Multi-scale analysis of responses of stream macrobenthos to forestry activities and environmental context

1. Forestry activities can greatly modify the structure and function of invertebrate communities in streams, but the ability to detect effects of forestry may depend on the spatial scale considered, the choice of response metric and the environmental context. In this study, a multi‐scale, multi‐metric approach was used to compare the usefulness of proximate and larger‐scale measurements of forestry activity for understanding the impacts of forestry on stream macrobenthos. 2. Site‐specific responses of macrobenthic communities to forestry activities measured at four spatial scales (sub‐basin and 8‐, 2‐ and 0.5‐km radii upstream of study sites) were examined for 90 riffle sites distributed among 22 tributary streams (Strahler order 1–5) of the Cascapedia River basin, Quebec, Canada. 3. Multiple regression models and canonical correspondence analysis were used to relate six biological metrics (taxonomic richness, numerical density, biomass density, normalised biomass spectrum, individual body mass and community structure) to variables quantifying logging 1–19 years prior to the study and road density. Environmental predictors (variables quantifying local habitat or landscape features) were included in all analyses to statistically account for environmental context and increase the likelihood of detecting potentially subtle forestry impacts. 4. Forestry activities measured at the larger (sub‐basin and 8 km) scales were linked to decline in taxonomic richness, increase in numerical and biomass densities and shift in size structure of benthic macroinvertebrates, indicating that analyses encompassing larger areas, up to the full basin, may allow for more sensitive detection of effects than those of more limited span. 5. These responses primarily reflected marked increases in the abundance of chironomids and decline in the number of trichopteran taxa with increasing areal coverage of recent (≤2–4 years) cuts, suggesting that larger, longer‐lived and possibly more specialised taxa were more vulnerable to forestry impacts than smaller, multivoltine, generalist invertebrates. After partialling out the influence of other variables, rapid decline in richness occurred even when <1% of the basin had been clear cut in the year prior to the study. 6. Effects of forestry were detected after statistically accounting for natural environmental variability, which may have otherwise concealed those effects. The combined use of multiple biological metrics, partialling out of environmental effects and measurement of impacts at multiple spatial scales may be a broadly applicable approach for enhancing sensitivity and facilitating interpretation in studies of anthropogenic effects on macroinvertebrate communities.     

Role of terpenes from aphid-infested potato on searching and oviposition behavior of Episyrphus balteatus

To cope with pathogen and insect attacks, plants develop different mechanisms of defence, in both direct （physical and chemical） and indirect ways （attractive volatiles to entomophagous beneficials）. Plants are then able to express traits that facilitate ＂top-down＂ control of pests by attracting herbivore predators. Here we investigate the indirect defence mechanism of potato plants by analyzing the volatile patterns of both healthy and aphid- infested plants. Important changes in the emitted terpene pattern by the Myzus persicae infested host plant were observed. Using Solid Phase MicroExtraction （SPME） and GC-MS, the （E）-fl-farnesene （EBF） appeared to be emitted by aphid-infested potato and not by healthy plants. To assess the infochemical role of these volatile releases after aphid damage on the aphidophagous predators Episyrphus balteams, the hoverfly foraging behavior was assessed using the Observer 5.0 software （Noldus, Wageningen, The Netherlands）. Aphidfree potato plants were also used as a control volatile source in the predator behavioral study. While aphid-infested plants induced efficient searching and acceptation behaviors leading to egg-laying, no kairomonal effect of healthy potato plants was observed, leading to longer immobility durations and shorter searching periods in the net cage. High oviposition rate of E. balteatus was observed when aphid-infested potato was used （mean of 48.9 eggs per laying and per female）. On the other hand, no egg was produced by the hoverfly on healthy aphid-free plants. The E. balteatus foraging and reproductive behaviors according to the volatile emission from aphid-infested plants are discussed in relation to the potential use of active infochemical molecules in integrated aphid pest management.     

Pollinator attraction in Anacamptis papilionacea (Orchidaceae): a food or a sex promise?

The Mediterranean orchid Anacamptis papilionacea , despite showing a typical food-deceptive floral display, has also been reported to frequently attract male pollinators, suggesting a potentiality for sexual attraction. In a survey from a southern Italian population of A. papilionacea and their hybrids with Anacamptis morio , we collected 37 pollinators belonging to five bee species carrying 126 orchid pollinia. The main pollinator of A. papilionacea was Anthophora crinipes male (48.6%), but the number of females was not negligible (22.9%). We also found pollinator sharing between the hybrid and the parental species. Our findings confirm that, contrary to other food-deceptive species, A. papilionacea mainly attracts male insects, but also that, in contrast to sexually deceptive species, this attraction is not specific. We suggest that A. papilionacea adopts a complex mix of food and sexually deceptive pollination and could represent a helpful model for studying the transition between different pollination strategies.