The Amazonian rainforest is arguably the most species-rich terrestrial ecosystem in the world, yet the timing of the origin and evolutionary causes of this diversity are a matter of debate. We review the geologic and phylogenetic evidence from Amazonia and compare it with uplift records from the Andes. This uplift and its effect on regional climate fundamentally changed the Amazonian landscape by reconfiguring drainage patterns and creating a vast influx of sediments into the basin. On this “Andean” substrate, a region-wide edaphic mosaic developed that became extremely rich in species, particularly in Western Amazonia. We show that Andean uplift was crucial for the evolution of Amazonian landscapes and ecosystems, and that current biodiversity patterns are rooted deep in the pre-Quaternary.

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Amazonia Through Time: Andean Uplift, Climate Change, Landscape Evolution, and Biodiversity

Summary
Deposits produced by microbial growth and metabolism have been important components of carbonate sediments since the Archaean. Geologically best known in seas and lakes, microbial carbonates are also important at the present day in fluviatile, spring, cave and soil environments. The principal organisms involved are bacteria, particularly cyanobacteria, small algae and fungi, that participate in the growth of microbial biofilms and mats. Grain-trapping is locally important, but the key process is precipitation, producing reefal accumulations of calcified microbes and enhancing mat accretion and preservation. Various metabolic processes, such as photosynthetic uptake of CO2 and/or HCO3– by cyanobacteria, and ammonification, denitrification and sulphate reduction by other bacteria, can increase alkalinity and stimulate carbonate precipitation. Extracellular polymeric substances, widely produced by microbes for attachment and protection, are important in providing nucleation sites and facilitating sediment trapping.

Microbial carbonate microfabrics are heterogeneous. They commonly incorporate trapped particles and in situ algae and invertebrates, and crystals form around bacterial cells, but the main component is dense, clotted or peloidal micrite resulting from calcification of bacterial cells, sheaths and biofilm, and from phytoplankton-stimulated whiting nucleation. Interpretation of these texturally convergent and often inscrutable fabrics is a challenge. Conspicuous accumulations are large domes and columns with laminated (stromatolite), clotted (thrombolite) and other macrofabrics, which may be either agglutinated or mainly composed of calcified or spar-encrusted microbes. Stromatolite lamination appears to be primary, but clotted thrombolite fabrics can be primary or secondary. Microbial precipitation also contributes to hot-spring travertine, cold-spring mound, calcrete, cave crust and coated grain deposits, as well as influencing carbonate cementation, recrystallization and replacement. Microbial carbonate is biologically stimulated but also requires favourable saturation state in ambient water, and thus relies uniquely on a combination of biotic and abiotic factors. This overriding environmental control is seen at the present day by the localization of microbial carbonates in calcareous streams and springs and in shallow tropical seas, and in the past by temporal variation in abundance of marine microbial carbonates. Patterns of cyanobacterial calcification and microbial dome formation through time appear to reflect fluctuations in seawater chemistry.

Stromatolites appeared at ∼3450 Ma and were generally diverse and abundant from 2800 to 1000 Ma. Inception of a Proterozoic decline variously identified at 2000, 1000 and 675 Ma, has been attributed to eukaryote competition and/or reduced lithification. Thrombolites and dendrolites mainly formed by calcified cyanobacteria became important early in the Palaeozoic, and reappeared in the Late Devonian. Microbial carbonates retained importance through much of the Mesozoic, became scarcer in marine environments in the Cenozoic, but locally re-emerged as large agglutinated domes, possibly reflecting increased algal involvement, and thick micritic reef crusts in the late Neogene. Famous modern examples at Shark Bay and Lee Stocking Island are composite coarse agglutinated domes and columns with complex bacterial–algal mats occurring in environments that are both stressed and current-swept: products of mat evolution, ecological refugia, sites of enhanced early lithification or all three?

Microbial carbonates: the geological record of the calcified bacterial-algal mats and biofilms

/pdf/processes-of-carbonate-precipitation-in-modern-microbial-176vfhaypi.pdf

Processes of carbonate precipitation in modern microbial mats

Coral reefs support immense biodiversity and provide important ecosystem services to many millions of people Yet reefs are degrading rapidly in response to numerous anthropogenic drivers In the coming centuries, reefs will run the gauntlet of climate change, and rising temperatures will transform them into new configurations, unlike anything observed previously by humans Returning reefs to past configurations is no longer an option Instead, the global challenge is to steer reefs through the Anthropocene era in a way that maintains their biological functions Successful navigation of this transition will require radical changes in the science, management and governance of coral reefs

/pdf/coral-reefs-in-the-anthropocene-31kb7o272c.pdf

Coral reefs in the Anthropocene

ECOLOGY/EVOLUTION: Phenotypic Plasticity

Hotspots of high species diversity are a prominent feature of modern global biodiversity patterns. Fossil and molecular evidence is starting to reveal the history of these hotspots. There have been at least three marine biodiversity hotspots during the past 50 million years. They have moved across almost half the globe, with their timing and locations coinciding with major tectonic events. The birth and death of successive hotspots highlights the link between environmental change and biodiversity patterns. The antiquity of the taxa in the modern Indo-Australian Archipelago hotspot emphasizes the role of pre-Pleistocene events in shaping modern diversity patterns.

/pdf/hopping-hotspots-global-shifts-in-marine-biodiversity-2ie4izfcxj.pdf

Hopping hotspots: global shifts in marine biodiversity.

Patterns and average rates of late Neogene-Recent uplift of the Betic Cordillera, SE Spain

Mediterranean Messinian Salinity Crisis: constraints from a coeval marginal basin, Sorbas, southeastern Spain

Messinian events in the Sorbas Basin in southeastern Spain and their implications in the recent history of the Mediterranean

Data from a comprehensive literature survey for the first time provide stage-level resolution of Early Cretaceous through Pleistocene species diversity for nongeniculate coralline algae. Distributions of a total of 655 species in 23 genera were compiled from 222 publications. These represent three family-subfamily groupings each with distinctive present-day distributions: (1) Sporolithaceae, low latitude, mainly deep water; (2) Melobesioid corallinaceans, high latitude, shallow water, to low latitude, deep water; (3) Lithophylloid/mastophoroid corallinaceans, mid- to low latitude, shallow water. Raw data show overall Early Cretaceous–early Miocene increase to 245 species in the Aquitanian, followed by collapse to only 43 species in the late Pliocene. Rarefaction analysis confirms the pattern of increase but suggests that scarcity of publications exaggerates Neogene decline, which was actually relatively slight. Throughout the history of coralline species, species richness broadly correlates with ...

Juan C. Braga

Papers

Hopping hotspots: global shifts in marine biodiversity.

Patterns and average rates of late Neogene-Recent uplift of the Betic Cordillera, SE Spain

Mediterranean Messinian Salinity Crisis: constraints from a coeval marginal basin, Sorbas, southeastern Spain

Messinian events in the Sorbas Basin in southeastern Spain and their implications in the recent history of the Mediterranean

Diversity of coralline red algae: origination and extinction patterns from the Early Cretaceous to the Pleistocene