A large-scale study on research code quality and execution.

This article presents a study on the quality and execution of research code from publicly-available replication datasets at the Harvard Dataverse repository. Research code is typically created by a group of scientists and published together with academic papers to facilitate research transparency and reproducibility. For this study, we define ten questions to address aspects impacting research reproducibility and reuse. First, we retrieve and analyze more than 2000 replication datasets with over 9000 unique R files published from 2010 to 2020. Second, we execute the code in a clean runtime environment to assess its ease of reuse. Common coding errors were identified, and some of them were solved with automatic code cleaning to aid code execution. We find that 74% of R files failed to complete without error in the initial execution, while 56% failed when code cleaning was applied, showing that many errors can be prevented with good coding practices. We also analyze the replication datasets from journals' collections and discuss the impact of the journal policy strictness on the code re-execution rate. Finally, based on our results, we propose a set of recommendations for code dissemination aimed at researchers, journals, and repositories.

Tree genotypes affect rock lichens and understory plants: examples of trophic-independent interactions.

Genetic variation in foundation tree species can strongly influence communities of trophic-dependent organisms, such as herbivorous insects, pollinators, and mycorrhizal fungi. However, the extent and manner in which this variation results in unexpected interactions that reach trophic-independent organisms remains poorly understood, even though these interactions are essential to understanding complex ecosystems. In pinyon-juniper woodland at Sunset Crater (Arizona, USA), we studied pinyon (Pinus edulis) that were either resistant or susceptible to stem-boring moths (Dioryctria albovittella). Moth herbivory alters the architecture of susceptible trees, thereby modifying the microhabitat beneath their crowns. We tested the hypothesis that this interaction between herbivore and tree genotype extends to affect trophic-independent communities of saxicolous (i.e., growing on rocks) lichens and bryophytes and vascular plants beneath their crowns. Under 30 pairs of moth-resistant and moth-susceptible trees, we estimated percent cover of lichens, bryophytes, and vascular plants. We also quantified the cover of leaf litter and rocks as well as light availability. Four major findings emerged. (1) Compared to moth-resistant trees, which exhibited monopodial architecture, the microhabitat under the shrub-like susceptible trees was 60% darker and had 21% more litter resulting in 68% less rock exposure. (2) Susceptible trees had 56% and 87% less cover, 42% and 80% less richness, and 38% and 92% less diversity of saxicolous and plant communities, respectively, compared to resistant trees. (3) Both saxicolous and plant species accumulated at a slower rate beneath susceptible trees, suggesting an environment that might inhibit colonization and/or growth. (4) Both saxicolous and plant communities were negatively affected by the habitat provided by susceptible trees. The results suggest that herbivory of moth-susceptible trees generated litter at high enough rates to reduce rock substrate availability, thereby suppressing the saxicolous communities. However, our results did not provide a causal pathway explaining the suppression of vascular plants. Nonetheless, the cascading effects of genetic variation in pinyon appear to extend beyond trophic-dependent moths to include trophic-independent saxicolous and vascular plant communities that are affected by specific tree-herbivore interactions that modify the local environment. We suggest that such genetically based interactions are common in nature and contribute to the evolution of complex communities.

Draft Aphaenogaster genomes expand our view of ant genome size variation across climate gradients.

Given the abundance, broad distribution, and diversity of roles that ants play in many ecosystems, they are an ideal group to serve as ecosystem indicators of climatic change. At present, only a few whole-genome sequences of ants are available (19 of >16,000 species), mostly from tropical and sub-tropical species. To address this limited sampling, we sequenced genomes of temperate-latitude species from the genus Aphaenogaster, a genus with important seed dispersers. In total, we sampled seven colonies of six species: Aphaenogaster ashmeadi, Aphaenogaster floridana, Aphaenogaster fulva, Aphaenogaster miamiana, Aphaenogaster picea, and Aphaenogaster rudis. The geographic ranges of these species collectively span eastern North America from southern Florida to southern Canada, which encompasses a latitudinal gradient in which many climatic variables are changing rapidly. For the six genomes, we assembled an average of 271,039 contigs into 47,337 scaffolds. The Aphaenogaster genomes displayed high levels of completeness with 96.1% to 97.6% of Hymenoptera BUSCOs completely represented, relative to currently sequenced ant genomes which ranged from 88.2% to 98.5%. Additionally, the mean genome size was 370.5 Mb, ranging from 310.3 to 429.7, which is comparable to that of other sequenced ant genomes (212.8-396.0 Mb) and flow cytometry estimates (210.7-690.4 Mb). In an analysis of currently sequenced ant genomes and the new Aphaenogaster sequences, we found that after controlling for both spatial autocorrelation and phylogenetics ant genome size was marginally correlated with sample site climate similarity. Of all examined climate variables, minimum temperature, and annual precipitation had the strongest correlations with genome size, with ants from locations with colder minimum temperatures and higher levels of precipitation having larger genomes. These results suggest that climate extremes could be a selective force acting on ant genomes and point to the need for more extensive sequencing of ant genomes.

If these data could talk.

In the last few decades, data-driven methods have come to dominate many fields of scientific inquiry. Open data and open-source software have enabled the rapid implementation of novel methods to manage and analyze the growing flood of data. However, it has become apparent that many scientific fields exhibit distressingly low rates of reproducibility. Although there are many dimensions to this issue, we believe that there is a lack of formalism used when describing end-to-end published results, from the data source to the analysis to the final published results. Even when authors do their best to make their research and data accessible, this lack of formalism reduces the clarity and efficiency of reporting, which contributes to issues of reproducibility. Data provenance aids both reproducibility through systematic and formal records of the relationships among data sources, processes, datasets, publications and researchers.

Genetics-based interactions of foundation species affect community diversity, stability and network structure.

We examined the hypothesis that genetics-based interactions between strongly interacting foundation species, the tree Populus angustifolia and the aphid Pemphigus betae, affect arthropod community diversity, stability and species interaction networks of which little is known. In a 2-year experimental manipulation of the tree and its aphid herbivore four major findings emerged: (i) the interactions of these two species determined the composition of an arthropod community of 139 species; (ii) both tree genotype and aphid presence significantly predicted community diversity; (iii) the presence of aphids on genetically susceptible trees increased the stability of arthropod communities across years; and (iv) the experimental removal of aphids affected community network structure (network degree, modularity and tree genotype contribution to modularity). These findings demonstrate that the interactions of foundation species are genetically based, which in turn significantly contributes to community diversity, stability and species interaction networks. These experiments provide an important step in understanding the evolution of Darwin's 'entangled bank', a metaphor that characterizes the complexity and interconnectedness of communities in the wild.

Genetically informed ecological niche models improve climate change predictions.

We examined the hypothesis that ecological niche models (ENMs) more accurately predict species distributions when they incorporate information on population genetic structure, and concomitantly, local adaptation. Local adaptation is common in species that span a range of environmental gradients (e.g., soils and climate). Moreover, common garden studies have demonstrated a covariance between neutral markers and functional traits associated with a species' ability to adapt to environmental change. We therefore predicted that genetically distinct populations would respond differently to climate change, resulting in predicted distributions with little overlap. To test whether genetic information improves our ability to predict a species' niche space, we created genetically informed ecological niche models (gENMs) using Populus fremontii (Salicaceae), a widespread tree species in which prior common garden experiments demonstrate strong evidence for local adaptation. Four major findings emerged: (i) gENMs predicted population occurrences with up to 12-fold greater accuracy than models without genetic information; (ii) tests of niche similarity revealed that three ecotypes, identified on the basis of neutral genetic markers and locally adapted populations, are associated with differences in climate; (iii) our forecasts indicate that ongoing climate change will likely shift these ecotypes further apart in geographic space, resulting in greater niche divergence; (iv) ecotypes that currently exhibit the largest geographic distribution and niche breadth appear to be buffered the most from climate change. As diverse agents of selection shape genetic variability and structure within species, we argue that gENMs will lead to more accurate predictions of species distributions under climate change.

Genotypic variation in foundation species generates network structure that may drive community dynamics and evolution.

Although genetics in a single species is known to impact whole communities, little is known about how genetic variation influences species interaction networks in complex ecosystems. Here, we examine the interactions in a community of arthropod species on replicated genotypes (clones) of a foundation tree species, Populus angustifolia James (narrowleaf cottonwood), in a long-term, common garden experiment using a bipartite "genotype-species" network perspective. We combine this empirical work with a simulation experiment designed to further investigate how variation among individual tree genotypes can impact network structure. Three findings emerged: (1) the empirical "genotype-species network" exhibited significant network structure with modularity being greater than the highly conservative null model; (2) as would be expected given a modular network structure, the empirical network displayed significant positive arthropod co-occurrence patterns; and (3) furthermore, the simulations of "genotype-species" networks displayed variation in network structure, with modularity in particular clearly increasing, as genotypic variation increased. These results support the conclusion that genetic variation in a single species contributes to the structure of ecological interaction networks, which could influence eco-ogical dynamics (e.g., assembly and stability) and evolution in a community context.

Plant-herbivore interactions in a trispecific hybrid swarm of Populus: assessing support for hypotheses of hybrid bridges, evolutionary novelty and genetic similarity.

UNLABELLED: Natural systems of hybridizing plants are powerful tools with which to assess evolutionary processes between parental species and their associated arthropods. Here we report on these processes in a trispecific hybrid swarm of Populus trees. Using field observations, common garden experiments and genetic markers, we tested the hypothesis that genetic similarities among hosts underlie the distributions of 10 species of gall-forming arthropods and their ability to adapt to new host genotypes. KEY FINDINGS: the degree of genetic relatedness among parental species determines whether hybridization is primarily bidirectional or unidirectional; host genotype and genetic similarity strongly affect the distributions of gall-forming species, individually and as a community. These effects were detected observationally in the wild and experimentally in common gardens; correlations between the diversity of host genotypes and their associated arthropods identify hybrid zones as centres of biodiversity and potential species interactions with important ecological and evolutionary consequences. These findings support both hybrid bridge and evolutionary novelty hypotheses. However, the lack of parallel genetic studies on gall-forming arthropods limits our ability to define the host of origin with their subsequent shift to other host species or their evolution on hybrids as their final destination.

Rapid plant evolution in the presence of an introduced species alters community composition.

Because introduced species may strongly interact with native species and thus affect their fitness, it is important to examine how these interactions can cascade to have ecological and evolutionary consequences for whole communities. Here, we examine the interactions among introduced Rocky Mountain elk, Cervus canadensis nelsoni, a common native plant, Solidago velutina, and the diverse plant-associated community of arthropods. While introduced species are recognized as one of the biggest threats to native ecosystems, relatively few studies have investigated an evolutionary mechanism by which introduced species alter native communities. Here, we use a common garden design that addresses and supports two hypotheses. First, native S. velutina has rapidly evolved in the presence of introduced elk. We found that plants originating from sites with introduced elk flowered nearly 3 weeks before plants originating from sites without elk. Second, evolution of S. velutina results in a change to the plant-associated arthropod community. We found that plants originating from sites with introduced elk supported an arthropod community that had ~35 % fewer total individuals and a different species composition. Our results show that the impacts of introduced species can have both ecological and evolutionary consequences for strongly interacting species that subsequently cascade to affect a much larger community. Such evolutionary consequences are likely to be long-term and difficult to remediate.

An elusive ectomycorrhizal fungus reveals itself: a new species of Geopora (Pyronemataceae) associated with Pinus edulis.

Species of the genus Geopora are important ectomycorrhizal associates that can dominate the communities of some plant taxa, such as pinyon pine (Pinus edulis), a widespread tree of the western United States. Several members of the genus Geopora are known only from ectomycorrhizal root tips and thus have not been described formally. The sporocarps of some Geopora species occur infrequently because they depend on wet years for sporulation. In addition, Geopora sporocarps can be small and may be hypogeous at some developmental stage, limiting the opportunities for describing their morphology. Using molecular and morphological data, we have described a new species of fungus, Geopora pinyonensis, which produced ascocarps after unusually high precipitation at a northern Arizona site in summer 2012. Based on analysis of the ITS and nuLSU regions of the rDNA, G pinyonensis is a new species of Geopora. It has small sporocarps and ascospores relative to other members of the genus; however, these morphological features overlap with other species. Using rDNA data from sporocarps and ectomycorrhizal root tips, we show that the sporocarps correspond to an abundant species of ectomycorrhizal fungus associated with pinyon pines that is increasing in abundance in drought-affected landscapes and may promote drought tolerance.

Tree genotype and genetically based growth traits structure twig endophyte communities.

PREMISE OF THE STUDY: Fungal endophytes asymptomatically inhabit plant tissues where they have mutualistic, parasitic, or commensal relationships with their hosts. Although plant-fungal interactions at the genotype scale have broad ecological and evolutionary implications, the sensitivity of endophytes in woody tissues to differences among plant genotypes is poorly understood. We hypothesize that (1) endophyte communities in Populus angustifolia (Salicaceae) twigs vary among tree genotypes, (2) endophyte variation is linked to quantitative tree traits, and (3) tree genotype influences interspecific fungal interactions. METHODS: Endophytes were isolated from twigs of replicated P. angustifolia genotypes in a common garden and characterized with PCR-RFLP and DNA sequencing. Twig length and diameter, aboveground tree biomass, and condensed tannins were also quantified. KEY RESULTS: (1) Aspects of fungal community structure, including composition and total isolation frequency (i.e., abundance), varied among genotypes. (2) Aboveground biomass and twig diameter were positively associated with isolation frequency and covaried with composition, whereas twig length and condensed tannin concentration were not significantly correlated to endophytes. (3) Fungal co-occurrence patterns suggested negative species interactions, but the presence of significant co-occurrences was genotype dependent. CONCLUSIONS: The species is often assumed to be the most important ecological unit; however, these results indicate that genetically based trait variation within a species can influence an important community of associated organisms. Given the dominance of plants as primary producers and the ubiquity of endophytes, the effect of host genetic variation on endophytes has fundamental implications for our understanding of terrestrial ecosystems.

Association study of the GSK-3B gene with tardive dyskinesia in European Caucasians.

There is solid evidence of a genetic predisposition to tardive dyskinesia (TD) although the pathophysiological mechanisms of TD are still unclear. Nevertheless, the dopamine overactivity hypothesis of the TD etiology receives support from both pharmacological and physiological evidence. Dopaminergic signaling modulates the glycogen synthase kinase 3B (GSK-3B), a kinase that may play a critical role in the pathogenesis of neurodegenerative diseases. GSK-3B is an essential element of the apoptotic signaling cascade induced by oxidative stress, which may be involved in TD pathogenesis. We investigated whether GSK-3B polymorphisms (rs11919783, rs6805251, rs7624540, rs6438552, rs4072520, rs9878473, rs6779828 and rs3755557) selected using tagging method were associated with TD manifestation and abnormal involuntary movement severity. We evaluated 215 schizophrenia subjects from whom 169 were European Caucasians. All eight evaluated variants had their minor allele carriers consistently showing lower risk to TD and lower Abnormal Involuntary Movement Scale. The rs6805251, rs6438552 and rs9878473 variants showed a trend for association with TD in European Caucasian subjects (permuted p=0.07). Furthermore, all tested markers showed p< or =0.0007 after we incorporated age as covariate in the analysis of the abnormal involuntary movement severity. Our results suggest that GSK-3B polymorphism may play a role in the genetic vulnerability to TD manifestation in schizophrenia subjects with European Caucasian background further implicating polymorphisms in the dopamine D2-like receptor signaling in this context. These findings should be read with caution particularly before independent replication.

The effects of circumcision on the penis microbiome.

BACKGROUND: Circumcision is associated with significant reductions in HIV, HSV-2 and HPV infections among men and significant reductions in bacterial vaginosis among their female partners. METHODOLOGY/PRINCIPAL FINDINGS: We assessed the penile (coronal sulci) microbiota in 12 HIV-negative Ugandan men before and after circumcision. Microbiota were characterized using sequence-tagged 16S rRNA gene pyrosequencing targeting the V3-V4 hypervariable regions. Taxonomic classification was performed using the RDP Naïve Bayesian Classifier. Among the 42 unique bacterial families identified, Pseudomonadaceae and Oxalobactericeae were the most abundant irrespective of circumcision status. Circumcision was associated with a significant change in the overall microbiota (PerMANOVA p = 0.007) and with a significant decrease in putative anaerobic bacterial families (Wilcoxon Signed-Rank test p = 0.014). Specifically, two families-Clostridiales Family XI (p = 0.006) and Prevotellaceae (p = 0.006)-were uniquely abundant before circumcision. Within these families we identified a number of anaerobic genera previously associated with bacterial vaginosis including: Anaerococcus spp., Finegoldia spp., Peptoniphilus spp., and Prevotella spp. CONCLUSIONS/SIGNIFICANCE: The anoxic microenvironment of the subpreputial space may support pro-inflammatory anaerobes that can activate Langerhans cells to present HIV to CD4 cells in draining lymph nodes. Thus, the reduction in putative anaerobic bacteria after circumcision may play a role in protection from HIV and other sexually transmitted diseases.