Article

Speciation collapse and invasive species dynamics during the Late Devonian “Mass Extinction”

GSA Today 01/2012; 22(1):4-9. DOI: 10.1130/g128a.1

ABSTRACT The Late Devonian (Frasnian-Famennian) interval includes one of the most dramatic intervals of biotic turnover in the Phanerozoic. Statistical evaluation of diversity change reveals that the primary cause of biodiversity decline was reduced speciation during the crisis interval, not elevated extinction rates. Although various hypotheses have been proposed to explain extinction increase during the Late Devonian, potential causes for reduced speciation have previously been largely unaddressed. Recent analyses focusing on biogeographic and phylogenetic patterns of species in shallow marine ecosystems of Laurentia indicate that a dramatic increase in interbasinal species invasions, facilitated by transgressive pulses, fundamentally affected biodiversity by enabling range expansion of ecological generalists and eliminating vicariance, the primary pathway by which new species typically form. Modern species invasions may result in similar speciation loss, exacerbating the current biodiversity crisis.

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Available from: Alycia L Stigall, Sep 04, 2015
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    • "It is bracketed by two oceanic anoxia events that are associated with major mass extinctions. The Kellwasser Event at the Frasnian– Famennian (F–F) boundary decimated coral reef and other benthic marine communities (Copper, 1994) while slightly older extinctions decimated terrestrial ecosystems (Stigall, 2012 and McGhee, 2013). In contrast, the Hangenberg Event at the Devonian–Carboniferous (D–C) boundary primarily affected pelagic marine communities including fish (Sallan and Coates, 2010) and cephalopods (Becker, 1993 and Zong et al., 2014). "
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    ABSTRACT: Sedimentary petrology and trace element geochemistry indicate that the Late Devonian to Early Carboniferous Heishantou Formation near Boulongour Reservoir (NW Xinjiang, China) was deposited on a steep slope, mid-latitude accreting island arc complex in an open oceanic system. Bulk 87Sr/86Sr ratios show excursion patterns that are consistent with excursions at the Devonian-Carboniferous (D-C) boundary in epicontinental margin sediments. Sedimentation rates for the Boulongour Reservoir sediments show highly variable rates that range from 0.5 cm/ky to 10 cm/ky, consistent with other Late Devonian sections and modern arc environments. Multiple whole rock geochemical proxies for anoxia and the size and distribution of pyrite framboids suggest the presence of the Hangenberg Event in the sediments associated with the D-C boundary, despite the lack of visible black shale. The presence of anoxia in an open ocean, island arc environment cannot be explained by upwelling of anoxic bottom waters at this paleolatitude, but can be explained by the global infliction of oceanic shallow water eutrophication on to a climate system in distress.
    Gondwana Research 03/2015; DOI:10.1016/j.gr.2015.02.009 · 8.12 Impact Factor
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    • "claim that widespread forest fires and massive soil erosion took place during the Frasnian–Famennian event, leading to eutrophication, the development of anoxic/euxinic conditions in the water column, and in consequence mass extinction (more correctly, biodiversity crisis; Stigall, 2012) of marine biota. Although this scenario is novel and intriguing, it does, in our opinion lack sufficient evidence. "
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    ABSTRACT: Kaiho et al. (2013, Palaeogeography, Palaeoclimatology, Palaeoecology 392 (2013): 272–280) interpreted the occurrence of elevated concentrations of high molecular weight polycyclic aromatic hydrocarbons and dibenzofuran as indicators of wildfires and enhanced run-off near the Frasnian-Famennian (F-F) boundary. We argue that other processes, including weathering or hydrothermal oxidation (not discussed by Kaiho et al.) lead to the observed increase in the concentration of these compounds and also change their distribution. Kaiho et al.’s evidence for soil erosion and eutrophication-induced euxinia is also weak in the case of the investigated Belgian sections. Finally, Kaiho et al. rather unfortunately omitted a great wealth of important data published elsewhere, choosing instead to include only those which support their ideas and interpretations.
    Palaeogeography Palaeoclimatology Palaeoecology 01/2015; 417:569-572. DOI:10.1016/j.palaeo.2014.02.027 · 2.75 Impact Factor
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    • "A new ecological severity metric ranks the Frasnian–Famennian event as the fourth most ecologically severe crisis in the Phanerozoic (McGhee et al., 2013). An alternate interpretation of the Frasnian–Famennian extinction suggests that a lack of origination rather than extinction caused the depletion in diversity (Bambach et al., 2004 and Stigall, 2012). "
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    ABSTRACT: The Frasnian-Famennian mass extinction event devastated tropical marine ecosystems and ranks in the top six in taxonomic and ecological severity. The close stratigraphic association between the extinction and the Kellwasser Anoxia Events support a link between oceanographic anoxia and extinction. The Upper and Lower Kellwasser horizons have been identified in epicontinental, basinal settings in Laurussia, Gondwana, Siberia, and South China. The Hongguleleng Formation (Late Devonian) in northwestern Xinjiang, China, contains both the Frasnian-Famennian boundary and the rebound from the Frasnian-Famennian extinction event in a highly fossiliferous shallow marine setting associated with a Devonian oceanic island arc complex (part of the Central Asian Orogenic Belt, or CAOB). Here we show that the Hongguleleng Formation also records the Upper Kellwasser Anoxia Event through analysis of multiple geochemical proxies. In contrast to previous studies asserting that the Kellwasser Events were restricted to epicontinental seaways and basins, our results indicate that it occurred not only along the shallow continental margins of the closing Rheic Ocean, but also in shallow water in the open oceanic part of Paleotethys. Previous explanations for the Kellwasser Events from epicontinental margins and basins call for the migration of deep anoxic bottom water into shallow water environments as a kill mechanism for shallow marine ecosystems or attribute it to sea level rise and subsequent stagnation. There is no evidence that the Devonian oceans completely overturned during the Kellwasser Events; similarly, many transgressive events in the Devonian are not associated with black shales. We therefore suggest an alternative mechanism for the Kellwasser Events based on new evidence from the CAOB, where anoxia is driven by episodic eutrophication of surface waters.
    Palaeogeography Palaeoclimatology Palaeoecology 04/2014; 399. DOI:10.1016/j.palaeo.2014.02.016 · 2.75 Impact Factor
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