Increases in crop pests caused by Wasmannia auropunctata in Solomon Islands subsistence gardens

The impacts of Wasmannia auropunctata (the little fire ant) on the native biota and subsistence agriculture in the Solomon Islands are poorly understood. This species was originally introduced as a biological control against nut‐fall bugs (Amblypelta sp.) around 30 years ago and in the intervening time has spread throughout the Solomon Islands, aided movement of produce and planting material. It is now itself a major pest of coconut, cocoa and subsistence agriculture. In this study, we show the negative effects of this invasive ant on subsistence agriculture in the Solomon Islands. We do this by (i) assessing the presence of insect pests that develop a mutual relationship with W. auropunctata on four common subsistence crops; and (ii) measuring the impact of a significant pest (Tarophagus sp.) and its natural predator the bug Cyrtohinus fulvus, in the presence and absence of W. auropunctata on taro crops. The existence of insect pests that form a mutual relationship with W. auropunctata was measured in a total of 36 gardens of the four subsistence crops. This was conducted through standardized visual searches, plus identification and collecting from randomly selected plants within the gardens. A number of additional insect pests causing major problems to subsistence crops have also developed mutual relationships with W. auropunctata. Infested taro gardens have more Tarophagus sp. compared with taro plants that are free of the little fire ant. The presence and abundance of Wasmannia therefore has the potential to inflict considerable crop loss in rural subsistence gardens in the Solomon Islands.     

Genotypic variation in Norway spruce correlates to fungal communities in vegetative buds

The taxonomically diverse phyllosphere fungi inhabit leaves of plants. Thus, apart from the fungi's dispersal capacities and environmental factors, the assembly of the phyllosphere community associated with a given host plant depends on factors encoded by the host's genome. The host genetic factors and their influence on the assembly of phyllosphere communities under natural conditions are poorly understood, especially in trees. Recent work indicates that Norway spruce (Picea abies) vegetative buds harbour active fungal communities, but these are hitherto largely uncharacterized. This study combines internal transcribed spacer sequencing of the fungal communities associated with dormant vegetative buds with a genome‐wide association study (GWAS) in 478 unrelated Norway spruce trees. The aim was to detect host loci associated with variation in the fungal communities across the population, and to identify loci correlating with the presence of specific, latent, pathogens. The fungal communities were dominated by known Norway spruce phyllosphere endophytes and pathogens. We identified six quantitative trait loci (QTLs) associated with the relative abundance of the dominating taxa (i.e., top 1% most abundant taxa). Three additional QTLs associated with colonization by the spruce needle cast pathogen Lirula macrospora or the cherry spruce rust (Thekopsora areolata) in asymptomatic tissues were detected. The identification of the nine QTLs shows that the genetic variation in Norway spruce influences the fungal community in dormant buds and that mechanisms underlying the assembly of the communities and the colonization of latent pathogens in trees may be uncovered by combining molecular identification of fungi with GWAS.     

Evolution of the Dynein Heavy Chain Family in Ciliates

Dynein heavy chains are motor proteins that comprise a large gene family found across eukaryotes. We have investigated this gene family in four ciliate species: Ichthyophthirius, Oxytricha, Paramecium, and Tetrahymena. Ciliates appear to encode more dynein heavy chain genes than most eukaryotes. Phylogenetic comparisons demonstrated that the last common ancestor of the ciliates that were examined expressed at least 14 types of dynein heavy chains with most of the expansion coming from the single‐headed inner arm dyneins. Each of the dyneins most likely performed different functions within the cell.     

Species discrimination in Sisyrinchium (Iridaceae): assessment of DNA barcodes in a taxonomically challenging genus

DNA barcoding aims to develop an efficient tool for species identification based on short and standardized DNA sequences. In this study, the DNA barcode paradigm was tested among the genera of the tribe Sisyrinchieae (Iridoideae). Sisyrinchium, with more than 77% of the species richness in the tribe, is a taxonomically complex genus. A total of 185 samples belonging to 98 species of Sisyrinchium, Olsynium, Orthrosanthus and Solenomelus were tested using matK, trnH‐psbA and internal transcribed spacer (ITS). Candidate DNA barcodes were analysed either as single markers or in combination. Detection of a barcoding gap, similarity‐based methods and tree‐based analyses were used to assess the discrimination efficiency of DNA barcodes. The levels of species identification obtained from plastid barcodes were low and ranged from 17.35% to 20.41% for matK and 5.11% to 7.14% for trnH‐psbA. The ITS provided better results with 30.61–38.78% of species identified. The analyses of the combined data sets did not result in a significant improvement in the discrimination rate. Among the tree‐based methods, the best taxonomic resolution was obtained with Bayesian inference, particularly when the three data sets were combined. The study illustrates the difficulties for DNA barcoding to identify species in evolutionary complex lineages. Plastid markers are not recommended for barcoding Sisyrinchium due to the low discrimination power observed. ITS gave better results and may be used as a starting point for species identification.     

Molecular mechanism underlying pseudopeloria in Habenaria radiata (Orchidaceae)

Habenaria radiata (Orchidaceae) has two whorls of perianth, comprising three greenish sepals, two white petals and one lip (labellum). By contrast, the pseudopeloric (with a decreased degree of zygomorphy) mutant cultivar of H. radiata , ‘Hishou’, has changes in the identities of the dorsal sepal to a petaloid organ and the two ventral sepals to lip‐like organs. Here, we isolated four DEFICIENS ‐ like and two AGL 6 ‐like genes from H. radiata , and characterized their expression. Most of these genes revealed similar expression patterns in the wild type and in the ‘Hishou’ cultivar, except Hr DEF ‐C3. The Hr DEF ‐C3 gene was expressed in petals and lip in the wild type but was ectopically expressed in sepal, petals, lip, leaf, root and bulb in ‘Hishou’. Sequence analysis of the Hr DEF ‐C3 loci revealed that the ‘Hishou’ genome harbored two types of Hr DEF ‐C3 genes: one identical to wild‐type Hr DEF ‐C3 and the other carrying a retrotransposon insertion in its promoter. Genetic linkage analysis of the progeny derived from an intraspecific cross between ‘Hishou’ and the wild type demonstrated that the mutant pseudopeloric trait was dominantly inherited and was linked to the Hr DEF ‐C3 gene carrying the retrotransposon. These results indicate that the pseudopeloric phenotype is caused by retrotransposon insertion in the Hr DEF ‐C3 promoter, resulting in the ectopic expression of Hr DEF ‐C3 . As the expression of Hr AGL 6‐C2 was limited to lateral sepals and lip, the overlapping expression of Hr DEF ‐C3 and Hr AGL 6‐C2 is likely to be responsible for the sepal to lip‐like identity in the lateral sepals of the ‘Hishou’ cultivar.     

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.     

Variation in Wolbachia cidB gene,but not cidA,is associated with cytoplasmic incompatibility mod phenotype diversity in Culex pipiens

Endosymbiotic Wolbachia bacteria are, to date, considered the most widespread symbionts in arthropods and are the cornerstone of major biological control strategies. Such a high prevalence is based on the ability of Wolbachia to manipulate their hosts' reproduction. One manipulation called cytoplasmic incompatibility (CI) is based on the death of the embryos generated by crosses between infected males and uninfected females or between individuals infected with incompatible Wolbachia strains. CI can be seen as a modification‐rescue system (or mod‐resc) in which paternal Wolbachia produce mod factors, inducing embryonic defects, unless the maternal Wolbachia produce compatible resc factors. Transgenic experiments in Drosophila melanogaster and Saccharomyces cerevisiae converged towards a model where the cidB Wolbachia gene is involved in the mod function while cidA is involved in the resc function. However, as cidA expression in Drosophila males was required to observe CI, it has been proposed that cidA could be involved in both resc and mod functions. A recent correlative study in natural Culex pipiens mosquito populations has revealed an association between specific cidA and cidB variations and changes in mod phenotype, also suggesting a role for both these genes in mod diversity. Here, by studying cidA and cidB genomic repertoires of individuals from newly sampled natural C. pipiens populations harbouring wPipIV strains from North Italy, we reinforce the link between cidB variation and mod phenotype variation fostering the involvement of cidB in the mod phenotype diversity. However, no association between any cidA variants or combination of cidA variants and mod phenotype variation was observed. Taken together our results in natural C. pipiens populations do not support the involvement of cidA in mod phenotype variation.     

Candidate gene polymorphisms for behavioural adaptations during urbanization in blackbirds

Successful urban colonization by formerly rural species represents an ideal situation in which to study adaptation to novel environments. We address this issue using candidate genes for behavioural traits that are expected to play a role in such colonization events. We identified and genotyped 16 polymorphisms in candidate genes for circadian rhythms, harm avoidance and migratory and exploratory behaviour in 12 paired urban and rural populations of the blackbird Turdus merula across the Western Palaearctic. An exonic microsatellite in the SERT gene, a candidate gene for harm avoidance behaviour, exhibited a highly significant association with habitat type in an analysis conducted across all populations. Genetic divergence at this locus was consistent in 10 of the 12 population pairs; this contrasts with previously reported stochastic genetic divergence between these populations at random markers. Our results indicate that behavioural traits related to harm avoidance and associated with the SERT polymorphism experience selection pressures during most blackbird urbanization events. These events thus appear to be influenced by homogeneous adaptive processes in addition to previously reported demographic founder events.     

Ramularia coleosporii,a Hyperparasite on Coleosporium plumeriae in India

During a survey of fungal plant diseases, parasitized uredinial pustules of Coleosporium plumeriae were observed in Umiam, Meghalaya, India. Microscopic examination was conducted using light and scanning electron microscopy which revealed the occurrence of the hyperparasitic hyphomycete Ramularia coleosporii. Molecular characterization using the ITS1‐5.8S‐ITS2 region of nrDNA also confirmed our results. This is the first record of R. coleosporii on C. plumeriae from India.     

Relationships between intra‐specific variation in seed size and recruitment in four species in two contrasting habitats

Large seeds contain more stored resources, and seedlings germinating from large seeds generally cope better with environmental stresses such as shading, competition and thick litter layers, than seedlings germinating from small seeds. A pattern with small‐seeded species being associated with open habitats and large‐seeded species being associated with closed (shaded) habitats has been suggested and supported by comparative studies. However, few studies have assessed the intra‐specific relationship between seed size and recruitment, comparing plant communities differing in canopy cover. Here, seeds from four plant species commonly occurring in ecotones between open and closed habitats (Convallaria majalis, Frangula alnus, Prunus padus and Prunus spinosa) were weighed and sown individually (3200 seeds per species) in open and closed‐canopy sites, and seedling emergence and survival recorded over 3 years. Our results show a generally positive, albeit weak, relationship between seed size and recruitment. In only one of the species, C. majalis, was there an association between closed canopy habitat and a positive seed size effect on recruitment. We conclude that there is a weak selection gradient favouring larger seeds, but that this selection gradient is not clearly related to habitat.     

Wheat's wild relatives vary in their response to nitrogen and ozone

The wild relatives of bread wheat ( Triticum aestivum ) are valued by plant breeders for their genetic diversity. However, increasing levels of nitrogen (N) deposition and ground‐level ozone (O₃) threaten plant biodiversity in the Mediterranean and Near‐East, a hotspot for many crop wild relatives. Knowledge of the effect of these air pollutants in combination is still limited, but early indications are that effects vary depending on the level of pollutants, and on the sensitivity of the species to N and O₃. This study examined the responses of four important wheat wild relatives ( Aegilops tauschii , Aegilops speltoides , Triticum dicoccoides and Triticum monococcum ) and one modern wheat cultivar ( T. aestivum ‘Cadenza’) to treatments of N (equivalent to 50 kg ha^?1 year^?1 ammonium nitrate) and O₃ (100 ppb for 21 days), alone and in combination. Measurements included root, shoot and seed biomass, and electrolyte ratios. The O₃ sensitivity of A. tauschii and T. aestivum ‘Cadenza’ were exacerbated by the addition of N, while A. speltoides was found to be nitrophilous, with N ameliorating the negative effect of O_3. Both T. aestivum ‘Cadenza’ and T. dicoccoides produced immature seed heads, with the cultivar's seed head biomass reduced in response to O₃ and N + O₃ while that of T. dicoccoides was largely unaffected. These data suggest that all four wild relatives are likely to be affected when N and O₃ air pollutants co‐occur, and there in situ populations may therefore be at risk. Equally, the results of this study can inform use of their beneficial traits by wheat breeders, and alert them to the inadvertent inclusion of N and O₃ sensitivity.     

Tree mineral nutrition is deteriorating in Europe

The response of forest ecosystems to increased atmospheric CO₂ is constrained by nutrient availability. It is thus crucial to account for nutrient limitation when studying the forest response to climate change. The objectives of this study were to describe the nutritional status of the main European tree species, to identify growth‐limiting nutrients and to assess changes in tree nutrition during the past two decades. We analysed the foliar nutrition data collected during 1992–2009 on the intensive forest monitoring plots of the ICP Forests programme. Of the 22 significant temporal trends that were observed in foliar nutrient concentrations, 20 were decreasing and two were increasing. Some of these trends were alarming, among which the foliar P concentration in F. sylvatica, Q. Petraea and P. sylvestris that significantly deteriorated during 1992–2009. In Q. Petraea and P. sylvestris, the decrease in foliar P concentration was more pronounced on plots with low foliar P status, meaning that trees with latent P deficiency could become deficient in the near future. Increased tree productivity, possibly resulting from high N deposition and from the global increase in atmospheric CO₂, has led to higher nutrient demand by trees. As the soil nutrient supply was not always sufficient to meet the demands of faster growing trees, this could partly explain the deterioration of tree mineral nutrition. The results suggest that when evaluating forest carbon storage capacity and when planning to reduce CO₂ emissions by increasing use of wood biomass for bioenergy, it is crucial that nutrient limitations for forest growth are considered.     

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.     

Bulb and Root Rot in Lily (Lilium longiflorum) and Onion (Allium cepa) in Israel

In the past 10 years, there has been a substantial increase in reports, from growers and extension personnel, on bulb and root rots in lily (Lilium longiflorum) in Israel. Rot in these plants, when grown as cut flowers, caused serious economic damage expressed in reduction in yield and quality. In lily, the fungal pathogens involved in the rot were characterized as binucleate Rhizoctonia AG‐A, Rhizoctonia solani, Pythium oligandrum, Fusarium proliferatum (white and purple isolates) and F. oxysporum, using morphological and molecular criteria. These fungi were the prevalent pathogens in diseased plants collected from commercial greenhouses. Pathogenicity trials were conducted on lily bulbs and onion seedlings under controlled conditions in a greenhouse to complete Koch's postulates. Disease symptoms on lily were most severe in treatments inoculated with binucleate Rhizoctonia AG‐A, P. oligandrum and F. proliferatum. Plant height was lower in the above treatments compared with the control plants. The least aggressive fungus was R. solani. In artificial inoculations of onion, seedling survival was significantly affected by all fungi. The most pathogenic fungus was F. proliferatum w and the least were isolates of F. oxysporum (II and III). All fungi were successfully re‐isolated from the inoculated plants.     

Karyotype diversity and genome size variation in Neotropical Maxillariinae orchids

• Orchidaceae is a widely distributed plant family with very diverse vegetative and floral morphology, and such variability is also reflected in their karyotypes. However, since only a low proportion of Orchidaceae has been analysed for chromosome data, greater diversity may await to be unveiled. Here we analyse both genome size (GS) and karyotype in two subtribes recently included in the broadened Maxillariinea to detect how much chromosome and GS variation there is in these groups and to evaluate which genome rearrangements are involved in the species evolution.
• To do so, the GS (14 species), the karyotype – based on chromosome number, heterochromatic banding and 5S and 45S rDNA localisation (18 species) – was characterised and analysed along with published data using phylogenetic approaches.
• The GS presented a high phylogenetic correlation and it was related to morphological groups in Bifrenaria (larger plants – higher GS). The two largest GS found among genera were caused by different mechanisms: polyploidy in Bifrenaria tyrianthina and accumulation of repetitive DNA in Scuticaria hadwenii. The chromosome number variability was caused mainly through descending dysploidy, and x=20 was estimated as the base chromosome number.
• Combining GS and karyotype data with molecular phylogeny, our data provide a more complete scenario of the karyotype evolution in Maxillariinae orchids, allowing us to suggest, besides dysploidy, that inversions and transposable elements as two mechanisms involved in the karyotype evolution. Such karyotype modifications could be associated with niche changes that occurred during species evolution.