Biodiversity is distributed unevenly from the poles to the equator, and among branches of the tree of life, yet how those patterns are related is unclear. We investigated global speciation-rate variation across crown Mammalia using a novel time-scaled phylogeny (N=5,911 species, ~70% with DNA), finding that trait- and latitude-associated speciation has caused uneven species richness among groups. We identify 24 branch-specific shifts in net diversification rates linked to ecological traits. Using time-slices to define clades, we show that speciation rates are a stronger predictor of clade richness than age. Mammals that are low dispersal or diurnal diversify the fastest, indicating roles for geographic and ecological speciation, respectively. Speciation is slower in tropical than extra-tropical lineages, consistent with evidence that longer tropical species durations underpin the latitudinal diversity gradient. These findings juxtapose modes of lineage diversification that are alternatively turnover-based, and thus non-adaptive, or persistence-based as associated with resource adaptations.
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Ecomorphological studies evaluating the impact of environmental and biological factors on the brain have so far focused on morphology or size measurements, and the ecological relevance of potential multi-level variations in brain architecture remains unclear in vertebrates. Here, we exploit the extraordinary ecomorphological diversity of squamates to assess brain phenotypic diversification with respect to locomotor specialization, by integrating single-cell distribution and transcriptomic data along with geometric morphometric, phylogenetic, and volumetric analysis of high-definition 3D models. We reveal significant changes in cerebellar shape and size as well as alternative spatial layouts of cortical neurons and dynamic gene _expression_ that all correlate with locomotor behaviours. These findings show that locomotor mode is a strong predictor of cerebellar structure and pattern, suggesting that major behavioural transitions in squamates are evolutionarily correlated with mosaic brain changes. Furthermore, our study amplifies the concept of âcerebrotypeâ, initially proposed for vertebrate brain proportions, towards additional shape characters.
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This review presents evidence to support the hypothesis that the reduced O2 during the Permian/Triassic period was the impetus for the evolutionary selection of endothermic animals. The evolution of smaller red blood cells with greater surface areas along with increased: capillary density, capillary surface area, hematocrits, blood pressure, blood flow rates, and shear rates were critical for efficient gas exchange in endothermy. The evolution of the fourâchambered mammalian/avian heart allowed for low pulmonary and high systemic blood pressure. It is proposed that hypoxiaâinduced angiogenesis led to increased vascularization in endothermic animals. The increased blood pressure, flow rates, and shear forces likely required changes in hemostatic mechanisms that were met in mammals by the evolution of anucleate platelets. The evolution of mammals and birds occurred in a parallel fashion with further genetic changes to anucleate RBCs/platelets occurring in mammals. Although it is possible that the evolution of endothermy in birds and mammals occurred as two independent events, it is more likely that a common ancestor developed genetic mutations that laid down the road map for parallel alterations of their cardiovascular system in response to environmental pressures. Model systems to support the proposed changes from ectotherm to endotherm were developed from published data. The evolutionary development of endothermy occurred over millions of years with a continuum of genetic alterations that involved skeletal, soft tissue, cardiovascular macrochanges along with numerous molecular alterations. Genetic signals and potential regulators for the evolutionary changes of endothermic blood cells from their bipotential stem cells are also proposed.
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Stephen M. Jones, Murray Hoggett, Sarah E. Greene & Tom Dunkley Jones Â(2019)
Large Igneous Province thermogenic greenhouse gas flux could have initiated Paleocene-Eocene Thermal Maximum climate change.
Nature Communications Â10, Article number: 5547
doi: Â
https://doi.org/10.1038/s41467-019-12957-1https://www.nature.com/articles/s41467-019-12957-1https://www.nature.com/articles/s41467-019-12957-1.pdfLarge Igneous Provinces (LIPs) are associated with the largest climate perturbations in Earthâs history. The North Atlantic Igneous Province (NAIP) and Paleocene-Eocene Thermal Maximum (PETM) constitute an exemplar of this association. As yet we have no means to reconstruct the pacing of LIP greenhouse gas emissions for comparison with climate records at millennial resolution. Here, we calculate carbon-based greenhouse gas fluxes associated with the NAIP at sub-millennial resolution by linking measurements of the mantle convection process that generated NAIP magma with observations of the individual geological structures that controlled gas emissions in a Monte Carlo framework. These simulations predict peak emissions flux of 0.2â0.5 PgC yrâ1 and show that the NAIP could have initiated PETM climate change. This is the first predictive model of carbon emissions flux from any proposed PETM carbon source that is directly constrained by observations of the geological structures that controlled the emissions.
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A new site containing a complete sequence through the terrestrial PTB
A new radiometric date for the terrestrial end-Permian extinction
Data suggests that the marine and terrestrial extinctions were synchronous.
The current placement of the PTB in the Karoo Basin of South Africa is retained.
Abstract
The end-Permian mass extinction (EPME) is widely recognised as the largest mass extinction in Phanerozoic history. In marine strata the main extinction event is well constrained, and has been radiometrically-dated to an interval of some 60âkyr, approximately 251.9âmillionâyears ago. However, the age and duration of the EPME in the terrestrial realm, as well as its possible synchronicity with that of the marine realm, is debated. Here, we shed light on issues pertaining to the identification and position of the terrestrial EPME in southern Africa. Using recently collected sedimentological (facies sequences), palaeontological (biostratigraphic ranges), geochemical (stable isotope analyses) and detrital zircon (ID-TIMS) data from a new site in the Xhariep District of the South African Karoo Basin, we demonstrate that the Permian-Triassic boundary sequence containing evidence for phased tetrapod extinctions is time equivalent with the marine extinction. We conclude that the terrestrial EPME recorded in the Karoo may be regarded as essentially synchronous with the EPME currently defined in the marine realm, and was likely the result of the same volcanically-induced atmospheric disturbances. This study describes the first single, vertical succession of vertebrate and plant fossils that span the terrestrial Permian-Triassic boundary that are also well-constrained both by relative (stable isotopes) and absolute (detrital zircon geochronology) dating methods.
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End-Permian extinction event (EPE) analyzed in a high-palaeolatitude continental setting.
Glossopteris peat-forming forests collapsed abruptly at the EPE.
Immediate post-EPE deposits rich in charcoal and fungi signify disaster interval.
Algae-rich mudstones indicate water-table rise and ponding following EPE.
Recovery of vascular plants evident <2 m above level of the EPE.
Abstract
Current large-scale deforestation poses a threat to ecosystems globally, and imposes substantial and prolonged changes on the hydrological and carbon cycles. The tropical forests of the Amazon and Indonesia are currently undergoing deforestation with catastrophic ecological consequences but widespread deforestation events have occurred several times in Earth's history and these provide lessons for the future. The end-Permian mass-extinction event (EPE; ~252 Ma) provides a global, deep-time analogue for modern deforestation and diversity loss. We undertook centimeter-resolution palynological, sedimentological, carbon stable-isotope and paleobotanical investigations of strata spanning the end-Permian event at the Frazer Beach and Snapper Point localities, in the Sydney Basin, Australia. We show that the typical Permian temperate, coal-forming, forest communities disappeared abruptly, followed by the accumulation of a 1-m-thick mudstone poor in organic matter that, in effect, represents a 'dead zone' hosting degraded wood fragments, charcoal and fungal spores. This signals a catastrophic scenario of vegetation die-off and extinction in southern high-latitude terrestrial settings. Lake systems, expressed by laterally extensive but generally less than a few-metres-thick laminated siltstones, generally lacking bioturbation, hosting assemblages of algal cysts and freshwater acritarchs, developed soon after the vegetation die-off. The first traces of vascular plant recovery occur ~1.6 m above the extinction horizon. Based on analogies with modern deforestation, we propose that the global fungal and acritarch events of the Permo-Triassic transition resulted directly from inundation of basinal areas following water-table rise as a response to the abrupt disappearance of complex vegetation from the landscape. The Corg values reveal a significant excursion toward low isotopic values, down to -31â Â(a shift of ~4â), across the end-Permian event. The magnitude of the shift at that time records a combination of changes in the global carbon cycle that were enhanced by the local increase in microbial activity, possibly also involving cyanobacterial proliferation. We envisage that elevated levels of organic and mineral nutrients delivered from inundated dead forests, enhanced weathering and erosion of extra-basinal areas, together with local contributions of volcanic ash, led to eutrophication and increased salinity of basinal lacustrineâlagoonal environments. We propose that the change in acritarch communities recorded globally in nearshore marine settings across the end-Permian event is to a great extent a consequence of the influx of freshwater algae and nutrients from the continents. Although this event coincides with the Siberian trap volcanic activity, we note that felsicâintermediate volcanism was extensively developed along the convergent Panthalassan margin of Pangea at that time and might also have contributed to environmental perturbations at the close of the Permian.
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When naming ichnotaxa based on uncollectable trace fossils, the holotype is the actual ichnofossil in the outcrop, though some ichnologists identify the holotype as a replica (cast) held in a museum collection, and refer to it as a "plastotype," although not all such replicas are made from plaster. Nevertheless, through its Code, the International Commission on Zoological Nomenclature (ICZN) makes it clear that an artificial, human-made replica (plaster cast or otherwise) is not eligible to be the holotype of an ichnotaxon. This directive is potentially destabilizing to much ichnological taxonomy, which is based on holotypes left in the field that have disappeared or will disappear. One possible solution for ichnologists will be to petition the ICZN to recognize that artificial, human-made replicas of ichnofossils can serve as name-bearing types. These may best be called "axiotypes" (from the Greek axios, meaning "of equal value").
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