On principles and standards in ecological restoration

The Society for Ecological Restoration (SER) has long debated how to define best practices. We argue that a principles‐first approach offers more flexibility for restoration practitioners than a standards‐based approach, is consistent with the developmental stage of restoration, and functions more effectively at a global level. However, the solution is not as simple as arguing that one approach to professional practice is sufficient. Principles and standards can and do operate effectively together, but only if they are coordinated in a transparent and systematic way. Effective professional guidance results when standards anchored by principles function in a way that is contextual and evolving. Without that clear relation to principles, the tendency to promote performance standards may lead to a narrowing of restoration practice and reduction in the potential to resolve very difficult and diverse ecological and environmental challenges. We offer recommendations on how the evolving project of restoration policy by SER and other agencies and organizations can remain open and flexible.     

Analysis of copia sequence variation within and between Drosophila species

The sequences of the 5' long-terminal repeat (LTR) and adjacent leader regions of 27 full-length copia elements isolated from natural populations of Drosophila melanogaster, D. simulans, and D. mauritiana are presented. Phylogenetic analyses indicate that although D. melanogaster copia elements are distinct from those of D. simulans and D. mauritiana, the elements of these latter two species are not distinguishable from one another. LTRs and adjacent 5' leader regions of elements isolated from D. simulans and D. mauritiana are structurally similar to one another and carry substantial deletional variation mapping to regions previously identified as being of potential importance for copia expression.      

Comparisons of the molecular evolutionary process at rbcL and ndhF in the grass family (Poaceae)

We examine rate heterogeneity among evolutionary lineages of the grass family at two plasmid loci, ndhF and rbcL, and we introduce a method to determine whether patterns of rate heterogeneity are correlated between loci. We show both that rates of synonymous evolution are heterogeneous among grass lineages and that are heterogeneity is correlated between loci at synonymous sites. At nonsynonymous sites, the pattern of rate heterogeneity is not correlated between loci, primarily due to an aberrant pattern of rate heterogeneity at nonsynonymous sites of rbcL. We compare patterns of synonymous rate heterogeneity to predictors based on the generation time effect and the speciation rate hypotheses. Although there is some evidence for generation time effects, neither generation time effects nor speciation rates appear to be sufficient to explain patterns of rate heterogeneity in the grass plastid sequences.      

Effects of inhibition of basement membrane collagen deposition on rat mammary gland development

DNA biosynthesis by a system containing giant nuclei isolated from rat trophoblast cells at Day 13 of pregnancy has been studied. A method for the isolation of giant nuclei in good yield has been described. These nuclei were capable of incorporating [³H]dTTP into DNA for 2 hr and the incorporation was proportional to the amount of DNA template (nuclei). The system was highly dependent on the four deoxyribonucleoside triphosphates, ATP, and Mg²⁺ and was stimulated by monovalent ions such as K⁺. The optimum pH was 8.6. The product of the reaction was insensitive to RNase, sensitive to DNase, and banded at 1.710 g/ml in neutral CsCl together with bulk rat trophoblast DNA. Pulse-chase and density labeling experiments utilizing bromodeoxyuridine have indicated that replicative, discontinuous synthesis was taking place at sites previously active in vivo. DNA polymerases α, β, and γ were shown to be present in the nuclei. Experiments utilizing selective inhibitors of polymerases have demonstrated that DNA replication by trophoblast nuclei in vitro was insensitive to the specific α-polymerase inhibitor, aphidicolin, but almost completely inhibited by 2′, 3′-dideoxythymidine 5′-triphosphate as well as by N-ethylmaleimide suggesting that DNA replication observed in these trophoblast nuclei in vitro may be carried out by DNA polymerase γ.     

The putative sigma factor KatF has a central role in development of starvation-mediated general resistance in Escherichia coli.

KatF is required for the expression of some 32 carbon starvation proteins in Escherichia coli including 6 previously identified as Pex. Mutants with the katF gene survive carbon and nitrogen starvation poorly. Many of the KatF-regulated starvation proteins are common to those induced by other stresses, and the mutant failed to develop starvation-mediated cross protection to osmotic, oxidative, and heat stresses. Furthermore, thermal resistance was not induced in the mutant by heat preadaptation, and it exhibited an altered pattern of protein synthesis at elevated temperature. Thus, KatF is a major switch that controls the starvation-mediated resistant state in E. coli.     

Evolution of Hybrid Dysgenesis Potential following P Element Contamination in Drosophila Melanogaster

P elements were introduced into M strain genomes by chromosomal contamination (transposition) from P strain chromosomes under conditions of P-M hybrid dysgenesis. A number of independently maintained contaminated lines were subsequently monitored for their ability to induce gonadal (GD) sterility in the progeny of reference crosses, over a period of 60 generations, in two experiments. The efficiency of chromosomal contamination was high; all tested lines acquired P elements following the association of M and P chromosomes in the same genome for a single generation. All the contaminated lines also sustained an initial unstable phase, marked by high frequencies of transposition and sterility within lines, in the absence of P element regulation. Subsequently, each of the lines rapidly evolved to one of three relatively stable strain types whose phenotypic and molecular properties correspond rather closely to those of the P, Q and M' strains that have previously been characterized. The numbers and structures of P elements and the presence or absence of P element regulation during the early generations appeared to be critical factors determining the subsequent course of evolution. On the basis of GD sterility frequencies, both the mean level of P activity, and the average capacity for P element regulation, were reduced in lines raised at 25 degrees, relative to those raised at 20 degrees, during the early generations. This latter result is consistent with the expectation that natural selection will tend to modify the manifestation of dysgenic traits, such as high temperature sterility, which cause a reduction of fitness. However, overall, stochastic factors appeared to predominate in determining the course of evolution of individual lines.     

Molecular systematics and paleobiogeography of the South American sigmodontine rodents [published erratum appears in Mol Biol Evol 1998 Feb;15(2):224]

The murid rodent subfamily Sigmodontinae contains 79 genera which are distributed throughout the New World. The time of arrival of the first sigmodontines in South America and the estimated divergence time(s) of the different lineages of South American sigmodontines have been controversial due to the lack of a good fossil record and the immense number of extant species. The "early-arrival hypothesis" states that the sigmodontines must have arrived in South America no later than the early Miocene, at least 20 MYA, in order to account for their vast present-day diversity, whereas the "late-arrival hypothesis" includes the sigmodontines as part of the Plio-Pleistocene Great American Interchange, which occurred approximately 3.5 MYA. The phylogenetic relationships among 33 of these genera were reconstructed using mitochondrial DNA (mtDNA) sequence data from the ND3, ND4L, arginine tRNA, and ND4 genes, which we show to be evolving at the same rate. A molecular clock was calibrated for these genes using published fossil dates, and the genetic distances were estimated from the DNA sequences in this study. The molecular clock was used to estimate the dates of the South American sigmodontine origin and the main sigmodontine radiation in order to evaluate the "early-" and "late-arrival" scenarios. We estimate the time of the sigmodontine invasion of South America as between approximately 5 and 9 MYA, supporting neither of the scenarios but suggesting two possible models in which the invading lineage was either (1) ancestral to the oryzomyines, akodonts, and phyllotines or (2) ancestral to the akodonts and phyllotines and accompanied by the oryzomyines. The sigmodontine invasion of South America provides an example of the advantage afforded to a lineage by the fortuitous invasion of a previously unexploited habitat, in this case an entire continent.      

Antisense RNA decreases AP33 gene expression and cytoadherence by <Emphasis Type="Italic">T. vaginalis</Emphasis>

Background  

Host parasitism by Trichomonas vaginalis is complex. Adherence to vaginal epithelial cells (VECs) is mediated by surface proteins. We showed before that antisense down-regulation of expression of adhesin AP65 decreased amounts of protein, which lowered levels of T. vaginalis adherence to VECs. We now perform antisense down-regulation of expression of the ap33 gene to evaluate and confirm a role for AP33 in adherence by T. vaginalis. We also used an established transfection system for heterologous expression of AP33 in T. foetus as an additional confirmatory approach.