A demographic analysis of vole population responses to fragmentation and destruction of habitat

 Fragmentation and destruction of natural habitats is currently considered to be the major threat to wildlife populations. We here perform a comprehensive analysis of the demographic effects of habitat fragmentation and destruction on 14 populations of the root vole. The experiment was divided into two consecutive periods. During the first period, we contrasted populations with the same initial size and structure in continuous and fragmented habitat. During the second period, we fragmented the continuous habitat into the same configuration as the permanently fragmented habitat so that the effect of habitat destruction could be evaluated. We estimated survival and fecundity parameters and combined them into population projection matrices to evaluate their relative impact on population growth. In the first period of the experiment there was no difference in population growth rate between fragmented and continuous populations, although litter size was significantly higher in the continuous populations. In the second period, we found higher population growth rates in populations that had experienced habitat destruction. By applying the transition matrix model to empirical estimates of demographic parameters, we demonstrate that the difference in population growth rate in the second period of the experiment was the result of a nonsignificant difference in adult survival. Movements out of the habitat patches were significantly lower in populations that had experienced habitat destruction. We conclude that predator-caused mortality of animals moving out of the habitat patches was the main determinant of demographic variation in this system. Received: January 31, 2002 / Accepted: March 25, 2003     

The body wall of Halicryptus spinulosus (Priapulida) — ultrastructure and changes induced by hydrogen sulfide

Halicryptus spinulosus (Priapulida) is extraordinarily resistant to hydrogen sulfide. As described previously, the body wall of specimens from oxic and from hydrogen sulfide-contaminated habitats differs strikingly in colour. In the present paper the ultrastructure of the body wall of specimens kept under oxic conditions is described. These findings serve as a reference for changes induced by exposure to hydrogen sulfide. There are marked ultrastructural differences between epidermal and muscular mitochondria exposed to hydrogen sulfide. Epidermal mitochondria of individuals subjected to hydrogen sulfide are often associated with dense granules of unknown composition. Findings are compared with those from other taxa which may encounter hydrogen sulfide in their environment.Contribution No. 386 of the Alfred-Wegener-Institut für Polar- and Meeresforschung (Awl Bremerhaven).     

Mitglieder-Versammlung 1970 im Haag

Ohne Zusammenfassung     

Die Wiederentdeckung der brasilianischen KolibrisAugastes scutatus undAugastes lumachellus

Zusammenfassung Seit vielen Jahrzehnten waren die KolibrisAugastes lumachellus undAugastes scutatus nicht wieder aufgefunden worden, bisA. Ruschi sie vor einigen Jahren wiederentdeckte. Verf. hat nunA. scutatus in gebirgigen Landschaften von Minas Gerais undA. lumachellus in der Serra Sincora (Bahia), einem vonRuschi ermittelten Fundort, aufgesucht. Beide Arten bewohnen mit niedriger xerophiler Vegetation bestandene felsige Berghänge in 1000–2000 m Höhe und sind dort häufig. Ihr Nest wird beschrieben.

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Summary A few years ags,A. Ruschi re-discovered the Brazilian Humming-birdsAugastes lumachellus andA. scutatus, which had not been traced for several decades. The present author visited the localities where they had previously been found. He came acrossA. scutatus at several places in the mountains of Minas Gerais andA. lumachellus in the Serra Sincora, Bahia. The habitat and the nest of both species are described.

     

Influence of sodium hydroxide on protein determination with the xylene brilliant cyanin G micromethod

The influence of sodium hydroxide on protein determination by two methods was investigated. Exposure of albumin to 0.1, 1.0, 5.0 and 9.0 m NaOH for up to 1 hr did not influence protein determination by a biuret method. In contrast to this, the presence of NaOH effected a pronounced reduction of the absorbances when a micromethod, involving adsorption of protein to cellulose filters followed by precipitation with TCA, was used.