Herbivore feeding preferences in captive and wild populations

Investigations into the mechanisms underpinning plant selection by herbivores have often yielded conflicting results. Such inconsistency might stem from whether selection experiments are conducted with captive or wild populations, and upon the different measures of plant selection used to determine herbivore preference. Here we compared the feeding preferences of captive and wild kangaroos (Macropus fuliginosus) using a standard set of plant species (14 Hakea spp., Proteaceae) and several measures of herbivore selection to examine how environment influenced relative consumption. Three indices of herbivore consumption were measured: number of plants (NP), total shoot volume per plant (TV) and percentage available shoot volume (PV) consumed. NP and TV were closely correlated in the wild and captive populations and consistently correlated with six morphological and chemical plant attributes examined, the most notable being a strong negative correlation with shoot phenolic content. This uniformity suggests that plant selection by captive kangaroos is broadly consistent with that observed in field trials, and consequently that for macropods, at least, captive trials offer a valid way to determine the relative acceptability of different plant species. However, the fact that our third measure of herbivore selection PV was weakly correlated in captive and wild populations and showed no relationship with shoot phenolic content highlights the importance of which measure of plant selection is applied. We suggest that, while NP and TV are potentially confounded by plant size and availability, they offer the clearest insight into plant selection from the point of view of the herbivore, while PV is more suitable for plant‐centred studies.     

Spatial and Temporal Patterns of Wolf Harvest on Registered Traplines in Alberta,Canada

Abstract: Gray wolf (Canis lupus) populations are recovering in many parts of the world and managers from various jurisdictions will be faced with difficult decisions as wolf populations continue to increase. Wolf management in Alberta, Canada, is achieved mostly through trapping on a registered trapline system. Wolf harvest increased over the last 22 years relative to population increases. Most wolf harvests occurred in the Rocky Mountains and surrounding foothills area and this pattern was consistent over time. On average, trappers only harvested an estimated 9.8% of the provincial population annually despite the lack of bag limits or quotas. Harvests are spatially autocorrelated with peak autocorrelation coinciding with average home-range size for wolves in Alberta. When wolf control actions are deemed necessary, trappers are unlikely to remove a sufficient number of wolves over a large enough area to limit subpopulations under the registered trapline system.     

Variations in bark-stripping by red deer Cervus elaphus across Europe

• 1 The literature on bark‐stripping by red deer Cervus elaphus in Europe is reviewed to reveal quantitative variation in this behaviour and relate it to deer density and local characteristics such as dominant tree species, occurrence of artificial feeding, altitude, region and size of the study site. We also review the importance of bark in red deer diets over the seasons and discuss the causes of bark‐stripping, focusing on the significance of bark as food.
• 2 Over the 36 sites examined, the rate of bark‐stripping was highly variable (from 0 to 84% of susceptible trees debarked), with less damage in Scotland than in other European sites for which bark‐stripping rates were higher at high red deer density. Altitude, the size of the study site, the number of dominant tree species and the occurrence of artificial feeding do not significantly relate to the rate of bark‐stripping.
• 3 Bark sometimes made up a large proportion of red deer diet (> 10%), especially in areas with severe winters (high levels of snow), whereas in study sites with mild winters, bark was practically not eaten at all.
• 4 These results suggest that severe bark‐stripping could be related to a reduction in food resource availability. This food availability hypothesis needs to be better documented, dealing particularly with the possible interaction between food availability and red deer density.

     

Woody biomass production during the second rotation of a bio-energy Populus plantation increases in a future high CO2 world

The quickly rising atmospheric carbon dioxide (CO₂)‐levels, justify the need to explore all carbon (C) sequestration possibilities that might mitigate the current CO₂ increase. Here, we report the likely impact of future increases in atmospheric CO₂ on woody biomass production of three poplar species (Populus alba L. clone 2AS‐11, Populus nigra L. clone Jean Pourtet and Populus×euramericana clone I‐214). Trees were growing in a high‐density coppice plantation during the second rotation (i.e., regrowth after coppice; 2002–2004; POPFACE/EUROFACE). Six plots were studied, half of which were continuously fumigated with CO₂ (FACE; free air carbon dioxide enrichment of 550 ppm). Half of each plot was fertilized to study the interaction between CO₂ and nutrient fertilization. At the end of the second rotation, selective above‐ and belowground harvests were performed to estimate the productivity of this bio‐energy plantation. Fertilization did not affect growth of the poplar trees, which was likely because of the high rates of fertilization during the previous agricultural land use. In contrast, elevated CO₂ enhanced biomass production by up to 29%, and this stimulation did not differ between above‐ and belowground parts. The increased initial stump size resulting from elevated CO₂ during the first rotation (1999–2001) could not solely explain the observed final biomass increase. The larger leaf area index after canopy closure and the absence of any major photosynthetic acclimation after 6 years of fumigation caused the sustained CO₂‐induced biomass increase after coppice. These results suggest that, under future CO₂ concentrations, managed poplar coppice systems may exhibit higher potential for C sequestration and, thus, help mitigate climate change when used as a source of C‐neutral energy.     

Novel microsatellite DNA markers for the threatened African endemic tree species,Milicia excelsa (Moraceae), and cross‐species amplification in Milicia regia

Eleven microsatellite primer pairs were developed for the tropical African tree Milicia excelsa. Genomic DNA was enriched for dinucleotide (TC_n and TG_n) and tretranucleotide (GATA_n), and 188 random clones were sequenced from both orientations. We designed and tested 44 oligonucleotide primer pairs, which were evaluated using genomic DNA from 30 M. excelsa mature trees collected from a natural population in Benin. Eleven of the 44 markers showed good amplification and were polymorphic. The number of putative alleles for polymorphic primer pairs varied from three to seven, with expected and observed heterozygosities ranging from 0.10 to 0.64 and from 0.10 to 0.80, respectively. All 11 loci amplified the related species Milicia regia, indicating that these primers will be useful for population and ecology genetic studies in other species of the genus Milicia.     

Characterization of polymorphic microsatellite loci within a young Boophilus microplus metapopulation

Nine microsatellite loci from the cattle tick Boophilus microplus were isolated and characterized within New Caledonia. This Pacific island was invaded by the cattle tick from a few immigration events dating from mid‐20th century. A population survey involving 94 adult ticks indicated monomorphism at one locus, presence of null alleles at another, and high genetic diversity (0.61–0.72) at seven loci apparently suitable for population genetics studies. This opens the opportunity to dissect the populational mechanisms involved in the spectacular capacity of B. microplus to cope with local environmental heterogeneity during its recurrent invasions of tropical areas.     

Association between DRD4 gene polymorphism and personality variation in great tits: a test across four wild populations

Polymorphisms in the dopamine receptor D4 gene (DRD4) have been related to individual variation in novelty‐seeking or exploratory behaviour in a variety of animals, including humans. Recently, the human DRD4 orthologue was sequenced in a wild bird, the great tit (Parus major) and a single nucleotide polymorphism in exon 3 of this gene (SNP830) was shown to be associated with variation in exploratory behaviour of lab‐raised individuals originating from a single wild population. Here we test the generality of this finding in a large sample of free‐living individuals from four European great tit populations, including the originally sampled population. We demonstrate that the association between SNP830 genotype and exploratory behaviour also exists in free‐living birds from the original population. However, in the other three populations we found only limited evidence for an association: in two populations the association appeared absent; while in one there was a nonsignificant tendency. We could not confirm a previously demonstrated interaction with another DRD4 polymorphism, a 15 bp indel in the promoter region (ID15). As yet unknown differences in genetic or environmental background could explain why the same genetic polymorphism (SNP830) has a substantial effect on exploratory behaviour in one population, explaining 4.5–5.8% of the total variance—a large effect for a single gene influencing a complex behavioural trait—but not in three others. The confirmation of an association between SNP830 genotype and personality‐related behaviour in a wild bird population warrants further research into potential fitness effects of the polymorphism, while also the population differences in the strength of the association deserve further investigation. Another important future challenge is the identification of additional loci influencing avian personality traits in the wild.     

Extended larval development time for aphid parasitoids in the presence of plant endosymbionts

Abstract 1. Variation in plant chemistry does not only mediate interactions between plants and herbivores but also those between herbivores and their natural enemies, and plants and natural enemies. 2. Endophytic fungi complete their whole life cycle within the host plant’s tissue and are associated with a large diversity of plant species. Endophytes of the genus Neotyphodium alter the chemistry of the host plant by producing herbivore toxic alkaloids. 3. Here we asked whether the endophyte‐tolerant aphid species Metopolophium festucae could be defended against its parasitoid Aphidius ervi when feeding on endophyte‐infected plants. In a laboratory experiment, we compared life‐history traits of A. ervi when exposed to hosts on endophyte‐infected or endophyte‐free Lolium perenne. 4. The presence of endophytes significantly increased larval and pupal development times, but did not affect the mortality of immature parasitoids or the longevity of the adults. Although the number of parasitoid mummies tended to be reduced on endophyte‐infected plants, the number of emerging parasitoids did not differ significantly between the two treatments. 5. This shows that the metabolism of individual aphids feeding on infected plants may be changed and help in the defence against parasitoids. An increase in parasitoid development time should ultimately reduce the population growth of A. ervi. Therefore, endophyte presence may represent an advantage for endophyte‐tolerant aphid species through extended parasitoid development and its effect on parasitoid population dynamics.