[ Essays on the Origin of Angiosperms ]
Molecular coevolution of insect and seed plant developmental tool kits, cis-regulatory modules (CRMs), and gene-regulatory networks (GRNs) might have underpinned diversification in Paleozoic seed plant lineages and evo-devo of short- [spur-] shoots, including protoflowers. Tool kit studies might help paleobiologists decipher angiosperm ancestry and illuminate ecologies of insect mutualisms in extinct seed plant populations.
Were insect and shrub coevolutionary compartments of the late Paleozoic hypoxic icehouse and later hot house, venues of the first angiosperms? ... ORIGIN OF ANGIOSPERMS
Pteridosperms might not constitute the "backbone of seed-plant phylogeny." Rather, the "lineage" could suffer spinal bifida ... PALEOBOTANY OF ANGIOSPERM ORIGINS
Studies of the genomic landscape of Amborella trichopoda are probably unhelpful in discerning angiosperm stem groups of Permo-triassic times and places, proving intergeneric hybridization in ancient zones of sympatry, and elucidating reproductive mechanisms leading to allopolyploid formation and dispersal of hybrid offspring.
"... Here I aim to highlight one key realization of this 'genomics era' in which we find ourselves, namely, that all modern flowering plant genomes derive from processes set in motion by a history of repeated, episodic whole-genome doubling or polyploidy" (page 1753, J. F. Wendel , American Journal of Botany 102: 1753-1756).
"Darwin himself referred to the 'early origin and diversification of angiosperms' as 'an abominable mystery,' and the origin of the flower- and therefore flowering plants- is still a question ..." (page 86, Pamela S. Soltis and Douglas E. Soltis , Chapter 4. Flower diversity and angiosperm diversification. Pp. 85-102 In: J. L. Riechmann and F. Wellmer [eds.], Flower Development: Methods and Protocols, Volume 1110. New York: Springer, 475 pp).
Biochemical and morphological evidence suggests that cones and flowers are reproductive short shoots. If fertile spur shoots are demonstrably ancient organs known from late Paleozoic seed plant fossils then how could the flower possibly originate in the late Mesozoic? Andre S. Chanderbali, B. A. Berger, D. A. Howarth, P. S. Soltis, and D. E. Soltis resuscitate this paradox (see first sentence, Evolving ideas on the origin and evolution of flowers: new perspectives in the genomic era, Genetics 202  1255). Genomic studies and APG IV might be unhelpful.
Further, tool kit studies of homeodomain proteins, transcription factors (TFs), and the nucleic acid homeobox, posit deep conservation of cone and floral CRMs, GRNs, auxin-based polarity networks, efflux carriers, and PINs.
There is growing consensus among molecular systematists and some paleobotanists on the existence of an angiosperm ghost lineage beginning with divergence(s) of flowering plants from the most recent common ancestor (MRCA) prior to the end-Permian extinction ... ANGIOSPERM GHOST LINEAGE
"Some authors seem curiously determined to prove that pre-Cretaceous fossils are crown-group angiosperms, but for understanding most aspects of the origin of angiosperms [other than their age], close stem relatives would be far more significant ..." (page 318, J. A. Doyle , Molecular and fossil evidence on the origin of angiosperms. Annual Review of Earth and Planetary Sciences 40: 301–326) ... COMMENTARY
[ Topics for Debate and Discussion ]
News analysis and commentary includes copyrighted illustrations and links to scientific research articles on the origin of flowering plants, Holometabola, and related subjects ... RESEARCH NEWS
The Charles Darwin Bicentennial Reading List and library book chapter ensemble is intended for students with advanced college level biology training ... KEY TO THE LITERATURE
Each year I will select a scientific paper, book chapter, or book as being of paramount importance toward finding a solution to the enigmatic origin of angiosperms and putative relationships with holometabolous insects ... PUBLICATION OF THE YEAR
[ Problems for Students of Paleobiology ]
Practice exercises on this web site include a seed plant character homology assessment and sample data matrix for morphological-phylogenetic analysis ... DATA MATRIX
A drill in angiosperm pollen phylogenetics is suggested to incorporate palynological data from core samples pulled-up from sediments, Triassic (Anisian) in age ... CLADISTICS OF PRE-CRETACEOUS ANGIOSPERM POLLEN RECORDS
Graduate students and post-doctoral research associates might wish to tackle a field- and laboratory research problem in understanding taphonomy of detached and shed foliar remains of reproductive short- [spur-] shoots, and computing theoretical morphospace ... RECONSTRUCTING CONES AND FLOWERS
Commercial software is available to sharpen skills in ARC-INFO/GIS and geo-referencing of paleontological resources needed to study ancient hybridizing angiosperm stem group populations ... VICARIANCE PALEOBIOGEOGRAPHY
[ The Clear Fork Gigantopteroid ]
The Clear Fork Group of sedimentary rocks was deposited in riverine oxbows along Artinskian and Cisuralian coastlines more than 256 million years ago (MYA) ... CENTRAL PANGAEAN MOUNTAINS AND HOVEY CHANNEL
Detached and shed leaves described as Evolsonia texana and the retuse-leaved morphotype Taeniopteris sp. co-occur in specific sedimentary rock layers of the Clear Fork red beds. Do these herbivorized foliar organs belong to short- and long-shoots of a gigantopteroid seed plant, which is neither a Auritifolia waggoneri or Supaia thinnfeldioides peltasperm, and not a gnetophyte, pteridosperm, or taeniopteroid cycadophyte?
Vojnovskyales and gigantopteroids are poorly understood Permo-carboniferous gymnosperms with possible evolutionary ties to the flowering plants or Gnetum according to some authors (V. A. Krassilov and V. I. Burago , New interpretation of Gaussia [Vojnovskyales], Review of Paleobotany and Palynology 32: 227-237; Chapter 19, T. N. Taylor, E. L. Taylor, and M. Krings , Paleobotany: The Biology and Evolution of Fossil Plants, Second Edition. Burlington: Elsevier-Academic Press, 1230 pp).
Anatomical studies of permineralized material of Delnortea abbottiae and Evolsonia texana foliar organs and their theoretical morphospace might help decipher the evolutionary relationships of these widespread gymnosperms with sympatric seed plant congeners ... DELNORTEAS AND EVOLSONIAS
The foliage of Vojnovskyales resembled the Triassic monocot-like plant Sanmiguelia according to P. R. Crane (1985), Phylogenetic analysis of seed plants and the origin of angiosperms, Annals of the Missouri Botanic Garden 72: 716-793. Leaf morphologies expressed by these ancient seed plants might reflect fingerprints of the monocotyledonous angiosperm developmental tool kit ... VOJNOVSKYALES and SANMIGUELIAS
During the Paleozoic Era as global atmospheric oxygen level fluctuated, chewing, crawling, ovipositioning, piercing, siphoning, sponging, stinging, and sucking insects were possible residents of some seed plant shrubs and trees. Potentially pigmented reproductive foliar organs once grew in spiral phyllotaxes from herbivorized short- [spur-] shoots.
Air pockets at the base of sheathing leathery leaves and around developing stems and organs, and reproductive modules of monopodial Permo-carboniferous seed plants might have provided phytophagous insects with oxygen gas, food, and shelter from predators, cold, and ultraviolet radiation.
Phytophagous insect associates of developmentally plastic Permian seed plant shrubs survived the end-Permian extinction. Long-term climate forcing [> precipitation and sedimentation] caused by optical effects of [pO2] has been reported by C. J. Poulsen, C. Tabor, and J. D. White , Long-term climate forcing by atmospheric oxygen concentrations, Science 348 : 1238-1241.
Pulsed acidification of substrates, hypoxia, increases in ambient temperature, and "trigger and kill" events could have affected insects, mycorrhizal fungi, and tetrapods in a hot-house world ... PALEOECOLOGY OF GLOBAL CATASTROPHE
"... new multidisciplinary data from the Karoo Basin call into question our current understanding of the terrestrial response to the end-Permian mass extinction. Paleoecological evidence does not support the reported coincidence of climate aridification, floral collapse, and tetrapod turnover ..." (Discussion and Conclusions on page 941, R. A. Gastaldo, S. L. Kamo, J. Neveling, J. W. Geissman, M. Bamford, and C. V. Looy (2015), Is the vertebrate-defined Permian-Triassic boundary in the Karoo Basin, South Africa, the terrestrial expression of the end-Permian marine event? Geology 43(10): 939-942).
Were Paleozoic changes in atmospheric [pO2] the selective force driving the molecular evolution of gas-binding hemocyanin respiratory enzymes and moulting storage proteins of early arthropods? ... INSECT HEXAMERINS
Are the helix-turn-helix (HTH) DNA-binding motifs of seed plant Leafy enzyme and the insect homeodomain protein Engraled, products of molecular coevolution? ... LFY ENZYME STRUCTURE
A key ingredient often left out of the steaming cauldron of past ideas on the origin of flowering plants is the potential modular evolution of a class of mobile chromosome parasites known as transposable elements (TEs) ... LTR RETROTRANSPOSONS
What did external biotic and physical factors have to do with the evo-devo of larval moult cycles and innovative mouthparts of phytophagous insects? ... ORIGIN OF THE HOLOMETABOLA
"... the WGD [α-swarm or ε?] that preceded the origin of the angiosperms clearly provided genetic fodder that appears to have resulted in the key innovation we know as the flower [protoflower?]" (Key innovations on page 160, P. S. Soltis and D. E. Soltis , Ancient WGD events as drivers of key innovations in angiosperms, Current Opinion in Plant Biology 30: 159-165, symbols [in brackets] are mine ... WGDs
Do models using paleo-proxies based on aspects of fossil plant anatomy such as cuticular impressions of stomates and wood permineralizations, and isotopic carbon estimates, cap atmospheric carbon dioxide "... at 1000 ppm over most of the past 300 million years"? (Abstract, J. C. McElwain, I. Montañez, J. D. White, J. P. Wilson, and Y. Yiotis , Palaeogeography, Palaeoclimatology, and Palaeoecology 441[3-4]: 653-658) ... PALEOPOLYPLOIDY, PROXIES, AND GLOBAL HOT HOUSES
Were secretions of insect eggs, instars, larvae, pupae, and adults, when applied to shoot apical meristems (SAMs) with mechanical force, a source of signals that affected plant growth and development at the genetic level in nuclei of host cells of certain monopodial Permo-triassic seed plants? ... SIGNALS
When supported by paleobotanical evidence, were reproductive short- [spur-] shoots of Permo-carboniferous seed plants with spiral phyllotaxis visually discernable to pollinivores, paleodictyopterans, and predatory wasps? ... COEVOLUTION
Based on biochemical studies of TFs and PINs, some molecular-phylogenetic analyses, and the stratigraphic distribution of Afropollis and other diverse palynomorphs, is the statement [below] on page 380 of Scott L. Wing and Lisa D. Boucher (1998), Ecological aspects of the Cretaceous flowering plant radiation, Annual Review of Earth and Planetary Sciences 26: 379-421, precise or accurate?
"Despite the singular ecological significance and species diversity of angiosperms, they are not in a genealogical sense one of the major branches of land plants and did not originate with other major land plant clades (e.g. lycopsids, ferns, conifers, cycads, ginkgos) during the middle or late Paleozoic."
The logic of CRMs, GRNs, PINs, and a deeply conserved floral tool kit might allow formulation of evo-devo models to explain curling, inrolling, and fusion of ovule-bearing Phasmatocycas bridwellii leaves to form carpels, ovaries, and pistils. Morphological constructs could be cast in theoretical morphospace computed from metrics and scaling of detached foliar and floral organs ... PALEOZOIC PROTOFLOWERS
[ Biostratigraphy of a Permian Standard Section ]
Folded and overthrust mountain belts of southwestern North America yield classic exposures of a nearly complete sequence of Paleozoic rocks.
A stratigraphic bedding sequence in the Del Norte and Glass Mountains constitutes the standard North American type section for the Permian Period.
Rocks of these mountain ranges yield fossilized coral reefs with brachiopods, conodonts, fusulinids, graptolites, and sponges, and deltaic transitional layers with preserved freshwater snails, walchian conifers, and gigantopteroid seed plants ... ARTICLE
[ Living "Fossil" Magnoliids: Degeneriaceae of Fiji ]
Several island groups of the southern Pacific Ocean possess harmonic faunas and floras reminiscent of larger, continental land masses. Consisting of a single genus and two species Degeneriaceae are endemic to three of the seven "high" islands of the Fiji archipelago.
Molecular phylogenetic studies of magnoliids by the Laboratoire Ecologie Systématique et Evolution, Equipe Evolution des Angiospermes, Université Paris-Sud, France, reveal unexpected relationships of Degeneria roseiflora with other magnoliids.
Degenerias combine several archetypic angiosperm characters including carpels with evaginating stigmatic secretions "plugs" laminar microsporophylls, monosulcate (boat-shaped) pollen, polycotyledony, and tiny embryos ... NOTES FROM THE FIELD
[ Statement on Evolution ]
The gigantopteroid web site owner and writer, peer reviewers, and contributors adopt the Botanical Society of America's policy on evolution ... BOTANICAL SOCIETY OF AMERICA