Rebecca B. Dikow

A target enrichment method for gathering phylogenetic information from hundreds of loci: An example from the Compositae

Premise of the study: The Compositae (Asteraceae) are a large and diverse family of plants, and the most comprehensive phylogeny to date is a meta-tree based on 10 chloroplast loci that has several major unresolved nodes. We describe the development of an approach that enables the rapid sequencing of large numbers of orthologous nuclear loci to facilitate efficient phylogenomic analyses. Methods and Results: We designed a set of sequence capture probes that target conserved orthologous sequences in the Compositae. We also developed a bioinformatic and phylogenetic workflow for processing and analyzing the resulting data. Application of our approach to 15 species from across the Compositae resulted in the production of phylogenetically informative sequence data from 763 loci and the successful reconstruction of known phylogenetic relationships across the family. Conclusions: These methods should be of great use to members of the broader Compositae community, and the general approach should also be of use to researchers studying other families.

Using phylogenomics to resolve mega‐families: An example from Compositae

Next‐generation sequencing and phylogenomics hold great promise for elucidating complex relationships among large plant families. Here, we performed targeted capture of low copy sequences followed by next‐generation sequencing on the Illumina platform in the large and diverse angiosperm family Compositae (Asteraceae). The family is monophyletic, based on morphology and molecular data, yet many areas of the phylogeny have unresolved polytomies and interpreting phylogenetic patterns has been historically difficult. In order to outline a method and provide a framework and for future phylogenetic studies in the Compositae, we sequenced 23 taxa from across the family in which the relationships were well established as well as a member of the sister family Calyceraceae. We generated nuclear data from 795 loci and assembled chloroplast genomes from off‐target capture reads enabling the comparison of nuclear and chloroplast genomes for phylogenetic analyses. We also analyzed multi‐copy nuclear genes in our data set using a clustering method during orthology detection, and we applied a network approach to these clusters—analyzing all related locus copies. Using these data, we produced hypotheses of phylogenetic relationships employing both a conservative (restricted to only loci with one copy per targeted locus) and a multigene approach (including all copies per targeted locus). The methods and bioinformatics workflow presented here provide a solid foundation for future work aimed at understanding gene family evolution in the Compositae as well as providing a model for phylogenomic analyses in other plant mega‐families.

Developing integrative systematics in the informatics and genomic era, and calling for a global Biodiversity Cyberbank

Systematics is the science of discovering, organizing and interpreting the diversity of all living organisms. Recent developments in genomics and biodiversity informatics are transforming systematics and have opened up many new opportunities. Major digitization efforts and developments in biodiversity informatics have helped the systematics community explore ways to enhance the efficiency in organizing, publishing, and utilizing systematic information. At the same time, genomics is rapidly facilitating construction of the tree of life, improving taxonomic classification, and disentangling complex evolutionary histories. In the informatics and genomics era, systematics has an incredible capacity to integrate with computational and exploratory platforms for discovery as well as with other, related disciplines while maintaining its core strengths in biological collections and morphology. We call for the establishment of a new global cyberinfrastructure or Biodiversity Cyberbank that will function as the main repository of many types of biodiversity data to ensure the long‐term sustainability of the vast and growing amount of systematic data. This Biodiversity Cyberbank will contain new and efficient analytical pipelines for systematics research, especially for efficiently generating taxonomic treatments (revisions, e‐monographs and floras). Integrative systematics requires the training of the next‐generation systematists with taxonomic, phylogenomic and informatics skills to address grand questions about biodiversity and its assembly and continue to develop the Biodiversity Cyberbank. Integrative systematics must also proactively educate the public and policy makers on the importance of systematics and collections for addressing the biodiversity crisis of the Anthropocene, and a Biodiversity Cyberbank may represent one powerful tool for outreach.

Utility of transcriptome sequencing for phylogenetic inference and character evolution

Transcriptome sequencing or RNA-Seq is one of the most efficient and cost-effective methods currently available for gene discovery in non-model organisms. Recent studies have demonstrated the utility of these data for resolving the relationships of diverse lineages of organisms, by extracting sequences of a large number of single-copy nuclear genes from transcriptomes of the taxa under study (i.e., RNA-Seq phylogenetics). Comparative transcriptomics has also been applied in several other areas in systematic biology, especially concerning polyploidy, introgression, hybridization, and horizontal gene transfer, as well as character evolution, including the identification of likely key innovations. This review focuses on the utility of transcriptomics in phylogenetic inferences and character evolution, and discusses the analytical framework, challenges, and prospects of transcriptome data in plant systematics, especially in phylogenetics. The main limitations are related to the high RNA-grade tissue quality requirement, the comparisons among expressed genes at a particular time point or developmental stage, orthology determination, and sequencing that arises from coding regions only, as well as several bioinformatics and analytical challenges. Comparative transcriptomics offers a rich set of genic sources for phylogenetic inference and singleor low-copy nuclear marker development. As whole genomes and genomic data become less costly and more prevalent, comparisons among transcriptomes will increase. With transcriptomeand genome-scale bioinformatics continuing to develop, we expect that the utility of transcriptomics will only increase in systematic biology, and that the RNA-Seq approach will offer tremendous insights into the understanding of the ontogeny and evolution of characters in the next decade.

Applications of deep convolutional neural networks to digitized natural history collections

Abstract Natural history collections contain data that are critical for many scientific endeavors. Recent efforts in mass digitization are generating large datasets from these collections that can provide unprecedented insight. Here, we present examples of how deep convolutional neural networks can be applied in analyses of imaged herbarium specimens. We first demonstrate that a convolutional neural network can detect mercury-stained specimens across a collection with 90% accuracy. We then show that such a network can correctly distinguish two morphologically similar plant families 96% of the time. Discarding the most challenging specimen images increases accuracy to 94% and 99%, respectively. These results highlight the importance of mass digitization and deep learning approaches and reveal how they can together deliver powerful new investigative tools.

Genomic and transcriptomic resources for assassin flies including the complete genome sequence of Proctacanthus coquilletti (Insecta: Diptera: Asilidae) and 16 representative transcriptomes

A high-quality draft genome for Proctacanthus coquilletti (Insecta: Diptera: Asilidae) is presented along with transcriptomes for 16 Diptera species from five families: Asilidae, Apioceridae, Bombyliidae, Mydidae, and Tabanidae. Genome sequencing reveals that P. coquilletti has a genome size of approximately 210 Mbp and remarkably low heterozygosity (0.47%) and few repeats (15%). These characteristics helped produce a highly contiguous (N50 = 862 kbp) assembly, particularly given that only a single 2 × 250 bp PCR-free Illumina library was sequenced. A phylogenomic hypothesis is presented based on thousands of putative orthologs across the 16 transcriptomes. Phylogenetic relationships support the sister group relationship of Apioceridae + Mydidae to Asilidae. A time-calibrated phylogeny is also presented, with seven fossil calibration points, which suggests an older age of the split among Apioceridae, Asilidae, and Mydidae (158 mya) and Apioceridae and Mydidae (135 mya) than proposed in the AToL FlyTree project. Future studies will be able to take advantage of the resources presented here in order to produce large scale phylogenomic and evolutionary studies of assassin fly phylogeny, life histories, or venom. The bioinformatics tools and workflow presented here will be useful to others wishing to generate de novo genomic resources in species-rich taxa without a closely-related reference genome.

The Compositae Tree of Life in the age of phylogenomics

Comprising more than 25 000 species, the Sunflower Family (Compositae or Asteraceae) is the largest family of flowering plants. Many of its lineages have experienced recent and rapid radiations, and the family has a deep and widespread history of large‐scale gene duplications and polyploidy. Many of the most important evolutionary questions about the familys diversity remain unanswered due to poor resolution and lack of support for major nodes of the phylogeny. Our group has employed a phylogenomics approach using Hyb‐Seq that includes sequencing ∼1000 low‐copy number nuclear markers, plus partial plastomes for large numbers of species. Here we discuss our progress to date and present two phylogenies comprising nine subfamilies and 25 tribes using concatenated and coalescence‐based analyses. We discuss future plans for incorporating high‐quality reference genomes and transcriptomes to advance systematic and evolutionary studies in the Compositae. While we have made great strides toward developing tools for employing phylogenomics and resolving relationships within Compositae, much work remains. Recently formed global partnerships will work to solve the unanswered evolutionary questions for this megafamily.

Another look at the phylogenetic relationships and intercontinental biogeography of eastern Asian – North American Rhus gall aphids (Hemiptera: Aphididae: Eriosomatinae): Evidence from mitogenome sequences via genome skimming

The Rhus gall aphids are sometimes referred to as subtribe Melaphidina (Aphididae: Eriosomatinae: Fordini) and comprise a unique group that forms galls on the primary host plants, Rhus. We examined the evolutionary relationships within the Melaphidina aphids using sequences of the complete mitochondrial genome and with samples of 11 of the 12 recognized species representing all six genera. Bayesian, maximum likelihood and parsimony analyses of the mitochondrial genome data support five well-supported clades within Melaphidina: (1) Nurudea (except N. ibofushi), (2) Schlechtendalia-Nurudea ibofushi, (3) Meitanaphis-Kaburagia, (4) Floraphis, and (5) Melaphis. Nurudea shiraii and N. yanoniella are sister to each other, but N. ibofushi is nested within Schlechtendalia. The Nurudea shiraii-N. yanoniella clade is sister to the large clade of the remaining taxa of Melaphidina aphids. The Bayesian and maximum likelihood analyses support the North American Melaphis rhois as sister to the clade of Floraphis-Kaburagia-Meitanaphis-Schlechtendalia from eastern Asia, whereas the parsimony analysis suggests Melaphis sister to Floraphis with low support (bootstrap support 38%), and the amino acid data weakly place it sister to Schlechtendalia-Nurudea ibofushi. The Melaphis position needs to be further tested with nuclear data. Meitanaphis flavogallis is sister to Kaburagia species instead of grouping with Meitanaphis elongallis. Using the Bayesian method, the North American Melaphis was estimated to have diverged from its closest Asian relatives around 64.6 (95% HPD 59.4-69.8) Ma, which is in the early Paleocene near the Cretaceous and Paleogene boundary (K/Pg boundary). At the K/Pg boundary, mass extinctions caused many types of insect-plant associations to disappear, and these extinctions may explain some of the difficulties in the phylogenetic placement of Melaphis within the analyses.