THE SOIL FUNGI OF THE DOVEY SALT MARSHES

In this investigation of the fungi of the soil of the Dovey Salt Marshes (Ynyslas) 48 fungi were isolated.
Twelve of the species found do not appear to have been recorded before for the British Isles.
The area investigated is a badly aerated, stiff, tenacious clay, alkaline in reaction ( p H 8), with a high water content, due mainly to periodical inundations by tidal salt water.
Method of investigation consisted in taking samples of soil from a depth of 11/2 and 31/2 inches and either planting portions of this directly on to specially prepared media, or first shaking up a portion in water and then inoculating the prepared media with some of the suspension.
Three fungi– Torula allii, Penicillium hyphomycetis and Fusarium oxysporium var. resupinatum —were almost invariably present in every sample of soil: almost equally common were Trichoderma lignorum, T. Köningi, Hormodendron cladosporoides, Mucor circinelloides and Periconia felina .
Most of the fungi found are species found above ground as saprophytes, and may have been introduced into the soil by drainage, etc.
The writer considers fungi are active only in association with organic material.
The vegetation covering this marsh shows marked zonation: soil samples were chiefly taken from the Glycerietum and Aimerietum.
The same species of fungi were common to the two associations.
Glyceria maritima is a most effective silt binder, because the stele of its rhizomes and roots consists almost entirely of lignified tissue which does not yield to the activities of the soil fungi; Armeria maritima is not so effective a silt binder because the stele of its rhizomes and roots contains very little lignified tissue—at a depth of a foot, the tap roots of Armeria are little more than hollow tubes, the interiors having been removed by fungi and bacteria.     

The effect of flight on reproduction in an outbreaking forest lepidopteran

Post‐flight reproductive investment by female insects may be limited as a result of a trade‐off in resource allocation between flight and reproduction. Outbreaking forest pests reduce their habitat quality as a result of severe defoliation when population densities are high. Female relocation to better‐quality habitats can increase offspring survival but reduce their reproductive fitness through flight. In the present study, the effect of flight on the capacity of female Choristoneura conflictana (Walker) (Lepidoptera: Tortricidae) to mate and produce eggs is examined. Females are flown on flight mills, and the subsequent reproductive capacity of each moth is assessed through measures of mating success and egg production. There is no effect of flight on commencement or the duration of mating. Although flight does not affect egg production directly, energy expenditure as a result of flight (as measured by weight loss) shows a negative correlation to potential fecundity, possibly indicating the resorption of eggs in some females. The effect of female size on fecundity is dependent on mating status, suggesting that energy allocated to reproduction is not dependent on flight treatment. Female moth longevity also has a significant effect on egg production but is dependent on flight and mating treatments. There is a relationship between energy expenditure to flight and reproduction in C. conflictana. Females that fly away from dense populations may produce fewer offspring, although this cost may be mitigated by improved offspring survivorship in less defoliated habitats.     

Temperature-induced changes in the life cycle of Leuctra nigra(Plecoptera: Leuctridae) from a Lake District stream

1. The life cycle of Leuctra nigra (Olivier) took 2 years in a small stream in the English Lake District and the exponential growth of the larvae was scarcely affected by variations in water temperature (range 4.2-14.0°C). Mean growth rates for three year-classes were 0.43±0.01, 0.42±0.01, 0.39±0.05% body length day^?1. There were thirteen or fourteen larval instars for males and fourteen or fifteen for females. The ratio between successive instars was a constant 1.20 (conformed with Dyar's rule). 2. Larval growth and mortality were exponential at six constant temperatures (5.9, 8.2, 12.1, 15.8, 18.2, 19.8°C) in the laboratory. Mean growth rates (% body length day^?1) increased directly with temperature from 0.37 (5.9°C) to 0.55 (19.8°C). Mean mortality rates (% day^?1) increased directly with temperature from 0.20 (5.9°C) to 0.26 (12.1°C) and then markedly increased to 0.54-0.58 at the three higher temperatures. Only 7-10% of animals completed their life cycle at the three higher temperatures compared with 23–27% at the three lower temperatures. Egg production also decreased considerably at the higher temperatures. 3. As growth rates in the stream and laboratory were similar at similar temperatures (<14°C), the optimum conditions for growth in the laboratory were probably similar to those in the stream; therefore resources such as food and space were not restricting growth in the stream. 4. The implications of the temperature-induced changes in growth and mortality are discussed and it is concluded that although the life cycle can change from semivoltine to univoltine with increasing temperature, the costs of a univoltine life cycle are high in terms of survival and egg production, both of which decreased markedly between 12.1 and 15.8°C. Therefore the optimum habitat for this species appears to be a summer cool stream (maximum temperature <14°C) and the optimal life cycle appears to be about 2 years from egg to adult.     

Temperature-related fluctuations in the timing of emergence and pupation of Windermere alder-flies over 30 years

1. From 1966 to 1995, dates were recorded when adult alder-flies, Sialis lutaria L., were first seen (30-year range: 23 April – 25 May), 50% of the maximum density occurred (4 May – 4 June), and maximum density occurred (11 May – 17 June) along 200 m of Windermere shore. These emergence dates occurred at similar temperatures, estimated by mean values for both the emergence date and the week prior to emergence. The latter was the least variable at 10.1 °C (95% CL ± 0.37) for start of emergence, 11.2 °C (± 0.49) for 50% maximum density, 14.2 °C (± 0.51) for maximum density.
2. Final-instar larvae pupated in damp soil just above the water line. As laboratory temperatures were increased slowly from an initial 5 °C, the cumulative number of larvae leaving the water to pupate increased. A quadratic equation described this relationship from a threshold temperature of 7.2 °C to completion at 14.0 °C (50% point, 9.3 °C). The relationship between successful pupations and constant temperatures in the laboratory was well described by a quadratic equation with an optimum 14.9 °C (over 90% success) and no success outside the range 7–23 °C. A negative power-function described the relationship between days required for pupation and temperature, ranging from c . 28 days at 8.2 °C to c . 4 days at 22.1 °C.
3. Dates for larvae leaving the lake to pupate were back-calculated from dates for adult emergence, using the power-function for pupation time. Mean temperatures for estimated dates on which larvae left the lake to pupate were less variable than those for adult emergence, being 7.5 °C (± 0.20) for the start of pupation, 9.4 °C (± 0.16) for 50% maximum density, 13.7 °C (± 0.16) for maximum density. These values are similar to those obtained in the laboratory and can be used to predict pupation and adult emergence for different temperature regimes.     

Radiation-induced improvement of the freeze-resistance of a cold-sensitive wheat variety: Freeze-tolerance and fatty acid patterns

Effects of 3–15 krad ⁶⁰Co gamma radiation on cereal seeds were investigated with regard to the frost hardiness of leaves of 5–7-day-old seedlings. Comparative studies were carried out on the gas-chromatographically determined distribution patterns of fatty acids in different pools (total fatty acid, total lipid, polar lipids) of a cold-resistant (cv. Mironowskaya 808) and a cold-sensitive (cv. Penjamo 62) cultivar of wheat (Triticum aestivum L.). Parallelism between fatty acid distribution pattern, empirical parameters suggested for quantitative measures of cold tolerance (the ratio unsat/sat and double-bond index), and the low-temperature behaviour of shoots grown from radiation treated seeds of ‘Penjamo 62’, was also examined. To monitor differences in the fatty acid syntheses of ‘Mironowskaya 808’and ‘Penjamo 62’, and to demonstrate radiation-induced changes in fatty acid turnover a [1–¹⁴C]-acetate incorporation technique was employed. The results of practical importance are: 1. A significant improvement in the frost-resistance of the cold-sensitive ‘Penjamo 62’variety could be achieved with 6–9 krad irradiation, the half-freeze-killing temperature dropping from ?6 to about ?18°C. 2. Freeze-hardiness, no matter whether inherited or gained, could be abolished by gamma irradiation with higher dose. The following conclusions of theoretical interest can be drawn: 1. Low-temperature behaviour of plant tissues is a dynamic property rather than a static one, not only the formation but also the breakdown of certain hydrocarbon chains may be of paramount relevance in cold-tolerance. 2. Not the linolenic (18:3) component, but rather the overall distribution pattern of the C₁₈ family seems to correlate with low-temperature-responses of shoots. 3. Empirical parameters investigated do not provide reliable quantitative measures of the susceptibility to freeze (and cold-) injuries. 4. Changes in the syntheses of some key proteins (e.g. peroxidase, water-soluble proteins, etc.) may also be important in adaptation to low-temperature conditions.     

A LIKELIHOOD JUSTIFICATION OF PARSIMONY

Abstract— A connection is established between maximally parsimonious cladograms and trees of highest likelihood. The assumptions needed to prove this are derivable from the structure of evolutionary theory and are independent of the frequency of homoplasy. The bearing of this justification on alternative methods of phylogenetic inference and on Felsenstein's (1978) proof that parsimony and other phylogenetic methods can be statistically inconsistent is discussed.