No description available.

This thesis investigates the relationship between spatial distribution of tropical trees and variation in edaphic factors, particularly soil nutrient supply, and tests the importance of interspecific differences in growth rates and foliar nutrient concentrations as determinants of habitat specialisation. The distribution of some tree species at Pasoh Forest Reserve, Peninsular Malaysia, was correlated with variation in soil properties, especially available P concentrations, on a 50 ha plot. Seeding relative growth rates were highest on the alluvial soils, which had higher available P than the shale-derived soils in the absence of nutrient addition. The effect of habitat variation (characterised in terms of their nutrient and water availability) on tree growth of 115 species was examined within and between species. Overall, differences in tree growth rates between habitats correspond to variation in the pattern of nutrient supply and not water availability. Despite significant differences in growth rates between habitat types for some of the species, the differences in tree growth were a poor indicator of habitat preferences of tree species as defined by bias in their spatial distribution. Foliar nutrient concentrations of habitat generalists and two kinds of habitat specialists (alluvial and non-alluvial specialists) were compared using phylogenetically controlled comparisons. Sign tests showed only one significant difference in mean foliar nutrient (N, P, K, Ca and Mg) concentrations between distribution categories. The distribution of the differences in foliar mg concentrations between habitat generalists and alluvial specialists was significant at P < 0.05 and suggested that Mg concentrations were significantly greater in the habitat generalists. These results suggest that foliar nutrient concentrations are unlikely to explain differences between species in their habitat associations with respect to soil types at Pasoh.

Oviposition behaviour <I>Dasineura tetensi</I> and its host plant <I>Ribes nigrum</I> was studied in both the laboratory and field. Monitoring of an unsprayed infested fieldsite using watertraps in S.E. Kent revealed that there were four generations occurring between the April - August 1996. 'Baldwin' (susceptible), 'Ben Alder' (susceptible) and 'Ben Connan' (resistant) <I>Ribes </I>cultivars were sampled for eggs in the field and assessed for midge shoot damage throughout the season. Oviposition was shown to be indiscriminate, however plant damage between cultivars varied significantly. In laboratory choice experiments using pairs of plants, mated female midges did not prefer susceptible shoots of 'Ben Alder' over resistant shoots of 'Ben Connan' for oviposition. In larval performance studies, larvae reared on resistant 'Ben Connan' shoots were significantly smaller than larvae reared on shoots of the susceptible variety of 'Ben Alder', suggesting that larval antibiosis to be the main mechanism for resistance to <I>D. tetensi</I>. Olfactory responses of <I>D. tetensi</I> to leaf volatiles of 'Baldwin' were also tested in a 4-way olfactometer. Newly emerged virgin males and females that were individually tested showed no attraction to the leaf volatiles emitted from a 'Baldwin' shoot. Mated females (2 hr post mating) however, responded positively in the olfactometer to leaf volatiles emitted from a 'Baldwin' shoot, showing that leaf volatiles play an important role in host plant finding. Scanning and Transmission electron microscopy of the antennae of <I>D. tetensi</I> show that males and females share five sensillum types. Sensilla chaetica have a structure typical of mechanoreceptors. They possess a single sensory neurone whose dendrite ends in a tubular body at the base of the hair.

No description available.

Two closely related and morphologically similar gadoid predators, saithe, <I>Pollachius virens</I> (L.), and pollack, <I>Pollachius pollachius</I> (L.), coexist in close proximity on a submerged reef and in other similar inshore habitats in Loch Ewe, Scotland. The degree of overlap between the niches of these two gadoids in the wild was investigated by means of acoustic tracking, underwater television and an examination of stomach contents. Their density and distribution in Loch Ewe was investigated by a tag-and-release sampling program. Simultaneous tracking of individuals of both species in proximity of the reef revealed that pollack generally swim more slowly than saithe, limiting much of their movements to restricted areas of the submerged reef. Saithe ranged more widely around the reef as part of a school during the day, moving onto the reef at night. Individual saithe were observed abandoning the reef, either temporarily or permanently. This is thought to be part of a gradual shift of the population towards the open waters. A sampling program in Loch Ewe provided further evidence for a seasonal migration of large immature saithe (2+) from inshore to offshore waters. Although the dietary overlap was considerable, saithe consumed a wider range of prey than pollack, including numerous species from the fauna encrusting the kelp. Both species were highly piscivorous and fed on the same species of fish, but their feeding behaviour appeared largely different. Video recordings showed that saithe swam actively and foraged in small groups, taking prey items from the kelp. They appeared to be active, 'opportunistic' foragers. Pollack were generally solitary and used the kelp forest exclusively for cover, behaving as 'sit-and-wait' predators and ambushing their potential prey beneath the kelp canopy. Pollack were often observed engaging in aggressive interactions with conspecifics, probably to defend feeding territories. The relationship between different aspects of behaviour and feeding ecology of saithe and pollack are discussed in the wider context of recruitment of juveniles to the commercial stocks.

NDVI and rainfall data covering 1982-90 of Amboseli ecosystem, Kenya were analysed with a view to detecting patterns which could be related to the structure and function of vegetation types. NDVI data were first normalised using a square root transformation and the 1988-89 integrated NDVI was calculated for months from August 1988-July 1989, which represented a biologically active year. Integrated NDVI was used to extract quartiles which were used in a linear mixture model to derive four vegetation classes: grassland, shrubland, bushland and woodland. Vegetation classes were further examined against mean annual and monthly NDVI/rainfall. A lag time analysis of peak NDVI/rainfall was carried out and the probability of any one month's contribution to the peak NDVI/rainfall assessed. Two hypotheses relating animal abundance and distribution to vegetation were developed and tested with Systematic Reconnaissance Flight animal data collected in March 1983, April 1986, March 1987 and May 1990. The animal species selected were Wildebeest, Zebra and livestock. The hypothesis related to animal abundance was tested using a one-way analysis of variance, while the hypothesis related to animal distribution was tested by a Chi-squared analysis. Finally, a correlation was calculated between integrated NDVI of a vegetation class and animal density for each species. The results show that in 1982-90, good rainfall years were 1988-90 with bimodal peaks occurring in April-May (long rains) and November-December (short rains). In general, woodlands showed highest NDVI, followed by bushlands, shrublands and lastly grasslands. Analysis of vegetation classes temporal profiles showed that dry years 1982-83, 1983-84 and 1986-87 had only one peak of rainfall while 1984-85, 1985-86, 1987-88, 1988-89 and 1989-90 had two peaks of rainfall. Years with bimodal peaks showed better vegetation classes NDVI compared to years with only one peak of rainfall. There were very high correlations between vegetation classes cumulative mean monthly NDVI against cumulative mean monthly rainfall. The lag time between peak rainfall and peak NDVI is usually two months, except in dry years, e.g. 1982-83/84 when it was 3 months and one month respectively. The peak rainfall (99%) occurs in April (long rains), November and December (short rains) while January, February and June contributed to the peak NDVI (99%).

After a discussion of the historical background and classification of the coagulase-positive staphylococcus, a critical review of the importance of nasal colonization in the pathogenesis of staphylococcal infection and its relevance today is followed by an account of work already reported during the few occasions when several men have been totally isolated in closed environments such as submarines, space craft analogues and space craft themselves. The work is divided into two parts. Firstly in the Adelaide Island study an intensive investigation of the anterior nares of the base members has been carried out. This is set against a background study of their physical and bacteriological environments, which involved the examination of the air and fomites and the swabbing of dogs and penguins. A systematic study of staphylococcal sepsis is also carried out. The physical environment of a 'typical' base member's nasal vestibule has been examined and the effect upon it of Antarctic climatic factors evaluated. The influence of nasal carriage of non-coagulase-positive organisms on that of Staph. pyoqenes has been studied. The interrelationships of the above factors, and the effect on the staphylococcal bacterial population of men living together, are discussed. The second part of the work involved the supplementary investigations of nasal carriage at Halley Bay and Argentine Islands base, at which many transfers of Staph. pyoqenes have been shown to have occurred thus confirming the findings of the Adelaide Island study.

The present study is an investigation into Eurasian otter (<I>Lutra lutra</I>) predation on the adult phase of the life-cycle of two amphibians, the common frog (<I>Rana temporaria</I>) and the common toad (<I>Bufo bufo</I>). The study aimed to determine whether otters showed preys selection when foraging on these species. The implications for the population dynamics of these species were examined. Initially, frog spawning population size and habitat use during the breeding season were examined. Although the number of females using each individual spawning site varied between years, the overall spawning population size appeared relatively stable over the course of the study. A number of interacting habitat variables were found to influence spawning site choice, the most important of these being the water body surface area, presence of toads, presence of loch edge and water flow. The migrations to and from the spawning sites and length of stay at the spawning sites were also examined in detail. Common frogs were found to have an earlier breeding season than common toads. Males were present at the breeding site for longer periods than females in both species. In general, a female's body length did not influence length of stay at the breeding site, but individuals which arrived at the site earlier tended to be present for longer. Habitat use within the summer home range was also examined for the two species of anuran. Both species were found in all habitats but relative abundance of the two species varied between habits. Toads occurred most frequently in birch woodland and rough-grazed fields, while frogs were most abundant in bogs. The species and sexes captured were strongly dependent on the capture techniques used. Key bones for identifying the remains of both species in otter spraints were then determined to enable the study of otter diet.

The study was based on six villages along two sample transects, i.e. the Karakoram Highway (KKH) transect (good road and market infrastructure) and the Gilgit Ghizar Region (GGR) transect (poor road and market infrastructure).  The primary objective was to examine if there were differences in pasture use due to infrastructure development.  In each village, pastures were categorised into three broad vegetation types on the basis of altitude, i.e. foothill (<1500m), dry temperate (1500-3000m) and alpine (>3000m).  Within each vegetation type pastures were selected for measuring vegetation by quadrats of varying sizes.  Vegetation changed from very sparse shrubs in foothill to less sparse shrubs in dry temperature to grass/forbs in alpine pastures.  One foothill, three dry temperate and four alpine communities were identified.  Availability of water was the main factor that affected the structure and composition of vegetation in the area.  Biomass and production was high in the alpine as compared to foothill and dry temperature pastures during different seasons.  Production was high during spring in the dry temperature pastures.  Altitude change did affect biomass, however production was less affected.  Both biomass and production were better on the moderate as compared to gentle slopes.  The nutritive value of herbage was highest during spring season overall.  Alpine pastures had higher use than dry temperate and foothill pastures in all seasons.  Production was higher than use in the dry temperate pastures during spring season.  The livestock density did not differ between the KKH and GGR transects.  The alpine pastures had higher livestock density.  There was no significant difference in pasture use by livestock between the KKH and GGR transects.  The main difference was in the use between different villages, particularly during spring season.  There was higher use of the alpine pastures of different villages on both the transects (concordant with livestock densities).

This thesis describes relationship of a facultative annual root hemiparasite, <I>Rhinanthus minor </I>with its hosts, and seeks to investigate how changes in the physical environment influence interactions between host and parasite. A field study reveals that the presence of <I>R. minor </I>reduces productivity of the host vegetation in a traditional Scottish hay meadow, in which grass species significantly suffer from the parasitism while the non-grass species do not. Photosynthetic rate, growth and nutrient status of <I>R. minor</I> are not affected by removal of above ground host vegetation. Growth of unattached <I>R. minor</I> is significantly poor compared to those attached to <I>Lathyrus pratensis</I> and <I>Galium verum. </I> Nutritional status and biomass allocation of <I>R. minor</I> are dependent on host species. Amongst host plants, <I>L. pratensis</I>, a legume, is a better host for <I>R. minor</I>, although it is most negatively affected by the parasitism. The sink strength of <I>R. minor</I> for host resources is not overridden by the sink activity in the hosts created by simulated grazing. It is also noted that recovery of host growth from grazing is negatively affected by infection with <I>R. minor</I>. Soil nitrogen has no direct effects on <I>R. minor</I> growth, number and size of haustoria. However, it has indirect beneficial effects on those parameters through improving host growth and nitrogen status. Increased nitrogen availability to host-parasite association does not alleviate negative effects of the parasitism. It is revealed that as a chlorophyllous parasite, <I>R. minor</I> can gain benefits from elevated CO₂ in terms of carbon assimilation rate and growth, but increased CO₂ availability to parasitised hosts fails to alleviate negative impacts of <I>R. minor</I> on host photosynthesis and growth. Shading does not negatively affect growth of attached <I>R. minor</I>, but stimulates height growth.