How robust are Palearctic migrants to habitat loss and degradation in the Sahel?

The Sahel region of West Africa is an important wintering ground for Palearctic migrants. It is, however, undergoing significant anthropogenic degradation that is likely to reduce its value in this regard. Despite there being evidence that the populations of several Palearctic species may be determined by conditions on their Sahelian wintering grounds, there are almost no baseline data on their habitat use there and so the effects that habitat change might have on their future density and distribution cannot be determined. This study measured which habitat variables were associated with the presence of Common Whitethroat Sylvia communis, Lesser Whitethroat S. curruca and Subalpine Warbler S. cantillans by carrying out point counts and habitat measurements at 1861 points at 16 sites in northern Nigeria during the winters of 2001 and 2002. Common Whitethroats were most common at intermediate tree heights and densities of Salvadora persica (with this effect strongest in the pre‐migratory period), and increased as Balanites aegyptiaca density increased initially, although this effect levelled off at higher Balanites densities. Subalpine Warblers were most common at intermediate tree heights and Balanites densities, increased as Acacia and Salvadora density increased, decreased with tree density and were least common at intermediate shrub densities. Lesser Whitethroats were most common at intermediate tree heights, Acacia and Salvadora densities, increased with Balanites density, and decreased with tree density and diversity. The shallow slopes of the significant relationships found between Palearctic warbler species and habitat parameters suggest that the group may be robust to habitat degradation, with densities remaining relatively constant across a wide range of habitat types. Common Whitethroats, in particular, appear to be able to survive in extremely degraded habitats, yet may be vulnerable to the disappearance of Salvadora, the fruit of which may allow pre‐migratory fattening.     

The Membrane-Bound Forms of the Mitochondrial ATPase of Turnip (Brassica napus L.) and Mung Bean (Phaseolus aureus): Characterization and Investigation of Factors Controlling Activity

Isolated intact plant mitochondria, including those from turnipand mung bean, show low endogenous Mg²⁺-ATPase activity and,unlike mammalian mitochondria, lack significant uncoupler-stimulatedATPase activity. In contrast, the rates of respiration-drivenATP synthesis are comparable to those in mammalian mitochondria,suggesting the presence of an ATPase inhibitor. Disruption ofintact turnip mitochondria only results in limited increasesin ATPase activity, indicating that a permeability barrier toATP transport is not primarily responsible for the low endogenousactivity. The ATPase activity of turnip mitochondria and membraneparticles can be increased up to 50-fold when assayed underoptimum conditions. Time-dependent increases in activity inducedby ageing, exposure to salts and trypsin treatment, are allconsistent with an inhibitor protein being responsible for thelow endogenous activity and lack of uncoupler-stimulation. TheATPase activity of particles under optimum conditions and afterageing is sufficient to account for the rates of ATP synthesis.After activation, turnip mitochondrial ATPase activity is similarto the mammalian enzyme in inhibitor sensitivity, pH optimum,bivalent cation requirement, and sensitivity to ‘activatinganions’. In mung bean mitochondria, a permeability barrierto ATP is only partly responsible for the low endogenous ATPaseactivity, together with the inhibitory factor. On the basisof variation in the relative Ca²⁺ and Mg²⁺ -ATPase activitiesafter various treatments, a Ca²⁺-regulatory site which affectsATPase activity is proposed to exist in the F₁ATPase complex. Key words: Plant mitochondrial ATPase, calcium/magnesium -ATPase, inhibitor+ nucleotide specificity, cation/anion effects     

Microgeographic distribution of immature Ixodes dammini ticks correlated with that of deer

In order to determine whether the small-scale distribution of immature Ixodes dammini Spielman et al. corresponds closely to the activity patterns of white-tailed deer, Odocoileus virginianus (Zimmerman), these relationships were examined in a site on Long Island, New York, U.S.A. We first determined the extent and temporal pattern of adult ticks feeding on deer by examining twenty-three resident deer tranquilized during September-December 1985. I. dammini adults infested deer throughout this fall period, most abundantly during October and November. With radio-telemetry collars attached to deer we determined the relative frequency that they occupied 0.25 ha quadrats of the study site. During the following summer, we examined white-footed mice, Peromyscus leucopus (Rafinesque), that inhabited these quadrats and removed immature ticks from each. 8975 larval and 163 nymphal I. dammini were removed from 208 mice trapped in forty-three such quadrats. The frequency of deer using these quadrats was positively correlated with both the number of larval and of nymphal ticks per mouse. These results suggest that risk of I. damminiborne zoonotic disease may be decreased by locally reducing deer density in sites that experience intense human activity.     

Wounding and the Regulation of Apoplasmic Retrieval in Source Leaf Tissue 5Spinacia oleracea L.

Kinetic studies were performed on fresh-cut and aged leaf discsof Spinacia oleracea L. in order to investigate the regulatoryprocesses involved in sugar transport across the mesophyll plasmamembrane. A comparison of the kinetic profiles for fructose,glucose, sucrose and arginine obtained on freshly-cut and ageddiscs revealed that during wound-recovery, uptake is enhanced,but that this enhancement varies considerably for the differentsubstrates tested. Variation in the saturable and first-orderkinetic components of uptake was also observed. The involvementof a phosphoinositide-signalling mechanism in the wounding processwas examined by pretreating spinach leaves with lithium. Lithiuminhibited the enhancement of uptake and this effect was reversedby the addition of miro-inositol. However, in some experimentsthe tissue appeared to be insensitive to Li⁺. Gas chromatographicanalyses performed on cut discs indicated that ethylene wasproduced in response to wounding and that the addition of cobaltto the ageing media inhibited this ethylene production. Comparativekinetic studies of control and cobalt-treated discs indicatedthat ethylene was essential for the enhancement of transportacross the plasma membrane. However, addition of ethylene touncut tissue caused only a partial increase in the uptake offructose, which indicates that some additional wound-signallingcomponent is involved. Addition of cycloheximide to the recoverymedia completely inhibited this enhancement phenomenon. Thecycloheximide-response was not due to an inhibition of ACC synthasesynthesis nor to a reduction of ATP levels. We concluded thatthe effect of cycloheximide was on protein synthesis. Our resultsare discussed in terms of possible cellular and molecular mechanismsregulating sugar transport. Key words: Sugar transport, wounding, ethylene production, spinach leaves     

Comparative Analysis of Tuber Development in Six Sweet Potato (Ipomoea batatas (L.) Lam) Cultivars: 1. Tuber initiation, tuber growth and partition of assimilate

Differences in tuber initiation, tuber growth and partitionof assimilate during development were investigated in six localsweet potato cultivars. Study of the quantitative morphogenesisof root types in the sweet potato root system indicated thattuber initiation was completed by 8 weeks after planting inmost cultivars and frustrated thereafter. Subsequent differencesin patterns of tuber development were not obviously relatedto final tuber yield. Thus, high yield resulted either froma short period of rapid tuber growth or a longer period of slowertuber growth. Maximum shoot growth was achieved by week 12 inall except one cultivar, and the cessation of shoot growth resultedin either increases or decreases in tuber growth rate or hadno affect on the rate of tuber growth (cv. A28/7). The partitionof assimilate to tubers at final harvest was the parameter mostclosely related to the yield of the six cultivars studied, butthere was some evidence that such partition was related to totaldry weight. It is suggested that limiting factors in sweet potatotuber yield, e.g. assimilate production and transport or capacityfor tuber growth varied with the cultivar studied.     

Timing of breeding in Black Grouse Tetrao tetrix and Capercaillie Tetrao urogallus and distribution of insect food for the chicks

In Perthshire (Scotland), Black Grouse Tetrao tetrix broods less than 3 weeks old preferred herb-rich grassy flushes with Bog Myrtle Myrica gale , whereas in the northern Pennines (England), all broods were found on grass-dominated moorland or enclosed rough grazing habitats chiefly of grass and rushes. In both areas, broods used habitats with taller vegetation that had more invertebrates, particularly moth caterpillars and sawfly larvae (Sym-phyta, Hymenoptera). Within preferred habitats, broods were found in vegetation containing more flies (Diptera), plant bugs (Hemiptera) and ichneumon flies (Hymenoptera) than at randomly chosen sites. The main hatch of Black Grouse chicks in Perthshire coincided with the peak availability of moth caterpillars preferred by chicks. Broods in the Pennines hatched 1 week later than those in Scotland, and this later breeding in the south may be an adaptation to utilize the later peak biomass of sawfly larvae, the chief insect prey there. Data collected for Capercaillie Tetrao urogallus suggest a similar degree of synchronization between their peak hatch and the availability of moth caterpillars on Bilberry Vaccinium myrtillus.