Testing some hypotheses on human evolution and sexual dimorphism

Research on human evolution and sexual dimorphism motivates an interesting test problem. In studying hominid phylogeny it is of interest to test whether parallel evolution plays a role. With regard to sexual dimorphism it is of interest to known whether the directions of sexual dimorphism in the populations being compared are the same. We show that testing these two problems gives rise to the same type of hypothesis testing, viz. the problem of testing the hypothesis that the means of independent, normally distributed random vectors with unit covariance matrices are situated on a straight line through the origin. A test is proposed and applied to study the sexual dimorphism of 20 recent skull populations. In this example the hypothesis of equal directions of sexual dimorphism is rejected. The classical theory of constructing multiple discriminant functions (canonical variates) is adapted to the problem of comparing sexual dimorphisms.     

Magnetic field effects on radical pair intermediates in bacterial photosynthesis

We have investigated the effects of magnetic fields on the formation and decay of excited states in the photochemical reaction centers of Rhodopseudomonas sphaeroides. In chemically reduced reaction centers, a magnetic field decreases the fraction of the transient state P^F that decays by way of the bacteriochlorophyll triplet state P^R. At room temperature, a 2-kG field decreases the quantum yield of P^R by about 40%. In carotenoid-containing reaction centers, the yield of the carotenoid triplet state which forms via P^R is reduced similarly. The effect of the field depends monotonically on field-strength, saturating at about 1 kG. The effect decreases at lower temperatures, when the yield of P^R is higher. Magnetic fields do not significantly affect the formation of the triplet state of bacteriochlorophyll in vitro, the photooxidation of P-870 in reaction centers at moderate redox potential, or the decay kinetics of states P^F and P^R.The effects of magnetic fields support the view that state P^F is a radical pair which is born in a singlet state but undergoes a rapid transformation into a mixture of singlet and triplet states. A simple kinetic model can account for the effects of the field and relate them to the temperature dependence of the yield of P^R.     

Legacies of Prehistoric Agricultural Practices Within Plant and Soil Properties Across an Arid Ecosystem

Closely integrated research between archaeologists and ecologists provides a long-term view of human land use that is rare in the ecological literature, allowing for investigation of activities that lead to enduring environmental outcomes. This extended temporal perspective is particularly important in aridlands where succession occurs slowly and ecosystem processes are mediated by abiotic, geomorphic factors. Numerous studies show that impacts from ancient human actions can persist, but few have explored the types of practices or mechanisms that lead to either transient or long-term environmental change. We compared plant and soil properties and processes from a range of landscape patch types in the Sonoran Desert of the US Southwest that supported different, well-documented prehistoric farming practices from AD 750–1300. Our results show that the types of ancient human activities that leave long-term ecological legacies in aridlands are those that fundamentally alter “slow variables” such as soil properties that regulate the timing and supply of water. Prehistoric Hohokam floodwater-irrigation practices, but not dryland farming techniques, substantially altered soil texture, which was strongly associated with desert plant community and functional composition. However, prehistoric agriculture did not consistently alter long-term nutrient availability and thus had no impact on “fast variables” such as production of seasonal annual plants that are restricted to periods of ample rainfall. In this arid ecosystem, the inverse texture model explained patterns in plant functional composition at large scales, but is less predictive of production of short-lived desert annuals that experience a more mesic precipitation regime.     

Development and parasitism by Aphelinus certus (Hymenoptera: Aphelinidae), a parasitoid of Aphis glycines (Hemiptera: Aphididae)

Since its introduction in 2000, the soybean aphid (Aphis glycines Matsumura) has been a serious pest of soybean in North America. Currently, insecticide application is the only recommended control method. However, a number of natural enemies have the potential to regulate soybean aphid populations. In 2007, Aphelinus certus Yasnosh, a soybean aphid parasitoid native to Asia, was found in commercial soybean fields in Ontario. This is the first record of this species in North America. To evaluate the potential biological control services provided by A. certus for soybean aphid management, temperature-dependent developmental parameters and functional response to soybean aphid were determined. A. certus is capable of completing its development between temperatures of 15.3 and 30.2°C. The lower thresholds of development for the egg-mummy and mummy-adult life stages were determined to be 9.1 and 11.6°C, respectively. The lethal temperature of development for the egg-mummy and mummy-adult life stages were 29.5 and 31.0°C, respectively. In this temperature range, A. certus did not exhibit temperature-dependent mortality; however, parasitism rate increased with temperature. A. certus exhibited a type II functional response to the soybean aphid.     

Casas Grandes and Its Hinterland: Regional Organization in Northwest Mexico

Casas Grandes and Its Hinterland: Regional Organization in Northwest Mexico. Michael E. Whalen and Paul E. Minnis. Tucson: University of Arizona Press, 2001. 250 pp.     

The influence of supplemental docosahexaenoic and arachidonic acids during pregnancy and lactation on neurodevelopment at eighteen months

Docosahexaenoic acid (DHA) and arachidonic acid (AA) are important for neurodevelopment. The effects of DHA (220 mg/day, n=41), DHA+AA (220 mg/day, n=39) or placebo (n=34) during pregnancy and lactation on neurodevelopment at 18 months, and the relations between umbilical cord DHA, AA and Mead acid and neurodevelopment were studied. An age-specific, standardized neurological assessment for the evaluation of minor neurological dysfunction (MND), and the Bayley Scales of Infant Development (BSID) were used. The intervention did not influence any of the outcomes. Umbilical venous (UV) Mead acid was negatively and n-6 fatty acids were weakly positively associated to the BSID mental developmental index. Children with simple MND had lower UV DHA compared to normally classified children. We conclude that relatively short-term maternal DHA or DHA+AA supplementation does not influence neurodevelopment at toddler age, although some parameters of brain development are related to perinatal DHA and AA status.     

Wheat curl mite (Acari: Eriophyidae) dispersal and its relationship with kernel red streaking in maize

Wheat curl mites, Aceria tosichella Keifer, dispersing from wheat (Triticum spp.) to nearby corn (Zea mays L.) fields play a role in the development of kernel red streaking in corn. These studies were undertaken to verify the relationship of wheat curl mite to kernel red streaking, to determine whether wheat is the main source of curl mites dispersing into corn and to determine whether planting corn in temporal or spatial isolation of wheat is a valid management strategy. These studies were conducted on farm fields using sticky traps to monitor mites, followed by sampling mature grain for kernel streaking in southwestern Ontario from 1999 to 2002. The dominant source mites were winter wheat. Mite dispersal occurred during the first 3 wk of winter wheat maturation after the wheat had reached Zadoks stage 87. Mite dispersal corresponded to prevailing winds in the area with the lowest number of mites and the lowest severity of kernel red streaking occurring 60 m from wheat fields planted to the north, south, and east of cornfields and 90 m from wheat fields planted to the west of cornfields. The severity of kernel red streaking was positively correlated with the density of wheat curl mites in corn; however, the correlation was weak and kernel red streaking was still high in many cornfields when few or no mites were present. These findings suggest that wheat curl mite migration into corn is not entirely predictive of the incidence and severity of kernel red streaking.     

Phenology and field biology of black cutworm (Lepidoptera: Noctuidae) in Ontario no-till corn

Black cutworm, Agrotis ipsilon (Hufnagel), is an occasional corn, Zea mays L., pest that is attracted to no-till fields. Understanding the phenology of black cutworm in Ontario no-till corn, particularly the time of arrival of adults in relation to the onset of crop damage and the stages of larvae that coincide with vulnerable corn seedling leaf stages, is important for their effective control. Pheromone and blacklight trap captures of moths first occurred in early April, whereas significant influxes did not occur until mid- to late April. Males and females were often captured simultaneously, in contrast to findings in Iowa and Illinois where males were captured in pheromone traps on average 3 wk ahead of females or males in blacklight traps. This may be a reflection of a more mature source population for the influxes into Ontario because first captures also were later than in the United States. Females arrived mated and corn seedling cutting occurred within 137 degree-days (DD) (base 10.4 degrees C) of first capture in Ontario corn. Cutworms were present in cornfields before planting, and the mean age of larvae increased along with corn leaf stage, suggesting that no new recruitment took place after planting. The apparent synchrony between corn and cutworm phenology in the northern areas of corn production seems more related to the availability and quality of food for young larvae relative to the development of the crop then the time of arrival of moths.