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Dadia Forest in north-eastern Greece is well known for its diversity of breeding birds of prey. In 1980, the area was declared a wildlife reserve. One of the most endangered species at that time was the Black Vulture Aegypius monachus. To help the population of Black Vultures a feeding station was established in 1987. A monitoring programme from 1984 until present indicates that the operation of the feeding station has coincided with an increase in the numbers of Black Vultures wintering in Dadia by nearly threefold, an increase in the number of breeding pairs from 10 to 21, and an increase in breeding success from 40% to a peak of 95%. A slight faltering in the continued rise in the numbers of Black Vultures in Dadia is attributed to a poisoning event in 1995.
Sitophilus oryzae (L.) is a serious pest of stored cereal grains, but recently a few populations have been found able to feed and breed on certain legumes also. Legumes contain many toxic phytochemicals. A technique is described to generate data suitable for probit analysis, enabling a dose- response line to a toxic food to be constructed. The toxic effects of two legumes, yellow split-pea and adzuki bean, on adult survival and reproduction in three geographical strains of S. oryzae were examined. The strains were shown to vary in their abilities to tolerate legume phytotoxins, but there was no correlation between the abilities to survive on different legumes in the same strain. Yellow split-pea was shown to have residual effects on adult survival and reproduction, but performance was enhanced rather than impaired. It is suggested that improved performance results from induction of certain enzymes by substances within yellow split-pea. The use of legumes mixed with cereals as a control measure against S. oryzae is also discussed.
Sitophilus oryzae (L.) is a pest of stored cereals and, because most populations are unable to survive on yellow split-pea and other legumes, admixture of legume with cereal has been suggested as a control method. However, some geographical strains have been found able to feed and breed on yellow split-pea. The ability is heritable and known to be controlled in one strain by a single recessive, autosomal gene. The inheritance pattern of the ability was investigated in three different geographical strains, two of which could feed and breed on yellow split-pea and one which could not. The genetic mechanism controlling the character in these strains was not a simple recessive allele, but differed between the two pea-breeding strains and was co-dominant with the inability to feed on yellow split-pea inthe non-pea-breeding strain. The results indicate there is considerable between-strain genetic variability for the character, which may render cereal-legume mixture of little value as a control method against S. oryzae.
With the decline in production of new insecticides, the development of resistance is likely to become more of a problem than at present. Models of the spread of resistance genes may become integral parts of many management programmes. A critical examination is made of the classical theory of inheritance of resistance, i.e. the spread of a single resistance- conferring allele through a population. The theoretical considerations suggest that simple Mendelian inheritance is unable always to account for the development of resistance. It is suggested that some resistance factors may be under multigenic control and that such inheritance could account for the rate at which resistance sometimes develops. Following on from the theory, an analysis was made of time to knockdown and dry body weight in Sitophilus oryzae (L.). A half-sib experimental design was employed which enabled quantitative analyses of the characters to be made. Both characters had substantial heritabilities and were phenotypically correlated. The analysis also indicated a positive genetic correlation between the characters. The implications for the development of tolerance in the light of the genetic analysis are discussed.