Nematodes associated with Ips cembrae (Coleoptera: Curculionidae): comparison of generations,sexes and sampling methods

A study of nematodes associated with the large larch bark beetle Ips cembrae (Heer 1836) was carried out at three locations in the Czech Republic. The proportion of beetles infested by endoparasitic nematodes (representatives of genera Contortylenchus, Parasitylenchus, Cryptaphelenchus and Parasitorhabditis) ranged from 29.9 to 50.9%. Significant differences were determined in nematode infestation levels among locations, generations and sampling methods. No differences were found in infestation rates between males and females. The percentage of bark beetles with phoretic nematodes ranged from 18 to 42.9%. Phoretic nematodes directly found under elytra, on wings and between body segments of the bark beetles belong to the genus Micoletzkya. However, adults and juveniles of other two phoretic species Laimaphelenchus penardi and Bursaphelenchus sp. were found in the gallery frass of I. cembrae. Infestation by phoretic nematodes positively correlated with the presence of mites under elytra.     

Concordance of bacterial communities of two tick species and blood of their shared rodent host

High‐throughput sequencing is revealing that most macro‐organisms house diverse microbial communities. Of particular interest are disease vectors whose microbiome could potentially affect pathogen transmission and vector competence. We investigated bacterial community composition and diversity of the ticks Dermacentor variabilis (n = 68) and Ixodes scapularis (n = 15) and blood of their shared rodent host, Peromyscus leucopus (n = 45) to quantify bacterial diversity and concordance. The 16S rRNA gene was amplified from genomic DNA from field‐collected tick and rodent blood samples, and 454 pyrosequencing was used to elucidate their bacterial communities. After quality control, over 300 000 sequences were obtained and classified into 118 operational taxonomic units (OTUs, clustered at 97% similarity). Analysis of rarefied communities revealed that the most abundant OTUs were tick species‐specific endosymbionts, Francisella and Rickettsia, and the commonly flea‐associated bacterium Bartonella in rodent blood. An Arsenophonus and additional Francisella endosymbiont were also present in D. variabilis samples. Rickettsia was found in both tick species but not in rodent blood, suggesting that it is not transmitted during feeding. Bartonella was present in larvae and nymphs of both tick species, even those scored as unengorged. Relatively, few OTUs (e.g. Bartonella, Lactobacillus) were found in all sample types. Overall, bacterial communities from each sample type were significantly different and highly structured, independent of their dominant OTUs. Our results point to complex microbial assemblages inhabiting ticks and host blood including infectious agents, tick‐specific endosymbionts and environmental bacteria that could potentially affect arthropod‐vectored disease dynamics.     

Classification of crucigenoid algae: phylogenetic position of the reinstated genus Lemmermannia,Tetrastrum spp. Crucigenia tetrapedia,and C. lauterbornii (Trebouxiophyceae,Chlorophyta)1

The subfamily Crucigenioideae was traditionally classified within the well‐characterized family Scenedesmaceae (Chlorophyceae). Several morpho‐logical revisions and questionable taxonomic changes hampered the correct classification of crucigenoid species resulting in a high number of synonymous genera. We used a molecular approach to determine the phylogenetic position of several Tetrastrum and Crucigenia species. The molecular results were correlated with morphological and ontogenetic characters. Phylogenetic analyses of the SSU rDNA gene resolved the position of Tetrastrum heteracanthum and T. staurogeniaeforme as a new lineage within the Oocystis clade of the Trebouxiophyceae. Crucigenia tetrapedia, T. triangulare, T. punctatum, and T. komarekii were shown to be closely related to Botryococcus (Trebouxiophyceae) and were transferred to Lemmer‐mannia. Crucigenia lauterbornii was not closely related to the other Crucigenia strains, but was recovered within the Chlorella clade of the Trebouxiophyceae.     

Efficacy of Acibenzolar‐S‐Methyl and β‐Aminobutyric Acid for Control of Downy Mildew in Greenhouse Grown Basil and Peroxidase Activity in Response to Treatment with these Compounds

Downy mildew, caused by the oomycete pathogen Peronospora belbahrii, is a devastating foliar disease of basil in the United States and worldwide. Currently there are very few chemistries or organic choices registered to control this disease. In this study, two systemic acquired resistance (SAR) inducers, acibenzolar‐S‐methyl (ASM) and β‐aminobutyric acid (BABA), were evaluated for their in vitro effects on the pathogen, for their potential to control basil downy mildew in greenhouses, and for changes in peroxidase activity in basil plants treated with these two SAR inducers. No significant inhibition of sporangial germination was detected in water agar amended with ASM at concentrations lower than 100 mg/l or with BABA at concentrations lower than 500 mg/l. Efficacy of ASM and BABA in greenhouses varied depending on the rate, method and timing of application. The area under the disease progress curve (AUDPC) of disease severity was significantly reduced compared to the non‐treated control when ASM was sprayed (in all experiments) or drenched (in one out of two experiments) pre‐, or pre‐ + post‐inoculation at rates of 25–400 mg/l. Three weekly post‐inoculation sprays of ASM at the rate of 50 mg/l reduced AUDPC by 93.0 and 47.2% when started 3 and 7 days after inoculation (DAI), respectively. The AUDPC of disease severity was also significantly reduced when BABA was sprayed pre‐ + post‐inoculation at rates of 125–500 mg/l. According to the prediction using a log‐logistic function, 50% maximum disease protection was achieved at a concentration of 27.5 mg/l of ASM. Basil plants treated with these two SAR inducers and challenged with the pathogen showed significantly higher peroxidase activity than the non‐treated control at 8 DAI. Temporally, the highest activity of peroxidase was detected at 8 DAI, decreased at 15 DAI and waned further at 23 DAI.     

How to deal with neglected tropical diseases in the light of an African ethic

Many countries in Africa, and more generally those in the Global South with tropical areas, are plagued by illnesses that the wealthier parts of the world (mainly ‘the West’) neither suffer from nor put systematic effort into preventing, treating or curing. What does an ethic with a recognizably African pedigree entail for the ways various agents ought to respond to such neglected diseases? As many readers will know, a characteristically African ethic prescribes weighty duties to aid on the part of those in a position to do so, and it therefore entails that there should have been much more contribution from the Western, ‘developed’ world. However, what else does it prescribe, say, on the part of sub‐Saharan governments and the African Union, and are they in fact doing it? I particularly seek to answer these questions here, by using the 2013‐16 Ebola crisis in West Africa to illustrate what should have happened but what by and large did not.     

An ecological genetic delineation of local seed‐source provenance for ecological restoration

An increasingly important practical application of the analysis of spatial genetic structure within plant species is to help define the extent of local provenance seed collection zones that minimize negative impacts in ecological restoration programs. Here, we derive seed sourcing guidelines from a novel range‐wide assessment of spatial genetic structure of 24 populations of Banksia menziesii (Proteaceae), a widely distributed Western Australian tree of significance in local ecological restoration programs. An analysis of molecular variance (AMOVA) of 100 amplified fragment length polymorphism (AFLP) markers revealed significant genetic differentiation among populations (Φ_PT = 0.18). Pairwise population genetic dissimilarity was correlated with geographic distance, but not environmental distance derived from 15 climate variables, suggesting overall neutrality of these markers with regard to these climate variables. Nevertheless, Bayesian outlier analysis identified four markers potentially under selection, although these were not correlated with the climate variables. We calculated a global R‐statistic using analysis of similarities (ANOSIM) to test the statistical significance of population differentiation and to infer a threshold seed collection zone distance of ~60 km (all markers) and 100 km (outlier markers) when genetic distance was regressed against geographic distance. Population pairs separated by >60 km were, on average, twice as likely to be significantly genetically differentiated than population pairs separated by <60 km, suggesting that habitat‐matched sites within a 30‐km radius around a restoration site genetically defines a local provenance seed collection zone for B. menziesii. Our approach is a novel probability‐based practical solution for the delineation of a local seed collection zone to minimize negative genetic impacts in ecological restoration.     

Molecular diversity and landscape genomics of the crop wild relative Triticum urartu across the Fertile Crescent

Modern plant breeding can benefit from the allelic variation that exists in natural populations of crop wild relatives that evolved under natural selection in varying pedoclimatic conditions. In this study, next‐generation sequencing was used to generate 1.3 million genome‐wide single nucleotide polymorphisms (SNPs) on ex situ collections of Triticum urartu L., the wild donor of the A^u subgenome of modern wheat. A set of 75 511 high‐quality SNPs were retained to describe 298 T. urartu accessions collected throughout the Fertile Crescent. Triticum urartu showed a complex pattern of genetic diversity, with two main genetic groups distributed sequentially from west to east. The incorporation of geographical information on sampling points showed that genetic diversity was correlated to the geographical distance (R² = 0.19) separating samples from Jordan and Lebanon, from Syria and southern Turkey, and from eastern Turkey, Iran and Iraq. The wild emmer genome was used to derive the physical positions of SNPs on the seven chromosomes of the A^u subgenome, allowing us to describe a relatively slow decay of linkage disequilibrium in the collection. Outlier loci were described on the basis of the geographic distribution of the T. urartu accessions, identifying a hotspot of directional selection on chromosome 4A. Bioclimatic variation was derived from grid data and related to allelic variation using a genome‐wide association approach, identifying several marker–environment associations (MEAs). Fifty‐seven MEAs were associated with altitude and temperature measures while 358 were associated with rainfall measures. The most significant MEAs and outlier loci were used to identify genomic loci with adaptive potential (some already reported in wheat), including dormancy and frost resistance loci. We advocate the application of genomics and landscape genomics on ex situ collections of crop wild relatives to efficiently identify promising alleles and genetic materials for incorporation into modern crop breeding.     

A combined morphological,ultrastructural, molecular,and biochemical study of the peculiar family Gomontiellaceae (Oscillatoriales) reveals a new cylindrospermopsin‐producing clade of cyanobacteria

Members of the morphologically unusual cyanobacterial family Gomontiellaceae were studied using a polyphasic approach. Cultured strains of Hormoscilla pringsheimii, Starria zimbabweënsis, Crinalium magnum, and Crinalium epipsammum were thoroughly examined, and the type specimen of the family, Gomontiella subtubulosa, was investigated. The results of morphological observations using both light microscopy and transmission electron microscopy were consistent with previous reports and provided evidence for the unique morphological and ultrastructural traits of this family. Analysis of the 16S rRNA gene confirmed the monophyletic origin of non‐marine repre‐sentatives of genera traditionally classified into this family. The family was phylogenetically placed among other groups of filamentous cyanobacterial taxa. The presence of cellulose in the cell wall was analyzed and confirmed in all cultured Gomontiellaceae members using Fourier transform infrared spectroscopy and fluorescence microscopy. Evaluation of toxins produced by the studied strains revealed the hepatotoxin cylindrospermopsin (CYN) in available strains of the genus Hormoscilla. Production of this compound in both Hormoscilla strains was detected using high‐performance liquid chromatography in tandem with high resolution mass spectrometry and confirmed by positive PCR amplification of the cyrJ gene from the CYN biosynthetic cluster. To our knowledge, this is the first report of CYN production by soil cyanobacteria, establishing a previously unreported CYN‐producing lineage. This study indicates that cyanobacteria of the family Gomontiellaceae form a separate but coherent cluster defined by numerous intriguing morphological, ultrastructural, and biochemical features, and exhibiting a toxic potential worthy of further investigation.     

Annual plants change in size over a century of observations

Studies have documented changes in animal body sizes over the last century, but very little is known about changes in plant sizes, even though reduced plant productivity is potentially responsible for declines in size of other organisms. Here, I ask whether warming trends in the Great Basin have affected plant size by measuring specimens preserved on herbarium sheets collected between 1893 and 2011. I asked how maximum and minimum temperatures, precipitation, and the Pacific Decadal Oscillation (PDO) in the year of collection affected plant height, leaf size, and flower number, and asked whether changes in climate resulted in decreasing sizes for seven annual forbs. Species had contrasting responses to climate factors, and would not necessarily be expected to respond in parallel to climatic shifts. There were generally positive relationships between plant size and increased minimum and maximum temperatures, which would have been predicted to lead to small increases in plant sizes over the observation period. While one species increased in size and flower number over the observation period, five of the seven species decreased in plant height, four of these decreased in leaf size, and one species also decreased in flower production. One species showed no change. The mechanisms behind these size changes are unknown, and the limited data available on these species (germination timing, area of occupancy, relative abundance) did not explain why some species shrank while others grew or did not change in size over time. These results show that multiple annual forbs are decreasing in size, but that even within the same functional group, species may have contrasting responses to similar environmental stimuli. Changes in plant size could have cascading effects on other members of these communities, and differential responses to directional change may change the composition of plant communities over time.     

Depolarization‐induced suppression of a glycinergic synapse in the superior olivary complex by endocannabinoids

The neuronal endocannabinoid system is known to depress synaptic inputs retrogradely in an activity‐dependent manner. This mechanism has been generally described for excitatory glutamatergic and inhibitory GABAergic synapses. Here, we report that neurones in the auditory brainstem of the Mongolian gerbil (Meriones unguiculatus) retrogradely regulate the strength of their inputs via the endocannabinoid system. By means of whole‐cell patch‐clamp recordings, we found that retrograde endocannabinoid signalling attenuates both glycinergic and glutamatergic post‐synaptic currents in the same types of neurones. Accordingly, we detected the cannabinoid receptor 1 in excitatory and inhibitory pre‐synapses as well as the endocannabinoid‐synthesising enzymes (diacylglycerol lipase α/β, DAGLα/β) post‐synaptically through immunohistochemical stainings. Our study was performed with animals aged 10–15 days, that is, in the time window around the onset of hearing. Therefore, we suggest that retrograde endocannabinoid signalling has a role in adapting inputs during the functionally important switch from spontaneously generated to sound‐related signals.

     

Taxonomic Characterization and Experimental Host Ranges of Four Newly Recorded Species of Alternaria from Japan

Alternaria fungi are important plant pathogens. Here, we identified three species new to the Japanese mycoflora: Alternaria celosiae, Alternaria crassa and Alternaria petroselini. We proposed a new name for A. celosiae (E.G. Simmons & Holcomb) Lawrence, Park & Pryor, a later homonym of A. celosiae (Tassi) O. S?vul. To characterize these and a fourth morphological taxon, Alternaria alstroemeriae, which was recently added to Japan's mycoflora, an integrated species concept was tested. We determined the host range of each isolate using inoculation tests and analysed its phylogenetic position using sequences of the internal transcribed spacer rDNA. The pathogenicity of our A. alstroemeriae isolate was strictly limited to Alstroemeria sp. (Alstroemeriaceae), but the species was phylogenetically indistinguishable from other small‐spored Alternaria. Alternaria celosiae on Celosia argentea var. plumosa (Amaranthaceae) was also pathogenic to Amaranthus tricolor, to Alternanthera paronychioides and weakly to Gomphrena globosa (all Amaranthaceae) and formed a clade with the former Nimbya celosiae. Alternaria crassa on Datura stramonium (Solanaceae) was also pathogenic to Brugmansia × candida and Capsicum annuum in Solanaceae, but not to other confamilial plants; phylogenetically it belonged to a clade of large‐spored species with filamentous beaks. Morphological similarity, phylogenetic relationship and experimental host range suggested that A. crassa, Alternaria capsici and Alternaria daturicola were conspecific. Alternaria petroselini on Petroselinum crispum (Apiaceae) was pathogenic to five species in the tribe Apieae as well as representatives of Bupleureae, Coriandreae, Seliaeae and Scandiceae in Apiaceae. Both phylogeny and morphology suggested conspecificity between A. petroselini and Alternaria selini.     

Sex‐specific responses of Asian citrus psyllid to volatiles of conspecific and host‐plant origin

Diaphorina citri Kuwayama (Hemiptera: Psyllidae) is the primary vector of Candidatus Liberibacter spp. bacteria that cause citrus greening, a disease of worldwide importance. Olfactometry was employed to test responses of D. citri to odours from intact citrus plants (Mexican lime, Citrus aurantifolia, sour orange, Citrus aurantium, Marsh grapefruit, Citrus paradisi and Valencia orange, Citrus sinensis), citrus plants previously infested with D. citri, and odours of conspecifics including nymphs, adult insects of same and opposite sex, and their products (honeydew), both alone and in combination. In contrast to other studies, psyllids of both sexes were attracted to volatiles of undamaged Mexican lime leaves, whereas undamaged grapefruit attracted only females, and leaves of Valencia and sour orange did not attract either sex. All four plant species attracted female psyllids when previously infested, but only Mexican lime and sour orange‐attracted males. Thus, Citrus species appear to vary in the production of both constituitive and induced volatiles that attract adult psyllids. Volatiles emitted by nymphs did not attract either sex, but psyllid honeydew was attractive to males, likely due to female pheromone residues. Males oriented to the odour of females, whereas the reverse was not true, and neither males nor females oriented to same‐sex volatiles. The addition of conspecific cues (adults, nymphs or honeydew) did not increase female attraction to previously infested leaves, but male response was increased by the presence of adults and honeydew, regardless of plant species. Thus, female psyllids appear to orient more strongly to volatiles of plant origin, whereas males respond more strongly to cues emanating from females and conspecific excretions. These results suggest that female psyllids drive the initial colonization of host plants, whereas males orient to females and infested plants. Identification of the specific volatiles involved may permit their use in monitoring and management of this pest.     

A diverse chasmataspidid (Arthropoda: Chelicerata) fauna from the Early Devonian (Lochkovian) of Siberia

Examination of material held at the Palaeontological Institute, Moscow, enables the identification of two novel chasmataspidid species: Nahlyostaspis bergstroemi gen. et sp. nov. and Skrytyaspis andersoni gen. et sp. nov. ‘Eurypterus’ stoermeri and ‘Tylopterella’ menneri are both redescribed as chasmataspidids, having previously been assigned to Eurypterida. ‘T’. menneri is transferred to the new genus Dvulikiaspis gen. nov. An identical prosomal structure is identified in ‘Eurypterus’ stoermeri and Heteroaspis novojilovi from the Devonian of Germany and the two species are synonymized, with ‘E’ stoermeri having priority. The previous synonymy of H. novojilovi with Diploaspis casteri is rejected. The presence of ophthalmic ridges is confirmed within Diploaspididae, and new structural characteristics of their bucklers are identified.     

Mitochondrial phylogenetics of the goshawk Accipiter [gentilis] superspecies

The Northern Goshawk Accipiter gentilis is a medium‐sized bird of prey inhabiting boreal and temperate forests. It has a Holarctic distribution with 10 recognized subspecies. Traditionally, it has been placed within the Accipiter [gentilis] superspecies, together with Henst's Goshawk A. henstii, the Black Sparrowhawk A. melanoleucus, and Meyer's Goshawk A. meyerianus. While those four taxa are geographically separated from each other, hence referred to as allospecies, their phylogenetic relationships are still unresolved. In the present study, we performed phylogenetic analyses on the Accipiter [gentilis] superspecies, including all recognized subspecies of all four allospecies, using partial sequences of two marker loci of the mitochondrial genome, the control region and the cytochrome b gene. We found a deep split within A. gentilis into two monophyletic groups, a Nearctic clade (three subspecies) and a Palearctic clade (seven subspecies). The Palearctic clade is closely related to A. meyerianus, and together these two were more closely related to the other Old World taxa A. henstii and A. melanoleucus, which in turn were reciprocally monophyletic sister species. As a consequence, A. gentilis as usually conceived (including all Holarctic subspecies) was non‐monophyletic. We found a strong genetic homogeneity within Palearctic A. gentilis despite the fact that it comprises seven subspecies distributed from the Atlantic coast in Western Europe to Eastern Siberia. Relationships between the four clades could not be resolved unambiguously. Our results, if confirmed by more integrative data, would imply a taxonomic revision of Nearctic A. gentilis into a separate allospecies, Accipiter [gentilis] atricapillus.