A preliminary checklist of saproxylic beetles (Coleoptera) in the Hyrcanian forests of Iran, with distributional data

Saproxylic beetles play a vital role in conservation as indicators of the status of unmanaged forests. In light of the concern regarding the adverse impact of anthropogenic pressure on biodiversity, an essential step in forest conserva-tion strategy is the identification of saproxylic beetles. The Hyrcanian forests are a unique remnant of natural broadleaf temperate forests, with an evolutionary history that can be traced to the Tertiary and a high diversity tree species. Here we present the first checklist of saproxylic beetles in the Hyrcanian forests, including 398 species of saproxylic beetles, belonging to 207 genera and 46 families, identified by us. Based on our results and literature data, at least 670 saproxylic beetles occur in the Hyrcanian forests. The bias in our results towards some families supports the view that the detection of additional species can be expected, particularly from the forests with a greater diversity of tree species

The contribution of insects to global forest deadwood decomposition

The amount of carbon stored in deadwood is equivalent to about 8 per cent of the global forest carbon stocks. The decomposition of deadwood is largely governed by climate with decomposer groups—such as microorganisms and insects—contributing to variations in the decomposition rates. At the global scale, the contribution of insects to the decomposition of deadwood and carbon release remains poorly understood. Here we present a field experiment of wood decomposition across 55 forest sites and 6 continents. We find that the deadwood decomposition rates increase with temperature, and the strongest temperature effect is found at high precipitation levels. Precipitation affects the decomposition rates negatively at low temperatures and positively at high temperatures. As a net effect—including the direct consumption by insects and indirect effects through interactions with microorganisms—insects accelerate the decomposition in tropical forests (3.9% median mass loss per year). In temperate and boreal forests, we find weak positive and negative effects with a median mass loss of 0.9 per cent and −0.1 per cent per year, respectively. Furthermore, we apply the experimentally derived decomposition function to a global map of deadwood carbon synthesized from empirical and remote-sensing data, obtaining an estimate of 10.9 ± 3.2 petagram of carbon per year released from deadwood globally, with 93 per cent originating from tropical forests. Globally, the net effect of insects may account for 29 per cent of the carbon flux from deadwood, which suggests a functional importance of insects in the decomposition of deadwood and the carbon cycle

Floral preferences of hoverflies (Diptera: Syrphidae) in response to the abundance and species richness of flowering plants

<p>For understanding the relationship between floral resources and the abundance of hoverflies, five meadows were selected at different elevations in a forested region. At each site the number of flowering herbaceous plants was assessed along a transect at 10-m intervals. To measure floral density, we counted the number of open flowers per species in each plot. Hoverflies visiting flowering plants were captured in each plot during 10 minutes. Path analysis showed that there was a negative correlation between plant species richness and syrphid abundance. Flower abundance had a strong positive direct effect on syrphid abundance but had indirect effects on the number of syrphid species. Only altitude had a strong positive direct effect on the number of syrphid species and this may be explained by the different climatic conditions. Some plant species attracted more syrphids than others. There were significantly fewer species of hoverfly per plot with increasing numbers of flowers. We interpret this to mean that plant species with a high density of flowers attracted more syrphids of the same species. Analysis of pollen grains extracted from two species of hoverflies showed that flower constancy occurred in three examined sites.</p