Female siskins choose mates by the size of the yellow wing stripe

Commonly, female birds use the brightly coloured patches on males to choose the best-quality mates. Coloured wing patches, however, have received little attention or have been previously related to social behaviour (as a signal to recruit conspecific individuals at feeding patches) or foraging (to flush prey) contexts, rather than to sexual selection. Here we provide evidence that in siskins (Carduelis spinus), wing patches function in mate choice. Mate-choice experiments showed that females were attracted by the size of the yellow wing stripe of the male, but not by the size of its black bib, body size, general plumage brightness or age. Experiments on birds with manipulated yellow wing stripes showed that females were sensitive to the size of this colour patch, irrespective of other male qualities. The preference of female siskins for males with larger wing patches when searching for a mate may be explained by the relationship of this trait to foraging ability, which would ensure females good parental investment from the chosen male.Communicated by W.A. Searcy     

Habitat fragmentation affects movement behavior of migrating juvenile common toads

Displacement characteristics in animals are crucial drivers of successful movement decisions in resources acquisition, migration, and dispersal. As landscape structure is modified by human activity, mobility patterns are likely to evolve in response to habitat fragmentation. In species with complex life cycles that involve obligatory migrations between different habitats, one can predict that movement propensity would be promoted by fragmentation as long as it allows to reaching a habitat patch. Here, we compare the movement characteristics of naive toadlets sampled in populations distributed over a fragmentation gradient to test the hypothesis of a positive correlation between fragmentation and mobility levels. We studied toadlet movement in experimental arenas providing small patches of suitable conditions. We recorded the use of these patches (patch behavior) or the absence of their use (overtaking behavior). The more fragmented the original landscape, the more prone the toadlets were to combine these two behaviors, thus showing a higher motivation to explore. Moreover, the more fragmented the original landscape, the less the toadlets exhibited patch behavior. As the toadlets were reared in a common environment, the behavioral differences detected, relating to the level of fragmentation, resulted from inheritance. Our results thus illustrate that fragmentation is likely to create cross-generational transmittable variations in movement characteristics.     

Effect of stage-specific vital rates on population growth rates and effective population sizes in an endangered iteroparous plant

Effective population size (N(e)) determines the strength of genetic drift and can influence the level of genetic diversity a population can maintain. Assessing how changes in demographic rates associated with environmental variables and management actions affect N(e) thus can be crucial to the conservation of endangered species. Calculation of N(e) through demographic models makes it possible to use elasticity analyses to study this issue. The elasticity of N(e) to a given vital rate is the proportional change in N(e) associated with a proportional increase in that vital rate. In addition, demographic models can be used to study N(e) and population growth rate (λ) simultaneously. Simultaneous examination is important because some vital rates differ diametrically in their associations with λ and N(e). For example, in some cases increasing these vital rates increases λ and decreases N(e). We used elasticity analysis to study the effect of stage-specific survival and flowering rates on N(e), annual effective population size (N(a)), and λ in seven populations of the endangered plant Austrian dragonhead (Dracocephalum austriacum). In populations with λ ≥ 1, the elasticities of N(e) and N(a) were similar to those of λ. Survival rates of adults were associated with greater elasticities than survival rates of juveniles, flowering rates, or fecundity. In populations with λ < 1, N(e) and N(a) exhibited greater elasticities to juvenile than to adult vital rates. These patterns are similar to those observed in other species with similar life histories. We did not observe contrasting effects of any vital rate on λ and N(e); thus, management actions that increase the λ of populations of Austrian dragonhead will not increase genetic drift. Our results show that elasticity analyses of N(e) and N(a) can complement elasticity analysis of λ. Moreover, such analyses do not require more data than standard matrix models of population dynamics.     

Tracking habitat and resource use for the jumbo squid Dosidicus gigas: a stable isotope analysis in the Northern Humboldt Current System

To determine the habitat and resource use of Dosidicus gigas in the Northern Humboldt Current System, we analysed carbon and nitrogen stable isotopes of 234 individuals collected during 2008–2010. Large variations in mantle stable isotope ratios were recorded, with values ranging from −19.1 to −15.1 ‰ (δ¹³C) and from 7.4 to 20.5 ‰ (δ¹⁵N). Most of the variation was explained by latitude, followed by distance to shelf break for carbon and by squid size for nitrogen. Latitudinal variations with increasing values from north to south were also found in zooplankton samples and were related to changes in isotope baseline values probably due to oxygen minimum zones that occur off Peru. This similar latitudinal trend in both zooplankton and D. gigas samples reveals that D. gigas is a relatively resident species at the scale of its isotopic turnover rate (i.e. a few weeks), even if this is not necessarily the case at the scale of its life. A small but significant size effect on δ¹³C values suggests that jumbo squid perform offshore–onshore ontogenic migration, with juveniles distributed offshore. For nitrogen, the high inter-individual variability observed with mantle length indicates that D. gigas can prey on a high variety of resources at any stage of their life cycle. This large-scale study off the coast of Peru provides further evidence that D. gigas have the capability to explore a wide range of habitats and resources at any stage of their life.     

Climate vs. soil factors in local adaptation of two common plant species

Evolutionary theory suggests that divergent natural selection in heterogeneous environments can result in locally adapted plant genotypes. To understand local adaptation it is important to study the ecological factors responsible for divergent selection. At a continental scale, variation in climate can be important while at a local scale soil properties could also play a role. We designed an experiment aimed to disentangle the role of climate and (abiotic and biotic) soil properties in local adaptation of two common plant species. A grass (Holcus lanatus) and a legume (Lotus corniculatus), as well as their local soils, were reciprocally transplanted between three sites across an Atlantic-Continental gradient in Europe and grown in common gardens in either their home soil or foreign soils. Growth and reproductive traits were measured over two growing seasons. In both species, we found significant environmental and genetic effects on most of the growth and reproductive traits and a significant interaction between the two environmental effects of soil and climate. The grass species showed significant home site advantage in most of the fitness components, which indicated adaptation to climate. We found no indication that the grass was adapted to local soil conditions. The legume showed a significant home soil advantage for number of fruits only and thus a weak indication of adaptation to soil and no adaptation to climate. Our results show that the importance of climate and soil factors as drivers of local adaptation is species-dependent. This could be related to differences in interactions between plant species and soil biota.     

Functional recovery of biofilm bacterial communities after copper exposure

Potential of bacterial communities in biofilms to recover after copper exposure was investigated. Biofilms grown outdoor in shallow water on glass dishes were exposed in the laboratory to 0.6, 2.1, 6.8 micromol/l copper amended surface water and a reference and subsequently to un-amended surface water. Transitions of bacterial communities were characterised with denaturing gradient gel electrophoresis (DGGE) and community-level physiological profiles (CLPP). Exposure to 6.8 micromol/l copper provoked distinct changes in DGGE profiles of bacterial consortia, which did not reverse upon copper depuration. Exposure to 2.1 and 6.8 micromol/l copper was found to induce marked changes in CLPP of bacterial communities that proved to be reversible during copper depuration. Furthermore, copper exposure induced the development of copper-tolerance, which was partially lost during depuration. It is concluded that bacterial communities exposed to copper contaminated water for a period of 26 days are capable to restore their metabolic attributes after introduction of unpolluted water in aquaria for 28 days.     

Trace metal speciation and fluxes within a major French wastewater treatment plant: impact of the successive treatments stages

Seven metals (Cd, Co, Cr, Cu, Fe, Ni and Pb) were monitored at the Seine-Aval wastewater treatment plant during 6 sampling campaigns in April 2004. Particulate and dissolved metals have been measured in 24 h composite samples at each treatment stage (primary settling, secondary activated sludge and tertiary flocculation by FeCl₃). In addition, the diffusive gradient in thin film technique (DGT) was used to determine the dissolved inert and labile metal fraction. Although all treatment stages were able to decrease particulate metals concentrations in wastewater, most dissolved metals concentrations were mainly affected during primary settling. This unexpected result was attributed to tertiary sludge filtrate recirculation. Metals added via the FeCl₃ reagent at the tertiary treatment were shown to lower the overall Cr removal from wastewater and to enrich Ni in effluents. The plant operating conditions (recirculation and reagent addition) appear therefore as important as treatment processes for the metals removal. Total metal fluxes were highly decreased by the whole treatment plant for Cd, Cr, Cu and Pb and to a lesser extend for Co and Ni. However, the labile metal fluxes were poorly decreased for Cu (18%), not significantly decreased for Ni and increased for Fe. The labile fraction of Cd, Co and Cr was not detectable at any stage of the plant. Discharged labile fluxes, at least for Ni, were potentially significant compared to the labile metal fluxes in the river measured downstream the plant. Treated urban wastewater discharges should be carefully considered as a possible source of bioavailable trace metals.     

Evaluation of the phytotoxicity of contaminated sediments deposited "on soil": II. Impact of water draining from deposits on the development and physiological status of neighbouring plants at growth stage

As part of a study of the phytotoxic risk of spreading contaminated sediments "on soil", a laboratory experiment was carried out to assess the impact of water draining from sediments on peripheral vegetation. Drainage water was obtained in the laboratory by settling three sediments with different pollutants levels, and the supernatant solutions (respectively A1, B1, C1 drainage waters) were used as soaking water for maize (Zea ma?s L.) and ryegrass (Lolium perenne L.). The physicochemical characteristics of the supernatant water, particularly metal contents, showed a pattern of contamination, with C1>A1>B1. The plants tested were grown on soil for 21 days, before being soaked for another 21-day period with drainage water (treatments) and distilled water (control). Biomass parameters (fresh weight, length, etc.), enzymatic activity [glutamine synthetase (GS), phosphoenolpyruvate carboxylase (PEPc)] and Zn, Cu, Cd and Cr contents were measured on both the shoots and roots of each plant. Biomass parameters were stimulated by C1, not affected by A1 and decreased with B1 for maize, whereas they increased for ryegrass in all the treatments. Compared to the control, GS activity was stimulated by C1 in the shoots of both plants and inhibited by treatments B1 and C1 in maize roots. PEPc activity in ryegrass was 1.5-5 times higher with contaminated water treatment, while contrasting effects were observed in maize plants. Both plants showed greater accumulation of chromium and zinc than cadmium and copper. Treatment A1 was found to be less active on plant growth and have a lower impact on the physiological status (enzymatic activities) of both plants. Treatment C1 stimulated the growth and physiological status of the plants, especially in shoots, with higher metal accumulation values in both plants. Treatment B1 was found to show more variable effects on growth indices, enzymatic activity and metal accumulation according to plant species.