A biogeographical perspective on ecological systems: some personal reflections

During my graduate studies, I characterized patterns of geographical distribution and taxonomic differentiation in birds of the West Indies, which suggested that species undergo phases of expansion and contraction similar to the taxon cycles that E. O. Wilson had described for Melanesian ants. Fieldwork in the early 1970s with George Cox confirmed that these phases were associated with variation in habitat distribution and abundance on individual islands, tying together local ecology and biogeography. Because taxon‐cycle stage was independent of taxonomic or ecological relationships among birds of the West Indies, George and I postulated that whether a species was in a phase of expansion or contraction reflected the outcome of coevolved relationships with antagonists, including pathogens. The taxon cycle concept had a cool reception initially, but subsequent phylogeographical analyses, beginning in the early 1990s with Eldredge Bermingham, provided a time scale that confirmed the relationship between taxon cycle stage and the relative age of the most recent population expansion. The discrete nature of islands allows one to visualize taxon cycles in island systems, but the principle should apply in a continental biota as well. The absence of strong phylogenetic effects in distribution and abundance is consistent with evolutionary lability caused by coevolutionary outcomes with specialized antagonists. Related species appear to compete for resources on a more‐or‐less equal footing across a broad range of environments, and their distribution at any particular time is likely to be determined primarily by their relationships with pathogens, among other antagonists. This model of distribution and abundance within a regional community is consistent with much of what we know about the interactions between pathogens and their host populations, but testing the model will require the development of a new research programme focused on endemic pathogen effects in natural communities.     

The influence of different nutrient levels on insect-induced plant volatiles in Bt and conventional oilseed rape plants

Transgenic Bt (expressing the cry1Ac endotoxin gene) and conventional oilseed rape plants grown in different soils were used to study nutrient uptake and emission of volatiles after herbivore damage. All plants were greenhouse-grown in soils representing low-, medium- and high-nutrient levels. The concentrations of N, P, K, Mg and Zn were significantly affected by the transgene, while the main effect of soil type appeared in N, P, Ca, Mg, B, Mn and Zn concentrations in the plants. Plants with four to five leaves were infested with the third instar larvae of Bt-susceptible Plutella xylostella for 48 h, and samples of volatiles were collected and analysed. In the first experiment, the soil nutrient level had a significant effect on the emissions of (Z)-3-hexen-1-ol, (Z)-3-hexenyl acetate, hexyl acetate, (E)-4,8-dimethyl-1,3,7-non-atriene (DMNT), beta-elemene, gamma-bisabolene, alpha-bisabolene and (E)-nerolidol. The induction of these volatiles was significantly higher in infested conventional plants grown at a high-soil nutrient level compared to infested conventional plants at a low-soil nutrient level. In the second experiment, the soil nutrient level had a significant effect on the emissions of (Z)-3-hexen-1-ol, (Z)-3-hexenyl acetate and beta-elemene and, again, this was significantly higher in infested conventional plants grown at high-soil nutrient levels in comparison with infested plants at a low-soil nutrient level. In both experiments, the transgene effect was significant on the emissions of DMNT and (E,E)-alpha-farnesene. The differences in emissions between the two separate experiments suggest that growth conditions (particularly daylength) and sampling procedure may affect the ratio of compounds detected in the emission blend, even though the response to herbivory, nutrient availability and the transgene were similar.     

Stochastic properties of generalised Yule models, with biodiversity applications

The Yule model is a widely used speciation model in evolutionary biology. Despite its simplicity many aspects of the Yule model have not been explored mathematically. In this paper, we formalise two analytic approaches for obtaining probability densities of individual branch lengths of phylogenetic trees generated by the Yule model. These methods are flexible and permit various aspects of the trees produced by Yule models to be investigated. One of our methods is applicable to a broader class of evolutionary processes, namely the Bellman-Harris models. Our methods have many practical applications including biodiversity and conservation related problems. In this setting the methods can be used to characterise the expected rate of biodiversity loss for Yule trees, as well as the expected gain of including the phylogeny in conservation management. We briefly explore these applications.     

Characterization of Hypericum perforatum L. (St. John’s wort) macerates prepared with different fatty oils upon processing and storage

Hypericum perforatum L. (St. John’s wort, SJW) is a traditional medicinal plant with a long history of pharmaceutical application. Today, besides formulations based on hydro-alcoholic extracts, lipophilic SJW preparations are widely used in phytomedicine e.g. for the symptomatic treatment of minor inflammations of the skin and subcutaneous tissue disorders. In the present study, SJW extracts were obtained with twelve different fatty oils according to a standardized protocol. In order to evaluate and compare the resulting macerates, a set of analytical parameters was chosen: the phytochemical profile of SJW oil extracts comprising acylphloroglucinol derivatives, flavonols, biflavones and naphthodianthrones was assessed using UHPLC-DAD and UV/VIS-spectroscopic methods Furthermore, overall appearance was monitored applying the CIE L*a*b* color system. Depending on the type of oil applied for extraction, a*-values, which are a measure of red color hues, ranged from 50.3 ± 0.2 (almond oil) to −3.8 ± 0.3 (macadamia nut oil). Considering total hypericin contents, extraction with almond oil also brought about highest amounts (5.5 ± 0.21 mg/100 g). In contrast, preparations with macadamia nut oil resulted in highest contents of hyperforin and adhyperforin, whereas a semi-synthetic extractant composed of medium-chain triglycerides (MCT) revealed highest yields of flavonoids, i.e. quercetin, kaempferol and I3, II8-biapigenin. Since the phytochemical composition and the corresponding specific characteristics of SJW oil preparations markedly differed, tailor-made SJW extracts may be prepared by systematic adaption of the manufacturing conditions, including the choice of a specific fatty oil. Additionally, SJW oil extracts were stored under different temperature (5 °C, 20 °C, 50 °C) and light (artificial light, darkness) regimes over a period of six months to evaluate their respective storage stability. For maximizing the retention of the investigated plant secondary metabolites in the corresponding oil extracts, cold storage (5 °C) under the exclusion of light is recommended.     

Simplified Resting Metabolic Rate—Predicting Formulas for Normal‐Sized and Obese Individuals

Objective: Resting metabolic rate (RMR) is known to be proportional to body weight and to follow allometric scaling principles. We hypothesized that RMR can be predicted from an allometric formula with weight alone as an independent variable. Research Methods and Procedures: An allometric, power‐law scaling model was fit to RMR measurements obtained from a cohort of patients being treated for weight loss. This, as well as many of the commonly used RMR‐predicting formulas, was tested for RMR prediction ability against a large publicly available RMR database. Bland‐Altman analysis was used to determine the efficacy of the various RMR‐predicting formulas in obese and non‐obese subjects. Results: Power law modeling of the RMR—body weight relationship yielded the following RMR‐predicting equations: RMR_Women = 248 × Weight^0.4356 ? (5.09 × Age) and RMR_Men = 293 × Weight^0.4330 ? (5.92 × Age). Partial correlation analysis revealed that age significantly contributed to RMR variance and was necessary to include in RMR prediction formulas. The James, allometric, and Harris‐Benedict formulas all yielded reasonable RMR predictions for normal sized and obese subjects. Discussion: A simple power formula relating RMR to body weight can be a reasonable RMR estimator for normal‐sized and obese individuals but still requires an age term and separate formulas for men and women for the best possible RMR estimates. The apparent performance of RMR‐predicting formulas is highly dependent on the methodology employed to compare the various formulas.     

Southern Trauma: Revisiting Caste and Class in the Mississippi Delta

Two classic ethnographies, Hortense Powdermaker's After Freedom: A Cultural Study in the Deep South and John Dollard's Caste and Class in a Southern Town , contributed to a "master narrative" of the Mississippi Delta and the South that viewed class largely through the lens of race. Their work contributed to the community studies and culture and personality traditions and became part of the public discourse of race in the United States. This article examines the institutional and theoretical frameworks within which they worked. We focus on three aspects of their work: (1) their definition of class that left race as the only salient social divide; (2) their portrayal of middle- and upper-class statements as normative; and (3) their uncritical use of data from elsewhere in the South to interpret their Indianola data. We report the events at the Yale Institute of Human Relations that led Dollard to publish before Powdermaker.     

Cadmium(II)-113 NMR studies of the mechanism of metal ion activation of yeast enolase

Yeast enolase binds one mole of 113Cd2+ per subunit at a site that consists of all oxyligands in a distorted octahedral environment. This "conformational" metal ion's environment undergoes further distortion on addition of substrate/product or analogs. At pH's below the optimum value the shifted resonance tends to break up into several, suggesting the existence of several slowly exchanging intermediate forms. At acid pH's, on addition of one additional mole/subunit of 113Cd2+, which greatly increases catalysis, "conformational" resonance(s) further broadens, suggesting that the second, "catalytic" metal ion increases the rates of interconversion between "conformational" species. At more alkaline pH's, near the optimum pH, the "conformational" peak is sharpened, which suggests that very fast interconversion is occurring. The position of the "catalytic" metal ion resonance also suggests all oxyligands in a distorted octahedral geometry. The "catalytic" resonance is often broadened to the point where it cannot be seen, suggesting rapid changes in its geometry due to interconversion of substrate and product.     

The Caribou Eskimo: General and specific disease

Reported here are two forms of skeletal pathology identified in an inclusive sample of Caribou Eskimo skeletons. Harris Lines, nonspecific indicators of stress, show marked periodicity in approximately one-half of the observable adults. This pattern is interpreted as the result of a recurrent, annual stress cycle, perhaps attributable to late winter famine. A second form of pathological change comprises resorptive lesions primarily localized in the spinal column and infrequently found on articular surfaces of the appendicular skeleton. Differential diagnosis is developed utilizing attributes of lesion form, lesion distribution, and epidemiology. Emphasis is placed upon deriving objective models which reflect disease in the absence of modern medical intervention. Major forms of pathology known to produce vertebral lesions are included. The model which best fits the Caribou Eskimo data is that of tuberculosis.     

Circular dichroism (CD) studies on yeast enolase: activation by divalent cations

The effect of divalent cations on the near ultraviolet circular dichroism (CD) spectrum of yeast enolase showed that calcium, magnesium, and nickel ions produced identical changes. This was interpreted as indicating that the cations bound to the same sites on the enzyme and produced identical changes in tertiary structure. There was no effect of magnesium ion on the far ultraviolet spectrum. Evidently magnesium ion has no effect on the secondary structure. Substrate bound to the enzyme when the above cations were present although calcium permits no enzymatic activity. The CD spectral difference produced by the substrate was nearly the reverse of that produced by the metal ions. Glycolic acid phosphate, a competitive inhibitor lacking carbon-3, produced no effect, indicating carbon-3 was necessary for the CD spectral changes. The CD and visible absorption spectra of nickel and cobalt bound to various sites on the enzyme showed that the binding sites were octahedral or distorted octahedral in coordination and that the ligands appeared to be oxyligands: water molecules, hydroxyl or carboxyl groups. Examination of the effects of substrate and two compounds thought to be "transition state analogues" showed that these perturbed the "conformational" sites of the enzyme. The "catalytic" and "inhibitory" sites did not appear to be very CD active.