Fredrik Schlyter - Academia.edu (original) (raw)

Papers by Fredrik Schlyter

Canadian Entomologist, Dec 1, 2000

The Canadian Entomologist 32: 965-981 (2000) Leaf and bark volatiles from non-host birches, Betul... more The Canadian Entomologist 32: 965-981 (2000) Leaf and bark volatiles from non-host birches, Betula pendula Roth. and Betula pubescens Ehrh. (Betulaceae), and aspen, Populus tremula L. (Salicaceae), were tested on spring-dispersing Tomicus piniperda (L.) and Tomicus minor (Hart.) by gas chromatographicelectroantennographic detection (GC-EAD) and by attractantbaited traps in southern Sweden. GC-EAD analysis of the head-space volatiles from fresh bark chips of B. pendula revealed two green leaf alcohols, I-hexanol and (273hexen-1-01, that consistently elicited antennal responses by T. piniperda and T. minor. Further analyses with synthetic mixtures showed that the antennae of these two Tomicus species also responded to other green leaf alcohols, such as (E)-2-hexen-1-01 found from the non-host leaves, and C,-alcohols, 3-octanol and I-octen-3-01, from bark of non-host birches and aspen. No antennal responses of the Tomicus species were observed to green leaf C6-aldehydes and C6-acetate or to non-host bark volatiles like trans-conophthorin, benzaldehyde, salicylaldehyde, and benzyl alcohol. In field trapping experiments, blends of electrophysiologically active green leaf alcohols or C,-alcohols resulted in reductions (>60%) in the number of T. piniperda captured compared with that for the kairomone-baited trap. When these two blends were combined, trap catch was further reduced (90%), which was not significantly different from that for the blank control. Neither the blend of two green leaf aldehydes plus the acetate nor the bark compounds trans-conophthorin or benzyl alcohol reduced trap catches. Tomicus minor had a response pattern similar to that of T. piniperda. Hylurgops palliarus (Gyll.) (Coleoptera: Scolytidae) was attracted to the combination of kairomone and verbenone but not to kairomone and was not affected by the blends of green leaf volatiles. Our results suggest that selected leaf-bark C6-alcohols and the bark C8-alcohols may have potential in developing semiochemical-based management programs against both pine shoot beetles by repelling them from suitable breeding and feeding sites.

Ecology and Evolution, Jul 1, 2022

The Eurasian spruce bark beetle, Ips typographus, is a major pest, capable of killing spruce fore... more The Eurasian spruce bark beetle, Ips typographus, is a major pest, capable of killing spruce forests during large population outbreaks. Recorded dispersal distances of individual beetles are typically within hundreds of meters or a few kilometers. However, the connectivity between populations at larger distances and longer time spans and how this is affected by the habitat is less studied, despite its importance for understanding at which distances local outbreaks may spread. Previous population genetic studies in I. typographus typically used low resolution markers. Here, we use genome‐wide data to assess population structure and connectivity of I. typographus in Sweden. We used 152 individuals from 19 population samples, distributed over 830 km from Strömsund (63° 46′ 8″ N) in the north to Nyteboda (56° 8′ 50″ N) in the south, to capture processes at a large regional scale, and a transect sampling design adjacent to a recent outbreak to capture processes at a smaller scale (76 km). Using restriction site‐associated DNA sequencing (RADseq) markers capturing 1409–1997 SNPs throughout the genome, we document a weak genetic structure over the large scale, potentially indicative of high connectivity with extensive gene flow. No differentiation was detected at the smaller scale. We find indications of isolation‐by‐distance both for relative (F ST) and absolute divergence (Dxy). The two northernmost populations are most differentiated from the remaining populations, and diverge in parallel to the southern populations for a set of outlier loci. In conclusion, the population structure of I. typographus in Sweden is weak, suggesting a high capacity to disperse and establish outbreak populations in new territories.

Six compounds previously identified from hindguts of unmated male Ips typographus (L.) during hos... more Six compounds previously identified from hindguts of unmated male Ips typographus (L.) during host colonization: 2-methyl-3-buten-2-ol (MB), cis-verbenol (cV), trans-verbenol (tV), myrtenol (Mt), trans-myrtanol (tM), and 2-phenylethanol (PE), were tested for their attractivity in the field with a subtractive method. The amounts of MB and cV released from a pipe trap were similar to those given off from the commercial bait Ipslure as well as that from a Norway spruce tree, Picea abies (L.) Karst., under mass attack. The blend of the compounds became nonattractive when either MB or cV was subtracted, while subtraction of any of the other four compounds bad no effect. Addition of ipsdienol (Id) to the blend did not significantly increase the attraction. In a second comparative test, the addition of three compounds as a group (tV + Mt + PE) to MB + cV again had no effect on the attraction, but the addition of Id increased the catch somewhat. Addition of host logs to a bait releasing MB + cV at a rate lower than in previous experiments did not influence the attraction to pipe traps. Sticky traps containing natural pheromone sources (50 males in a log), which released 1-5 rag/day of MB as determined by aerations with deuterated MB as internal standard, were less attractive than a synthetic source releasing similar amounts of MB.

BMC Genomics, 2013

Background: The European spruce bark beetle, Ips typographus, and the North American mountain pin... more Background: The European spruce bark beetle, Ips typographus, and the North American mountain pine beetle, Dendroctonus ponderosae (Coleoptera: Curculionidae: Scolytinae), are severe pests of coniferous forests. Both bark beetle species utilize aggregation pheromones to coordinate mass-attacks on host trees, while odorants from host and non-host trees modulate the pheromone response. Thus, the bark beetle olfactory sense is of utmost importance for fitness. However, information on the genes underlying olfactory detection has been lacking in bark beetles and is limited in Coleoptera. We assembled antennal transcriptomes from next-generation sequencing of I. typographus and D. ponderosae to identify members of the major chemosensory multi-gene families. Results: Gene ontology (GO) annotation indicated that the relative abundance of transcripts associated with specific GO terms was highly similar in the two species. Transcripts with terms related to olfactory function were found in both species. Focusing on the chemosensory gene families, we identified 15 putative odorant binding proteins (OBP), 6 chemosensory proteins (CSP), 3 sensory neuron membrane proteins (SNMP), 43 odorant receptors (OR), 6 gustatory receptors (GR), and 7 ionotropic receptors (IR) in I. typographus; and 31 putative OBPs, 11 CSPs, 3 SNMPs, 49 ORs, 2 GRs, and 15 IRs in D. ponderosae. Predicted protein sequences were compared with counterparts in the flour beetle, Tribolium castaneum, the cerambycid beetle, Megacyllene caryae, and the fruit fly, Drosophila melanogaster. The most notable result was found among the ORs, for which large bark beetle-specific expansions were found. However, some clades contained receptors from all four beetle species, indicating a degree of conservation among some coleopteran OR lineages. Putative GRs for carbon dioxide and orthologues for the conserved antennal IRs were included in the identified receptor sets. Conclusions: The protein families important for chemoreception have now been identified in three coleopteran species (four species for the ORs). Thus, this study allows for improved evolutionary analyses of coleopteran olfaction. Identification of these proteins in two of the most destructive forest pests, sharing many semiochemicals, is especially important as they might represent novel targets for population control.

bioRxiv (Cold Spring Harbor Laboratory), Nov 28, 2020

The Eurasian spruce bark beetle (Ips typographus [L.]), is a major killer of spruce forests acros... more The Eurasian spruce bark beetle (Ips typographus [L.]), is a major killer of spruce forests across the Palearctic. During epidemics, it can destroy over 100 million cubic meters of spruce trees in a single year. Here we report a 236 Mb, highly contiguous I. typographus genome assembly using PacBio long-read sequencing. The final phased assembly had a contig N50 of 6.65 Mb in 272 contigs and was predicted to contain 23,923 protein-coding genes. Comparative genomic analysis revealed expanded gene families associated with plant cell wall degradation, including pectinases, aspartyl proteases, and glycosyl hydrolases. In today's forests, increasingly stressed by global warming, this resource can assist in mitigating bark beetle outbreaks by developing novel pest control strategies. Further, this first whole-genome sequence from the genus Ips provides timely resources to address important questions about the evolutionary biology and ecology of Curculionidae, the true weevils, one of the largest animal families.

Insect Biochemistry and Molecular Biology, Apr 1, 2016

Adaption to dietary changes is critical in the evolution of host plant ranges in polyphagous inse... more Adaption to dietary changes is critical in the evolution of host plant ranges in polyphagous insects. We compared three taxa of lepidopteran herbivores from the predominantly generalist genus Spodoptera showing different degrees of polyphagy: Spodoptera littoralis, with a broad host range including both mono-and dicotyledonous plants, and two Spodoptera frugiperda strains [Corn (i.e. maize) (C) and Rice (R)] adapted primarily to different grass species. When feeding on maize we show a lower performance in the broad generalist taxon compared to the grass adapted taxa. Among these taxa, the maize adapted S. frugiperda C-strain generally performed better than the R-strain on maize leaves. On artificial pinto diet, all taxa performed well. Our RNA-Seq analysis of midgut transcriptomes from 3rd instar larvae feeding on maize showed broader transcriptional readjustments in the generalist S. littoralis compared to grass adapted S. frugiperda strains. Substantial alteration in the expression levels of midgut physiological function related transcripts, such as digestive and detoxifying enzymes, transporters, immunity, and peritrophic membrane associated transcripts, existed in all taxa. We found high background expression of UDP-glucosyl transferases, which are known to neutralize maize leaf toxins, in the maize adapted S. frugiperda C-strain, contributing to its fitness on maize compared to the R-strain. Our findings provide evidence for divergent diet specific response of digestive physiology within these Spodoptera taxa. Unexpectedly, the C-and R-strains of S. frugiperda fed on the same diet showed large differences in expression patterns between these two closely related taxa.

PLOS ONE

Bark beetles vector symbiotic fungal species into their host trees during mass attacks. The symbi... more Bark beetles vector symbiotic fungal species into their host trees during mass attacks. The symbiotic relationship with blue stain fungi of the Ascomycetes, including genera of Endoconidiophora (syn. = Ceratocystis), promotes successful establishment whereby the microbes help to overcome the host trees’ defence and degrade toxic resins. This is the first study to evaluate both the volatile emissions from an insect-associated blue stain fungus over time and the insect response in a field trapping experiment. Volatile emissions from isolates of Endoconidiophora rufipennis (ER) were collected by solid-phase microextraction (SPME) and analysed by gas chromatography—mass spectroscopy (GC-MS) over a period of 30 days. This virulent North American fungus is closely related to E. polonica, a symbiotic fungus known from Eurasian spruce bark beetle Ips typographus.Nine volatiles were emitted by ER in substantial amounts: isoamyl acetate, sulcatone, 2-phenethyl acetate, geranyl acetone, gerany...

Forests, Dec 18, 2022

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

Agricultural and Forest Meteorology

Arthropod-Plant Interactions, 2021

The present study was conducted to determine the role of guava fruit volatiles in attraction, ovi... more The present study was conducted to determine the role of guava fruit volatiles in attraction, oviposition and associated fitness parameters of the peach fruit fly, Bactrocera zonata Saunders, which is a key pest of guava and many other fruits. B. zonata female flies’ attraction was observed in a Y-tube olfactometer using fruits of three locally grown guava varieties; Gola, Larkana Small Surahi (LSS) and Larkana Large Surahi (LLS). Female flies showed significantly higher levels of attraction to both un-infested and infested guava fruit odors compared to control (blank). In pairwise comparisons between different fruit varieties, females B. zonata showed significantly greater levels of attraction towards un-infested Gola compared to un-infested LSS, while in the case of the same variety, significantly higher number of flies were attracted to un-infested compared to infested fruit in all three tested varieties. In two-choice oviposition bioassays, B. zonata females made significantly more visits, greater numbers of ovipositions, spent a significantly longer time, and larger numbers of pupae and adults developed on Gola fruits compared to LSS fruits. However, in no-choice bioassays, females made more visits and spent a significantly greater amount of time on LSS compared to Gola and LLS. GC–MS analysis of guava headspace revealed presence of aliphatic and aromatic esters as a dominant group of compounds in both un-infested and fruit-fly-infested guava fruits, with a higher quantity mostly occurring in fruit-fly-infested fruits. Role of guava volatiles is discussed in an ecological context of attraction and oviposition behaviors of adult females and fitness of their offspring.

in the flour beetle, Tribolium castaneum, the cerambycid beetle, Megacyllene caryae, and the frui... more in the flour beetle, Tribolium castaneum, the cerambycid beetle, Megacyllene caryae, and the fruit fly, Drosophila

Pest Management Science, 2022

BACKGROUNDArvicolinae rodents are known pests causing damage to both agricultural and forest crop... more BACKGROUNDArvicolinae rodents are known pests causing damage to both agricultural and forest crops. Today, rodenticides for rodent control are widely discouraged owing to their negative effects on the environment. Rodents are the main prey for several predators, and their complex olfactory system allows them to identify risks of predation. Therefore, the potential use of predators' scents as repellents has gained interest as an ecologically based rodent control method. In a two‐choice experiment, we investigated the potential repellent effects of five synthetic predator compounds: 2‐phenylethylamine (2‐PEA), 2‐propylthietane (2‐PT), indole, heptanal and 2,5‐dihydro‐2,4,5‐trimethylthiazoline (TMT), at 1% and 5% doses, using the bank vole (Myodes glareolus) as a rodent model.RESULTSThe compound 2‐PEA reduced both the food contacts and the time spent by voles in the treatment arm compared to the control arm. Likewise, 2‐PT‐treated arms reduced the food contacts, and the voles spent...

PLOS ONE, 2014

Synthesis of racemic dehydro-conophthorin.</p

Pest Management Science, 2022

BACKGROUND Eurasian spruce bark beetles use both attractant and anti-attractant semiochemicals to... more BACKGROUND Eurasian spruce bark beetles use both attractant and anti-attractant semiochemicals to find suitable mature host trees. trans-4-thujanol is abundant in young, unsuitable spruce trees. The electrophysiological studies have demonstrated its high activity levels, but field data are lacking. RESULTS Enantioselective GC-MS analysis showed that only (1R,4S)-(+)-trans-4-thujanol was present in Norway spruce bark volatiles. In a factorial design field-trapping experiment, trans-4-thujanol alone was not attractive to Ips typographus. Traps baited with I. typographus' aggregation pheromone and trans-4-thujanol or the known anti-attractant 1,8-cineole caught fewer beetles than those baited with the aggregation pheromone alone. Catches for trans-4-thujanol and 1,8-cineole were dose-dependent. Intermediate doses of trans-4-thujanol and 1,8-cineole had the similar effect. Surprisingly, in contrast to 1,8-cineole and other known Ips anti-attractants, which all inhibit males more strongly than females, the addition of trans-4-thujanol to the aggregation pheromone reduced the attraction of females more. CONCLUSION The Norway spruce volatile (+)-trans-4-thujanol is a novel I. typographus anti-attractant with potency comparable to the known anti-attractants 1,8-cineole and verbenone and is more effective for females than for males. Incorporating (+)-trans-4-thujanol into anti-attractant lures could improve protection of trees from mass attack by I. typographus.

ESM_1 Fig. Educational scent platform. (PDF) <strong&gt... more ESM_1 Fig. Educational scent platform. (PDF) ESM_2 Fig. Training platform stimuli layout and decline in response to no target scent. (PDF) ESM_3 Table. Evaluation of the dog detection performance as number of indications with decreasing amounts of scent molecules over time. (PDF) ESM_4_V1 Video. Educational scent platform in operation. (AVI) ESM_4_V2 Video. Placement of cotton scent pad and the location of the scent by dog on a pine (a non-host tree of the beetle). (AVI) ESM_4_V3 Video. The search, GPS tracking, and location of natural attacks. (AVI) ESM_4_V4 Video. The search, location of two adjacent natural attacks, and rewarding. (AVI) The dog detection allows timely removal by sanitation logging of first beetle-attacked trees before offspring emergence, preventing local beetle increases. Detection dogs rapidly learned responding to synthetic bark beetle pheromone components, with known chemical titres, allowing search training during winter in laboratory and field. Dogs trained on synthetics detected naturally attacked trees in summer at a distance of >100 m.

Journal of Chemical Ecology, 2015

Eastern Palearctic conifers are subject to frequent bark beetle outbreaks. However, neither the s... more Eastern Palearctic conifers are subject to frequent bark beetle outbreaks. However, neither the species responsible nor the semiochemicals guiding these attacks are well understood. Two high-mountain Ips species on Qinghai spruce, Picea crassifolia, I. shangrila and I. nitidus, are typical in this regard. Six synthetic candidate pheromone components that we earlier identified from hindguts of unmated males of these two Ips species were tested for field activity in Qinghai province, P. R. China. For I. nitidus, racemic ipsdienol ((±)-Id) could replace the naturally-produced blend of enantiomers containing 74 % (-)-(S)-Id (74:26 S:R), in attractive ternary or binary blends. In contrast, sympatric I. shangrila were attracted mainly to blends including Id of opposite chirality, 97 %-(+)-(R)-Id. Of the verbenols, (-)-trans-verbenol was inactive for I. nitidus or inhibitory for I. shangrila, but (-)-cis-verbenol (cV) was a key component of the pheromone in both species. Two fully factorial experiments demonstrated that (±)-Id, cV, and 2-methyl-3-buten-2-ol (MB) are components of the aggregation pheromone of I. nitidus, whereas only (+)-Id and cV are essential components of the aggregation pheromone of I. shangrila. While MB is not necessary for attraction of I. shangrila, it is an active antagonist and likely functions in species isolation. A review of the pheromone production and responses in Palearctic Ips and Pseudoips showed that cV is more common than methylbutenols, and both elicit qualitatively variable responses. Ipsdienol is the most common component with variable chirality, and is a necessary, but often not sufficient, factor for determining pheromone specificity.

Annals of Forest Science, 2007

The adsorption method of Tenax-TA absorbent with GC-MS was used to analyze diurnal rhythms of vol... more The adsorption method of Tenax-TA absorbent with GC-MS was used to analyze diurnal rhythms of volatiles from undamaged holly plants, Viburnum awabuki Kock (Dipsacales: Adoxaceae) holly infested by the white-striped longhorned beetle, Batocera lineolata Chevrolat (Coleoptera: Cerambycidae). Electroantennography and a Y-tube olfactometer were used to compare and analyze electroantennogram and behavioral responses of unmated male and female adults to the volatiles from V. awabuki (both undamaged and infested plants). The results of the GC-MS analysis showed that phytosterol and alkane are major volatiles for V. awabuki. The relative content of V. awabuki volatiles changed during the day. Electroantennogram and behavioral responses of unmated male and female adults to the volatiles from both undamaged and infested plants of V.

Canadian Entomologist, Dec 1, 2000

Ecology and Evolution, Jul 1, 2022

BMC Genomics, 2013

bioRxiv (Cold Spring Harbor Laboratory), Nov 28, 2020

Insect Biochemistry and Molecular Biology, Apr 1, 2016

PLOS ONE

Forests, Dec 18, 2022

Agricultural and Forest Meteorology

Arthropod-Plant Interactions, 2021

Pest Management Science, 2022

PLOS ONE, 2014

Synthesis of racemic dehydro-conophthorin.</p

Pest Management Science, 2022

Journal of Chemical Ecology, 2015

Annals of Forest Science, 2007