Benzothiadiazole affects the leaf proteome in arctic bramble (Rubus arcticus)

Benzothiadiazole (BTH) induces resistance to the downy mildew pathogen, Peronospora sparsa, in arctic bramble, but the basis for the BTH‐induced resistance is unknown. Arctic bramble cv. Mespi was treated with BTH to study the changes in leaf proteome and to identify proteins with a putative role in disease resistance. First, BTH induced strong expression of one PR‐1 protein isoform, which was also induced by salicylic acid (SA). The PR‐1 was responsive to BTH and exogenous SA despite a high endogenous SA content (20–25 µg/g fresh weight), which increased to an even higher level after treatment with BTH. Secondly, a total of 792 protein spots were detected in two‐dimensional gel electrophoresis, eight proteins being detected solely in the BTH‐treated plants. BTH caused up‐ or down‐regulation of 72 and 31 proteins, respectively, of which 18 were tentatively identified by mass spectrometry. The up‐regulation of flavanone‐3‐hydroxylase, alanine aminotransferase, 1‐aminocyclopropane‐1‐carboxylate oxidase, PR‐1 and PR‐10 proteins may partly explain the BTH‐induced resistance against P. sparsa. Other proteins with changes in intensity appear to be involved in, for example, energy metabolism and protein processing. The decline in ATP synthase, triosephosphate isomerase, fructose bisphosphate aldolase and glutamine synthetase suggests that BTH causes significant changes in primary metabolism, which provides one possible explanation for the decreased vegetative growth of foliage and rhizome observed in BTH‐treated plants.     

Foraging activity and dietary spectrum of wood ants (Formica rufa group) and their role in nutrient fluxes in boreal forests

Abstract 1. We monitored three different‐sized wood ant (Formica aquilonia Yarrow) mounds over a 3‐year period in Finnish boreal forests dominated by Norway spruce (Picea abies Karst.), to assess the seasonal temperature dependency of ant activity. Additionally, we also monitored Norway spruce trees around the mounds for descending honeydew foragers. 2. The amount of collected honeydew and prey and its composition, as well as the carbon (C), nitrogen (N), and phosphorus (P) in honeydew and invertebrate prey was also investigated. 3. The number of warm days (average temperature above 20 °C) and the amount of precipitation differed among the years. Ant activity at the mounds (but not on the trees) was highly correlated with air temperature throughout the ant‐active season (May–September), but ant activity in spring and autumn was lower than in summer at similar temperatures. During all 3 years, honeydew played a major role in wood ant nutrition (78–92% of dry mass). Invertebrate prey was mainly Diptera (on average 26.2%), Coleoptera (12.5%), Aphidina (9.3%), and Arachnoida (8.5%). 4. The total amounts of C, N, and P input brought into the ant mounds in the form of food (both honeydew and prey) on the stand level were 12.6–39.0, 1.6–4.6 and 0.1–0.4 kg ha^?1 year^?1, respectively, which is equivalent to 2–6%, 12–33% and 27–58% of the fluxes in annual needle litterfall in typical boreal Norway spruce forests. Thus, wood ants can play a significant role in short term and local N and P cycling of boreal forest ecosystems.     

Concordant phylogeography and cryptic speciation in two Western Palaearctic oak gall parasitoid species complexes

Little is known about the evolutionary history of most complex multi‐trophic insect communities. Widespread species from different trophic levels might evolve in parallel, showing similar spatial patterns and either congruent temporal patterns (Contemporary Host‐tracking) or later divergence in higher trophic levels (Delayed Host‐tracking). Alternatively, host shifts by natural enemies among communities centred on different host resources could disrupt any common community phylogeographic pattern. We examined these alternative models using two Megastigmus parasitoid morphospecies associated with oak cynipid galls sampled throughout their Western Palaearctic distributions. Based on existing host cynipid data, a parallel evolution model predicts that eastern regions of the Western Palaearctic should contain ancestral populations with range expansions across Europe about 1.6 million years ago and deeper species‐level divergence at both 8–9 and 4–5 million years ago. Sequence data from mitochondrial cytochrome b and multiple nuclear genes showed similar phylogenetic patterns and revealed cryptic genetic species within both morphospecies, indicating greater diversity in these communities than previously thought. Phylogeographic divergence was apparent in most cryptic species between relatively stable, diverse, putatively ancestral populations in Asia Minor and the Middle East, and genetically depauperate, rapidly expanding populations in Europe, paralleling patterns in host gallwasp species. Mitochondrial and nuclear data also suggested that Europe may have been colonized multiple times from eastern source populations since the late Miocene. Temporal patterns of lineage divergence were congruent within and across trophic levels, supporting the Contemporary Host‐tracking Hypothesis for community evolution.     

A microsatellite linkage map for Drosophila montana shows large variation in recombination rates,and a courtship song trait maps to an area of low recombination

Current advances in genetic analysis are opening up our knowledge of the genetics of species differences, but challenges remain, particularly for out‐bred natural populations. We constructed a microsatellite‐based linkage map for two out‐bred lines of Drosophila montana derived from divergent populations by taking advantage of the Drosophila virilis genome and available cytological maps of both species. Although the placement of markers was quite consistent with cytological predictions, the map indicated large heterogeneity in recombination rates along chromosomes. We also performed a quantitative trait locus (QTL) analysis on a courtship song character (carrier frequency), which differs between populations and is subject to strong sexual selection. Linkage mapping yielded two significant QTLs, which explained 3% and 14% of the variation in carrier frequency, respectively. Interestingly, as in other recent studies of traits which can influence speciation, the strongest QTL mapped to a genomic region partly covered by an inversion polymorphism.     

Avian predation on a parasitic fly of cervids during winter: can host‐related cues increase the predation risk?

The deer ked (Lipoptena cervi) is an ectoparasitic fly on cervids that has expanded its distribution rapidly in Northern Europe. However, the regulating biotic factors such as predation remain unknown. The host‐independent pupal stage of the fly lasts for several months. Blackish pupae are visible against snow, especially on the bedding sites of hosts, and are thus exposed to predators. To evaluate the role of predation on the invasion dynamics and evolution of L. cervi, we monitored pupal predation on artificial bedding sites in three geographical areas in Finland during winter. We explored: (1) possible predators; (2) magnitude of predation; and (3) whether predation risk is affected by host‐derived cues. We demonstrate that pupae are predated by a number of tit species. Any reddish brown snow discoloration on bedding sites, indicating heavy infestation of the host, serves as an exploitable cue for avian predators, thereby increasing the risk of pupal predation. The ability of tits to use this host‐derived cue seems to be dependent on the prevalence of L. cervi and the period of invasion history, which suggests that it may be a learned behavioural response. Predation by tits may potentially affect the L. cervi population dynamics locally. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 106 , 275–286.     

The influence of large wood on brown trout (Salmo trutta) behaviour and surface foraging

1. Changes in riparian vegetation owing to forest harvesting may affect the input of large wood, a major structural element, to streams. Studies of large wood impacts on stream fish have focused on population‐level responses, whereas little attention has been given to how wood affects fish behaviour. 2. In a laboratory stream experiment, we tested how two size classes of brown trout, Salmo trutta, (mean size of 85 and 125 mm), alone and together, responded to a gradient of large wood in terms of activity, foraging on terrestrial drift and interactions between conspecifics. 3. The results showed that the presence of large wood significantly reduced the overall activity of the fish, the number of agonistic interactions between individuals and the proportion of captured prey. However, activity decreased relatively more than the proportion of captured prey, resulting in a significant positive net effect of wood on the number of prey captures per time spent active (PTA). This indicates that trout living in habitats with high wood density may have a higher net energy gain than trout living in habitats with less wood. 4. There were no observable size‐class differences in the benefits of large wood or in the utilisation of surface‐drifting terrestrial prey. 5. These results suggest that the presence of large wood may be an important factor shaping stream communities and that a lack of structural complexity may decrease energy gain, increase agonistic interactions and, consequently, lower the production of brown trout.     

Ultrastructure of the Fusion Area during Conjugation in the Suctorian Heliphrya erhardi (Rieder) Matthes*

SYNOPSIS. The suctorian Heliophrya erhardi (Rieder) Matthes is attached to the substrate by the flattened ventral side of the cell body. The dorsal is covered by a pellicle composed of 3 unit membranes. Below the pellicle is a 0.4–0.8-μm thick epiplasm composed of 6–8-nm thick fibrils. Microtubules form a network beneath the epiplasm. The epipalsm is penetrated by tube-like pellicular pits, which are lined by the cell membrane and end beneath the epiplasm in a saccule-like enlargement. During conjugation, 2 neighboring organisms form cytoplasmic processes which come into contact and fuse, thus forming a cytoplasmic bridge between the 2 cells. Around the bridge the pellicles of both organisms fuse, and the partners become united by a continuous common membrane system. Across the entire conjugation bridge the 2 fused epiplasms form a septum. Tube-like structures can be seen lying partly in the epiplasmic septum and partly in the adjacent cytoplasm. These structures are open at both ends and represent remnants of the pellicular pits. No trace of the original pellicular membranes can be found at the fusion area within the epiplasmic septum. The cytoplasm of the conjugation partners is separated only by the fused epiplasms forming the epiplasmic septum.     

Aphid and host‐plant genotype × genotype interactions under elevated CO2

1. Elevated CO₂ can alter plant physiology and morphology, and these changes are expected to impact diet quality for insect herbivores. While the plastic responses of insect herbivores have been well studied, less is known about the propensity of insects to adapt to such changes. Genetic variation in insect responses to elevated CO₂ and genetic interactions between insects and their host plants may exist and provide the necessary raw material for adaptation. 2. We used clonal lines of Rhopalosiphum padi (L.) aphids to examine genotype‐specific responses to elevated CO₂. We used the host plant Schedonorus arundinaceus (tall fescue; Schreb), which is capable of asexual reproduction, to investigate host plant genotype‐specific effects and possible host plant‐by‐insect genotype interactions. The abundance and density of three R. padi genotypes on three tall fescue genotypes under three concentrations of CO₂ (ambient, 700, and 1000 ppm) in a controlled greenhouse environment were examined. 3. Aphid abundance decreased in the 700 ppm CO₂ concentration, but increased in the 1000 ppm concentration relative to ambient. The effect of CO₂ on aphid density was dependent on host plant genotype; the density of aphids in high CO₂ decreased for two plant genotypes but was unchanged in one. No interaction between aphid genotype and elevated CO₂ was found, nor did we find significant genotype‐by‐genotype interactions. 4. This study suggests that the density of R. padi aphids feeding on tall fescue may decrease under elevated CO₂ for some plant genotypes. The likely impact of genotype‐specific responses on future changes in the genetic structure of plant and insect populations is discussed.