Homeotic transformation of the occipital bones of the skull by ectopic expression of a homeobox gene.

Murine Hox genes have been postulated to play a role in patterning of the embryonic body plan. Gene disruption studies have suggested that for a given Hox complex, patterning of cell identity along the antero-posterior axis is directed by the more 'posterior' (having a more posterior rostral boundary of expression) Hox proteins expressed in a given cell. This supports the 'posterior prevalence' model, which also predicts that ectopic expression of a given Hox gene would result in altered structure only in regions anterior to its normal domain of expression. To test this model further, we have expressed the Hox-4.2 gene more rostrally than its normal mesoderm anterior boundary of expression, which is at the level of the first cervical somites. This ectopic expression results in a homeotic transformation of the occipital bones towards a more posterior phenotype into structures that resemble cervical vertebrae, whereas it has no effect in regions that normally express Hox-4.2. These results are similar to the homeotic posteriorization phenomenon generated in Drosophila by ectopic expression of genes of the homeotic complex HOM-C (refs 7-10; reviewed in ref. 3).     

The Role of Symmetry in Mathematics

Over the past few decades the notion of symmetry has played a major role in physics and in the philosophy of physics. Philosophers have used symmetry to discuss the ontology and seeming objectivity of the laws of physics. We introduce several notions of symmetry in mathematics and explain how they can also be used in resolving different problems in the philosophy of mathematics. We use symmetry to discuss the objectivity of mathematics, the role of mathematical objects, the unreasonable effectiveness of mathematics and the relationship of mathematics to physics.     

Food spectrum analysis of the Asian toad,Duttaphrynus melanostictus (Schneider, 1799) (Anura: Bufonidae), from Timor Island,Wallacea

The Asian toad, Duttaphrynus melanostictus (Schneider, 1799), is widespread throughout tropical Asia and very abundant where it occurs. It was relatively recently introduced to Timor, the second largest island in the biogeographic region called Wallacea. Timor Island shows an exceptionally high level of endemism in a wide range of faunal groups and there are concerns that D. melanostictus may have a negative impact on this diversity, including vertebrates, through direct predation. To evaluate the impact the diet of D. melanostictus might have on the local fauna, gut contents of 83 preserved toad specimens from five habitat types in Timor-Leste, a country occupying the eastern half of Timor Island, were examined. We identified 5581 prey items, comprising the following animal groups: annelids; snails and slugs; spiders and harvestmen; woodlice; millipedes and centipedes; grasshoppers, crickets and earwigs; termites; thrips and true bugs; beetles; ants; hymenopterans other than ants; true flies; butterflies; unidentified insects; and insect larvae. Small eusocial insects (ants and termites) constituted the major part of the diet (61.6% and 23.4%, respectively). No vertebrate prey was recorded. Prey item composition did not differ between habitats. The wide prey spectrum well indicates that D. melanostictus is a generalist invertebrate feeder, as other studies, from regions where this species occurs naturally, have already shown. Although the Asian toad seems to not generally prey on vertebrates, vertebrate species that are morphologically similar to invertebrates in their overall appearance may be consumed. Hence, a negative effect on some taxa (e.g. blindsnakes) may be possible. We also present some limited data on intestinal parasites occurring in D. melanostictus.     

Rab protein evolution and the history of the eukaryotic endomembrane system

Spectacular increases in the quantity of sequence data genome have facilitated major advances in eukaryotic comparative genomics. By exploiting homology with classical model organisms, this makes possible predictions of pathways and cellular functions currently impossible to address in intractable organisms. Echoing realization that core metabolic processes were established very early following evolution of life on earth, it is now emerging that many eukaryotic cellular features, including the endomembrane system, are ancient and organized around near-universal principles. Rab proteins are key mediators of vesicle transport and specificity, and via the presence of multiple paralogues, alterations in interaction specificity and modification of pathways, contribute greatly to the evolution of complexity of membrane transport. Understanding system-level contributions of Rab proteins to evolutionary history provides insight into the multiple processes sculpting cellular transport pathways and the exciting challenges that we face in delving further into the origins of membrane trafficking specificity.     

A classification of aquatic plant communities within the Nothern Rocky Mountains

A synecological study of aquatic macrophyte plant communities was conducted across northern Idaho and western Montana during the summers of 1997, 1998, and 1999. A total of 111 natural and man-made water bodies were sampled based on a stratification of environmental variables thought to influence plant species distribution (i.e., elevation, landform, geology, and water body size). Plant species foliar cover data were used to develop a hierarchical, floristic-based community type classification with TWINSPAN and DECORANA software. Six planmergent (conspicuous portion of vegetative plant body on the water surface) and 24 submergent (vegetative plant body found primarily underwater) community types were identified. Multivariate analysis indicated that all community types displayed significant differences in plant species composition, and the Sorensons floristic similarity between communities averaged 10% for planmergent and 8% for submergent types. Canonical correspondence analysis was used to inspect relationships between abiotic factors and plant species abundance. Results of this analysis indicated some relationships between species distributions and abiotic factors; however, chance introduction of plant species to water bodies is a process considered to be equally important to the presence of the community types described.     

A 4000-year record of woodland vegetation from Wind River Canyon, central Wyoming

Plant macrofossil analyses of 16 radiocarbon-dated woodrat middens spanning the past 4000 years from the Wind River Canyon region in central Wyoming provide information concerning late Holocene development of juniper woodlands. The study sites are currently dominated by Juniperus osteosperma , with J. scopulorum present locally. Woodlands in the region were dominated by J. scopulorum from ca 4000 yr BP until at least 2800 yr BP. Juniperus osteosperma invaded and expanded before 2000 yr BP. This expansion fits a regional pattern of J. osteosperma colonization and expansion in north central Wyoming during a relatively dry period between 2800 and 1000 yr BP. At the time the Wind River Canyon region was colonized by J. osteosperma , the species had populations 50-100 km to both the north and south. Long-distance seed dispersal was required for establishment in the study area. Genetic studies are necessary to identify source populations and regions.     

Effects of habitat disturbance on diets of Great Horned Owl ( Bubo virginianus ) in a cold desert

To determine the potential effect of habitat disturbance, Great Horned Owl ( Bubo virginianus ) diets were quantified in disturbed and undisturbed habitats over a 2-year period at Dugway Proving Ground in the Great Basin Desert of Tooele County, Utah. Invertebrates were the most abundant prey by count, whereas mammals constituted the majority of diet by biomass. Species richness in the diet did not differ between habitats or among seasons after correcting for the number of pellets in each sample. However, the number of vertebrate species was greater than the number of invertebrate species in the diet, and this ratio differed between disturbed and undisturbed habitats. Invertebrate species made up a greater proportion of total species richness in the diet in the undisturbed than the disturbed habitat. Nineteen species occurred in the diet in only 1 of the 2 habitat types (7 unique species in disturbed habitat, 12 unique species in undisturbed), but all such species were rare and contributed little both by count and biomass to the overall diet. Of the 20 most important species found in owl diets in both habitats (based on percent biomass), none were more common in 1 habitat than the other after correcting for multiple tests. Although there were minor differences in the diet between disturbed and undisturbed habitats, habitat alteration and degradation of native vegetation on Dugway Proving Ground did not affect the major components of the diet of Great Horned Owls.     

Winter habitat selection patterns of Merriam's turkeys in the southern Black Hills, South Dakota

In northern areas of their expanded range, information on Merriam's turkeys ( Meleagris gallopavo merriami ) is lacking, specifically pertaining to wintering behavior and factors associated with winter habitat selection. Forest managers need detailed quantification of the effects of logging and other management practices on wintering habitats needed by Wild Turkeys and other wildlife. Therefore, we examined winter habitat selection patterns within ponderosa pine ( Pinus ponderosa ) forests and determined factors associated with use of farmsteads by Merriam's turkeys in the southern Black Hills, South Dakota. We radio-marked 86 female Merriam's turkeys (70 adults and 16 yearlings) and monitored them during winter (1 December–31 March), 2001–2004. Female Wild Turkeys used recently burned pine forest less than expected but selected farmsteads and stands of mature ponderosa pine ( 22.9 cm diameter at breast height [DBH] trees) for foraging sites. Within forests, female Wild Turkeys selected foraging sites with less understory vegetation and visual obstruction, and larger-diameter ponderosa pine. Ponderosa pine seed abundance varied among years, and pine seeds were most abundant in stands of 30–35 cm DBH with basal area of 22–28 m2 ? ha–1. Abundance of pine seeds may have influenced use of farmsteads by Wild Turkeys, more so than ambient temperatures or snow depth. In the southern Black Hills, management should emphasize open- to mid-canopy and mature-structural-stage pine stands, where seed production was greatest. During winters when mast from pine is unavailable, farmsteads likely provide nutritional supplementation and may be important for maintaining Merriam's turkey populations.     

A New Species of Asclepias (Asclepiadaceae) from Northwestern New Mexico

Asclepias sanjuanensis Heil, Porter, & Welsh, a new species from the pinyon-juniper woodlands of the San Juan River Valley, San Juan County, New Mexico, is described and illustratred. The species appears to be local and rare. Similar to A. ruthiae Maguire, it is distinguished by the greater number of flowers per inflorescence, the larger number of stems, and the pubescence characters.