This chapter investigates the effects of steam habitat loss and fragmentation on the density, genetic diversity, and persistence of Ephemerella inconstans in twenty-four steams across nine headwater stream networks in Maryland and Virginia. It discusses the differences in population density and local extinction in forested versus deforested headwater systems, and analyzes genetic diversity in populations of Ephemerella inconstans and three closely related species. The analysis reveals very low polymorphism across the entire two hundred kilometer range of the study, suggesting that a prehistoric bottleneck occurred in this species.

Plant tolerance to herbivory is a key approach for managing pests. In alfalfa, Medicago sativa, the potato leafhopper, Empoasca fabae, is a major pest as a result of the cascade of plant responses to piercing-sucking injury. To identify tolerance to its injury based on alfalfa physiology, experiments were conducted in the field and greenhouse. In our comparison of the response of field-grown alfalfa cultivars to standardized leafhopper densities, net photosynthesis and transpiration rates of 'Geneva' leaves were reduced by 18 and 21%, respectively, by leafhopper presence compared with a rate change of <1% of resistant 'EverGreen' leaves. Under greenhouse conditions, alfalfa clones varied in their level of gas exchange (net photosynthesis and transpiration) and stem elongation responses to leafhopper injury. For example, in the comparison of seven clones, net photosynthesis declined an average of 40.7% with leafhopper injury, although individual clones varied from 26.6 to 74.3% reduction. Internode elongation after 2 d was 60.3% less on injured stems compared with healthy stems, but again, the individual clones varied from 17.3 to 91.9%. In a time-course study of selected clones, clones varied in their level of injury just after and 3 d after insect removal. Gas exchange responses of all clones recovered by 7 d after cessation of injury. In a choice test, leafhoppers spent similar amounts of time on the susceptible clone and the most tolerant clone; however, their precise feeding behaviors were not measured. Thus, the variable response of clones to injury may be either true physiological tolerance or antixenosis from a change in feeding behavior. This study showed putative tolerance to leafhopper injury among alfalfa genotypes, suggesting that tolerance could be the basis for crop protection in alfalfa from potato leafhopper injury.

Patterns of starch accumulation in alfalfa, Medicago sativa L., were studied in response to injury caused by potato leafhopper, Empoasca fabae (Harris). Using image analysis of iodine-stained leaf tissues, we compared lightness scores of leaves from leafhopper-injured and healthy plants sampled at early morning and mid-afternoon. In addition, we related lightness scores to standard chemical analyses for starch and sugar. The lightness scores were significantly related to starch concentrations but not to sugar concentrations. In the morning samples, all fully developed and developing leaves above the site of feeding indicated higher starch concentrations than comparable leaves on healthy plants. In contrast, all leaves from mid-afternoon samples and leaves below the site of feeding from morning samples did not significantly differ between injured and healthy plants. The observation that the lack of starch degradation during the night occurs in all tissues distal to the feeding site, and especially in developing leaves, suggests that the mechanism of starch accumulation is not just feedback from phloem blockage caused by leafhopper feeding but also a change in starch degradation in all chloroplasts without regard to source-sink status.

The circulating levels of pregnancy-specific beta 1-glycoproteins (SP1) were measured in 71 normal pregnant women in Northern Nigeria by immunoelectrophoresis. The levels showed a steady rise up to 34 weeks as in Caucasians and then plateaued with a slight fall just before term. The mean individual values were lower than those found in Caucasians at comparable gestation periods. This was thought to be related to the lower mean fetal weight in the Nigerian women.