Steven Dodsworth

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Verified

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• MA, MRes, MSc, PhD
• Lecturer at Birkbeck, University of London

In petaloid monocots expansion of B-gene expression into whorl 1 of the flower results in two whorls of petaloid organs (tepals), as opposed to sepals in whorl 1 of typical eudicot flowers. Recently, new gene-silencing technologies have provided the first functional data to support this, in the genus Tricyrtis (Liliaceae).

Nicotiana sect. Repandae is a group of four allotetraploid species originating from a single allopolyploidisation event approximately 5 million years ago. Previous phylogenetic analyses support the hypothesis of N. nudicaulis as sister to the other three species. This is concordant with changes in genome size, separating those with genome downsizin...

Genome size varies enormously across the eukaryotic tree of life (c. 64,000-fold), with the largest reported nuclear genomes found in vertebrates (e.g. salamanders, lungfish) and angiosperms (e.g. mistletoe, fritillaries). Yet despite this huge diversity, most genomes are considerably smaller than the largest reported (c. 150 Gb), with the mean siz...

Mitochondrial genomes are readily sequenced with recent technology and thus evolutionary lineages can be sampled more densely. This permits better phylogenetic estimates and assessment of potential biases resulting from heterogeneity in nucleotide composition and rate of change. We gathered 245 mitochondrial sequences for the Coleoptera representin...

The Urticaceae (ca. 2600 species) were first formally recognized by Jussieu in the 18th century and last comprehensively monographed by Weddell in the 19th century. Since Weddell's work, family delimitation has been modified and many genera described in a fragmented manner. Over the past two decades, numerous molecular studies have supported the in...

The tribe Physalideae comprises two monophyletic subtribes, Iochrominae and Physalidinae, along with the polyphyletic Withaninae. However, consensus regarding phylogenetic relationships within and between subtribes remains elusive. To contribute to a better understanding of the evolutionary history and relationships among Physalideae species, we se...

The Nicotiana megalosiphon Van Heurck & Müll.Arg. species complex has been shown to be composed of several morphologically cryptic species similar to N. simulans N.T.Burb. Using phylogenetic and population genetic approaches (maximum likelihood, co-ancestry, admixture proportions, Bayesian species delimitation and coalescent methods), we demonstrat...

Over the last 6 million years, the arid Australian Eremaean Zone (EZ) has remained as dry as it is today. A widely accepted hypothesis suggests that the flora and fauna of arid regions were more broadly distributed before aridification began. In Australia, this process started around 20 million years ago (Ma), leading to gradual speciation as the c...

Angiosperms are the cornerstone of most terrestrial ecosystems and human livelihoods1,2. A robust understanding of angiosperm evolution is required to explain their rise to ecological dominance. So far, the angiosperm tree of life has been determined primarily by means of analyses of the plastid genome3,4. Many studies have drawn on this foundation...

Amorphophallus ongsakulii Hett. & A.Galloway is illustrated from plants cultivated by the authors. Its ecology, distribution, and systematics are described, along with notes on cultivation.

Copepoda are one of the most significant animal groups present in aquatic ecosystems. Ecologists, evolutionary biologists, and biotechnologists continue to test new methods to study the application of Copepoda as model organisms in various fields of pure and applied science, from evolution and ecology to aquaculture as live feed, as biological cont...

Telomerase, telomeric DNA and associated proteins together represent a complex, finely tuned and functionally conserved mechanism that ensures genome integrity by protecting and maintaining chromosome ends. Changes in its components can threaten an organism's viability. Nevertheless, molecular innovation in telomere maintenance has occurred multipl...

Angiosperm genome sizes (GS) range ~2400-fold and comprise genes and their regulatory regions, repeats, semi-degraded repeats, and ‘dark matter’. The latter represents repeats so degraded that they can no longer be recognised as repetitive. In exploring whether the histone modifications associated with chromatin packaging of these contrasting genom...

How have orchid species diversified in the campos rupestres, Brazil? Fiorini et al. (2023) use genomic datasets and multidisciplinary approaches, including phylogenetics and population genomics, to investigate the diversity of Bulbophyllum. They demonstrate that geographic isolation alone does not explain diversification patterns in Bulbophyllum sp...

Although some authors previously questioned the circumscription of Nicotiana benthamiana, it has never been treated taxonomically as more than a single widespread, variable species. A recent study employing phylogenetic and population genetic analyses has demonstrated that N. benthamiana comprises five species that are geographically and morphologi...

Genome size varies 2400‐fold across plants, influencing their evolution through changes in cell size and cell division rates which impact plants' environmental stress tolerance. Repetitive element expansion explains much genome size diversity, and the processes structuring repeat ‘communities’ are analogous to those structuring ecological communiti...

Reliably documenting plant diversity is necessary to protect and sustainably benefit from it. At the heart of this documentation lie species concepts and the practical methods used to delimit taxa. Here, we apply a total-evidence, iterative methodology to delimit and document species in the South American genus Victoria (Nymphaeaceae). The systemat...

One of the most commonly encountered and frequently cited laboratory organisms worldwide is classified taxonomically as Nicotiana benthamiana (Solanaceae), an accession of which, typically referred to as LAB, is renowned for its unique susceptibility to a wide range of plant viruses and hence capacity to be transformed using a variety of methods. T...

One of the most commonly encountered and frequently cited laboratory organisms worldwide is classified taxonomically as Nicotiana benthamiana (Solanaceae), an accession of which, typically referred to as LAB, is renowned for its unique susceptibility to a wide range of plant viruses and hence capacity to be transformed using a variety of methods. H...

Premise of the study: Evolutionary studies require solid phylogenetic frameworks, but increased volumes of phylogenomic data have revealed incongruent topologies among gene trees in many organisms both between and within genomes. Some of these incongruences indicate polytomies that may remain impossible to resolve. Here we investigate the degree o...

Background and aims: The extent to which genome size and chromosome numbers evolve in concert is little understood, particularly after polyploidy (whole-genome duplication), when a genome returns to a diploid-like condition (diploidisation). We study this phenomenon in 46 species of allotetraploid Nicotiana section Suaveolentes (Solanaceae), which...

The Northern Andean Cordillera in Colombia hosts unique, megadiverse, and fragile ecosystems, including wet tropical lowland, cloud forest, and paramo that are essential for climate regulation and the subsistence of human settlements. The Serrania de Los Paraguas on the Pacific slope of the western range of the Northern Andes, Colombia, is an ecosy...

Genome size varies 2,400-fold across plants, influencing their evolution through changes in cell size and cell division rates which impact plants’ environmental stress tolerance. Repetitive element expansion explains much genome size diversity, and the processes structuring repeat ‘communities’ are analogous to those structuring ecological communit...

The Australian species Nicotiana walpa is newly described here from plants collected at the Uluru-Kata Tjuta National Park in the Northern Territory, Australia, and illustrated from plants cultivated at the Royal Botanic Gardens, Kew. Its discovery, ecology, cytology and cultivation are discussed.

In this volume of Curtis's Botanical Magazine, we increase the number of species recognised in Nicotiana sect. Suaveolentes to 38, up from the 21 recorded in the Flora of Australia published 39 years ago, but we estimate the final number is likely to exceed 60. We examine the reasons why so many unrecognised species exist. Several Australian and Am...

Nicotiana ingulba is returned to species level here. It is illustrated from plants cultivated at the Royal Botanic Gardens, Kew, which were grown from seeds collected in the Uluru‐Kata Tjuta National Park in the Northern Territory, Australia. Its taxonomic history, ecology, cytology, etymology and cultivation are discussed.

Premise To further advance the understanding of the species-rich, economically and ecologically important angiosperm order Myrtales in the rosid clade, comprising nine families, approximately 400 genera and almost 14,000 species occurring on all continents (except Antarctica), we tested the Angiosperms353 probe kit. Methods We combined high-throug...

In this special issue of the American Journal of Botany, together with a companion issue of Applications in Plant Sciences, we gather a set of papers that focus on a new, common phylogenomic toolkit, the Angiosperms353 probe set, and illustrate its potential for evolutionary synthesis by promoting open collaboration across our community.

Premise: The inference of evolutionary relationships in the species-rich family Orchidaceae has hitherto relied heavily on plastid DNA sequences and limited taxon sampling. Previous studies have provided a robust plastid phylogenetic framework, which was used to classify orchids and investigate the drivers of orchid diversification. However, the e...

We present a densely sampled phylogenomic study of the mulberry tribe (Moreae, Moraceae), an economically important clade with a global distribution, revealing multiple losses of inflexed stamens, a character traditionally used to circumscribe Moreae. Inflexed stamens facilitate ballistic pollen release and are associated with wind pollination, and...

The date palm, Phoenix dactylifera, has been a cornerstone of Middle Eastern and North African agriculture for millennia. It was first domesticated in the Persian Gulf, and its evolution appears to have been influenced by gene flow from two wild relatives, P. theophrasti, currently restricted to Crete and Turkey, and P. sylvestris, widespread from...

Premise: Speciation not associated with morphological shifts is challenging to detect unless molecular data are employed. Using Sanger-sequencing approaches, the Lomatium packardiae/L. anomalum subcomplex within the larger Lomatium triternatum complex could not be resolved. Therefore, we attempt to resolve these boundaries here. Methods: The Ang...

Background and Aims With the advance of high-throughput sequencing (HTS), reduced-representation methods such as target capture sequencing (TCS) emerged as cost-efficient ways of gathering genomic information, particularly from coding regions. As the off-target reads from such sequencing are expected to be similar to genome skimming (GS), we assess...

The tree of life is the fundamental biological roadmap for navigating the evolution and properties of life on Earth, and yet remains largely unknown. Even angiosperms (flowering plants) are fraught with data gaps, despite their critical role in sustaining terrestrial life. Today, high-throughput sequencing promises to significantly deepen our under...

Premise of the study Evolutionary studies require solid phylogenetic frameworks, but increased volumes of phylogenomic data have revealed incongruent topologies among gene trees in many organisms both between and within genomes. Some of these incongruences indicate polytomies that may remain impossible to resolve. Here we investigate the degree of...

Recent phylogenomic analyses based on the maternally inherited plastid organelle have enlightened evolutionary relationships between the subfamilies of Orchidaceae and most of the tribes. However, uncertainty remains within several subtribes and genera for which phylogenetic relationships have not ever been tested in a phylogenomic context. To addr...

The tree of life is the fundamental biological roadmap for navigating the evolution and properties of life on Earth, and yet remains largely unknown. Even angiosperms (flowering plants) are fraught with data gaps, despite their critical role in sustaining terrestrial life. Today, high-throughput sequencing promises to significantly deepen our under...

Boehmeria, as currently circumscribed, comprises 52 species and has a pantropical distribution. Liang et al. propose a sectional classification of Boehmeria based on the phylogenetic analysis of SNP data for 20 species and an additional 10 subspecific taxa of these at the rank of variety or form. They restrict their sampling to species documented i...

With the advance of high-throughput sequencing (HTS), reduced-representation methods such as target capture sequencing (TCS) emerged as cost-efficient ways of gathering genomic information. As the off-target reads from such sequencing are expected to be similar to genome skims (GS), we assessed the quality of repeat characterization using this data...

The date palm ( Phoenix dactylifera ) has been a cornerstone of Middle Eastern and North African agriculture for millennia. It is presumed that date palms were first domesticated in the Persian Gulf and subsequently introduced into North Africa, where their evolution in the latter region appears to have been influenced by gene flow from the wild re...

Urera Gaudich, s.l. is a pantropical genus comprising c. 35 species of trees, shrubs, and vines. It has a long history of taxonomic uncertainty, and is repeatedly recovered as polyphyletic within a poorly resolved complex of genera in the Urticeae tribe of the nettle family (Urticaceae). To provide generic delimitations concordant with evolutionary...

Premise of the study Evolutionary relationships in the species-rich Orchidaceae have historically relied on organellar DNA sequences and limited taxon sampling. Previous studies provided a robust plastid-maternal phylogenetic framework, from which multiple hypotheses on the drivers of orchid diversification have been derived. However, the extent to...

Given the 2,400-fold range of genome sizes (0.06-148.9 Gbp (gigabase pair)) of seed plants (angiosperms and gymno-sperms) with a broadly similar gene content (amounting to approximately 0.03 Gbp), the repeat-sequence content of the genome might be expected to increase with genome size, resulting in the largest genomes consisting almost entirely of...

Copepods are important ecologically and represent a large amount of aquatic biomass in both freshwater and marine systems. Despite this, the taxonomy of copepods and other meiofauna is not well understood, hampered by tiny sizes, cryptic taxa, intraspecific polymorphisms and total specimen destruction where DNA methods are employed. In this article...

Seed size shapes plant evolution and ecosystems, and may be driven by plant size and architecture, dispersers, habitat and insularity. How these factors influence the evolution of giant seeds is unclear, as are the rate of evolution and the biogeographical consequences of giant seeds. We generated DNA and seed size data for the palm tribe Borasseae...

Nicotiana section Suaveolentes is the largest section of Nicotiana and is a monophyletic group of allotetraploid species. Most of the species are endemic to Australia, but three species occur on islands in the South Pacific as far east as French Polynesia and one species is native to Namibia. Here, we present phylogenetic results based on genome sk...

We present a densely-sampled phylogenomic study of the mulberry tribe (Moreae, Moraceae), an economically important clade with a global distribution, revealing multiple losses of inflexed stamens, a character traditionally used to circumscribe Moreae. Inflexed stamens facilitate ballistic pollen release and are associated with wind pollination, and...

Large variations in genome size are observed in angiosperms as a result of whole-genome duplications and the balance between amplification and deletion of repetitive DNA, together explaining the observed variation in plant genome size. In the genus Nicotiana, there are 42 cytogenetically diploid species that have been classified into eight sections...

Nicotiana section Suaveolentes is the largest section of Nicotiana and is a monophyletic group of allotetraploid species. Most of the species are endemic to Australia, but three species occur on islands in the South Pacific as far east as French Polynesia and one species is native to Namibia. Here, we present phylogenetic results based on genome sk...

Poor morphological and molecular differentiation in recently diversified lineages is a widespread phenomenon in plants. Phylogenetic relationships within such species complexes are often difficult to resolve because of the low variability in traditional molecular loci. Furthermore, biological phenomena responsible for topological incongruence such...

Allopolyploidy is acknowledged as an important force in plant evolution. Frequent allopolyploidy in Nicotiana across different timescales permits the evaluation of genome restructuring and repeat dynamics through time. Here we use a clustering approach on high-throughput sequence reads to identify the main classes of repetitive elements following t...

A recent phylogenetic method based on genome-wide abundance of different repeat types proved to be useful in reconstructing the evolutionary history of several plant and animal groups. Here, we demonstrate that an alternative information source from the repeatome can also be employed to infer phylogenetic relationships among taxa. Specifically, thi...

Large variations in genome size are observed in angiosperms as a result of whole-genome duplications and the balance between amplification and deletion of repetitive DNA, together explaining the observed variation in plant genome size. In the genus Nicotiana, there are 42 cytogenetically diploid species that have been classified into eight sections...

Extremely high levels of plant diversity in the American tropics are derived from multiple interactions between biotic and abiotic factors. Previous studies have focused on macro-evolutionary dynamics of the Tropical Andes, Amazonia, and Brazil’s Cerrado and Atlantic forests during the last decade. Yet, other equally important Neotropical biodivers...

The world’s herbaria collectively house millions of diverse plant specimens, including endangered or extinct species and type specimens. Unlocking genetic data from the typically highly degraded DNA obtained from herbarium specimens was difficult until the arrival of high-throughput sequencing approaches, which can be applied to low quantities of s...

Recent phylogenomic analyses have solved evolutionary relationships between most of the Orchidaceae subfamilies and tribes, yet phylogenetic relationships remain unclear within the hyperdiverse tribe Cymbidieae and within the Orchidoideae subfamily. Here we address these knowledge-gaps by focusing taxon sampling on the Cymbidieae subtribes Stanhope...

High-throughput DNA sequencing (HTS) presents great opportunities for plant systematics, yet genomic complexity needs to be reduced for HTS to be effectively applied. We highlight Hyb-Seq as a promising approach, especially in light of the recent development of probes enriching 353 low-copy nuclear genes from any flowering plant taxon

More than 31,000 useful plant species have been documented to fulfil needs and services for humans or the animals and environment we depend on. Despite this diversity, humans currently satisfy most requirements with surprisingly few plant species; for example, just three crops – rice, wheat and maize – comprise more than 50% of plant derived calori...

A recent phylogenetic method based on genome-wide abundance of different repeat types proved to be useful in reconstructing the evolutionary history of several plant and animal groups. Here, we demonstrate that an alternative information source from the repeatome can also be employed to infer phylogenetic relationships among taxa. Specifically, thi...

Local adaptation in plants often requires coordinated shifts among resources. Lowry et al. (2019) provide evidence for physiological and genomic mechanisms underpinning adaptive shifts in yellow monkeyflower (Mimulus guttatus), such as the transition between annual and perennial life histories. In M. guttatus, differential activity of gibberellins...

The genomic abundance of different types of repetitive DNA elements contains a phylogenetic signal useful for inferring the evolutionary history of different groups of organisms. Here we test the reliability of this approach using the Hominidae family of primates, whose consensus phylogeny is well accepted. We used the software RepeatExplorer to id...

Herbarium specimens have become a major source of information in molecular biodiversity research, framing the term “herbarium genomics”. However, obtaining good DNA from old herbarium specimens is still a challenge. Currently, DNA extraction methods from old herbarium material often yield highly degraded and fragmented DNA. A number of studies have...

Sequencing of target-enriched libraries is an efficient and cost-effective method for obtaining DNA sequence data from hundreds of nuclear loci for phylogeny reconstruction. Much of the cost of developing targeted sequencing approaches is associated with the generation of preliminary data needed for the identification of orthologous loci for probe...

Repetitive DNA has an important role in angiosperm genomes and is relevant to our understanding of genome size variation, polyploidisation and genome dynamics more broadly. Much recent work has harnessed the power of high-throughput sequencing (HTS) technologies to advance the study of repetitive DNA in flowering plants. Herbarium collections provi...

Poor morphological and molecular differentiation in recently diversified lineages is a widespread phenomenon in plants. Phylogenetic relationships within such species complexes are often difficult to resolve because of the low variability in traditional molecular loci, as well as various other biological phenomena responsible for topological incong...

Poor morphological and molecular differentiation in recently diversified lineages is a widespread phenomenon in plants. Phylogenetic relationships within such species complexes are often difficult to resolve because of the low variability in traditional molecular loci, as well as various other biological phenomena responsible for topological incong...

This special issue highlights some of the wonderful species of native Australian tobacco (Nicotiana sect. Suaveolentes). We here present twelve species of this genus, four of which are new to science. Many Nicotiana species have a high ornamental value, and we hope that particularly the rarer Australian species will find a way into horticulture to...

Background: Satellite DNA is a rapidly diverging, largely repetitive DNA component of many eukaryotic genomes. Here we analyse the evolutionary dynamics of a satellite DNA repeat in the genomes of a group of Asian subtropical lady slipper orchids (Paphiopedilum subgenus Parvisepalum and representative species in the other subgenera/sections across...

Sequencing of target-enriched libraries is an efficient and cost-effective method for obtaining DNA sequence data from hundreds of nuclear loci for phylogeny reconstruction. Much of the cost associated with developing targeted sequencing approaches is preliminary data needed for identifying orthologous loci for probe design. In plants, identifying...

CALL FOR PAPERS Difficulties in sequencing and assembly of long arrays composed of highly similar tandem repeats have resulted in the fact that those sequences are seriously underrep-resented in genome sequencing outputs, either due to the challenges posed by their assembly, or due to their masking by genome annotation pipelines. With the advent of...

Providing science and society with an integrated, up‐to‐date, high quality, open, reproducible and sustainable plant tree of life would be a huge service that is now coming within reach. However, synthesizing the growing body of DNA sequence data in the public domain and disseminating the trees to a diverse audience are often not straightforward du...

Genome size is a biodiversity trait that shows staggering diversity across eukaryotes, varying over 64,000-fold. Of all major taxonomic groups, land plants stand out due to their staggering genome size diversity, ranging ca. 2400-fold. As our understanding of the implications and significance of this remarkable genome size diversity in land plants...

Change in floral shape is thought to be driven by pollinator-mediated selection, but drivers of floral shape evolution have been little studied at a macro-evolutionary scale. Smith and Kriebel (2018) examine floral shape across species within Iochrominae (Solanaceae) using geometric morphometrics and statistical regression analyses, and show signif...

Coral reefs are of great ecological importance to marine ecosystems, yet their origins are still poorly understood. Using a robust phylogenetic framework, Huang et al. (2017) show that most diversity within the Indo-Pacific Coral Triangle region is driven by range expansions of lineages from outside the region, rather than rapid diversification wit...

We investigate the timing of diversification in allopolyploids of Nicotiana (Solanaceae) utilising sequence data of maternal and paternal origin to look for evidence of a lag phase during which diploidisation took place. Bayesian relaxed clock phylogenetic methods show recent allopolyploids are a result of several unique polyploidisation events, an...

We investigate the timing of diversification in allopolyploids of Nicotiana (Solanaceae) utilising sequence data of maternal and paternal origin to look for evidence of a lag phase during which diploidisation took place. Bayesian relaxed clock phylogenetic methods show recent allopolyploids are a result of several unique polyploidisation events, an...

Endopolyploidy is a general term describing the multiplication of nuclear DNA within the cell. In plants, this takes place via several mechanisms but mainly through the process of endoreduplication. Endoreduplication involves the replication of chromosomal deoxyribonucleic acid (DNA) without intervening mitoses and no obvious chromatin condensation...

Platystele misera (Lindl.) Garay is illustrated as the first of two species of Platystele Schltr., a genus of tiny Pleurothallid orchids from South and Central America. The ecology and distribution of Platystele are discussed, accompanied by brief notes on the cultivation of this species.

Platystele ovatilabia (Ames & C. Schweinf.) Garay is illustrated, as the second of two Platystele species. The history, taxonomy and phylogenetic relationships of Platystele are discussed further.