Student Exercise in ARC-INFO/GIS, Geo-referencing, and Paleobiogeography:
Several books, book chapters, and articles in classical and contemporary scientific literature contain detailed but speculative arguments on the paleobiogeography of stem group flowering plants and possible ancestors (some key references appear below). A late Paleozoic origin of angiosperms has been proposed by Axelrod (1952), among others. While others suggest a Jurassic or early Cretaceous origin of the clade (Friis et al. 2011, among others).
"... we hypothesize that proto-South-East Asia served both as the cradle and centre of diversification of early angiosperms" (page 332, Is the Most Recent Common Ancestor of Angiosperms Now Lost in Proto-southeast Asia Terranes That Are Underwater or Subducted?, Buerki et al. 2014).
Hypotheses suggested by Buerki et al. (2014) contradict classical ideas expressed by Axelrod (1952, 1959) and Krassilov (1997). Dispersal of early angiosperm floras from the tropics poleward was proposed by Axelrod in 1959. A statement quoted from this often overlooked paper is probably pertinent.
"... since angiosperms [Vojnovskyales?] may already have been in existence in upland areas by the Permian [Axelrod 1952], and because the record of the group is exceedingly fragmentary into the Early Cretaceous, the data obviously do not permit us to suggest any one area as the cradle of origin" (page 207, Discussion, Axelrod 1959, the words in [brackets] are mine).
Further, an important study of pollen samples recovered from isolated sedimentary layers in [at least one] continuous stratigraphic sequence in two deep well cores, reports monosulcate, columellate palynomorphs, and Afropollis, from the Middle Triassic (Anisian) about 240 MYA (Hochuli and Feist-Burkhardt 2013). Definitive paleontological evidence published by Peter Hochuli and Susanne Feist-Burkhardt should be read together with a review of Sanmiguelia paleobiology, also reporting three new localities from the Lower Triassic (Norian) Chinle Formation of southwestern North America (Ash and Hasiotis 2013).
Based on Axelrod and Krassilov's cogent arguments and unequivocal palynological evidence published by Hochuli and Feist-Burkhardt (2004, 2013), the Buerki team (2014) should do more homework and rethink their ideas, in my opinion.
Based on controversial research in connection with oil and gas exploration, the Hovey Channel is a southerly bay on the edge of the prominent gulf (left-center of Ron Blakey's paleomap, above) just to the north of the westernmost terminus of the Central Pangaean Mountains at the edge of the Panthalassa Ocean (C. A. Hill 1999).
The well-reasoned "Coastal Hypothesis," which was proposed by Retallack and Dilcher in 1981, could be extended more deeply in geologic time to putative angiosperm stem group seed plant populations of tropical maritime swamps, riparian scrub and woodlands, and semiarid hills bordering the Hovey Channel described above, and reconstructed by Ron Blakey, Ph.D.
When vojnovskyalean elements in Angaran, Cathaysian, and Euramerian floras are considered together with wide-ranging paleopopulations of delnorteas and evolsonias (Mamay et al. 1988, Mamay 1989), among other gigantopteroids (Schachat et al. 2015), potential sites for natural hybridization and intergeneric gene flow were spread across thousands of kilometers.
"Analysis of a wider set of proxies confirms that semi-arid and then arid conditions gradually expanded from west to east across equatorial Pangaea during the latter half of the LPIA" [Late Palaeozoic Ice Age, 305 to 270 MYA] (page 111, 2. The LPIA, 2.2 Glaciation and tropical precipitation during the LPIA: geological evidence and modeling, Heavens et al. 2015).
As the LPIA drew to a close with the demise of Central Pangaean Mountain glaciers, and aridity spread from west to east across early Pangaea, possible new habitats opened opportunities and venues for natural interspecific hybridization in sympatric seed plant populations. Colorful reproductive short- [spur-] shoots of certain species of these seed plants ("coevolutionary compartments") might have attracted pollen-eating and predatory insects with paleobiological consequences.
Were insect and shrub coevolutionary compartments of the late Paleozoic hypoxic icehouse and later hot house, venues of the first angiosperms? Possibly.
A paraphyletic (or polyphyletic) "origin" of stem group flowering plants potentially involving insect- or wind-pollination, natural interspecific hybridization, and paleopolyploidy was possible, but in ancient zones of sympatry from potentially widespread seed plant populations indigenous to coastal and extrabasinal, upland habitats of Pangaea (or pre-Pangaea). This premise eliminates any of the late Mesozoic southwest Pacific Ocean archipelagos, island arcs, spreading centers, or now submerged continental cratons (Buerki et al. 2014) from consideration as "The Cradle of the Flowering Plants" (page 137, Chapter 12, Armen Takhtajan [1969 translation by C. Jeffrey], Flowering Plants Origin and Dispersal, Washington, Smithsonian Institution Press, 310 pp.).
Computer-assisted exercises. As a student drill in ARC-INFO/GIS, geo-referencing, and paleobiogeography, plot the Angaran, Cathaysian, and Euramerian localities where fossils of Permian gigantopteroids and Vojnovskyales have been reported by Mamay et al. (1988) and Naugolnykh (2001), among others. Trace the assembly of Lower Permian continental cratons with "rafting" populations of gigantopteroids and vojnovskyaleans to potential locations on Triassic Pangaea.
Published work reveals that populations of Delnortea abbottiae, Evolsonia texana, Lonesomia mexicana, and Sandrewia texana were spread across a couple thousand kilometers of coastal regions bordering the Hovey Channel of the Panthalassa Sea at the western end of the Central Pangaean Mountains, and to the south of the western tip of the massif where the Artinskian Palmarito Formation was deposited (center left on Ron Blakey's paleomap, above). Plot the source rocks and geo-referenced localities where these fossils have been reported on one or more of the paleomaps obtained or purchased from the sources listed above.
Two other gigantopteroid species, Cathaysiopteris yochelsonii and Zeilleropteris wattii co-occur with so-called "Taeniopteris sp. nov." Taeniopteris sp. [aff. T. multinervis] is the "probable [problematical?] cycadophyte" on page 856, and in Table 1 on page 858 of Schachat et al. (2014) in Permian rock layers. The words [in brackets] are mine. Students should add these geo-referenced sites to the Permian paleomaps constructed as suggested above.
Now apply PAUP or other software of your choice to the sample datasets located on another page of this web site. How do your phylogenetic analyses compare with published work?
Scholars realize that there was never one "source" of an allopolyploid angiosperm "ancestor." Further, a single "origin" of an ancient hybrid flowering plant population was probably unlikely, based on some evidence that species of several possible Permo-triassic flowering plant-antecedents and progenitors including delnorteas, evolsonias, and Vojnovskyales, were spread across thousands of kilometers of Permo-carboniferous terrestrial landscapes.
In reality, scientists might never fully understand paleoecologies of insect- and fungal-plant mutualisms, ancient saltational speciation and coevolution, or past episodes of pollen- and gene-flow in once sympatric seed plant populations, long dead and gone. This begs several questions, among others.
Is the single paleopolyploid event discerned from study of the Amborella genome including an epsilon (ε)- whole genome duplication (WGD), which is depicted as the asterisk in the figured Structured Abstract of Amborella Genome Project (2013), part of the late Paleozoic alpha (α)- swarm of whole genome duplications (WGDs) modeled by Jiao et al. (2011)?
If angiosperms as broadly defined, are fundamentally paraphyletic (and/or polyphyletic), and WGDs (including the γ-triplication) are a result of classic allopolyploidy in paleopopulations of genetically unrelated evolutionary lines, how can a single ancestral Amborella genome be manifest "throughout angiosperm history" (Structured Abstract Discussion, Amborella Genome Project 2013) without genetic input from unrelated, extinct seed plant populations?
"Whereas some authors considered it [Sanmiguelia] as an angiosperm [Brown 1956; Cornet 1986, 1989a] others suggested an attribution to ginkgophytes and rejected a possible relation to angiosperms [Crane 1987, Doyle and Donoghue 1993]" (Discussion-Cretaceous and Pre-cretaceous Records, Hochuli and Feist-Burkhardt 2013).
Surprisingly, Peter Crane (page 779, 1985) once drew a connection between foliar material of Vojnovskya paradoxa and Sanmiguelia lewisii.
How does the paleogeographic distribution of Permo-carboniferous vojnovskyalean seed plant populations match-up with paleomaps based on georeferenced localities of sanmiguelias from the Triassic Chinle Formation of southwestern North America reported by Ash and Hasiotis (2013)?
Based on leaf morphologies and vicariance are Triassic paleopopulations of Sanmiguelia possible descendants of Permo-carboniferous Vojnovskyales?
"... angiosperms could have descended from highlands where they grew for millions of years, perhaps even since the Paleozoic, without leaving fossil traces. The highland hypothesis accords with the Lyellian-Darwinian doctrine of imperfection of the fossil record" (page 109-110, Krassilov 1997).
Do your animated paleomaps fit with Daniel Axelrod's classical ideas on the Permo-triassic origin and early distribution of angiosperms?
"... the absence of Permo-Triassic records of angiosperms is not surprising, but is fully consistent with the thesis that they may have evolved in upland regions of that period" (page 34, Axelrod 1952).
Does palynological evidence published by Hochuli and Feist-Burkhardt (2004, 2013) suggesting that populations of angiosperms occurred in arid, boreal, and tropical environments of the Triassic Period fit with opinions expressed by Axelrod (1959), J. A. Doyle (2012), Buerki et al. (2014), Chaboureau et al. (2014), and others (references appear below)?
"... Allopatric speciation and radiation, usually enhanced by orogeny processes and relief creation, rather involves here the fragmentation of the supercontinent into many small land masses ... " (page 14068, Introduction: Global Climate and Angiosperm Expansion and Diversification, Chaboureau et al. 2014).
Does APG IV have any bearing on the origin and early dispersal of flowering plants, including ANA grade angiosperms, as suggested by J. A. Doyle (2012) and Buerki et al. (2014)? No.
"... The congruence of the stratigraphic sequence of pollen types and their presumed evolutionary sequence would make no sense if angiosperms had already diversified in a hidden homeland area; there is no reason to expect that groups would migrate into better-known areas in the order in which they evolved much earlier ... " (page 303, Status of the Problem Prior to Molecular Systematics, J. A. Doyle 2012).
Taking into account a possible "evolutionary sequence" (chronocline) of leaf morphologies seen in Permo-carboniferous Vojnovskyales and Triassic sanmiguelias, and a "stratigraphic sequence of pollen types," which is evident from palynological evidence published by Hochuli and Feist-Burkhardt (2004, 2013), is the preceding statement accurate or precise?
Together with animations and/or graphics produced by application of commercial and/or educational software (see above), what can your team conclude on the phylogeography of paraphyletic clades of gymnosperms (including delnorteas, evolsonias, and sanmiguelias, among other seed plant lineages) discerned from computer-assisted analyses?
Tropical maritime swamps, riparian scrub and woodlands, and dry tropical shrublands and glades and rocky outcrops in walchian coniferous forests of the Central Pangaean Mountains bordering the Hovey Channel might offer convenient paleogeographic settings for J. A. Doyle's "hidden homeland area" where the ancestors of flowering plants including delnorteas, evolsonias, and sandrewias, "had already diversified." Daniel Axelrod proposed a similar idea in 1952.
Finally, C. S. P. Foster et al. (2017) conclude that, "using analyses of near-complete chloroplast genomes, we have estimated that crown group Angiospermae arose 221 Ma (251-192 Ma) in the mid-Triassic."
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