Phylogenomics and the rise of the angiosperms

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 foundational work, such as classification and first insights into angiosperm diversification since their Mesozoic origins5,6,7. However, the limited and biased sampling of both taxa and genomes undermines confidence in the tree and its implications. Here, we build the tree of life for almost 8,000 (about 60%) angiosperm genera using a standardized set of 353 nuclear genes8. This 15-fold increase in genus-level sampling relative to comparable nuclear studies9 provides a critical test of earlier results and brings notable change to key groups, especially in rosids, while substantiating many previously predicted relationships. Scaling this tree to time using 200 fossils, we discovered that early angiosperm evolution was characterized by high gene tree conflict and explosive diversification, giving rise to more than 80% of extant angiosperm orders. Steady diversification ensued through the remaining Mesozoic Era until rates resurged in the Cenozoic Era, concurrent with decreasing global temperatures and tightly linked with gene tree conflict. Taken together, our extensive sampling combined with advanced phylogenomic methods shows the deep history and full complexity in the evolution of a megadiverse clade

Genome size diversity in orchids: consequences and evolution

The amount of DNA comprising the genome of an organism (its genome size) varies a remarkable 40 000-fold across eukaryotes, yet most groups are characterized by much narrower ranges (e.g. 14-fold in gymnosperms, 3- to 4-fold in mammals). Angiosperms stand out as one of the most variable groups with genome sizes varying nearly 2000-fold. Nevertheless within angiosperms the majority of families are characterized by genomes which are small and vary little. Species with large genomes are mostly restricted to a few monocots families including Orchidaceae.|A survey of the literature revealed that genome size data for Orchidaceae are comparatively rare representing just 327 species. Nevertheless they reveal that Orchidaceae are currently the most variable angiosperm family with genome sizes ranging 168-fold (1C = 0.33-55.4 pg). Analysing the data provided insights into the distribution, evolution and possible consequences to the plant of this genome size diversity.|Superimposing the data onto the increasingly robust phylogenetic tree of Orchidaceae revealed how different subfamilies were characterized by distinct genome size profiles. Epidendroideae possessed the greatest range of genome sizes, although the majority of species had small genomes. In contrast, the largest genomes were found in subfamilies Cypripedioideae and Vanilloideae. Genome size evolution within this subfamily was analysed as this is the only one with reasonable representation of data. This approach highlighted striking differences in genome size and karyotype evolution between the closely related Cypripedium, Paphiopedilum and Phragmipedium. As to the consequences of genome size diversity, various studies revealed that this has both practical (e.g. application of genetic fingerprinting techniques) and biological consequences (e.g. affecting where and when an orchid may grow) and emphasizes the importance of obtaining further genome size data given the considerable phylogenetic gaps which have been highlighted by the current study

Fuel additive effects on soot across a suite of laboratory devices, part 2: Nitroalkanes

This is the second in a series of papers to summarize results of the impact of nonmetallic fuel additives on soot. The research was conducted by a university, industry, and government team with the primary objective of obtaining fundamental understanding of the mechanisms through which additive compounds blended into a fuel affect soot emissions. The work involved coordinated testing across a suite of laboratory devices: a shock tube, a well-stirred reactor, a premixed flat flame, an opposed-jet diffusion flame, and a high-pressure turbulent reactor. This article summarizes results on the addition of nitroalkanes to a base fuel consisting of n-heptane and toluene as a simple surrogate for jet fuels. In these experiments, the nitroalkanes serve as chemical probes of key reactions leading to soot. The effects of nitroalkane addition on soot were found to be device and condition dependent with no simple trends across the suite of devices. Copyright © Taylor & Francis Group, LLC

Combustion Measurements of Synthetic Fuels at Gas Turbine Conditions

Synthetic fuels are of interest as a replacement for aviation, diesel, and other petroleum-based fuels, and the present paper outlines a joint project to study the combustion behavior of Fischer-Tropsch (FT) synthetic fuels. To this end, shock-tube kinetics, shock-tube spray, and high-recirculation combustion rig experiments are being utilized to study the ignition delay times, chemical kinetics, and the formation of soot and emissions of FT jet fuels. The conditions for the present ignition delay times and CH* profiles ranged from 1391 to 1680 K with an average pressure of 2 atm and equivalence ratio of 1, highly diluted in argon. Undiluted experiments were conducted using a recently developed heterogeneous technique wherein the fuel is sprayed directly into the test region of a shock tube. The high recirculation combustion rig is a complete gas turbine where syntroleum was combusted and soot formation and particulates measured. Reduction of soot and emissions was observed, agreeing with previous investigations

Phylogenomics and the rise of the angiosperms

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 foundational work, such as classification and first insights into angiosperm diversification since their Mesozoic origins5,6,7. However, the limited and biased sampling of both taxa and genomes undermines confidence in the tree and its implications. Here, we build the tree of life for almost 8,000 (about 60%) angiosperm genera using a standardized set of 353 nuclear genes8. This 15-fold increase in genus-level sampling relative to comparable nuclear studies9 provides a critical test of earlier results and brings notable change to key groups, especially in rosids, while substantiating many previously predicted relationships. Scaling this tree to time using 200 fossils, we discovered that early angiosperm evolution was characterized by high gene tree conflict and explosive diversification, giving rise to more than 80% of extant angiosperm orders. Steady diversification ensued through the remaining Mesozoic Era until rates resurged in the Cenozoic Era, concurrent with decreasing global temperatures and tightly linked with gene tree conflict. Taken together, our extensive sampling combined with advanced phylogenomic methods shows the deep history and full complexity in the evolution of a megadiverse clade

Phylogenomics and the rise of the angiosperms

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 foundational work, such as classification and first insights into angiosperm diversification since their Mesozoic origins5–7. However, the limited and biased sampling of both taxa and genomes undermines confidence in the tree and its implications. Here, we build the tree of life for almost 8,000 (about 60%) angiosperm genera using a standardized set of 353 nuclear genes8. This 15-fold increase in genus-level sampling relative to comparable nuclear studies9 provides a critical test of earlier results and brings notable change to key groups, especially in rosids, while substantiating many previously predicted relationships. Scaling this tree to time using 200 fossils, we discovered that early angiosperm evolution was characterized by high gene tree conflict and explosive diversification, giving rise to more than 80% of extant angiosperm orders. Steady diversification ensued through the remaining Mesozoic Era until rates resurged in the Cenozoic Era, concurrent with decreasing global temperatures and tightly linked with gene tree conflict. Taken together, our extensive sampling combined with advanced phylogenomic methods shows the deep history and full complexity in the evolution of a megadiverse clade