The rust fungus, Puccinia psidii, is a devastating pathogen of introduced eucalypts (Eucalyptus spp.) in Brazil where it was first observed in 1912. This pathogen is hypothesized to be endemic to South and Central America and to have first infected eucalypts via a host jump from native guava (Psidium guajava). Ten microsatellite markers were used to genotype 148 P. psidii samples from eucalypts and guava plus five additional myrtaceous hosts across a wide geographic range of south-eastern Brazil and Uruguay. Principal coordinates analysis, a Bayesian clustering analysis and a minimum-spanning network revealed two major genetic clusters among the sampled isolates, one associated with guava and another associated with eucalypts and three additional hosts. Multilocus genotypes infecting guava differed by multiple mutational steps at eight loci compared with those infecting eucalypts. Approximate Bayesian computation revealed that evolutionary scenarios involving a coalescence event between guava- and eucalypt-associated pathogen populations within the past 1000 years are highly unlikely. None of the analyses supported the hypothesis that eucalypt-infecting P. psidii in Brazil originated via host jump from guava following the introduction of eucalypts to Brazil approximately 185 years ago. The existence of host-associated biotypes of P. psidii in Brazil indicates that this diversity must be considered when assessing the invasive threat posed by this pathogen to myrtaceous hosts worldwide.

Armillaria possesses several intriguing characteristics that have inspired wide interest in understanding phylogenetic relationships within and among species of this genus. Nuclear ribosomal DNA sequence-based analyses of Armillaria provide only limited information for phylogenetic studies among widely divergent taxa. More recent studies have shown that translation elongation factor 1-α (tef1) sequences are highly informative for phylogenetic analysis of Armillaria species within diverse global regions. This study used Neighbor-net and coalescence-based Bayesian analyses to examine phylogenetic relationships of newly determined and existing tef1 sequences derived from diverse Armillaria species from across the Northern Hemisphere, with Southern Hemisphere Armillaria species included for reference. Based on the Bayesian analysis of tef1 sequences, Armillaria species from the Northern Hemisphere are generally contained within the following four superclades, which are named according to the specific epithet of the most frequently cited species within the superclade: (i) Socialis/Tabescens (exannulate) superclade including Eurasian A. ectypa, North American A. socialis (A. tabescens), and Eurasian A. socialis (A. tabescens) clades; (ii) Mellea superclade including undescribed annulate North American Armillaria sp. (Mexico) and four separate clades of A. mellea (Europe and Iran, eastern Asia, and two groups from North America); (iii) Gallica superclade including Armillaria Nag E (Japan), multiple clades of A. gallica (Asia and Europe), A. calvescens (eastern North America), A. cepistipes (North America), A. altimontana (western USA), A. nabsnona (North America and Japan), and at least two A. gallica clades (North America); and (iv) Solidipes/Ostoyae superclade including two A. solidipes/ostoyae clades (North America), A. gemina (eastern USA), A. solidipes/ostoyae (Eurasia), A. cepistipes (Europe and Japan), A. sinapina (North America and Japan), and A. borealis (Eurasia) clade 2. Of note is that A. borealis (Eurasia) clade 1 appears basal to the Solidipes/Ostoyae and Gallica superclades. The Neighbor-net analysis showed similar phylogenetic relationships. This study further demonstrates the utility of tef1 for global phylogenetic studies of Armillaria species and provides critical insights into multiple taxonomic issues that warrant further study.

The translation elongation factor-1 alpha (EF-1a) gene was used to examine the phylogenetic relationships among 30 previously characterized isolates representing ten North American Armillaria species:American biological species X, A. cepistipes, and A. tabescens. The phylogenetic relationships revealed clear separation of all ten North American Armillaria species, with the exception of one A. gallica isolate that perhaps represents an unnamed cryptic species. These results indicate that the EF-1a gene could potentially serve as a diagnostic tool for distinguishing among currently recognized North American biological species of Armillaria.

Summary Since the myrtle rust pathogen (Austropuccinia psidii) was first reported (as Puccinia psidii) in Brazil on guava (Psidium guajava) in 1884, it has been found infecting diverse myrtaceous species. Because A. psidii has recently spread rapidly worldwide with an extensive host range, genetic and genotypic diversities were evaluated within and among A. psidii populations in its putative native range and other areas of myrtle rust emergence in the Americas and Hawaii. Microsatellite markers revealed several unique multilocus genotypes (MLGs), which grouped isolates into nine distinct genetic clusters [C1–C9 comprising C1: from diverse hosts from Costa Rica, Jamaica, Mexico, Puerto Rico, and USA‐Hawaii, and USA‐California; C2: from eucalypts (Eucalyptus spp.) in Brazil/Uruguay and rose apple (Syzygium jambos) in Brazil; C3: from eucalypts in Brazil; C4: from diverse hosts in USA‐Florida; C5: from Java plum (Syzygium cumini) in Brazil; C6: from guava and Brazilian guava (Psidium guineense) in Brazil; C7: from pitanga (Eugenia uniflora) in Brazil; C8: from allspice (Pimenta dioica) in Jamaica and sweet flower (Myrrhinium atropurpureum) in Uruguay; C9: from jabuticaba (Myrciaria cauliflora) in Brazil]. The C1 cluster, which included a single MLG infecting diverse host in many geographic regions, and the closely related C4 cluster are considered as a “Pandemic biotype,” associated with myrtle rust emergence in Central America, the Caribbean, USA‐Florida, USA‐Hawaii, Australia, China‐Hainan, New Caledonia, Indonesia and Colombia. Based on 19 bioclimatic variables and documented occurrences of A. psidii contrasted with reduced sets of specific genetic clusters (subnetworks, considered as biotypes), maximum entropy bioclimatic modelling was used to predict geographic locations with suitable climate for A. psidii which are at risk from invasion. The genetic diversity of A. psidii throughout the Americas and Hawaii demonstrates the importance of recognizing biotypes when assessing the invasive threats posed by A. psidii around the globe.

Summary Armillaria species display diverse ecological roles ranging from beneficial saprobe to virulent pathogen. Armillaria solidipes (formerly A. ostoyae), a causal agent of Armillaria root disease, is a virulent primary pathogen with a broad host range of woody plants across the Northern Hemisphere. This white‐rot pathogen grows between trees as rhizomorphs and attacks sapwood as mycelial fans under the bark. Armillaria root disease is responsible for reduced forest productivity due to direct tree mortality and non‐lethal infections that impact growth. Here, we characterize a transcriptome of a widespread, virulent genet (vegetative clone) of A. solidipes isolated from a mycelial fan on a natural grand fir (Abies grandis) sapling in northern Idaho, USA. cDNA from polyA+‐purified total RNA was sequenced using a single‐end read approach on the Illumina GAIIx platform which generated 24 170 384 reads. A BLASTx search against the NCBI nr database using 39 943 de novo assembled contigs resulted in 24 442 sequences with significant hits (e‐value < 1e−3), predominantly to fungi (85%). A filtered data set of 20 882 assembled transcripts that encoded putative homologous fungal proteins was created and used for all subsequent analyses. Signal P identified 10 668 putative signal peptides from these fungal transcripts, and 14 360 were annotated with gene ontology terms. Several sequences showed strong homology to annotated genes with functions in pathogenesis, specifically those involved in plant cell wall degradation and response to the post‐infection host environment. This transcriptome contributes to the growing body of resources for studies on fungal pathogens of woody plants, and our results provide useful insights towards identifying specific genes with potential roles associated with pathogenesis and other metabolic functions.

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Forestry researchers frequently conduct surveys to assess woodland owner attitudes, behavior, behavioral intentions, and program adoption. However, the ability to utilize survey results in applied research is dependent upon how accurately the sample respondents reflect the reference population. One major issue in survey research is nonresponse bias. Nonresponse bias occurs when individuals do not respond to a questionnaire and is a concern because of the potential inability to make accurate inferences to a population based on responses. Researchers in this study compare two methods of questionnaire distribution (Drop-off/Pick-up and the Tailored Design Method) in terms of cost effectiveness and response rate. When compared to the Tailored Design Method (TDM), use of the Drop-off/Pick-Up (DOPU) method resulted in significantly higher response rates, provided an alternative method by which to determine survey eligibility, and had significantly higher survey implementation costs. The DOPU technique is an effective means to reduce potential nonresponse bias through increased response rate. When implementing the DOPU method, face-to-face contact and verbal communication with respondents permitted researchers to better determine eligibility than did leaving the questionnaire on the doorknob. Relying solely on respondents to indicate ineligibility on the survey instrument was not as effective as verbal confirmation of eligibility in the DOPU.

To address concern for loss of bryophyte biodiversity within managed forests, we compared community composition and environmental characteristics among three disturbance regimes: (i) naturally regenerated clear-cut forests, (ii) cutover spruce plantations (established on clear-cut forest land), and (iii) afforested field spruce plantations (established on agricultural fields) across a range of ages (19–102 years) in the Acadian Forest region of New Brunswick, Canada. Abundances of all forest floor bryophyte species, available substrates, microtopographical features, and tree canopy were measured as percent cover (1 m2) in 26 stands: 12 naturally regenerated clear-cut forests, eight cutover plantations, and six afforested field plantations. Multivariate analyses indicated that both bryophyte community composition and associated environment differed significantly across disturbance regimes, with no strong trends related to time since clearing (i.e., stand age). Spruce plantations were characterized by low substrate diversity and microtopographic and canopy homogeneity. Both plantation types had lower bryophyte species richness, evenness, and diversity (H') relative to naturally regenerated clear-cut forests; cutover plantations had the highest total bryophyte cover. The bryophyte community of plantations was composed of a subset of species found within naturally regenerated clear-cut forests: many liverworts and epixylic mosses were absent, with fewer pioneer species and more perennial stayers (equivalent to K-strategists) than expected.Key words: bryophyte, disturbance regime, substrate, canopy, microtopography, plantation.