Speciation rates

Nee, S. (2001) Inferring speciation rates from phylogenies. Evolution, 55 661-668. 

The Late Devonian was a time of profound evolutionary and environmental change associated with the Frasnian-Famennian Biodiversity Crisis, including reduction in speciation rates, increased extinction rates, rampant species invasions, and ecosystem restructuring (Sepkoski, 1986 McGhee, 1996 Droser et al., 2000). The biodiversity crisis may have lasted as long as three million years with a final pulse of more severe extinction in the last few hundred thousand years of the Frasnian. To unravel the faunal dynamics of this complex crisis, it is critical to understand both the spatial and temporal patterns associated with biodiversity decline. 

FIGURE 5.8 Instantaneous rates of taxonomic turnover, (a) Rate of net biodiversity change calculated from Equation (5.1), (b) speciation rate calculated from Equation (5.2), (c) extinction rate calcnlated from Equation (3). Taxon symbols solid line, Schizophoria (Schizophoria), short dash, Floweria long-short dash, Leptodesma (Leiopteria). 

Lieberman, B.S. (2001) Analyzing speciation rates in macroevolutionary studies. In Speciation in the Fossil Record (eds. J.M. Adrain, G.D. Edgecombe, and B.S. Lieberman), Kluwer Academic Press, New York, pp. 323-339. 

Sodium-silicate glass, 151 Sol-gel films, 120, 173 Solid electrodes, 110 Solid state devices, 160 Solvents, 102 Speciation, 84 Spectroelectrochenristry, 40 Spherical electrode, 6, 8, 9, 61 Square-wave voltammetry, 72, 92 Staircase voltammetry, 74 Standard potential, 3 Standard rate constant, 12, 18 Stripping analysis, 75, 79, 110 Supporting electrolyte, 102 Surface-active agents, 79... 

From the beginnings of ecology as a discipline, the mining industry has been at the center of the battle over preservation versus exploitation. As discussed in the introduction to this chapter, human activities such as mining, power production from fossil fuels and discharges of industrial and municipal wastes not only increase the rate at which metals enter the biosphere but may also drastically alter the speciation of metals from what it would be in the undisturbed geologic cycle. 

The distribution of metals between dissolved and particulate phases in aquatic systems is governed by a competition between precipitation and adsorption (and transport as particles) versus dissolution and formation of soluble complexes (and transport in the solution phase). A great deal is known about the thermodynamics of these reactions, and in many cases it is possible to explain or predict semi-quantita-tively the equilibrium speciation of a metal in an environmental system. Predictions of complete speciation of the metal are often limited by inadequate information on chemical composition, equilibrium constants, and reaction rates. 

This paper discusses (1) soil and groundwater and (2) aquatic equilibrium and ranking models. The second category deals with the chemical speciation in soil and groundwater, and with the environmental rating of waste sites, in cases where detailed modeling is not desirable. 

Advantages High analysis rate 3-4 elements per hour Applicable to many more metals than voltammetric methods Superior to voltammetry for mercury and arsenic particularly in ultratrace range Disadvantages Nonspecific absorption Spectral interferences Element losses by molecular distillation before atomisation Limited dynamic range Contamination sensitivity Element specific (or one element per run) Not suitable for speciation studies in seawater Prior separation of sea salts from metals required Suspended particulates need prior digestion About three times as expensive as voltammetric equipment Inferior to voltammetry for cobalt and nickel... 

Cadmium is a silver-white, blue-tinged, lustrous metal that melts at 321°C and boils at 767°C. This divalent element has an atomic weight of 112.4, an atomic number of 48, and a density of 8.642 g/cm3. It is insoluble in water, although its chloride and sulfate salts are freely soluble (Windholz et al. 1976 USPHS 1993). The availability of cadmium to living organisms from their immediate physical and chemical environs depends on numerous factors, including adsorption and desorption rates of cadmium from terrigenous materials, pH, Eh, chemical speciation, and many... 

Numerous and disparate copper criteria are proposed for protecting the health of agricultural crops, aquatic life, terrestrial invertebrates, poultry, laboratory white rats, and humans (Table 3.8) however, no copper criteria are now available for protection of avian and mammalian wildlife, and this needs to be rectified. Several of the proposed criteria do not adequately protect sensitive species of plants and animals and need to be reexamined. Other research areas that merit additional effort include biomarkers of early copper stress copper interactions with interrelated trace elements in cases of deficiency and excess copper status effects on disease resistance, cancer, mutagenicity, and birth defects mechanisms of copper tolerance or acclimatization and chemical speciation of copper, including measurement of flux rates of ionic copper from metallic copper. 

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