Publications by authors named "Diana M Percy"

19 Publications

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transect of Europe: records of willow-associated weevils (Coleoptera: Curculionoidea) from Greece to Arctic Norway, with insights from DNA barcoding.

Biodivers Data J 2020 3;8:e52881. Epub 2020 Jun 3.

University of British Columbia, Vancouver, Canada University of British Columbia Vancouver Canada.

Background: Curculionid beetles associated with willow ( spp.) were surveyed at 42 sites across Europe, from Greece (lat. 38.8 °N) to arctic Norway (lat. 69.7 °N). DNA sequence data provide additional verification of identifications and geographic clustering.

New Information: In all, 73 curculionid species were collected from willows, of which seven were particularly abundant. The most widespread species were: Fabricius, 1793 at 15 sites; Germar, 1821 at 13 sites; (Linnaeus, 1758) at 11 sites; Germar, 1824 at 10 sites; and (Paykull, 1792), (Herbst, 1797), and (Linnaeus, 1758) all at nine sites. The mean number of curculionid species collected on willow at each site was 5.5 (range 0-14). Compared to chrysomelids, curculionids were richer in species but the species had relatively low average abundance. Widespread curculionid species appear to have scattered and patchy observed distributions with limited geographical structuring in our data. However, deeper sampling (e.g. over multiple seasons and years), would give a better indication of distribution, and may increase apparent geographical structuring. There is some site-to-site variation in colour in a few taxa, but little notable size variation. DNA barcoding, performed on some of the more common species, provides clear species clusters and definitive separation of the taxonomically more challenging species, as well as some interesting geographic insights. Our northernmost sample of is unique in clustering with Canadian samples of this species. On the other hand, our samples of cluster with European samples and are distinct from a separate Canadian cluster of this species. We provide the first available DNA sequences for Gyllenhal, 1834 (Hungary).
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http://dx.doi.org/10.3897/BDJ.8.e52881DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7286951PMC
June 2020

transect of Europe: additional leaf beetle (Chrysomelidae) records and insights from chrysomelid DNA barcoding.

Biodivers Data J 2019 4;7:e46663. Epub 2019 Nov 4.

Natural History Museum, London, United Kingdom Natural History Museum London United Kingdom.

Occurrence patterns of chrysomelid beetles (Coleoptera: Chrysomelidae), associated with willow ( spp.) at 42 sites across Europe, have previously been described. The sites form a transect from Greece (lat. 38.8 °N) to arctic Norway (lat. 69.7 °N). This paper reports additional records and the results of DNA sequencing in certain genera. Examination of further collections from the transect has added 13 species in the genera , (2 spp.), (2 spp.), (3 spp.) and We also report the sequencing of the DNA regions cytochrome oxidase 1 (CO1) and cytochrome B (cytB) for a number of samples in the genera and The cytB sequences are the first available for some of these taxa. The DNA barcoding largely confirmed previous identifications but allowed a small number of re-assignments between related species. Most notably, however, it was evident that the southernmost material (Greece and Bulgaria) of specimens, previously treated as sens. lat., belonged to a distinctive molecular cluster. Morphological re-examination revealed these to be Allard, 1878. This is an example of how morphotaxonomy and DNA barcoding can work iteratively to refine identification. Our sequences for appear to be the first available for this taxon. Finally, there is little geographic structure evident, even in widely dispersed species.
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http://dx.doi.org/10.3897/BDJ.7.e46663DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6848237PMC
November 2019

On the origin of orphan hybrids between and .

AoB Plants 2019 Feb 19;11(1):ply071. Epub 2018 Nov 19.

Department of Botany, University of British Columbia, Vancouver, British Columbia, Canada.

We report the investigation of an × population in British Columbia that is disjunct from its parents-the latter species is present locally but ecologically separated, while the former is entirely absent. To confirm hybridity, we used multivariate analysis of floral characters of field-sampled populations to ordinate phenotypes of putative hybrids in relation to those of the parental species. Microsatellite genotypes at 11 loci from 72 parental-type and putative hybrid individuals were analysed to assess evidence for admixture. Maternally inherited plastid sequences were analysed to infer the direction of hybridization and test hypotheses on the origin of the orphan hybrid population. Plants from the orphan hybrid population are on average intermediate between typical and for most phenotypes examined and show evidence of genetic admixture. This population lies beyond the range of , but within the range of . No pure individuals were observed in the vicinity, nor is this species known to occur within 200 km of the site. The hybrids share a plastid haplotype with local populations. Alternative explanations for this pattern are evaluated. While we cannot rule out long-distance pollen dispersal followed by proliferation of hybrid genotypes, we consider the spread of an plastid during genetic swamping of a historical population to be more parsimonious.
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http://dx.doi.org/10.1093/aobpla/ply071DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6341775PMC
February 2019

Phylogenomics and the evolution of hemipteroid insects.

Proc Natl Acad Sci U S A 2018 12 26;115(50):12775-12780. Epub 2018 Nov 26.

Systematic Entomology, Hokkaido University, Sapporo, 060-8589 Japan.

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.
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http://dx.doi.org/10.1073/pnas.1815820115DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6294958PMC
December 2018

Revision of the Hawaiian psyllid genus , with descriptions of seven new species (Hemiptera, Psylloidea, Triozidae).

Authors:
Diana M Percy

Zookeys 2018 15(758):75-113. Epub 2018 May 15.

Department of Life Sciences, Natural History Museum, Cromwell Road, London, UK.

The endemic Hawaiian genus Caldwell, 1940 is highly distinctive due to the extremely long genal processes. In addition, some of the immatures are ornamented with extraordinary tubercles and tentacles. Two species are redescribed, and seven new species are described, bringing the total number of species in the genus to nine. All species are hosted by a single, endemic host plant, (Sapotaceae), which is distributed across all major islands in the archipelago. The majority of species are single island endemics. A sister taxon pair is found sympatrically on the same individual plants on Kauai, and putative sister or at least closely related species are also found sympatrically on Oahu and Hawaii, suggesting these taxa may have diversified in sympatry. However, there is no observed ecological niche partitioning, despite some striking morphological diversity, as all species have free-living immatures that are found on the leaf surface, and therefore no apparent biological shifts are coincident with occupying the same host plant. Two species groups are represented by strikingly different female terminalia structure and endoskeletal development, although ovipositor structure is very similar between the two groups. Mitochondrial DNA barcodes (COI and cytB) are provided for eight of the nine species. A phylogenetic analysis of the mitochondrial barcode regions indicates species relationships within and provides a comparison of genetic divergence with other Hawaiian endemic genera.
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http://dx.doi.org/10.3897/zookeys.758.23019DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5964088PMC
May 2018

Using herbarium-derived DNAs to assemble a large-scale DNA barcode library for the vascular plants of Canada.

Appl Plant Sci 2017 Dec 22;5(12). Epub 2017 Dec 22.

Centre for Biodiversity Genomics, University of Guelph, 50 Stone Road East, Guelph, Ontario N1G 2W1, Canada.

Premise Of The Study: Constructing complete, accurate plant DNA barcode reference libraries can be logistically challenging for large-scale floras. Here we demonstrate the promise and challenges of using herbarium collections for building a DNA barcode reference library for the vascular plant flora of Canada.

Methods: Our study examined 20,816 specimens representing 5076 of 5190 vascular plant species in Canada (98%). For 98% of the specimens, at least one of the DNA barcode regions was recovered from the plastid loci and and from the nuclear ITS2 region. We used beta regression to quantify the effects of age, type of preservation, and taxonomic affiliation (family) on DNA sequence recovery.

Results: Specimen age and method of preservation had significant effects on sequence recovery for all markers, but influenced some families more (e.g., Boraginaceae) than others (e.g., Asteraceae).

Discussion: Our DNA barcode library represents an unparalleled resource for metagenomic and ecological genetic research working on temperate and arctic biomes. An observed decline in sequence recovery with specimen age may be associated with poor primer matches, intragenomic variation (for ITS2), or inhibitory secondary compounds in some taxa.
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http://dx.doi.org/10.3732/apps.1700079DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5749818PMC
December 2017

Making the most of your host: the -feeding psyllids (Hemiptera, Psylloidea) of the Hawaiian Islands.

Authors:
Diana M Percy

Zookeys 2017 31(649):1-163. Epub 2017 Jan 31.

Department of Life Sciences, Natural History Museum, Cromwell Road, London, UK, and University of British Columbia, Faculty of Science, University Boulevard, Vancouver, BC, Canada.

The Hawaiian psyllids (Psylloidea, Triozidae) feeding on Metrosideros (Myrtaceae) constitute a remarkable radiation of more than 35 species. This monophyletic group has diversified on a single, highly polymorphic host plant species, Metrosideros polymorpha. Eleven Metrosideros-feeding species included in the Insects of Hawaii by Zimmerman are redescribed, and an additional 25 new species are described. Contrary to previous classifications that placed the Metrosideros-feeders in two genera, Trioza Foerster, 1848 and Kuwayama Crawford, 1911, all 36 named species are placed in Pariaconus Enderlein, 1926; and the relationship of this genus to other Pacific taxa within the family Triozidae, and other Austro-Pacific taxa feeding on host plants in Myrtaceae is clarified. The processes of diversification in Pariaconus include shifts in galling habit, geographic isolation within and between islands, and preferences for different morphotypes of the host plant. Four species groups are recognized: the bicoloratus and minutus groups are free-living or form pit galls, and together with the kamua group (composing all of the Kauai species) form a basal assemblage; the more derived closed gall species in the ohialoha group are found on all major islands except Kauai. The diversification of Pariaconus has likely occurred over several million years. Within island diversification is exemplified in the kamua group, and within species variation in the ohialoha group, but species discovery rates suggest this radiation remains undersampled. Mitochondrial DNA barcodes are provided for 28 of the 36 species. Genetic divergence, intraspecific genetic structure, and parallel evolution of different galling biologies and morphological traits are discussed within a phylogenetic framework. Outgroup analysis for the genus Pariaconus and ancestral character state reconstruction suggest pit-galling may be the ancestral state, and the closest outgroups are Palaearctic-Australasian taxa rather than other Pacific Metrosideros-feeders.
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http://dx.doi.org/10.3897/zookeys.649.10213DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5345378PMC
January 2017

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

PLoS One 2017 4;12(1):e0167764. Epub 2017 Jan 4.

Natural History Museum, Department of Life Sciences, London, United Kingdom.

Food security is threatened by newly emerging pests with increased invasive potential accelerated through globalization. The Neotropical jumping plant louse Russelliana solanicola Tuthill is currently a localized potato pest and probable vector of plant pathogens. It is an unusually polyphagous species and is widely distributed in and along the Andes. To date, introductions have been detected in eastern Argentina, southern Brazil and Uruguay. Species distribution models (SDMs) and trait comparisons based on contemporary and historical collections are used to estimate the potential spread of R. solanicola worldwide. We also extend our analyses to all described species in the genus Russelliana in order to assess the value of looking beyond pest species to predict pest spread. We investigate the extent to which data on geographical range and environmental niche can be effectively extracted from museum collections for comparative analyses of pest and non-pest species in Russelliana. Our results indicate that R. solanicola has potential for invasion in many parts of the world with suitable environmental conditions that currently have or are anticipated to increase potato cultivation. Large geographical ranges are characteristic of a morphological subgeneric taxon group that includes R. solanicola; this same group also has a larger environmental breadth than other groups within the genus. Ecological modelling using museum collections provides a useful tool for identifying emerging pests and developing integrated pest management programs.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0167764PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5214844PMC
August 2017

The transcriptional landscape of insect galls: psyllid (Hemiptera) gall formation in Hawaiian Metrosideros polymorpha (Myrtaceae).

BMC Genomics 2015 Nov 16;16:943. Epub 2015 Nov 16.

School of Biological and Chemical Sciences, Queen Mary University of London, London, E1 4NS, UK.

Background: Recent studies show that galling Hymenoptera and Diptera are able to synthesize the plant hormone indole-3-acetic acid (auxin) from tryptophan and that plant response to insect-produced auxin is implicated in gall formation. We examined the leaf transcriptome of galled and ungalled leaves of individuals of the Hawaiian endemic plant Metrosideros polymorpha (Myrtaceae) subject to infestation by psyllid (Hemiptera) gall-makers in the genus Trioza (Triozidae).

Results: Transcript libraries were sequenced using Illumina technology and the reads assembled de novo into contigs. Functional identification of contigs followed a two-step procedure, first identifying contigs by comparison to the completely sequenced genome of the related Eucalyptus, followed by identifying the equivalent Arabidopsis gene using a pre-computed mapping between Eucalyptus and Arabidopsis genes. This allowed us to use the rich functional annotation of the Arabidopsis genome to assess the transcriptional landscape of galling in Metrosideros. Comparing galled and ungalled leaves, we find a highly significant enrichment of expressed genes with a gene ontology (GO) annotation to auxin response in the former. One gene consistently expressed in all galled trees examined but not detected in any libraries from ungalled leaves was the Metrosideros version of SMALL AUXIN UPREGULATED (SAUR) 67 which appears to be a marker for leaf-galling in Metrosideros.

Conclusions: We conclude that an auxin response is involved in galling by Metrosideros psyllids. The possibility should therefore be considered that psyllids (like other insects examined) are able to synthesize auxin.
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http://dx.doi.org/10.1186/s12864-015-2109-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4647832PMC
November 2015

Understanding the spectacular failure of DNA barcoding in willows (Salix): does this result from a trans-specific selective sweep?

Mol Ecol 2014 Oct 15;23(19):4737-56. Epub 2014 Jul 15.

Department of Botany, University of British Columbia, Vancouver, BC, Canada, V6T 1Z4; Biodiversity Research Centre, University of British Columbia, Vancouver, BC, Canada, V6T 1Z4.

Willows (Salix: Salicaceae) form a major ecological component of Holarctic floras and consequently are an obvious target for a DNA-based identification system. We surveyed two to seven plastid genome regions (~3.8 kb; ~3% of the genome) from 71 Salix species across all five subgenera, to assess their performance as DNA barcode markers. Although Salix has a relatively high level of interspecific hybridization, this may not sufficiently explain the near complete failure of barcoding that we observed: only one species had a unique barcode. We recovered 39 unique haplotypes, from more than 500 specimens, that could be partitioned into six major haplotype groups. A unique variant of group I (haplotype 1*) was shared by 53 species in three of five Salix subgenera. This unusual pattern of haplotype sharing across infrageneric taxa is suggestive of either a massive nonrandom coalescence failure (incomplete lineage sorting), or of repeated plastid capture events, possibly including a historical selective sweep of haplotype 1* across taxonomic sections. The former is unlikely as molecular dating indicates that haplotype 1* originated recently and is nested in the oldest major haplotype group in the genus. Further, we detected significant non-neutrality in the frequency spectrum of mutations in group I, but not outside group I, and demonstrated a striking absence of geographical (isolation by distance) effects in the haplotype distributions of this group. The most likely explanation for the patterns we observed involves recent repeated plastid capture events, aided by widespread hybridization and long-range seed dispersal, but primarily propelled by one or more trans-species selective sweeps.
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http://dx.doi.org/10.1111/mec.12837DOI Listing
October 2014

Semiochemical and Vibrational Cues and Signals Mediating Mate Finding and Courtship in Psylloidea (Hemiptera): A Synthesis.

Insects 2014 Jul 21;5(3):577-95. Epub 2014 Jul 21.

Department of Zoology, La Trobe University, Melbourne, Victoria 3086, Australia.

Mate finding and courtship involve complex interactions that require close coordination between individuals of the opposite gender. Well-organized signalling systems, sometimes involving a combination of signal modalities, are required to convey species-specific and individual information to members of the opposite gender. Previous studies of psyllids have focused on single-signal modalities and have largely ignored the potentially interdependent nature of different types of signals. Several studies have shown that semiochemicals play a role in psyllid mate finding. However, long-range semiochemical sex attractants, such as the highly volatile sex pheromones used by many Lepidoptera (molecular weights <300), are yet to be identified. The compounds identified thus far, namely 13-methylheptacosane (from Cacopsylla pyricola) and dodecanoic acid (from Diaphorina citri), seem to have short range activity or no activity under field conditions. The possible role played by cuticular hydrocarbons in psyllid courtship remains largely ignored. Conversely, many psyllid species rely on vibrational signals for mate finding and mate assessment during courtship. This apparent disproportional reliance on vibrational rather than semiochemical signals suggests that vibrational signals have been more influential in sexual selection in psyllids. However, male fitness, female choice and benefits accrued from selecting fitter males remain poorly understood.
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http://dx.doi.org/10.3390/insects5030577DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4592587PMC
July 2014

Spatial patterns of plant diversity below-ground as revealed by DNA barcoding.

Mol Ecol 2011 Mar 22;20(6):1289-302. Epub 2011 Jan 22.

Department of Integrative Biology, University of Guelph, Guelph, Ontario, Canada.

Our understanding of the spatial organization of root diversity in plant communities and of the mechanisms of community assembly has been limited by our ability to identify plants based on root tissue, especially in diverse communities. Here, we test the effectiveness of the plastid gene rbcL, a core plant DNA barcoding marker, for investigating spatial patterns of root diversity, and relate observed patterns to above-ground community structure. We collected 3800 root fragments from four randomly positioned, 1-m-deep soil profiles (two vertical transects per plot), located in an old-field community in southern Ontario, Canada, and extracted and sequenced DNA from 1531 subsampled fragments. We identified species by comparing sequences with a DNA barcode reference library developed previously for the local flora. Nearly 85% of sampled root fragments were successfully sequenced and identified as belonging to 29 plant species or species groups. Root abundance and species richness varied in horizontal space and were negatively correlated with soil depth. The relative abundance of taxa below-ground was correlated with their frequency above-ground (r = 0.73, P = 0.0001), but several species detected in root tissue were not observed in above-ground quadrats. Multivariate analyses indicated that diversity was highly structured below-ground, and associated with depth, root morphology, soil chemistry and soil texture, whereas little structure was evident above-ground. Furthermore, analyses of species co-occurrence indicates strong species segregation overall but random co-occurrence among confamilials. Our results provide insights into the role of environmental filtering and competitive interactions in the organization of plant diversity below-ground, and also demonstrate the utility of barcoding for the identification of plant roots.
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http://dx.doi.org/10.1111/j.1365-294X.2010.04989.xDOI Listing
March 2011

Are plant species inherently harder to discriminate than animal species using DNA barcoding markers?

Mol Ecol Resour 2009 May;9 Suppl s1:130-9

Department of Integrative Biology, University of Guelph, Guelph, ON, Canada.

The ability to discriminate between species using barcoding loci has proved more difficult in plants than animals, raising the possibility that plant species boundaries are less well defined. Here, we review a selection of published barcoding data sets to compare species discrimination in plants vs. animals. Although the use of different genetic markers, analytical methods and depths of taxon sampling may complicate comparisons, our results using common metrics demonstrate that the number of species supported as monophyletic using barcoding markers is higher in animals (> 90%) than plants (~70%), even after controlling for the amount of parsimony-informative information per species. This suggests that more than a simple lack of variability limits species discrimination in plants. Both animal and plant species pairs have variable size gaps between intra- and interspecific genetic distances, but animal species tend to have larger gaps than plants, even in relatively densely sampled genera. An analysis of 12 plant genera suggests that hybridization contributes significantly to variation in genetic discontinuity in plants. Barcoding success may be improved in some plant groups by careful choice of markers and appropriate sampling; however, overall fine-scale species discrimination in plants relative to animals may be inherently more difficult because of greater levels of gene-tree paraphyly.
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http://dx.doi.org/10.1111/j.1755-0998.2009.02652.xDOI Listing
May 2009

Genetic structure of the polymorphic metrosideros (Myrtaceae) complex in the Hwaiian islands using nuclear microsatellite data.

PLoS One 2009 4;4(3):e4698. Epub 2009 Mar 4.

Department of Botany, National Museum of Natural History, Smithsonian Institution, Washington, DC, United States of America.

Background: 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.

Methodology/principal Findings: 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.

Conclusions/significance: 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.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0004698PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2649539PMC
April 2009

Multiple multilocus DNA barcodes from the plastid genome discriminate plant species equally well.

PLoS One 2008 Jul 30;3(7):e2802. Epub 2008 Jul 30.

Department of Integrative Biology, University of Guelph, Guelph, Ontario, Canada.

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.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0002802PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2475660PMC
July 2008

Progressive island colonization and ancient origin of Hawaiian Metrosideros (Myrtaceae).

Proc Biol Sci 2008 Jul;275(1642):1479-90

National Museum of Natural History, Box 37012, Smithsonian Institution, Washington, DC 20013, USA.

Knowledge of the evolutionary history of plants that are ecologically dominant in modern ecosystems is critical to understanding the historical development of those ecosystems. Metrosideros is a plant genus found in many ecological and altitudinal zones throughout the Pacific. In the Hawaiian Islands, Metrosideros polymorpha is an ecologically dominant species and is also highly polymorphic in both growth form and ecology. Using 10 non-coding chloroplast regions, we investigated haplotype diversity in the five currently recognized Hawaiian Metrosideros species and an established out-group, Metrosideros collina, from French Polynesia. Multiple haplotype groups were found, but these did not match morphological delimitations. Alternative morphologies sharing the same haplotype, as well as similar morphologies occurring within several distinct island clades, could be the result of developmental plasticity, parallel evolution or chloroplast capture. The geographical structure of the data is consistent with a pattern of age progressive island colonizations and suggests de novo intra-island diversification. If single colonization events resulted in a similar array of morphologies on each island, this would represent parallel radiations within a single, highly polymorphic species. However, we were unable to resolve whether the pattern is instead explained by ancient introgression and incomplete lineage sorting resulting in repeated chloroplast capture. Using several calibration methods, we estimate the colonization of the Hawaiian Islands to be potentially as old as 3.9 (-6.3) Myr with an ancestral position for Kaua'i in the colonization and evolution of Metrosideros in the Hawaiian Islands. This would represent a more ancient arrival of Metrosideros to this region than previous studies have suggested.
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http://dx.doi.org/10.1098/rspb.2008.0191DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2602662PMC
July 2008

Plant-insect interactions: double-dating associated insect and plant lineages reveals asynchronous radiations.

Syst Biol 2004 Feb;53(1):120-7

Division of Environmental and Evolutionary Biology, Institute of Biomedical and Life Sciences, University of Glasgow, Glasgow G12 8QQ, U.K.

An increasing number of plant-insect studies using phylogenetic analysis suggest that cospeciation events are rare in plant-insect systems. Instead, nonrandom patterns of phylogenetic congruence are produced by phylogenetically conserved host switching (to related plants) or tracking of particular resources or traits (e.g., chemical). The dominance of host switching in many phytophagous insect groups may make the detection of genuine cospeciation events difficult. One important test of putative cospeciation events is to verify whether reciprocal speciation is temporally plausible. We explored techniques for double-dating of both plant and insect phylogenies. We use dated molecular phylogenies of a psyllid (Hemiptera)-Genisteae (Fabaceae) system, a predominantly monophagous insect-plant association widespread on the Atlantic Macaronesian islands. Phylogenetic reconciliation analysis suggests high levels of parallel cladogenesis between legumes and psyllids. However, dating using molecular clocks calibrated on known geological ages of the Macaronesian islands revealed that the legume and psyllid radiations were not contemporaneous but sequential. Whereas the main plant radiation occurred some 8 million years ago, the insect radiation occurred about 3 million years ago. We estimated that >60% of the psyllid speciation has resulted from host switching between related hosts. The only evidence for true cospeciation is in the much more recent and localized radiation of genistoid legumes in the Canary Islands, where the psyllid and legume radiations have been partially contemporaneous. The identification of specific cospeciation events over this time period, however, is hindered by the phylogenetic uncertainty in both legume and psyllid phylogenies due to the apparent rapidity of the species radiations.
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http://dx.doi.org/10.1080/10635150490264996DOI Listing
February 2004

Radiation, diversity, and host-plant interactions among island and continental legume-feeding psyllids.

Authors:
Diana M Percy

Evolution 2003 Nov;57(11):2540-56

Division of Environmental and Evolutionary Biology, Institute of Biomedical and Life Sciences, University of Glasgow, Glasgow G12 8QQ, United Kingdom.

Island archipelagos and insect-plant associations have both independently provided many useful systems for evolutionary study. The arytainine psyllid (Sternorrhyncha: Hemiptera) radiation on broom (Fabaceae: Genisteae) in the Canary Island archipelago provides a discrete system for examining the speciation of highly host-specific phytophagous insects in an island context. Phylogenetic reconstructions based on three datasets (adult and nymph morphological characters, and two mitochondrial DNA regions: part of the small subunit rRNA, and part of cytochrome oxidase I, cytochrome oxidase II and the intervening tRNA leucine) are generally consistent. The combined molecular tree provides a well-supported estimate of psyllid relationships and shows that there have been several colonizations of the Macaronesian islands but that only one has resulted in a significant radiation. Psyllid diversification has apparently been constrained by the presence of suitable host groups within the genistoid legumes, and the diversity, distribution, and abundance of those groups. The phylogeny, by indicating pairs of sister species, allows putative mechanisms of speciation to be assessed. The most common conditions associated with psyllid speciation are geographical allopatry with a host switch to closely related hosts (six examples), or geographical allopatry on the same host (four examples). Where allopatric speciation involves a host switch, these have all been to related hosts. There is some evidence that switches between unrelated host plants may be more likely in sympatry. Only one sister pair (Aryrtainilla cytisi and A. telonicola) and the putative host races of Arytinnis modica are sympatric but on unrelated hosts, which may be a necessary condition for sympatric speciation in these insects. Where several psyllids share the same host, resources appear to be partitioned by ecological specialization and differing psyllid phenology.
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http://dx.doi.org/10.1111/j.0014-3820.2003.tb01498.xDOI Listing
November 2003

Different fates of island brooms: contrasting evolution in Adenocarpus, Genista, and Teline (Genisteae, Fabaceae) in the Canary Islands and Madeira.

Am J Bot 2002 May;89(5):854-64

Division of Environmental and Evolutionary Biology, Institute of Biomedical and Life Sciences, University of Glasgow, Glasgow G12 8QQ, United Kingdom;

Analysis of sequence data from the internal transcribed spacers (ITS) and 5.8S region of nuclear ribosomal DNA show that Canarian and Madeiran brooms (Genisteae) of the genera Teline, Adenocarpus, and Genista are related to Mediterranean species and not to species from adjacent parts of Morocco. Each separate colonization of the islands has resulted in contrasting patterns of adaptation and radiation. The genus Teline is polyphyletic, with both groups (the "T. monspessulana group" and the "T. linifolia group") separately nested within Genista. Genista benehoavensis (La Palma) and G. tenera (Madeira) form, with G. tinctoria of Europe, a single clade characterized by vestigially arillate seeds. The Canarian species of Adenocarpus have almost identical sequence to the Mediterranean A. complicatus and are likely to be the result of island speciation after a very recent colonization event. This Canarian/Mediterranean A. complicatus group is sister to the afrotropical montane A. mannii which is probably derived from an earlier colonization from the Mediterranean, possibly via the Red Sea hills. The independent colonization and subsequent radiation of the two Teline groups in the Canary Islands make an interesting comparison: the phylogenies both show geographical structuring, each with a central and western island division of taxa. Within the "T. monspessulana group" there is some evidence that both continental and Madeiran taxa could be derived from the Canary Islands, although it is likely that near contemporaneous speciation occurred via rapid colonization of the mainland and islands. The finding of two groups within Teline also has implications for patterns of hybridization in those parts of the world where Teline species are invasive; in California members of the T. monspessulana group hybridize readily, but no hybrids have been recorded with T. linifolia which has been introduced in the same areas.
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http://dx.doi.org/10.3732/ajb.89.5.854DOI Listing
May 2002
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