The evolutionary history of Trichoptera (Insecta): A case of successful adaptation to life in freshwater

The insect order Trichoptera (caddisflies) forms the second most species‐rich monophyletic group of animals in freshwater. So far, several attempts have been made to elucidate its evolutionary history with both morphological and molecular data. However, none have attempted to analyse the time frame for its diversification. The order is divided into three suborders – Annulipalpia, Integripalpia and ‘Spicipalpia’. Historically, the most problematic taxon to place within the order is ‘Spicipalpia’, whose larvae do not build traditional cases or filtering nets like the majority of the caddisflies. They have previously been proposed to be the sister group of all other Trichoptera or more advanced within the order, with equivocal monophyly and with different interordinal placements among various studies. In order to resolve the evolutionary history of the caddisflies as well as timing their diversification, we utilized fragments of three nuclear (carbamoylphosphate synthethase, isocitrate dehydrogenase and RNA polymerase II) and one mitochondrial (cytochrome oxidase I) protein coding genes, with 16 fossil trichopteran taxa used for time calibration. The ‘spicipalpian’ families are recovered as ancestral to all other caddisflies, though paraphyletic. We recover stable relationships among most families and superfamilies, resolving many previously unrecognized phylogenetic affinities amongst extant families. The origin of Trichoptera is estimated to be around 234 Ma, i.e. Middle – Late Triassic.     

Fatty acid composition of consumers in boreal lakes – variation across species,space and time

1. Fatty acids (FAs) have been widely applied as trophic biomarkers in aquatic food web studies. However, current knowledge of inter‐ and intraspecific variation in consumer FA compositions across spatial and temporal scales is constrained to a few pelagic taxa. 2. We analysed the FAs of 22 taxa of benthic macroinvertebrates, zooplankton and fish collected from the littoral, pelagic and profundal habitats of nine boreal oligotrophic lakes over spring, summer and autumn. We quantified and compared the FA variance partitions contributed by species identity (i.e. an integrative effect of phylogenetic origin, life history and functional feeding guild of individual taxa), site and season using partial redundancy analysis both on all consumers and on benthic arthropods alone. 3. Species identity alone contributed 84.4 and 72.8% of explained FA variation of all consumers and benthic arthropods, respectively. Influences of site, season and all joint effects accounted for 0–11.3% only. Fatty acid profiles of primary consumers differentiated below class level, but those of predators were distinguishable only when they became more taxonomically distinct (i.e. among classes or higher). 4. Pelagic and profundal consumers showed stronger reliance on autochthonous resources than did their littoral counterparts as reflected by their higher ω3 to ω6 FA ratios. Polyunsaturated FAs (PUFAs) were increasingly retained with trophic levels, and saturated FAs (e.g. FA 16 : 0) gradually reduced. Ecologically, this trade‐off enhances the trophic transfer efficiency and confirms the importance of PUFA‐rich autotrophs in aquatic food webs. 5. Our findings indicate strong interspecific differences in FA requirements and assimilation among aquatic consumers from a wide range of taxonomic levels, habitats and lakes. Consumers were able to maintain homoeostasis in FA compositions across spatial and temporal changes in resource FAs, but consumer homoeostasis did not limit the effectiveness of FAs as trophic biomarkers.     

Molecular phylogeny of Sericostomatoidea (Trichoptera) with the establishment of three new families

We inferred the phylogenetic relationships among 58 genera of Sericostomatoidea, representing all previously accepted families as well as genera that were not placed in established families. The analyses were based on five fragments of the protein coding genes carbamoylphosphate synthetase (CPSase of CAD), isocitrate dehydrogenase (IDH), Elongation factor 1a (EF‐1a), RNA polymerase II (POL II) and cytochrome oxidase I (COI). The data set was analysed using Bayesian methods with a mixed model, raxml , and parsimony. The various methods generated slightly different results regarding relationships among families, but the shared results comprise support for: (i) a monophyletic Sericostomatoidea; (ii) a paraphyletic Parasericostoma due to inclusion of Myotrichia murina, leading to synonymization of Myotrichia with Parasericostoma; (iii) a polyphyletic Sericostomatidae, which is divided into two families, Sericostomatidae sensu stricto and Parasericostomatidae fam.n. ; (iv) a polyphyletic Helicophidae which is divided into Helicophidae sensu stricto and Heloccabucidae fam.n. ; (v) hypothesized phylogenetic placement of the former incerta sedis genera Ngoya, Seselpsyche and Karomana; (vi) a paraphyletic Costora (Conoesucidae) that should be divided into several genera after more careful examination of morphological data; (vii) reinstatement of Gyrocarisa as a valid genus within Petrothrincidae. A third family, Ceylanopsychidae fam.n. , is established based on morphological characters alone. A hypothesis of the relationship among 14 of the 15 families in the superfamily is presented. A key to the families is presented based on adults (males). Taxonomic history, diagnosis, habitat preference and distribution data for all sericostomatoid families are presented. This published work has been registered in ZooBank, http://zoobank.org/urn:lsid:zoobank.org:pub:CF6A6B9F‐6A72‐4265‐BD09‐3A710DFCD7B1 .     

Effect of nitrogen nutrition on the concentration of viruses, phospholipids and galactolipids of barley leaves infected with barley stripe mosaic virus (BSMV)

The effect of infection of barley with barley stripe mosaic virus on the chlorophyll, phospholipid and galactolipid content was examined in plants grown in sand culture with a range of nitrogen concentrations. The systemic yellowing and mosaic symptoms of infection were associated with a reduction in the chlorophyll and galactolipid content and an increase in the phospholipid content of leaves. The effects of the virus were not reversed by high nitrogen. The effects of virus infection are interpreted as a stress-induced phenomenon and the effects compared with those brought about by other stresses.     

Somatic Hybridization of Nitrate Reductase Deficient Mutants of Nicotiana tabacum by Protoplast Fusion

Protoplasts were isolated from two mutant cell lines of Nicotiana tabacum L. cv. Gatersleben and fused with the aid of polyethylene glycol. Both mutants lacked nitrate reductase and were thus auxotrophic for reduced nitrogen. The fusion resulted in a high frequency of hybrid cells which were detected by their regained ability to grow in media containing nitrate as sole nitrogen source. Thus, the two mutants were found to complement each other in the hybrids. In control experiments, back mutation and cross-feeding were excluded as possible explanations for the occurrence of cell lines utilizing nitrate. A total of 1061 hybrid lines capable of sustained proliferation were isolated. Some of them were further characterized with respect to nitrate reductase activity, chlorate sensitivity, chromosome number, and shoot formation. The results demonstrate that protoplast fusion can be used for the genetic analysis of cell variants of higher plants and that nitrate reductase-deficient mutants provide efficient selective systems for hybrid cells.     

Selective Degradation of Wood Components by White-Rot Fungi

In order to find naturally occurring white-rot fungi which preferentially degrade lignin. 25 different species of such fungi were cultivated on pine wood blocks and on kraft lignin agar plates with and without cellulose. Due to differences in phenol oxidase reactions on the kraft lignin agar plates, the 25 fungi could be divided into two groups, 1 and 2, which also differed in other properties. The three Group I fungi Sporotrichum pulverulentum, Phanerochaete sp. L1 and Polyporus dichrous produced high levels of endo-l,4-β-glucanase and cellobiose:quinone oxidoreductase in shaking cellulose flasks and a low level of phenol oxidase in standing wood meal flasks, The four fungi Merulius tremellosus, Phlebia radiata, Pycuoporus cinnabarinus and Pleurotus ostreatus from Group 2, on the other hand, produced low levels of endo-1,4-β-glucanase and cellobiose:.quinone oxidoreductase in the cellulose. flasks and a high level of phenol oxidase in the wood meal flasks. Analyses of pine wood blocks degraded by the above-mentioned fungi in the presence of either malt extract, asparagine or NH₄H₂PO₄ revealed that malt extract gave good lignin degradation. In the presence of this nutrient source. P. cinnabarinus, at 3.4% weight loss, even degraded 12.5% lignin without loss of cellulose or mannan. No common degradation pattern was, however, obtained using mall extract, asparagine or NH₄H₂PO₄, It is suggested that while-rot fungi, which preferentially degrade lignin, may be found among Group 2 fungi producing large amounts of phenol oxidases.