Identification and siting of native vegetation types on disturbed land: demonstration of statistical methods

Question: How does one best choose native vegetation types and site them in reclamation of disturbed sites ranging from cropland and strip mines? Application: World‐wide, demonstrated in SE Montana. Methods: We assumed that pre‐disturbance native communities are the best targets for revegetation, and that the environmental facet each occupies naturally provides its optimal habitat. Given this assumption, we used pre‐strip‐mine data (800 points from a 88 km² site) to demonstrate statistical methods for identifying native communities, describing them, and determining their environments. Results and conclusions: Classification and pruning analysis provided an objective method for choosing the number of target community types to be used in reclamation. The composition of eight target types, identified with these analyses, was described with a relevé table to provide a species list, target cover levels and support the choice of species to be seeded. As a basis for siting communities, we modeled community presence as a function of topography, slope/aspect, and substrate. Logistic GLMs identified the optimal environment for each community. Classification and Regression Tree (CART) analysis identified the most probable community in each environmental facet. Topography and slope were generally the best predictors in these models. Because our analyses relate native vegetation to undisturbed environments, our results may apply best to sites with minimal substrate disturbance (i.e. better to abandoned cropland than to strip‐mined sites).     

Balancing forces: architectural control of mechanotransduction

All cells exist within the context of a three-dimensional microenvironment in which they are exposed to mechanical and physical cues. These cues can be disrupted through perturbations to mechanotransduction, from the nanoscale-level to the tissue-level, which compromises tensional homeostasis to promote pathologies such as cardiovascular disease and cancer. The mechanisms of such perturbations suggest that a complex interplay exists between the extracellular microenvironment and cellular function. Furthermore, sustained disruptions in tensional homeostasis can be caused by alterations in the extracellular matrix, allowing it to serve as a mechanically based memory-storage device that can perpetuate a disease or restore normal tissue behaviour.     

The pi-helix translates structure into function

A search for the occurrence of the rare pi-helix was performed with Iditis from the Oxford Molecular Group upon the Protein Data Bank. In 8 of the 10 confirmed crystal structures that harbor the pi-helix, its unique conformation has been linked directly to the formation or stabilization of a specific binding site within the protein. In the discussion to follow, the role for each of these eight pi-helices will be addressed in regard to protein function. It is clear upon closer examination that the conformation of the pi-helix has evolved to provide unique structural features within a variety of proteins.     

Mitochondrial DNA sequence evolution in sharks: rates, patterns, and phylogenetic inferences

Abundant representation of sharks in the fossil record makes this group a superb system in which to investigate rates and patterns of molecular evolution and to explore the strengths and weaknesses of phylogenetic inferences from molecular data. In this report, the molecular evolution of the cytochrome b gene in sharks is described and the information related to results from phylogenetic analysis of the data evaluated in the light of a phylogeny derived independently of the molecular data. Across divergent lineages of sharks there is evidence for significant substitution rate variation, departure from compositional equilibrium, and substantial homoplasy; nevertheless, the signal of evolutionary history is evident in patterns of shared transversions and amino acid replacements.