Distinct communities under the snow: describing characteristics of subnivium arthropod communities.

Arthropods are active during the winter in temperate regions. Many use the seasonal snowpack as a buffer against harsh ambient conditions and are active in a refugium known as the subnivium. While the use of the subnivium by arthropods is well established, far less is known about subnivium community composition, abundance, biomass, and diversity and how these characteristics compare with the community in the summer. Understanding subnivium communities is especially important given the observed and anticipated changes in snowpack depth and duration due to the changing climate. We compared subnivium arthropod communities with those active during the summer using pitfall trapping in northern New Hampshire. We found that compositions of ground-active arthropod communities in the subnivium differed from those in the summer. The subnivium arthropod community featured moderate levels of richness and other measures of diversity that tended to be lower than the summer community. More strikingly, the subnivium community was much lower in overall abundance and biomass. Interestingly, some arthropods were dominant in the subnivium but either rare or absent in summer collections. These putative "subnivium specialists" included the spider Cicurina brevis (Emerton 1890) (Araneae: Hahniidae) and 3 rove beetles (Coleoptera: Staphylinidae): Arpedium cribratum Fauvel, 1878, Lesteva pallipes LeConte, 1863, and Porrhodites inflatus (Hatch, 1957). This study provides a detailed account of the subnivium arthropod community, establishes baseline information on arthropod communities in temperate forests of northeastern North America, and explores the idea of subnivium specialist taxa that are highly active in winter and might be especially vulnerable to climate change.

A high-quality draft genome sequence of Neonectria faginata, causative agent of beech bark disease of Fagus grandifolia.

The draft genome of Neonectria faginata was sequenced with Oxford Nanopore and Illumina 250 bp paired-end sequencing technologies. The assembled genome was 42.9 Mb distributed over 24 contigs, with N50 of 4.4 Mb and 98.6% BUSCO completeness. This genome sequence will aid in understanding N. faginata population structure and ecology.

Southern pine beetle (Coleoptera: Curculionidae) and its associated insect community: similarities and key differences between northeastern and southeastern pine forests.

We examine consequences of climate-induced range expansion on community composition and diversity within trees attacked by the southern pine beetle (Dendroctonus frontalis Zimmermann). At the northernmost limit of the southern pine beetle range where populations have persisted for multiple years (currently Long Island, NY), we collected and reared bark samples and placed emergence traps on southern pine beetle-attacked pitch pine, Pinus rigida Mill. (Pinales: Pinaceae). From these samples, we quantified southern pine beetle gallery length and emergence as well as the diversity and abundance of all associated insects including known and suspected competitors, predators, and parasitoids. We compared our results to that of historic sampling data (1975-1997) in the core of southern pine beetle's range in the southern United States. Key community members were present in both the northern and southern regions; composition and relative abundances differed markedly. A key predator, the clerid beetle Thanasimus dubius (Fabricius) (Coleoptera: Cleridae), was present in similar densities in both regions. Southern pine beetle infested a greater proportion of the length of the tree bole in the North. This increased tree utilization may be a consequence of a lack of resource competition by Ips De Geer (Coleoptera: Curculionidae) engraver beetles, which we found only in very low abundance in the northern sites. We discuss the implications of these results in the context of southern pine beetle range expansion. Continued study of the southern pine beetle community and temporal southern pine beetle dynamics in the North will add to our current knowledge base and aid preservation of rare and ecologically valuable pine barrens of New England.

Characterization of mating type genes in heterothallic Neonectria species, with emphasis on N. coccinea, N. ditissima, and N. faginata.

Neonectria ditissima and N. faginata are canker pathogens involved in an insect-fungus disease complex of American beech (Fagus grandifolia) in North America commonly known as beech bark disease (BBD). In Europe, both N. ditissima and N. coccinea are involved in BBD on European beech (Fagus sylvatica). Field observations across the range of BBD indicate ascospores to be the dominant spore type in the environment. Several studies report a heterothallic (self-sterile) mating strategy for Neonectria fungi, but one study reported homothallism (self-fertility) for N. ditissima. As such, investigations into mating strategy are important for understanding both the disease cycle and population genetics of Neonectria. This is particularly important in the United States given that over time N. faginata dominates the BBD pathosystem despite high densities of nonbeech hosts for N. ditissima. This study utilized whole-genome sequences of BBD-associated Neonectria spp. along with other publicly available Neonectria and Corinectria genomes and in vitro mating assays to characterize mating type (MAT) locus and confirm thallism for select members of Neonectria and Corinectria. MAT gene-specific primer pairs were developed to efficiently characterize the mating types of additional single-ascospore strains of N. ditissima, N. faginata, and N. coccinea and several other related species lacking genomic data. These assays also confirmed the sexual compatibility among N. ditissima strains from different plant hosts. Maximum likelihood phylogenetic analyses of both MAT1-1-1 and MAT1-2-1 sequences recovered trees with similar topology to previously published phylogenies of Neonectria and Corinectria. The results of this study indicate that all Neonectria and Corinectria tested are heterothallic based on our limited sampling and, as such, thallism cannot help explain the inevitable dominance of N. faginata in the BBD pathosystem.

Biotic and abiotic effects on density, body size, sex ratio, and survival in immature stages of the European woodwasp, Sirex noctilio.

Resource quality can have direct or indirect effects on female oviposition choice, offspring growth and survival, and ultimately on body size and sex ratio. We examined these patterns in Sirex noctilio Fabricus, the globally invasive European pine woodwasp, in South African Pinus patula plantations. We studied how tree position as well as natural variation in biotic and abiotic factors influenced sex-specific density, larval size, tunnel length, male proportion, and survival across development. Twenty infested trees divided into top, middle, and bottom sections were sampled at three time points during larval development. We measured moisture content, bluestain fungal colonization, and co-occurring insect density and counted, measured, and sexed all immature wasps. A subset of larval tunnels was measured to assess tunnel length and resource use efficiency (tunnel length as a function of immature wasp size). Wasp density increased from the bottoms to the tops of trees for both males and females. However, the largest individuals and the longest tunnels were found in bottom sections. Male bias was strong (~10:1) and likewise differed among sections, with the highest proportion in the middle and top sections. Sex ratios became more strongly male biased due to high female mortality, especially in top and middle sections. Biotic and abiotic factors such as colonization by Diplodia sapinea, weevil (Pissodes sp.) density, and wood moisture explained modest residual variation in our primary mixed effects models (0%-22%). These findings contribute to a more comprehensive understanding of sex-specific resource quality for S. noctilio and of how variation in key biotic and abiotic factors can influence body size, sex ratio, and survival in this economically important woodwasp.

Rapid evolution of insects to global environmental change: conceptual issues and empirical gaps.

Understanding how insects will respond both ecologically and evolutionarily to complex and interacting factors linked to global change is an important challenge that underpins our ability to produce better predictive models and to anticipate and manage ecosystem-scale disruption in the Anthropocene. Insects have the capacity to rapidly adapt to changing conditions via a variety of mechanisms which include both phenotypically plastic and evolutionary responses that interact in important ways. This short review comments on the current state of knowledge surrounding rapid evolution in insects and highlights conceptual and empirical gaps. Emphasis is placed on the need to consider direct and indirect community-level feedbacks via both ecological and evolutionary mechanisms when examining the consequences of global change, with particular focus on insects and their facultative and obligate symbionts.

Ion Torrent PGM as tool for fungal community analysis: a case study of endophytes in Eucalyptus grandis reveals high taxonomic diversity.

The Kingdom Fungi adds substantially to the diversity of life, but due to their cryptic morphology and lifestyle, tremendous diversity, paucity of formally described specimens, and the difficulty in isolating environmental strains into culture, fungal communities are difficult to characterize. This is especially true for endophytic communities of fungi living in healthy plant tissue. The developments in next generation sequencing technologies are, however, starting to reveal the true extent of fungal diversity. One of the promising new technologies, namely semiconductor sequencing, has thus far not been used in fungal diversity assessments. In this study we sequenced the internal transcribed spacer 1 (ITS1) nuclear encoded ribosomal RNA of the endophytic community of the economically important tree, Eucalyptus grandis, from South Africa using the Ion Torrent Personal Genome Machine (PGM). We determined the impact of various analysis parameters on the interpretation of the results, namely different sequence quality parameter settings, different sequence similarity cutoffs for clustering and filtering of databases for removal of sequences with incomplete taxonomy. Sequence similarity cutoff values only had a marginal effect on the identified family numbers, whereas different sequence quality filters had a large effect (89 vs. 48 families between least and most stringent filters). Database filtering had a small, but statistically significant, effect on the assignment of sequences to reference sequences. The community was dominated by Ascomycota, and particularly by families in the Dothidiomycetes that harbor well-known plant pathogens. The study demonstrates that semiconductor sequencing is an ideal strategy for environmental sequencing of fungal communities. It also highlights some potential pitfalls in subsequent data analyses when using a technology with relatively short read lengths.