Assessing multi-taxa sensitivity to the human footprint,habitat fragmentation and loss by exploring alternative scenarios of dispersal ability and population size: a simulation approach

Quantifying the effects of landscape change on population connectivity is compounded by uncertainties about population size and distribution and a limited understanding of dispersal ability for most species. In addition, the effects of anthropogenic landscape change and sensitivity to regional climatic conditions interact to strongly affect habitat fragmentation and loss. To further develop conservation theory and to understand the interplay between all of these factors, we simulated habitat fragmentation and loss across the Western United States for several hypothetical species associated with four biome types, and a range of habitat requirements and dispersal abilities. We found dispersal ability and population size of the focal species to be equally sensitive to habitat extent, while dispersal ability is more sensitive to habitat fragmentation. There were also strong critical threshold effects where habitat connectivity decreased disproportionately to decreases in life-history traits making these species near these thresholds more sensitive to changes in habitat loss and fragmentation. Overall, grassland and forest associated species are also most at risk from habitat loss and fragmentation driven by human related land-use. These two largest biome types were most sensitive at large contiguous patch sizes which is often considered most important for metapopulation viability and biodiversity conservation. Hypothetical simulation studies such as this can be of great value to scientists in further conceptualizing and developing conservation theory, and evaluating spatially-explicit scenarios of habitat connectivity. Our results are available for download in a web-based interactive mapping prototype useful for accessing the results of this study.     

Cell surface T antigen in cells infected with simian virus 40 or an adenovirus-simian virus 40 hybrid, Ad2+D2.

Cell surface T antigen, detected by a radioimmune assay that uses 125I-labeled Staphylococcus aureus protein A and antibodies against either authentic T antigen or D2 hybrid T antigen, was found in simian virus 40-transformed and -infected cells and in cells infected with an adenovirus-simian virus 40 hybrid, Ad2+D2. In simian virus 40 lytic infection, the surface T antigen appeared at the same time as the nuclear T antigen.     

Further characterization of the phenotype of ts20, a DNAts mutant of BALB/3T3 cells

Ts20 is a temperature-sensitive mutant cell line derived from BALB/3T3 cells that is blocked at a step in DNA synthesis involving chain elongation. Following a shift from 33 degrees to 39 degrees C, mutant cells lost ability to grow or form colonies. When mutant cells were infected with polyomavirus, both cell and virus DNA synthesis were inhibited at the restrictive temperature of 39 degrees C. When cell extracts from wild-type cells were added in vitro to lysed infected mutant cells that had been incubated in vivo at 39 degrees C for expression of the mutation, cell DNA synthesis was increased 3-fold (similar to the effect in uninfected mutant cells), whereas virus DNA synthesis was increased only 60%. With harsher lysis conditions, the effect of added extract on virus DNA synthesis was greater, although baseline DNA synthesis (prior to addition of extracts) was much lower. Analysis by alkaline sucrose gradients showed that the addition of cell extract converted small cellular DNA molecules into larger ones, while it increased the synthesis of small virus DNA molecules rather than completed genomes. Analysis of cytosol extracts (in which the activity stimulating DNA synthesis resides) showed that DNA topo-isomerase I activity was more heat-labile when assayed in mutant extracts compared to wild-type extracts. In contrast, cytosol DNA polymerase activity was equally heat-labile in mutant and wild-type extract. This suggested the factor in extract was likely associated with the activity of DNA topo-isomerase I. Analysis of virus DNA synthesized in vitro in restricted mutant cells by gel electrophoresis and fluorography showed an accumulation of topo-isomers migrating between form I and II. These topo-isomers, thought to be a manifestation of the ts defect, did not disappear when extract from wild-type cells was added back in vitro or when mutant cells were shifted back to permissive temperature prior to lysis for in vitro synthesis. The results indicate that polyoma DNA synthesis and cell DNA synthesis differ in their response to the mutant gene product in ts20, although both are inhibited at a step early in DNA chain elongation that may involve DNA topo-isomerase I.     

Production of sexual morphs by the monoecious cereal aphid Sitobion avenae

The effects of photoperiod and temperature on the production of sexual forms by two clones of Sitobion avenae, the grain aphid, were examined. One clone did not produce sexual forms, whereas the other did under conditions of short light (<14 h) and low temperature (15°C). Temperature and photoperiod interacted to some extent both in the production of oviparae and of males. Even when the sexual forms were produced there was always a proportion of virginoparae.

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Production de sexués par Sitobion avenae, puceron monoécique

Résumé Un clone de Sitobion avenae a produit sans difficulté jusqu'à 7 générations de sexués en réaction à des photopériodes courtes (<14 h) et à de faibles températures (15°C) tandis qu'un autre clone n'en produit aucune.La proportion de sexués différait suivant les parents. La production de mâles avait une nette tendance à apparaître lors des reproduction les plus tardives. Dans les générations tardives avec jours courts, les vivipares (virginopares et gynopares) avaient eu tendance à être produits à la fin de la période de reproduction.Les gynopares (c'est à dire les parents d'ovipares) de S. avenae étaient surtout aptères, mais comprenaient beaucoup plus d'ailés que les virginopares obtenus dans les mêmes conditions. Un vivipare était induit comme gynopare (ou ses embryons étaient déterminés comme ovipares) avant la naissance, mais cette détermination pouvait apparemment encore être inversée en soumettant l'insecte à de longues photopériodes et à de hautes températures jusqu'à deux jours après la naissance.Aucun S. avenae ovipare n'a été produit jusqu'à la troisième génération. Aucun ovipare n'a été produit avec des photopériodes supérieures à 13 H 30 à 10°C, 13 H à 15°C et 8 H à 20°C. La proportion d'individus produisant des ovipares à 15°C a été plus faible qu'à 10°C pour toutes les photopériodes, et à cette dernière température beaucoup plus de vivipares étaient gynopares que virginopares.Les basses températures ont été vraisemblablement le facteur dominant de stimulation de la production de mâles de S. avenae, mais cependant il semble qu'un plus grand nombre de mâles a été produit aux températures et photopériodes intermédiaires qu'aux extrêmes.La capture de mâles ailés de S. avenae dans des pièges à succion a été généralement limitée à Octobre-soit à peu prés le moment prévu par les expériences de laboratoire. Des mâles de S. avenae sont aussi capturés fréquemment et été, ce qui peut être lié à des hivers précédents doux.

     

Correction of the defect in initiation of DNA replication in a temperature-sensitive mutant hamster cell line by in vitro addition of extracts from normal cells.

ts BN-2 is a temperature-sensitive hamster cell line that is defective in DNA synthesis at the restrictive temperature. The mutant expresses its defect during in vitro replication in whole-cell lysates. Addition of a high-salt-concentration extract from wild-type BHK-21, revertant RBN-2, or CHO cells to mutant cells lysed with 0.01% Brij 58 increased the activity in the mutant three- to fourfold, so that it reached 85% of the control value, and restored replicative synthesis. The presence of extract had an insignificant effect on wild-type and revertant replication and on mutant replication at the permissive temperature. Extract prepared from mutant cells was less effective than the wild-type cell extract was. Also, the stimulatory activity was more heat labile in the mutant than in the wild-type extract. Nuclear extract was as active as whole-cell extract.     

Identification of an S-locus glycoprotein allele introgressed from B. napus ssp. rapifera to B. napus ssp. oleifera.

We have previously described a developmentally regulated mRNA in maize that accumulates in mature embryos and is involved in a variety of stress responses in the plant. The sequence of the encoded 16 kDa protein (MA16) predicts that it is an RNA-binding protein, since it possesses a ribonucleoprotein consensus sequence-type RNA-binding domain (CS-RBD). To assess the predicted RNA binding property of the protein and as a starting point to characterize its function we have used ribohomopolymer-binding assays. Here we show that the MA16-encoded protein binds preferentially to uridine- and guanosine-rich RNAs. In light of these results a likely role for this protein in RNA metabolism during late embryogenesis and in the stress response is discussed.     

Antibodies to phase related proteins in juvenile and mature Prunus avium

In the search for biochemical and molecular markers of juvenility in trees proteins have been identified which are preferentially or differentially expressed in either the juvenile or the mature phases of Prunus avium cv. Stella. These fall into two classes: those which are phase-related and those which may be affected by root-shoot distance. N-terminal amino acid sequence data from some of these proteins were used to produce polyclonal antibodies to corresponding synthetic peptides in order to determine if they could be used as markers of phase state in woody plants. Western blot analysis was performed on proteins extracted from three sources; juvenile trees, mature trees and rooted cuttings from mature trees. The results showed that the antibodies recognised differentially-expressed proteins. In particular, one antibody to a juvenile specific protein cross-reacted with a polypeptide of approx. 28 kDa which was present in greater amounts in shoot tips of juvenile P. avium cv. Stella seedlings compared with rooted cuttings of mature plants placed in the same growth environment.