofiléticos que difieren genéticamente (2.54%), nivel que se acerca al observado entre otras especies hermanas de Peromyscus. Además, el clado de Dos Aguas/Aguililla y Zinapécuaro está más estrechamente alineado con un clado que contenía representantes de P. carletoni y P. levipes en lugar de aquellos de proximidades geográficas más cercanas (P. kilpatricki) ubicados en el este de Michoacán. Estos resultados indicaron que estas dos poblaciones aparentemente representan dos especies no descritas en el grupo de especies P. boylii para las cuales proponemos los nombres Peromyscus greenbaumi para poblaciones en el oeste de Michoacán (hacia Dos Aguas y Aguililla) y Peromyscus ensinki para poblaciones en el noreste de Michoacán (circa Zinapécuaro).

Characterization of the prion protein gene in axis deer (Axis axis) and implications for susceptibility to chronic wasting disease.

Axis deer (Axis axis) occur both in captivity and free-ranging populations in portions of North America, but to-date, no data exist pertaining to the species' susceptibility to CWD. We sequenced the prion protein gene (PRNP) from axis deer. We then compared axis deer PrPC sequences and amino acid polymorphisms to those of CWD susceptible species. A single PRNP allele with no evidence of intraspecies variation was identified in axis deer that indicates axis deer PRNP is most similar to North American elk (Cervus canadensis) PRNP. Therefore, axis deer may be susceptible to CWD. We recommend proactively increasing CWD surveillance for axis deer, particularly where CWD has been detected and axis deer are sympatric with native North American CWD susceptible species.

Differential Expression in Testis and Liver Transcriptomes from Four Species of Peromyscus (Rodentia: Cricetidae).

The genus Peromyscus represents a rapidly diverged clade of Cricetid rodents that contains multiple cryptic species and has a propensity for morphologic conservation across its members. The unresolved relationships in previously proposed phylogenies reflect a suspected rapid adaptive radiation. To identify functional groups of genes that may be important in reproductive isolation in a reoccurring fashion across the Peromyscus phylogeny, liver and testis transcriptomes from four species (P. attwateri, P. boylii, P. leucopus, and P. maniculatus) were generated and differential expression (DE) tests were conducted. Taxa were selected to represent members diverged from a common ancestor: P. attwateri + P. boylii (clade A), and P. leucopus + P. maniculatus (clade B). Comparison of clades (A vs. B) suggested that 252 transcripts had significant DE in the liver data set, whereas significant DE was identified for 657 transcripts in the testis data set. Further, 45 genes had DE isoforms in the 657 testis transcripts and most of these functioned in major reproductive roles such as acrosome assembly, spermatogenesis, and cell cycle processes (meiosis). DE transcripts in the liver mapped to more broad gene ontology terms (metabolic processes, catabolic processes, response to chemical, and regulatory processes), and DE transcripts in the testis mapped to gene ontology terms associated with reproductive processes, such as meiosis, sperm motility, acrosome assembly, and sperm-egg fusion. These results suggest that a suite of genes that conduct similar functions in the testes may be responsible for the adaptive radiation events and potential reoccurring speciation of Peromyscus in terms of reproduction through varying expression levels.

Morphometric and genetic variation in 8 breeds of Ethiopian camels (Camelus dromedarius).

Dromedary camels (Camelus dromedarius) are a domesticated and closely guarded economic staple of indigenous people located throughout Ethiopian territorial states. Seventeen morphometric variables were examined to determine intraspecific variation among 8 pastoralist-designated breeds of camels. Additionally, DNA sequences from mitochondrial cytochrome-b gene and genotyping of 6 nuclear microsatellite loci were examined to assess genetic diversity and phylogenetic relationship of Ethiopian camels. Examination of 525 individuals revealed significant morphometric differentiation in Afar as compared with the remaining 7 breeds. Analysis of cytochrome-b sequences failed to recover monophyletic groups associated with pastoralist-recognized breeds. Analysis of 6 microsatellite loci from 104 individuals depicted no resolution of distinct genetic lineages in accordance to geographical or designated breeds. Overall, separation of 2 ecotypes based on the morphometric data was supported; however, genetic analysis of cytochrome-b and microsatellite data failed to support any unique genetic lineage or statistically significant population structure.

Muleshoe Virus and Other Hantaviruses Associated with Neotomine or Sigmodontine Rodents in Texas.

The broad objective of this study was to increase our knowledge of Muleshoe virus and other hantaviruses associated with cricetid rodents in Texas. Anti-hantavirus antibody was found in 38 (3.2%) of 1171 neotomine rodents and 6 (1.8%) of 332 sigmodontine rodents from 10 Texas counties; hantaviral RNA was detected in 23 (71.9%) of 32 antibody-positive rodents. Analyses of nucleocapsid protein gene sequences indicated Muleshoe virus infection in four hispid cotton rats (Sigmodon hispidus) from northern Texas; Bayou virus, three Texas marsh oryzomys (Oryzomys texensis) from the Gulf Coast; Limestone Canyon virus, five brush mice (Peromyscus boylii) from western Texas; and Sin Nombre virus-five Texas mice (P. attwateri), one Lacey's white-ankled deer mouse (P. laceianus), four white-footed mice (P. leucopus), and one fulvous harvest mouse (Reithrodontomys fulvescens) from northern, central, or southern Texas. The results of this study together with the results of a previous study revealed that Muleshoe virus, perhaps in association with S. hispidus, is distributed across northern Texas. Finally, the results of Bayesian analyses of glycoprotein precursor (GPC) gene sequences and pairwise comparisons of complete GPC (amino acid) sequences strengthened support for the notion that Muleshoe virus is distinct from Black Creek Canal virus, Bayou virus, and all other species included in the Bunyaviridae, genus Hantavirus.

A new species of big-eared climbing rat, genus Ototylomys (Cricetidae: Tylomyinae), from Chiapas, Mexico.

An allopatric population of big-eared climbing rats (Ototylomys) from the Northern Highlands of Chiapas, Mexico, is described as a new species. The new taxon is part of a unique montane rainforest community that includes several other endemic species in the limited geographic range between the Río Grijalva and the Central Depression of Chiapas. Several cranial, external, and molecular characters distinguish this new species of big-eared climbing rat from its more widely distributed congener, Ototylomys phyllotis. We performed principal component and discriminate function analyses of cranial measurements, and found that specimens of the new species consistently could be distinguished from other Ototylomys with strong statistical support. Compared with exemplars of Ototylomys from elsewhere in their range, the new species possesses a karyotype that differs by 3 additional biarmed chromosome pairs, is fixed or nearly fixed for distinct electromorphs at 12 allozyme loci, and the mean genetic distance exceeds 14%, based on comparisons of the mitochondrial cytochrome b gene between the new species of Ototylomys and representatives of O. phyllotis. The restricted distribution in montane karst rainforest suggests that the species and its habitat may be a matter of conservation concern.

Una población alopátrica de rata orejuda trepadora (Ototylomys) de las Tierras Altas del Norte de Chiapas, México se describe como una nueva especie. El nuevo taxón es parte de una comunidad única de bosque lluvioso montano que incluye varias especies endémicas en el área de distribución geográfica limitada entre el Río Grijalva y la Depresión Central de Chiapas. Varios caracteres craneales, externos, y moleculares distinguen la nueva rata orejuda trepadora de su congénere más ampliamente distribuido, Ototylomys phyllotis. Se realizaron análisis de componentes principales y de función discriminante de los caracteres craneales, y se encontró que los especímenes de La Pera fueron consistentemente distinguidos de otros Ototylomys con un fuerte soporte estadístico. En comparación con ejemplares de Ototylomys del rango, la nueva especie posee un cariotipo que difiere por 3 pares adicionales de cromosomas biarmados, está fijo o casi fijo por distintos electromorfos en 12 loci alozímicos. Adicionalmente, la media de la distancia genética comparada del gen mitochondrial citocromo b entre la nueva especie de Ototylomys y representantes de O. phyllotis, excede el 14%. La distribución restringida en el bosque lluvioso montano kárstico sugiere que la especie y su hábitat pueden ser de importancia para la conservación.

Epizootiology of Tacaribe serocomplex viruses (Arenaviridae) associated with neotomine rodents (Cricetidae, Neotominae) in southern California.

The objective of this study was to advance our knowledge of the epizootiology of Bear Canyon virus and other Tacaribe serocomplex viruses (Arenaviridae) associated with wild rodents in California. Antibody (immunoglobulin G [IgG]) to a Tacaribe serocomplex virus was found in 145 (3.6%) of 3977 neotomine rodents (Cricetidae: Neotominae) captured in six counties in southern California. The majority (122 or 84.1%) of the 145 antibody-positive rodents were big-eared woodrats (Neotoma macrotis) or California mice (Peromyscus californicus). The 23 other antibody-positive rodents included a white-throated woodrat (N. albigula), desert woodrat (N. lepida), Bryant's woodrats (N. bryanti), brush mice (P. boylii), cactus mice (P. eremicus), and deer mice (P. maniculatus). Analyses of viral nucleocapsid protein gene sequence data indicated that Bear Canyon virus is associated with N. macrotis and/or P. californicus in Santa Barbara County, Los Angeles County, Orange County, and western Riverside County. Together, analyses of field data and antibody prevalence data indicated that N. macrotis is the principal host of Bear Canyon virus. Last, the analyses of viral nucleocapsid protein gene sequence data suggested that the Tacaribe serocomplex virus associated with N. albigula and N. lepida in eastern Riverside County represents a novel species (tentatively named "Palo Verde virus") in the genus Arenavirus.

Molecular and morphologic data reveal multiple species in Peromyscus pectoralis.

DNA sequence and morphometric data were used to re-evaluate the taxonomy and systematics of Peromyscus pectoralis. Phylogenetic analyses (maximum likelihood and Bayesian inference) of DNA sequences from the mitochondrial cytochrome-b gene in 44 samples of P. pectoralis indicated 2 well-supported monophyletic clades. The 1st clade contained specimens from Texas historically assigned to P. p. laceianus; the 2nd was comprised of specimens previously referable to P. p. collinus, P. p. laceianus, and P. p. pectoralis obtained from northern and eastern Mexico. Levels of genetic variation (~7%) between these 2 clades indicated that the genetic divergence typically exceeded that reported for other species of Peromyscus. Samples of P. p. laceianus north and south of the Río Grande were not monophyletic. In addition, samples representing P. p. collinus and P. p. pectoralis formed 2 clades that differed genetically by 7.14%. Multivariate analyses of external and cranial measurements from 63 populations of P. pectoralis revealed 4 morpho-groups consistent with clades in the DNA sequence analysis: 1 from Texas and New Mexico assignable to P. p. laceianus; a 2nd from western and southern Mexico assignable to P. p. pectoralis; a 3rd from northern and central Mexico previously assigned to P. p. pectoralis but herein shown to represent an undescribed taxon; and a 4th from southeastern Mexico assignable to P. p. collinus. Based on the concordance of these results, populations from the United States are referred to as P. laceianus, whereas populations from Mexico are referred to as P. pectoralis (including some samples historically assigned to P. p. collinus, P. p. laceianus, and P. p. pectoralis). A new subspecies is described to represent populations south of the Río Grande in northern and central Mexico. Additional research is needed to discern if P. p. collinus warrants species recognition.

What Is Peromyscus? Evidence from nuclear and mitochondrial DNA sequences suggests the need for a new classification.

The evolutionary relationships between Peromyscus, Habromys, Isthmomys, Megadontomys, Neotomodon, Osgoodomys, and Podomys are poorly understood. In order to further explore the evolutionary boundaries of Peromyscus and compare potential taxonomic solutions for this diverse group and its relatives, we conducted phylogenetic analyses of DNA sequence data from alcohol dehydrogenase (Adh1-I2), beta fibrinogen (Fgb-I7), interphotoreceptor retinoid-binding protein (Rbp3), and cytochrome-b (Cytb). Phylogenetic analyses of mitochondrial and nuclear genes produced similar topologies although levels of nodal support varied. The best-supported topology was obtained by combining nuclear and mitochondrial sequences. No monophyletic Peromyscus clade was supported. Instead, support was found for a clade containing Habromys, Megadontomys, Neotomodon, Osgoodomys, Podomys, and Peromyscus suggesting paraphyly of Peromyscus and confirming previous observations. Our analyses indicated an early divergence of Isthmomys from Peromyscus (approximately 8 million years ago), whereas most other peromyscine taxa emerged within the last 6 million years. To recover a monophyletic taxonomy from Peromyscus and affiliated lineages, we detail 3 taxonomic options in which Habromys, Megadontomys, Neotomodon, Osgoodomys, and Podomys are retained as genera, subsumed as subgenera, or subsumed as species groups within Peromyscus. Each option presents distinct taxonomic challenges, and the appropriate taxonomy must reflect the substantial levels of morphological divergence that characterize this group while maintaining the monophyletic relationships obtained from genetic data.

Multilocus Characterization of a Woodrat (Genus Neotoma) Hybrid Zone.

In order to investigate hybridization between 2 species of woodrats, Neotoma floridana and Neotoma micropus, 103 specimens were collected, in March of 1988, from a known area of sympatry, and compared with reference collections from areas of allopatry. Ten genetic markers, consisting of 7 microsatellite loci, 1 mitochondrial gene (cytochrome-b [Cytb]), and 2 nuclear introns (intron 2 of the vertebrate alcohol dehydrogenase gene [Adh1-I2] and intron 7 of the beta-fibrinogen gene [Fgb-I7]) were used to develop a composite genotype for each individual and for detection of hybridization. Six individuals were identified as pure parental N. micropus, 96 as hybrids, and 1 as pure parental N. floridana Hybrids were formed primarily through matings between complex genotypes, resulting in a high prevalence of individuals classified as backcrosses. The ratio of hybrid classes, population substructure, and presence of significant linkage disequilibrium within the zone of contact could not reject either the hybrid superiority or hybrid equilibrium model as responsible for maintenance of this hybrid zone. The collection date of this dataset (1988) provided not only a point in time assessment of the hybrid zone but also provided opportunities for future comparisons of temporal datasets with the purpose of examining hybrid zone characteristics over multiple generations.

Multilocus analyses indicate a mosaic distribution of hybrid populations in ground squirrels (genus Ictidomys).

DNA sequence data from mitochondrial cytochrome-b (Cytb) and Y-linked structural maintenance of chromosomes (SmcY) genes were combined with 478 nuclear loci obtained from amplified fragment length polymorphisms (AFLP) to assess the extent of hybridization and genetic spatial structure of populations in two hybridizing species of ground squirrel (Ictidomys parvidens and Ictidomys tridecemlineatus). Based on AFLP analyses of 134 individuals from 28 populations, 10 populations were identified that possessed hybrid individuals. Overall estimates of F ST values revealed strong support for population structure in the Cytb data set; however, analyses of the SmcY gene and the AFLP data indicated ongoing gene flow between species. Pairwise F ST comparisons of populations were not significant for the SmcY gene; although they were significant for the Cytb gene, indicating that these populations were structured and that gene flow was minimal. Therefore, gene flow between I. parvidens and I. tridecemlineatus appeared to be restricted to populations that exhibited hybridization. In addition, the fragmented nature of the geographic landscape suggested limited gene flow between populations. As a result, the distributional pattern of interspersed parental and hybrid populations were compatible with a mosaic hybrid zone model. Because ground squirrels display female philopatry and male-biased dispersal, the ecology of these species is compatible with this hypothesis.

Diversity among Tacaribe serocomplex viruses (Family Arenaviridae) associated with the southern plains woodrat (Neotoma micropus).

The southern plains woodrat (Neotoma micropus) is the principal host of Catarina virus in southern Texas and a natural host of other North American Tacaribe serocomplex viruses. The objectives of this study were to increase our knowledge of the genetic diversity among Tacaribe serocomplex viruses associated with N. micropus and to define better the natural host relationships of these viruses. Pairwise comparisons of complete glycoprotein precursor gene sequences and complete nucleocapsid protein gene sequences revealed a high level of genetic diversity among Tacaribe serocomplex viruses associated with N. micropus in western Oklahoma, southern New Mexico, and northern and southern Texas. Collectively, the results of Bayesian analyses of nucleotide sequences and pairwise comparisons of amino acid sequences confirmed that the arenaviruses associated with N. micropus in Oklahoma and New Mexico should be included in the Whitewater Arroyo species complex, and indicated that that the arenaviruses associated with N. micropus in northern Texas are strains of a novel arenaviral species--tentatively named "Middle Pease River virus". Together, the results of assays for arenavirus and assays for anti-arenavirus antibody in 54 southern plains woodrats and 325 other rodents captured at 2 localities suggested that the southern plains woodrat is the principal host of Middle Pease River virus in northern Texas.