Sex dependent transcriptome responses of the diamondback moth, Plutella xylostella L. to cold stress.

Temperature has fundamental influences on the performance and distribution of insects. While considerable attention has been devoted to extreme conditions, particularly extreme cold conditions, few studies have investigated effects of mild cold conditions on insects. We examined the transcriptomic changes in mid-fourth instar larvae of both sexes reared at 10 °C and 25 °C to investigate sex-dependent responses of Plutella xylostella to mild cold stress. There were 624 differentially expressed genes (DEGs) in females, the majority of which (n = 386) were down-regulated. In males 3239 genes were differentially expressed and the majority (n = 2341) were up-regulated. Only 280 DEGs were common to both sexes. In females, there were no DEGs encoding heat shock or cold shock proteins, but six of these DEGs were found in males. These differences suggest that females and males might adopt some different strategies to cope with cold stress and/or that they were affected by rearing under cold conditions to different degrees and in different ways. In addition, DEGs encoding antimicrobial peptides, cytochrome P450 monooxygenases, fatty acid-related enzymes, cuticle proteins, myofilament, and hormone-related proteins were found in both sexes under cold stress. The transcriptome study reveals unexpected sex-dependent thermal responses and provides new information of how an insect that does not diapause copes with low temperatures.

Responses of diamondback moth to diverse entomopathogenic fungi collected from non-agricultural habitats - Effects of dose, temperature and starvation.

We evaluated the virulence of Beauveria bassiana and Metarhizium isolates from soil collected across different vegetation types in Queensland, against chlorantraniliprole-resistant and insecticide-susceptible diamondback moth (DBM) larvae. Host insecticide resistance status had no effect on susceptibility to the pathogens when conidia were topically applied to larvae in the laboratory, and one B. bassiana isolate was significantly more virulent to larvae than the others (seven days after inoculation). The influence of temperature (15, 20, 25 or 30 °C): (i) at the point of host inoculation with conidia and (ii) when the pathogens had already initiated infection and were proliferating in the host haemocoel, was determined experimentally for its influence on virulence, disease progression, and sporulation. Temperature at inoculation had a greater effect on host insect mortality than it did when the fungus was already proliferating in the host haemocoel. The rearing temperature of hosts prior to inoculation had a greater effect on host susceptibility to disease than starvation of the larvae at the time of inoculation. Our results also show that each fungal isolate has its own temperature relations and that these can vary considerably across isolates, and at different points in the pathogen life cycle (germination and cuticular penetration versus growth in the host haemocoel). Temperature also had an idiosyncratic effect, across isolates and across the variables typically used to assess the potential of fungal entomopathogens as biological control agents (time to death, mortality and sporulation rates). This study demonstrates that in addition to pathogenicity and virulence, the temperature relationships of each fungal isolate when infecting insects needs to be taken into account if we are to understand their ecology and use them effectively in pest management.

Genome-Guided Analysis of Seven Weed Species Reveals Conserved Sequence and Structural Features of Key Gene Targets for Herbicide Development.

Herbicides are commonly deployed as the front-line treatment to control infestations of weeds in native ecosystems and among crop plants in agriculture. However, the prevalence of herbicide resistance in many species is a major global challenge. The specificity and effectiveness of herbicides acting on diverse weed species are tightly linked to targeted proteins. The conservation and variance at these sites among different weed species remain largely unexplored. Using novel genome data in a genome-guided approach, 12 common herbicide-target genes and their coded proteins were identified from seven species of Weeds of National Significance in Australia: Alternanthera philoxeroides (alligator weed), Lycium ferocissimum (African boxthorn), Senecio madagascariensis (fireweed), Lantana camara (lantana), Parthenium hysterophorus (parthenium), Cryptostegia grandiflora (rubber vine), and Eichhornia crassipes (water hyacinth). Gene and protein sequences targeted by the acetolactate synthase (ALS) inhibitors and glyphosate were recovered. Compared to structurally resolved homologous proteins as reference, high sequence conservation was observed at the herbicide-target sites in the ALS (target for ALS inhibitors), and in 5-enolpyruvylshikimate-3-phosphate (EPSP) synthase (target for glyphosate). Although the sequences are largely conserved in the seven phylogenetically diverse species, mutations observed in the ALS proteins of fireweed and parthenium suggest resistance of these weeds to ALS-inhibiting and other herbicides. These protein sites remain as attractive targets for the development of novel inhibitors and herbicides. This notion is reinforced by the results from the phylogenetic analysis of the 12 proteins, which reveal a largely consistent vertical inheritance in their evolutionary histories. These results demonstrate the utility of high-throughput genome sequencing to rapidly identify and characterize gene targets by computational methods, bypassing the experimental characterization of individual genes. Data generated from this study provide a useful reference for future investigations in herbicide discovery and development.

Has the Australian Endemic Grey Falcon the Most Extreme Dietary Specialization among all Falco Species?

A clear understanding of a species' diet is crucial in understanding its spatio-temporal dynamics, and is, therefore, pertinent to conservation considerations. The diet of the Grey Falcon (Falco hypoleucos), a rare and threatened predator endemic to the Australian arid and semi-arid zone, is subject to diverging assertions; therefore, we studied its diet through direct observation of food ingestion during more than 17 years of fieldwork across the species' distribution. We found that Grey Falcons of all ages fed almost exclusively on a single type of food, namely, birds, and non-avian food items never constituted a substantial portion of any individual's diet. The extraordinary circumstances that were associated with the ingestion of non-avian food suggest strongly that, across its vast distribution, throughout the year, and throughout its life, the Grey Falcon feeds almost exclusively on birds. Further, we compared the diets of all Falco species and found that the dietary specialization is most extreme in the Grey Falcon, more so than even in the Taita (F. fasciinucha) and Peregrine Falcons (F. peregrinus). Based on aspects of the species' environment and relative prey availability, we offer an evolutionary explanation of the apparently unique dietary specialization of the arid-adapted Grey Falcon.

Low activity levels are an adaptation to desert-living in the Grey Falcon, an endotherm that specializes in pursuing highly mobile prey.

Endothermic animals that live permanently in hot deserts must avoid harmful hyperthermia when their body temperature increases from heat gained through external and internal sources. This is true particularly for endotherms that are exclusively diurnal. We investigated the Grey Falcon (Falco hypoleucos), a predatory Australian endemic restricted to the hot arid/semi-arid zone. To understand how this species' entire population persists exclusively and permanently in this extreme environment we examined its activity levels and compared these with equivalent variables from the Peregrine Falcon (F. peregrinus), a cosmopolitan species that inhabits similar environments without being restricted to them. Further, we compared, across a selected group of Falco species, specific plumage characteristics (measured on museum specimens) that we anticipated would enhance the Grey Falcons' ability to cope with high heat loads. We found no morphological or physiological characteristics that would allow them to cope with heat better than other birds, but the chicks seem to have unusually high thermal tolerances. Grey Falcons do, however, possess a suite of unusual behavioural adaptations that, as we propose, enable them to cope with climatic extremes in arid environments. Specifically, throughout their lives Grey Falcons keep activity levels and thus physical exertion low. This behaviour contrasts strikingly with that of the Peregrine Falcon, which also actively hunts birds in flight. Keeping activity levels low is expected to minimize endogenous heat production and thus ease the Grey Falcon's thermoregulation during periods of high heat load. These birds may rely on low levels of relative humidity for efficient evaporative cooling, and this may explain their absolute restriction to hot arid/semi-arid zones.

Insights from an ancient gymnosperm lineage: ambient temperature and light and the timing of thermogenesis in cycad cones.

PREMISE: Although maintaining the appropriate mid-day timing of the diel thermogenic events of cones of the dioecious cycads Macrozamia lucida and M. macleayi is central to the survival of both plant and pollinator in this obligate pollination mutualism, the nature of the underlying mechanism remains obscure. We investigated whether it is under circadian control. Circadian mechanisms control the timing of many ecologically important processes in angiosperms, yet only a few gymnosperms have been studied in this regard. METHODS: We subjected cones to different ambient temperature and lighting regimens (constant temperature and darkness; stepwise cool/warm ambient temperatures in constant darkness; stepwise dark/light exposures at constant temperature) to determine whether the resulting timing of their thermogenic events was consistent with circadian control. RESULTS: Cones exposed to constant ambient temperature and darkness generated multiple temperature peaks endogenously, with an average interpeak-temperature period of 20.7 (±0.20) h that is temperature-compensated (Q10 = 1.02). Exposure to 24-h ambient temperature cycles (12 h cool/12 h warm, constant darkness) yielded an interpeak-temperature period of 24.0 (±0.05) h, accurately and precisely replicating the ambient temperature period. Exposure to 24-h photo-cycles (12 h light/12 h dark, constant ambient temperature) yielded a shorter, more variable interpeak-temperature period of 23 (±0.23) h. CONCLUSIONS: Our results indicate that cycad cone thermogenesis is under circadian clock control and differentially affected by ambient temperature and light cycles. Our data from cycads (an ancient gymnosperm lineage) adds to what little is known about circadian timing in gymnosperms, which have rarely been studied from the circadian perspective.

Differential temperature responses between Plutella xylostella and its specialist endo-larval parasitoid Diadegma semiclausum-Implications for biological control.

Understanding the thermal dynamics of host-parasitoid interactions is crucial to predicting how biological control of pest insects by parasitoids might be affected by geographic location and climate change. We compared performance traits of Plutella xylostella (Lepidoptera: Plutellidae) and its solitary endo-larval parasitoid Diadegma semiclausum (Hymenoptera: Ichneumonidae), over a wide range of constant rearing temperatures (10-30°C). Parasitoids reared at 30°C experienced reductions in pupation rate, pupal mass, egg load, and adult life span when compared with those reared at lower temperatures. Our analyses of the fate of parasitoids and their hosts and intergenerational population growth at different rearing temperatures show that D. semiclausum and P. xylostella respond differently to temperature, leading to divergent outcomes under different temperature conditions. Some parasitoid larvae could not complete development at 30°C, the temperature at which the host biomass was least and the metabolic demands of the parasitoid could be high, suggesting that parasitoid development might be constrained by lack of host resources at higher temperatures. We discuss the potential mechanisms of parasitoid susceptibility to elevated temperatures, which likely explain the pronounced seasonal dynamics of D. semiclausum in subtropical regions and its failure to establish in lowland tropical regions, where P. xylostella is a serious pest. Similar interactions in other host-parasitoid associations would constrain the efficacy of parasitoids as biological control agents as global temperatures increase.

Delayed juvenile behavioral development and prolonged dependence are adaptations to desert life in the grey falcon.

Rapid learning in the young of most endothermic animals can be expected to be favored by natural selection because early independence reduces the period of vulnerability. Cases of comparatively slow juvenile development continue, therefore, to attract scientific attention. In most species of birds, including raptors, the young depend on their parents for some time after fledging for the provisioning of food and for protection while they learn to become nutritionally and otherwise independent. Among raptors, post-fledging dependence periods that exceed 6 months are exclusive to the largest species and these have reproductive cycles that exceed 12 months. By contrast, young of the medium-sized grey falcon Falco hypoleucos have been reported in close company with their parents up to 12 months after fledging, that is, at a time when the adults are expected to breed again. We investigated the occurrence and characteristics of prolonged adult-juvenile association relative to other falcons and similar-sized raptors. We found that the behavioral development of grey falcon young is extremely delayed, and that they even depend nutritionally on their parents for up to 12 months after fledging. We suggest that these 2 distinctive features are, ultimately, adaptations of the grey falcon to its extreme environment, Australia's arid and semi-arid zone, one of the hottest environments in the world.

Unique chemistry associated with diversification in a tightly coupled cycad-thrips obligate pollination mutualism.

Cycad cone thermogenesis and its associated volatiles are intimately involved in mediating the behavior of their obligate specialist pollinators. In eastern Australia, thrips in the Cycadothrips chadwicki species complex are the sole pollinators of many Macrozamia cycads. Further, they feed and reproduce entirely in the pollen cones. M. miquelii, found only in the northern range of this genus, is pollinated only by a C. chadwicki cryptic species that is the most distantly related to others in the complex. We examined the volatile profile from M. miquelii pollen and ovulate (receptive and non-receptive) cones to determine how this mediates pollination mechanistically, using GC-MS (gas chromatography-mass spectrometry) and behavioral tests. Monoterpenes comprise the bulk of M. miquelii volatile emissions, as in other Macrozamia species, but we also identified compounds not reported previously in any cycad, including three aliphatic esters (prenyl acetate and two of uncertain identity) and two aliphatic alcohols. The two unknown esters were confirmed as prenyl (3-methylbut-2-enyl) esters of butyric and crotonic ((E))-but-2-enoic) acids after chemical synthesis. Prenyl crotonate is a major component in emissions from pollen and receptive ovulate cones, is essentially absent from non-receptive cones, and has not been reported from any other natural source. In field bioassays, Cycadothrips were attracted only to those volatile treatments containing prenyl crotonate. We discuss M. miquelii cone odorants relative to those of other cycads, especially with respect to prenyl crotonate being a species-specific signal to this northern C. chadwicki cryptic species, and how this system may have diversified.

Interactions of Helicoverpa punctigera (Lepidoptera: Noctuidae) Larvae and Adults With Four Native Host Plants Relative to Field Use Patterns.

Generalist insect herbivores may be recorded from a great variety of host plants. Under natural conditions, however, they are almost invariably associated with a few primary host species on which most of the juveniles develop. We experimentally investigated the interaction of the generalist moth Helicoverpa punctigera Wallengren (Lepidoptera: Noctuidae) with four of its native host plants, two designated primary hosts and two secondary hosts (based on field observations). We tested whether primary host plants support higher survival rates of larvae and whether they are more attractive to ovipositing moths and feeding larvae. We also evaluated whether relative attractiveness of host plants for oviposition matches larval survival rates on them-the preference-performance hypothesis. Moths laid significantly more eggs on two of the four host plant species, one of them a primary host, the other a secondary host. Larvae developed best when reared on the attractive secondary host, developed at intermediate levels on the two primary hosts, and performed worst on the less attractive secondary host. Relative attractiveness of the four host plants to caterpillars differed from that of the moths. Neither adult nor larval attraction to host plants fully supported the preference-performance hypothesis, but oviposition was better correlated with larval survival rates than was larval attraction. Our results suggest the relative frequency at which particular host species are used in the field may depend on factors not yet considered including the long-distance attractants used by moths and the relative distribution of host species.

Migration dynamics of an important rice pest: The brown planthopper (Nilaparvata lugens) across Asia-Insights from population genomics.

INTRODUCTION: Brown planthoppers (Nilaparvata lugens) are the most serious insect pests of rice, one of the world's most important staple crops. They reproduce year-round in the tropical parts of their distribution, but cannot overwinter in the temperate areas where they occur, and invade seasonally from elsewhere. Decades of research have not revealed their source unambiguously. METHODS AND RESULTS: We sequenced the genomes of brown planthopper populations from across temperate and tropical parts of their distribution and show that the Indochinese peninsula is the major source of migration into temperate China. The Philippines, once considered a key source, is not significant, with little evidence for their migration into China. We find support for immigration from the west of China contributing to these regional dynamics. DISCUSSION: The lack of connectivity between the Philippine population and the mainland Chinese populations explains the different evolution of Imidacloprid resistance in these populations. This study highlights the promise of whole-genome sequence data to understand migration when gene flow is high-a situation that has been difficult to resolve using traditional genetic markers.

The Gene Introgression Approach and the Potential Cost of Genes that Confer Strong Phosphine Resistance in Red Flour Beetle (Coleoptera: Tenebrionidae).

Resistance in pest insects to the grain fumigant phosphine (PH3) poses a threat to trade and food security. The possible pleiotropic effects of PH3 resistance on development and reproduction were investigated in the red flour beetle, Tribolium castaneum (Herbst), by introgressing two genes known to be major contributors to strong resistance (tc_rph1 and tc_rph2) into a susceptible background. The tc_rph2 allele was the G135S variant, whereas the identity of tc_rph1 allele was unknown but could have been one of the three known variants (L119W, V123F, or S349G). The introgressed resistant strain was 288× more resistant than the susceptible strain, based on mortality after a 20 h fumigation with PH3. Molecular screening confirmed that the introgressed strain was homozygous for the resistance genes, but was otherwise indistinguishable from the susceptible strain based on screening with 12 neutral DNA markers. We found no differences of consequence in developmental time between the susceptible and introgressed resistant strains. Similarly, the number of F1 adults produced by these strains was more or less equal, as was the weight of individual F1 adults. The conclusions remained the same regardless of whether the experiments were conducted on a flour-based medium or wheat. Thus, we found no evidence that being fully strongly PH3 resistant (i.e., homozygous for tc_rph1 and tc_rph2) has major consequences in terms of development or reproduction in T. castaneum.

The recognition concept and genetic approaches to interpreting species.

1. Introduction. 2. The Specific-mate Recognition System (SMRS). 3. The Genetic Change As sociated with Speciation.

Gene flow across host-associated populations of the rice stem borer Chilo suppressalis Walker (Lepidoptera: Crambidae): implications for Bt resistance management in rice.

BACKGROUND: The rice stem borer, Chilo suppressalis, is a serious pest of rice, but also damages an aquatic vegetable, water oats (Zizania latifolia Turcz.). The time at which mating occurs is different between populations of rice stem borer associated with rice and those associated with water-oats, which suggests that undetected cryptic species may be associated with these plant hosts. If true, this would have significant management implications. This study is the first empirical test of this idea, using population genetic tools from two sampling cohorts. We genotyped 320 rice stem borer individuals from 2014, collected from rice and water-oats across five locations (where they exist in sympatry), using seven microsatellite loci. RESULTS: We found no genetic structuring associated with host plant species. On water oats, some rice stem borers were found that had a similar mating time to the rice population, so in 2016, a second cohort of samples was screened by their timing of mating to get 'pure rice feeders' and 'pure water oats feeders'. These samples were genotyped with microsatellites, mitochondrial DNA (mtDNA) (COI and COII), and a nuclear gene (EF1-α). Our mtDNA data suggest a relatively low amount of population subdivision associated with plant host, but the microsatellite data revealed no such genetic structure, and we were only able to identify one haplotype of EF1-α. CONCLUSIONS: Our results indicate gene flow between rice and water oats populations of rice stem borer, indicating that water oats will likely provide a refuge for resistance management of Bt rice. © 2019 Society of Chemical Industry.

Origins, Divergence, and Contrasting Invasion History of the Sweet Potato Weevil Pests Cylas formicarius (Coleoptera: Brentidae) and Euscepes batatae (Coleoptera: Curculionidae) in the Asia-Pacific.

Cylas formicarius F. and Euscepes batatae Waterhouse are the most damaging sweet potato insect pests globally. Both weevils are thought to have invaded the Pacific alongside the movement of sweet potato (Ipomoea batatas (L.) Lam. Convolvulaceae), with C. formicarius having originated in India and E. batatae in Central or South America. Here we compare the genetic relationships between populations of the pests, primarily in the Asia-Pacific, to understand better their contemporary population structure and their historical movement relative to that of sweet potato. Cylas formicarius has divergent mitochondrial lineages that indicate a more complex biogeographic and invasive history than is presently assumed for this insect, suggesting it was widespread across the Asia-Pacific before the arrival of sweet potato. Cylas formicarius must have originally fed on Ipomoea species other than I. batatas but the identity of these species is presently unknown. Cylas formicarius was formerly designated as three species or subspecies and the genetic data presented here suggests that these designations should be reinvestigated. Euscepes batatae has very low genetic diversity which is consistent with its historical association with sweet potato and a recent introduction to the Asia-Pacific from the Americas. The distribution of E. batatae may be narrower than that of C. formicarius in the Asia-Pacific because it has relied relatively more on human-assisted movement. Consequently, E. batatae may become more widespread in the future. Investigating the invasion history of both species will help to understand the probability and nature of future invasions.

Cyclooctatetraene: A Bioactive Cubane Paradigm Complement.

Cubane was recently validated as a phenyl ring (bio)isostere, but highly strained caged carbocyclic systems lack π character, which is often critical for mediating key biological interactions. This electronic property restriction associated with cubane has been addressed herein with cyclooctatetraene (COT), using known pharmaceutical and agrochemical compounds as templates. COT either outperformed or matched cubane in multiple cases suggesting that versatile complementarity exists between the two systems for enhanced bioactive molecule discovery.

Complete chloroplast genome of glyphosate resistant Sonchus oleraceus L. from Australia, with notes on the small single copy (SSC) region orientation.

Sonchus oleraceus, common sowthistle, is an asteraceous weed in Australian agricultural systems and has recently developed resistance to glyphosate. We present the complete chloroplast sequence of S. oleracueus reconstructed from Illumina whole genome shotgun sequencing. This is the first complete chloroplast genome available for the genus Sonchus. The complete chloroplast sequence is 151,808 bp long. A Bayesian phylogeny of the chloroplast coding regions of the tribe Cichorieae (Asteraceae) is presented. The S. oleraceus chloroplast genome is deposited at GenBank under accession number MG878405.

The complete chloroplast genome of the invasive fern Lygodium microphyllum (Cav.) R. Br.

The Old World climbing fern, Lygodium microphyllum, is a rapidly spreading environmental weed in Florida, United States. We reconstructed the complete chloroplast genome of L. microphyllum from Illumina whole-genome shotgun sequencing, and investigate the phylogenetic placement of this species within the Leptosporangiate ferns. The chloroplast genome is 158,891 bp and contains 87 protein-coding genes, four rRNA genes, and 27 tRNA genes. Thirty-three genes contained internal stop codons, a common feature in Leptosporangiate fern genomes. The L. microphyllum genome has been deposited in GenBank under accession number MG761729.