Diversification of Legume-Feeding Psyllids (Hemiptera, Psylloidea) and Their Host Plants (Leguminosae, Genisteae)

Psyllids ('jumping plant lice') are small phytophagous insects that are related to aphids, scales and whiteflies (Hemiptera, sternorrhyncha). Psyllids are highly host specific, occurring on one or a few closely related hosts, and they predominantly feed on dicotyledonous angiosperms. In the subfamily Arytaininae (Psylloidea, Psyllinae) there are five psyllid genera that feed exclusively on shrubby legumes in the Genisteae (Leguminosae, Papilionoideae), and the species diversity for both plant and insect groups is highest in the Mediterranean. I made a detailed field survey of psyllids on Genisteae hosts in the western Mediterranean, including southern Iberia, NW Africa and two of the Macaronesian archipelagos (Canary Islands and Madeira). These collections (over 300) of both psyllids and legumes provided the basis for the taxonomic, phylogenetic and co-diversification analyses presented in this study. I have reassessed the classification of the legume-feeding psyllids native to Macaronesia, and I have revised the taxonomy of one genus (Arytainilla). I present evidence that the largest Macaronesian group has a unique island origin distinct from the predominantly continental genera. This Macaronesian group, which also has three continental members, is described as a new genus in order to clarify the monophyly and placement of this group within the Arytaininae. Seventeen new psyllid species in four arytainine genera, discovered in continental and Macaronesian regions, are proposed. I constructed phylogenies for both the arytainine psyllids and their legume host plants, in order to compare colonization, biogeographic patterns and island radiations. I present a phylogenetic study of the Palaearctic arytainine psyllids that incorporates both morphological data (adult and nymphal characters) and molecular data (mitochondrial genes: cytochrome oxidase I and II, including the intervening tRNA leucine; and the small ribosomal subunit tRNA). To investigate the evolution of the island legumes and to establish the relationships between continental and island host plants, a molecular phylogeny of part of the Genisteae was generated from sequences of the nuclear region: ITS1-5.8S-ITS2. The legume phylogeny shows a Mediterranean origin for the Canarian Genisteae (Adenocarpus, Genista and Teline), and a diphyletic origin for Teline - with two distinct island groups nested within Genista. The psyllid phylogeny shows that the two largest genera are paraphyletic, but there is some evidence that the Genisteae-feeders, as a whole, are monophyletic. The phylogenetic analyses for both psyllids and legumes highlight the problems of establishing host-parasite interactions using traditional morphological classifications alone. Colonization and biogeographic patterns among the island psyllid species implies a close correlation between the radiation of psyllids and the diversity of their host plants. Psyllid and legume phylogenies are compared in order to establish the extent of phylogenetic congruence between the insects and their host plants. To test assumptions of cospeciation, an absolute time scale is applied to both plant and insect phylogenies. A comparison of psyllid and legume phylogenies suggests that, whilst rare cospeciation events may play a significant role in promoting diversification, historical reconstructions of psyllid-legume interactions are complicated by systemic host switching. Psyllids appear to be opportunistic specialists with host switching occurring when the plant lineage fluctuates in geographical abundance, population structure or through dispersal. However, preadaptation is evident in many cases where selection of a new host may be constrained by plant chemistry and architecture. Successful establishment by a psyllid colonist is more likely when available hosts are phylogenetically and ecologically related to the original host. A history of parallel cladogenesis between psyllid and legume lineages is rejected in favour of a fluctuating lineage model of co-diversification which presents a more realistic interpretation of the present day pattern of host associations

New State Record of the Psyllid Heterotrioza chenopodii (Reuter, 1876) (Hemiptera: Psylloidea: Triozidae) for Hawaii

We report the first state record of a widespread palaearctic psyllid species, Heterotrioza chenopodii (Reuter, 1876), for the state of Hawaii. This species belongs to a small genus of 13 species feeding exclusively on host plants in the plant family Amaranthaceae (Lauterer 1982, Burckhardt and Ouvrard 2012, Ouvrard 2019). Recorded host genera are Atriplex, Beta, Chenopodium, and Spinacia (Ouvrard 2019). In Hawaii, a likely host plant is Atriplex suberecta, and possibly A. semibaccata and Chenopodium oahuense

Genetic Structure of the Polymorphic Metrosideros (Myrtaceae) Complex in the Hawaiian Islands Using Nuclear Microsatellite Data

Five species of Metrosideros (Myrtaceae) are recognized in the Hawaiian Islands, including the widespread M. polymorpha, and are characterized by a multitude of distinctive, yet overlapping, habit, ecological, and morphological forms. It remains unclear, despite several previous studies, whether the morphological variation within Hawaiian Metrosideros is due to hybridization, genetic polymorphism, phenotypic plasticity, or some combination of these processes. The Hawaiian Metrosideros complex has become a model system to study ecology and evolution; however this is the first study to use microsatellite data for addressing inter-island patterns of variation from across the Hawaiian Islands.Ten nuclear microsatellite loci were genotyped from 143 individuals of Metrosideros. We took advantage of the bi-parental inheritance and rapid mutation rate of these data to examine the validity of the current taxonomy and to investigate whether Metrosideros plants from the same island are more genetically similar than plants that are morphologically similar. The Bayesian algorithm of the program structure was used to define genetic groups within Hawaiian Metrosideros and the closely related taxon M. collina from the Marquesas and Austral Islands. Several standard and nested AMOVAs were conducted to test whether the genetic diversity is structured geographically or taxonomically.The results suggest that Hawaiian Metrosideros have dynamic gene flow, with genetic and morphological diversity structured not simply by geography or taxonomy, but as a result of parallel evolution on islands following rampant island-island dispersal, in addition to ancient chloroplast capture. Results also suggest that the current taxonomy requires major revisions in order to reflect the genetic structure revealed in the microsatellite data

Emerging New Crop Pests: Ecological Modelling and Analysis of the South American Potato Psyllid Russelliana solanicola (Hemiptera: Psylloidea) and Its Wild Relatives

© 2017 Syfert et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited

Phylogenomics and the evolution of hemipteroid insects.

Hemipteroid insects (Paraneoptera), with over 10% of all known insect diversity, are a major component of terrestrial and aquatic ecosystems. Previous phylogenetic analyses have not consistently resolved the relationships among major hemipteroid lineages. We provide maximum likelihood-based phylogenomic analyses of a taxonomically comprehensive dataset comprising sequences of 2,395 single-copy, protein-coding genes for 193 samples of hemipteroid insects and outgroups. These analyses yield a well-supported phylogeny for hemipteroid insects. Monophyly of each of the three hemipteroid orders (Psocodea, Thysanoptera, and Hemiptera) is strongly supported, as are most relationships among suborders and families. Thysanoptera (thrips) is strongly supported as sister to Hemiptera. However, as in a recent large-scale analysis sampling all insect orders, trees from our data matrices support Psocodea (bark lice and parasitic lice) as the sister group to the holometabolous insects (those with complete metamorphosis). In contrast, four-cluster likelihood mapping of these data does not support this result. A molecular dating analysis using 23 fossil calibration points suggests hemipteroid insects began diversifying before the Carboniferous, over 365 million years ago. We also explore implications for understanding the timing of diversification, the evolution of morphological traits, and the evolution of mitochondrial genome organization. These results provide a phylogenetic framework for future studies of the group

Multiple Multilocus DNA Barcodes from the Plastid Genome Discriminate Plant Species Equally Well

A universal barcode system for land plants would be a valuable resource, with potential utility in fields as diverse as ecology, floristics, law enforcement and industry. However, the application of plant barcoding has been constrained by a lack of consensus regarding the most variable and technically practical DNA region(s). We compared eight candidate plant barcoding regions from the plastome and one from the mitochondrial genome for how well they discriminated the monophyly of 92 species in 32 diverse genera of land plants (N = 251 samples). The plastid markers comprise portions of five coding (rpoB, rpoC1, rbcL, matK and 23S rDNA) and three non-coding (trnH-psbA, atpF–atpH, and psbK–psbI) loci. Our survey included several taxonomically complex groups, and in all cases we examined multiple populations and species. The regions differed in their ability to discriminate species, and in ease of retrieval, in terms of amplification and sequencing success. Single locus resolution ranged from 7% (23S rDNA) to 59% (trnH-psbA) of species with well-supported monophyly. Sequence recovery rates were related primarily to amplification success (85–100% for plastid loci), with matK requiring the greatest effort to achieve reasonable recovery (88% using 10 primer pairs). Several loci (matK, psbK–psbI, trnH-psbA) were problematic for generating fully bidirectional sequences. Setting aside technical issues related to amplification and sequencing, combining the more variable plastid markers provided clear benefits for resolving species, although with diminishing returns, as all combinations assessed using four to seven regions had only marginally different success rates (69–71%; values that were approached by several two- and three-region combinations). This performance plateau may indicate fundamental upper limits on the precision of species discrimination that is possible with DNA barcoding systems that include moderate numbers of plastid markers. Resolution to the contentious debate on plant barcoding should therefore involve increased attention to practical issues related to the ease of sequence recovery, global alignability, and marker redundancy in multilocus plant DNA barcoding systems

Control of hyperglycaemia in paediatric intensive care (CHiP): study protocol.

BACKGROUND: There is increasing evidence that tight blood glucose (BG) control improves outcomes in critically ill adults. Children show similar hyperglycaemic responses to surgery or critical illness. However it is not known whether tight control will benefit children given maturational differences and different disease spectrum. METHODS/DESIGN: The study is an randomised open trial with two parallel groups to assess whether, for children undergoing intensive care in the UK aged <or= 16 years who are ventilated, have an arterial line in-situ and are receiving vasoactive support following injury, major surgery or in association with critical illness in whom it is anticipated such treatment will be required to continue for at least 12 hours, tight control will increase the numbers of days alive and free of mechanical ventilation at 30 days, and lead to improvement in a range of complications associated with intensive care treatment and be cost effective. Children in the tight control group will receive insulin by intravenous infusion titrated to maintain BG between 4 and 7.0 mmol/l. Children in the control group will be treated according to a standard current approach to BG management. Children will be followed up to determine vital status and healthcare resources usage between discharge and 12 months post-randomisation. Information regarding overall health status, global neurological outcome, attention and behavioural status will be sought from a subgroup with traumatic brain injury (TBI). A difference of 2 days in the number of ventilator-free days within the first 30 days post-randomisation is considered clinically important. Conservatively assuming a standard deviation of a week across both trial arms, a type I error of 1% (2-sided test), and allowing for non-compliance, a total sample size of 1000 patients would have 90% power to detect this difference. To detect effect differences between cardiac and non-cardiac patients, a target sample size of 1500 is required. An economic evaluation will assess whether the costs of achieving tight BG control are justified by subsequent reductions in hospitalisation costs. DISCUSSION: The relevance of tight glycaemic control in this population needs to be assessed formally before being accepted into standard practice

Consistent patterns of common species across tropical tree communities

Trees structure the Earth’s most biodiverse ecosystem, tropical forests. The vast number of tree species presents a formidable challenge to understanding these forests, including their response to environmental change, as very little is known about most tropical tree species. A focus on the common species may circumvent this challenge. Here we investigate abundance patterns of common tree species using inventory data on 1,003,805 trees with trunk diameters of at least 10 cm across 1,568 locations1,2,3,4,5,6 in closed-canopy, structurally intact old-growth tropical forests in Africa, Amazonia and Southeast Asia. We estimate that 2.2%, 2.2% and 2.3% of species comprise 50% of the tropical trees in these regions, respectively. Extrapolating across all closed-canopy tropical forests, we estimate that just 1,053 species comprise half of Earth’s 800 billion tropical trees with trunk diameters of at least 10 cm. Despite differing biogeographic, climatic and anthropogenic histories7, we find notably consistent patterns of common species and species abundance distributions across the continents. This suggests that fundamental mechanisms of tree community assembly may apply to all tropical forests. Resampling analyses show that the most common species are likely to belong to a manageable list of known species, enabling targeted efforts to understand their ecology. Although they do not detract from the importance of rare species, our results open new opportunities to understand the world’s most diverse forests, including modelling their response to environmental change, by focusing on the common species that constitute the majority of their trees.Publisher PDFPeer reviewe

The global abundance of tree palms

Aim Palms are an iconic, diverse and often abundant component of tropical ecosystems that provide many ecosystem services. Being monocots, tree palms are evolutionarily, morphologically and physiologically distinct from other trees, and these differences have important consequences for ecosystem services (e.g., carbon sequestration and storage) and in terms of responses to climate change. We quantified global patterns of tree palm relative abundance to help improve understanding of tropical forests and reduce uncertainty about these ecosystems under climate change. Location Tropical and subtropical moist forests. Time period Current. Major taxa studied Palms (Arecaceae). Methods We assembled a pantropical dataset of 2,548 forest plots (covering 1,191 ha) and quantified tree palm (i.e., ≥10 cm diameter at breast height) abundance relative to co‐occurring non‐palm trees. We compared the relative abundance of tree palms across biogeographical realms and tested for associations with palaeoclimate stability, current climate, edaphic conditions and metrics of forest structure. Results On average, the relative abundance of tree palms was more than five times larger between Neotropical locations and other biogeographical realms. Tree palms were absent in most locations outside the Neotropics but present in >80% of Neotropical locations. The relative abundance of tree palms was more strongly associated with local conditions (e.g., higher mean annual precipitation, lower soil fertility, shallower water table and lower plot mean wood density) than metrics of long‐term climate stability. Life‐form diversity also influenced the patterns; palm assemblages outside the Neotropics comprise many non‐tree (e.g., climbing) palms. Finally, we show that tree palms can influence estimates of above‐ground biomass, but the magnitude and direction of the effect require additional work. Conclusions Tree palms are not only quintessentially tropical, but they are also overwhelmingly Neotropical. Future work to understand the contributions of tree palms to biomass estimates and carbon cycling will be particularly crucial in Neotropical forests