The Osteology of Infants and Children

The Osteology of Infants and Children . Brenda J. Baker, Tosha L. Dupras, and Matthew W. Tocheri. College Station: Texas A&M University Press, 2005. 178 pp.     

Speciation mirrors geomorphology and palaeoclimatic history in African laminate-toothed rats (Muridae: Otomyini) of the Otomys denti and Otomys lacustris species-complexes in the 'Montane Circle' of East Africa

We adopted an integrated systematic approach to delimit evolutionary species and describe phylogeographic, morphometric and ecological relationships in Otomys denti (from the Albertine Rift, Southern Rift in Malawi and the northern Eastern Arc Mountains) and Otomys lacustris (from the Southern Rift in Tanzania and Zambia, and the southern Eastern Arc Mountains). Molecular [cytochrome (cyt) b sequences, 1143 bp, N  = 18], craniometric (classical, N  = 100 and geometric, N  = 60) and ecological (Partial Least Squares regression of shape and ecogeographic variables) approaches show a profound, parallel disjunction between two groups: (1) Eastern Arc and Southern Rift (including the Malawi Rift) ( O. lacustris and Otomys denti sungae ) and (2) Albertine Rift ( Otomys denti denti and Otomys denti kempi ) taxa. Within both groups, cyt b sequences or craniometric analysis provided evidence for the differentiation of both southern and northern Eastern Arc from Southern Rift lineages (across the so-called Makambako Gap). Within the Albertine Rift ( denti – kempi ) lineage, populations from individual mountain ranges differed significantly in skull shape (but not size), but were similar genetically. Over-reliance in the past on very few morphological characters (e.g. number of molar laminae) and a polytypic species concept has obscured phylogenetic relationships and species discrimination in this group. We recognize at least three species in this group, and distinct lineages within two of these species. Each species or lineage was endemic to one of three regions: the Albertine Rift, the Malawi Rift or the Eastern Arc. Our result echo conclusions of recent studies of other mammalian and bird taxa and reflect the geomorphology and palaeoclimatic history of the region.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 96 , 913–941.     

Perspectives on polyploidy in plants – ancient and neo

It is timely to re-examine the phenomenon of polyploidy in plants. Indeed, the power of modern molecular technology to provide new insights, and the impetus of genomics, make polyploidy a fit, fashionable and futuristic topic for review. Some historical perspective is essential to understand the meaning of the terms, to recognize what is already known and what is dogma, and to frame incisive questions for future research. Polyploidy is important because life on earth is predominantly a polyploid phenomenon. Moreover, civilization is mainly powered by polyploid food – notably cereal endosperm. Ongoing uncertainty about the origin of triploid endosperm epitomizes our ignorance about somatic polyploidy. New molecular information makes it timely to reconsider how to identity polyploids and what is a polyploid state. A functional definition in terms of a minimal genome may be helpful. Genes are known that can raise or lower ploidy level. Molecular studies can test if, contrary to dogma, the relationship between diploids and polyploids is a dynamic two-way system. We still need to understand the mechanisms and roles of key genes controlling ploidy level and disomic inheritance. New evidence for genome duplications should be compared with old ideas about cryptopolyploidy, and new views of meiosis should not ignore premeiotic genome separation. In practice, new knowledge about polyploidy will be most useful only when it reliably predicts which crops can be usefully improved as stable autopolyploids and which genomes combined to create successful new allopolyloids.  © 2004 The Linnean Society of London, Biological Journal of the Linnean Society , 2004, 82 , 411–423.     

Foraging strategies and patch distributions: intraguild interactions between Dicyphus hesperus and Encarsia formosa

Abstract 1. Competing foragers are affected by the distribution of resources, but can also affect resource distribution. Intraguild predators may affect the distribution of both the shared prey and the intraguild prey, which are also their competitors. 2. Variation in foraging strategies and their effects on resource distributions may influence the outcome of intraguild interactions between an intraguild predator and its intraguild prey. This was tested using whitefly Trialeurodes vaporariorum as the shared resource, the parasitoid Encarsia formosa as the intraguild prey, and Dicyphus hesperus, an omnivore, as the intraguild predator on tomato (Lycopersicon esculentum) and mullein (Verbascum thapsus) plants, within enclosures in a greenhouse. Treatments were established with and without the intraguild predator and at high and low intraguild prey densities. 3. The interaction between D. hesperus and E. formosa showed significant asymmetry, with D. hesperus populations being unaffected by E. formosa densities, although E. formosa populations were reduced by the inclusion of D. hesperus. However, the inclusion of D. hesperus diminished density‐dependent effects limiting E. formosa populations at high release densities. 4. Dicyphus hesperus reduced the average patch size and the proportion of patches occupied by whitefly. Increasing the release rate of E. formosa had no effect on any distributional measure. Based upon the foraging ecology of both species, the foraging activities of D. hesperus appear to have modified the patch distribution so that its foraging strategy becomes more successful than that of E. formosa. These properties may provide an important mechanism determining the outcome of species interactions.     

Immunofluorescent Visualization of 100 Å Filaments in Different Cultured Chick Embryo Cell Types

Antibody prepared against the 55,000 dalton subunit of reconstituted chick gizzard 100 A filaments (anti-G55K) bound to the 100 Å filaments of chick smooth muscle, cardiac muscle, and skeletal muscle cells, and to the 100 Å filaments of Schwann cells and satellite glial cells of the peripheral nervous system. Anti-G55K did not bind to replicating presumptive myoblasts, fibroblasts, chondroblasts, pigment cells, neurons, or to central nervous system glial cells. This contrasted with the wider range of binding of antibody to the 58,000 dalton subunit of chick fibroblast 100 A filaments (anti-F58K) which bound to the 100 Å filaments of all cell types examined except hepatocytes and skin epithelial cells. Anti-G55K staining revealed a morphologically distinct distribution of 100 A filaments in the three types of muscle cells. Spindle shaped smooth muscle cells exhibited dense fluorescent staining near the poles of the cells, and also exhibited unique patches of fluorescent material after cytochalasin B and Colcemid treatment. In myotubes, the fluorescence was limited to longitudinal bundles of filaments between the striated myofibrils. Cardiac cells contained uniformly distributed fine filaments. Lastly, smooth muscle cells in various phases of mitosis bound the anti-G55K, whereas replicating presumptive skeletal myoblasts failed to bind the anti-G55K.