Assessment of the potential for and development of organophosphorus resistance in field populations of Myzus persicae

A survey of esterases in field populations of the peach-potato aphid, Myzus persicae was made during the spring of 1975. Assay was by electrophoresis of single aphid homogenates, and the known association between the activity of an esterase and resistance to organophosphorus insecticide (OP) was used to infer resistance in field populations. The resistant variant replaced the susceptible in populations which had been treated with OP and another variant with threefold (approximately) more esterase activity appeared to be replacing the resistant variant in populations which have been treated twice with OP. The significance of this for control of M. persicae is discussed. Differences in resistance between aphids in different parts of the same field, and the widespread association of these esterase variants in favoured combinations with two electrophoretic variants at another locus have also been investigated.     

Ornithological Surveys of Nature Reserves, 1954

A survey of Hen Harrier winter roosts traced 202 sites in Britain to the end of 1985/86 winter, and 12 in Ireland. Communal roosting had been recorded at more than 90% of sites, and 43% were known to be used every winter. Of reported sites 39% were in E England, where coverage was undoubtedly more comprehensive. The majority of sites in England were reported to have been discovered since the mid 1970s. Hen Harriers almost invariably roosted amongst rank ground vegetation, in a variety of open habitats, and 28% of sites were on d rtl ground. Most sites were at low altitudes, but some had been found up to 427 m above sea level. Co-ordinated counts at roosts recorded maximum overall numbers at mid-winter in both 1983/84 and 1984/85, although the pattern of occupancy varied between regions. No estimate could be made of the sizes of the winter populations in Scotland, Ireland and Wales, but extrapolation of counts to estimate the numbers wintering in England indicated populations which peaked at about 400 birds in 1983/84 and 1984/85. Roosts in western Britain held a higher proportion of grey males than in the east. Ringing recoveries indicate that Hen Harriers wintering in England have mixed origins.     

Comparison of Anopheles gambiae and Culex pipiens acetycholinesterase 1 biochemical properties

Selection of insensitive acetycholinesterase 1 (AChE1) has occurred in several mosquito species controlled with carbamate (CX) and organophosphate (OP) insecticides. In case of pyrethroid resistance, these insecticides represent an alternative for disease vector control program. Their heavy use in agriculture has selected resistant populations of Anopheles gambiae in West Africa. The evolution of resistance has to be studied to prevent, or at least slow down, the spread of resistant mosquito in wild populations. An. gambiae shares the same resistance mechanism to CX and OP insecticides as Culex pipiens, which was attributed to the G119S substitution in the AChE1 enzyme. By comparing resistant AChE1 from both species, we show here that similar resistance levels are obtained toward 10 insecticides of both classes. Moreover, similar AChE1 activity levels are recorded between either susceptible or resistant mosquitoes of both species. Enzymes belonging to both species seem thus to share identical properties. Consequently, we hypothesize that fitness cost associated with AChE1 insensitivity in C. pipiens mosquitoes should be similar in An. gambiae and thus be used in strategies to control resistant populations where malaria is prevalent.     

Strong parasitoid-mediated selection in experimental populations of aphids

Clonal diversity in asexual populations may be maintained if different clones are favoured under different environmental conditions. For aphids, parasitoids are an important variable of the biotic environment. To test whether parasitoids can mediate selection among host clones, we used experimental populations consisting of 10 clones of the peach-potato aphid, Myzus persicae, and allowed them to evolve for several generations either without parasitoids or in the presence of two species of parasitoid wasps. In the absence of parasitoids, strong shifts in clonal frequencies occurred, mostly in favour of clones with high rates of increase. The parasitoid Diaeretiella rapae hardly affected aphid densities but changed the outcome of competition by favouring one entirely resistant clone and disfavouring a highly susceptible clone. Aphidius colemani, the more infective parasitoid, strongly reduced aphid densities and dramatically changed host clonal frequencies. The most resistant clone, not a successful clone without parasitoids, became totally dominant. These results highlight the potential of temporal or spatial variation in parasitoid densities to maintain clonal diversity in their aphid hosts.     

A multivariate comparison between three NW. European populations ofArtemisia norvegica (Asteraceae) by means of chemometric and morphometric data

Specimens from Scotland, S. and C. Norway were grown in the botanical garden of Bergen, Norway. Some of the Scottish specimens came from a meristem tissue culture. The specimens were compared by a principal component analysis of lipids and related compounds, and of morphological characters from leaves and flowers. The populations differed from each other, but some overlap was found in leaf characters. The results are discussed in relation to distribution and immigration history, and it is argued that the differences among the populations may have evolved in postglacial time.     

Biochemistry of Esterases Associated with Organophosphate Resistance in Lucilia cuprina with Comparisons to Putative Orthologues in Other Diptera

Esterase activities associated with organophosphate insecticide resistance in the Australian sheep blowfly, Lucilia cuprina, are compared with similar activities in other Diptera. The enzymes making the major contribution to methyl butyrate hydrolysis (ali-esterase) in L. cuprina, M. domestica, and D. melanogaster comigrate during electrophoresis. The enzymes in L. cuprina and D. melanogaster correspond to the naphthyl acetate hydrolyzing E3 and EST23 isozymes of those species. These and previously published data suggest that the ali-esterases of all three species are orthologous. Strains of L. cuprina fall into four groups on the basis of quantitative determinations of their ali-estesterase, OP hydrolase, and malathion carboxylesterase activities and these groups correspond to their status with respect to two types of OP resistance. Strains susceptible to OPs have high ali-esterase, low OP hydrolase, and intermediate MCE activities; those resistant to malathion but not diazinon have low ali-esterase, intermediate OP hydrolase, and high MCE activities; those resistant to diazinon but not malathion have low ali-esterase, high OP hydrolase, and low MCE activities; those resistant to both OPs have low ali-esterase, high OP hydrolase, and high MCE activities. The correlated changes among the three biochemical and two resistance phenotypes suggest that they are all properties of one gene/enzyme system; three major allelic variants of that system explain OP susceptibility and the two types of OP resistance. Models are proposed to explain the joint contribution of OP hydrolase and MCE activities to malathion resistance and the invariant association of low ali-esterase and elevated OP hydrolase activities in either type of resistance.     

Haemoglobin polymorphism in the Bank vole, Clethrionomys glareolus, in Britain

Three hundred and twenty-two Clethrionomys glareolus from 17 localities in England, Wales and southern Scotland were typed for haemoglobin and two phenotypes were discovered. They have been designated HbS and HbF. The latter is more electronegative at physiological pH. The nature of the molecular difference between the phenotypes was examined and it was concluded that HbF polymerises more readily than does HbS. Haematological investigations showed that although the red cells of animals with HbF contain more potassium, thereby ensuring electrostatic neutrality, there has not been concomitant dilution of the cell contents. It is suggested that the osmotic stress imposed by this high concentration of particles might be reduced by in vivo polymerisation of haemoglobin. HbS was found to predominate in the north of Britain and HbF in the south. As none of the populations sampled contained animals of both types, it is not yet known whether there is a north-south cline in haemoglobin type, or a sharp disjunction.     

Stress-induced assortative mating and the evolution of stress resistance

We show with a model that variation in environmental stress between generations facilitates the evolution of stress resistance through assortative mating. Stress induces delayed maturation of susceptible phenotypes, segregating their fertile period from resistant phenotypes. Assortment of mates enhances the responsiveness of populations to natural selection by inflating genetic variance. Thus, positive selection and inflated genetic variance in stressful environments can cause a strong evolutionary increase in resistance. By contrast, benign environments do not segregate phenotypes, and the random mating among phenotypes deflates genetic variance, leading to a weaker response to selection against resistance, assuming that resistance is costly. When environments vary randomly from benign to stressful, populations respond asymmetrically to negative and positive selection. This asymmetry (1) accelerates fixation of a resistance allele if resistance is generally favoured (stressful generations more frequent) but delays the loss of the allele if it is generally disfavoured (benign generations more frequent), and (2) it can push a resistance allele to fixation even when long‐term costs modestly exceed benefits. When resistance alleles pleiotropically delay mating, stress‐induced random mating has complementary effects. Serial autocorrelation in the stressor amplifies these effects. These results suggest a novel mechanism for the persistence of resistance polymorphisms.     

Studies of the responses of basophil and eosinophil leucocytes and mast cells to the nematode Trichostrongylus colubriformis: Comparison of cell populations in parasite resistant and susceptible guinea-pigs

Handlinger J. H. and Rothwell T. L. W. 1981. Studies of the responses of basophil and eosinophil leucocytes and mast cells to the nematode Trichostrongylus colubriformis: comparison of cell populations in parasite resistant and susceptible guinea-pigs. Internationaljournal for Parasitology11: 67–70. Basophil and eosinophil leucocytes and mast cells in T. colubriformis resistant and susceptible guinea-pigs were compared. There were significantly more circulating and small intestinal eosinophils in the resistant guinea-pigs. Intestinal eosinophils increased in both groups following infection with T. colubriformis but after 10 days the count in susceptible animals had only reached the pre-infection count in the resistant group. Pre-infection intestinal mast cell counts in the two groups were similar. Mast cell counts in susceptible guinea-pigs did not change during the period of observation but almost doubled within seven days of infection in the resistant animals.     

Frequency and geographical distribution of specific virulence factors in Bremia lactucae populations in England from 1973 to 1975

Samples of lettuces infected with Bremia lactucae were collected from seven areas of England during 1973-5. These were tested under controlled environmental conditions on a range of differentially resistant cultivars to determine the frequency of virulence (V) factors in the pathogen population. In most cases the results could be accommodated by the relationship advanced by Crate & Johnson (1976). A virulence phenotype was determined for each isolate and individual virulences within isolates were identified as present at high or low frequencies. The most common V factors were V3, V4, V6 and V8 which reflected the resistance (R) factor complement of lettuce cultivars currently in commercial production. There were few gross differences in the geographical distribution of virulence factors between the seven areas. In the West Central region, however, which encompasses the Evesham and Lancashire production areas, results indicated that the use of cultivars containing resistance (R) factors 2 and 8 respectively would have provided protection from the disease during 1974. There were differences in virulence combinations at the holding or locality level within each large area, which could be exploited by growers providing testing was done in their particular locality. Universally susceptible cultivars and those with only limited resistance factors were often found to be infected with B. lactucae populations which contained large numbers of V-factors. It might have been expected that these pathogen populations would have been restricted to cultivars with large numbers of R-factors. This finding conflicts with the suggestion that pathogen populations with complex virulence patterns are ‘unfit’ as compared with those with more simple virulence components.     

Multiplication of English isolates of potato pale cyst- nematode, Globodera pallida, on potatoes of differing nematode resistance and the identity of potato cyst- nematode populations

In pots, 25 populations of potato pale cyst-nematode, Globodera pallida Stone, differed significantly in their ability to multiply on potato clones P55/7 and ZC83/ 6, both fully resistant to G. pallida pathotype Pal. Neither clone was fully resistant to any of the populations. For 21 populations common to this and an earlier experiment, increase on the more resistant potatoes (P55/7, ZC83/6, cvs Sante, Paladin and Glenna) was correlated with their increase on less resistant potatoes (cvs Morag, Fingal and Valiant). Variation in virulence on these partially resistant potatoes was not matched by differences in the electrophoretic patterns of the nematodes' proteins. The identification of populations of G. rostochiensis (Woll.) Skarbilovich used in these experiments was confirmed by electrophoresis. All populations of G. pallida Stone, appeared to contain very small numbers of G. rostochiensis after subculture on susceptible potatoes (cv. Désirée).     

The behaviour of populations of potato cyst eelworm Heterodera rostochiensis Woll. Towards resistant potato varieties derived from Solarium tuberosum ssp. andigena Juz & Buk

Many populations of Heterodera rostochiensis mostly from the main potato growing areas of England and Wales, were tested with eelworm-resistant potato varieties (andigena hybrids). Except in the Eastern Region, where resistant varieties were planted alongside commercial varieties in infested fields, tests were done in pots inoculated with a standard number of cysts extracted from a single soil sample from each field. The tests showed that England and Wales could be divided into areas according to the percentage of cysts(< 10%, 11–70%,> 70%) produced on the resistant compared with a commercial non-resistant variety. On the peat soils of the East Anglian fens and in Bedfordshire, Essex and Kent (area A) most populations produce few cysts on resistant varieties. In much of the East Midlands and Yorkshire (area D), populations produce many cysts on resistant varieties which behave much as ordinary susceptible potatoes. Populations in the rest of England and Wales (areas B, C) vary and in many districts every field must be tested separately. If the pathotypes occurring in Britain had separate origins in South America, the present distribution in England and Wales is probably due to chance introductions dispersed with seed and following the patterns of trade in seed potatoes. As all commercial varieties, before the release of eelworm-resistant ones, were about equally susceptible to the different pathotypes, the varieties themselves probably played little part in determining the present distribution of pathotypes.     

Genetic Analysis of Parasitism in the Soybean Cyst Nematode Heterodera Glycines

A genetic analysis of parasitic ability in the soybean cyst nematode Heterodera glycines was performed. To identify and characterize genes involved in parasitism, we developed three highly inbred H. glycines lines, OP20, OP25 and OP50, for use as parents for controlled crosses. Through these crosses, we have identified genes in the inbred parents that control reproduction of the nematode on hosts that carry resistance genes. These genes, designated as ror-* for reproduction on a resistant host, segregate in a normal Mendelian fashion as independent loci. Host range tests of F(1) generation progeny indicated that at least one parasitism gene in both the OP20 and OP50 lines for host PI 88788 was dominant. Parasitism genes in OP50 for hosts ``Peking' and PI 90763 are recessive. Two types of single female descent populations, a single backcrossed BC(1)F(2)-derived and a double backcrossed BC(2)F(1)-derived, were established on the susceptible soybean cultivar ``Lee 68.' Host range tests for parasitism in these lines demonstrated the presence of two independent genes in OP50, one for host PI 88788 designated ror-1 and one for host PI 90763 designated ror-2. OP20 carries two independent genes for parasitism on PI 88788, designated as alleles kr3 and kr4.     

82 Taxonomic revision of sphaerotrichia divaricata (C. AG.) kylin (ectocarpales S.L., phaeophyceae), with a reappraisal of s. firma (GEPP) a. zinova from the northwestern pacific

Specimens of Sphaerotrichia in Japan can be classified into two morphotypes based on mode of branching and anatomy: 1) specimens having an obvious (traceable) main axis associated with more first-order branches, and the distance between the branches is relatively constant; 2) specimens that branches more or less divaricately and the distance between branches tends to be shorter in the distal portion. Molecular analyses of North Atlantic and North Pacific Sphaerotrichia using ribo-somal RNA (ITS1-5.8S-ITS2 and IGS regions between 26S and 5S rDNA) and Rubisco (almost complete rbcL gene and the spacer between rbcL and rbcS) gene sequences revealed that there are two major genetic groups (i.e. Group-1 and Group-2), whereas the sequence length variation in ITS1 suggested subdivisions of Group-2 into two subgroups (Group-2Atlantic and Group-2Pacific). Specimens belonging to Group-1 were generally epilithic, and morphologically corresponded to Sphaerotrichia firma (Gepp) A. Zinova. Specimens belonging to Group-2 were epiphytic or epilithic and morphologically corresponded to S. divaricata (C. Ag.) Kylin.     

Investigating connectivity and seasonal differences in wind assistance in the migration of Common Sandpipers

Many migratory bird species have undergone recent population declines, but there is considerable variation in trends between species and between populations employing different migratory routes. Understanding species-specific migratory behaviours is therefore of critical importance for their conservation. The Common Sandpiper Actitis hypoleucos is an Afro-Palaearctic migratory bird species whose European populations are in decline. We fitted geolocators to individuals breeding in England or wintering in Senegal to determine their migration routes and breeding or non-breeding locations. We used these geolocator data in combination with previously published data from Scottish breeding birds to determine the distributions and migratory connectivity of breeding (English and Scottish) and wintering (Senegalese) populations of the Common Sandpiper, and used simulated random migrations to investigate wind assistance during autumn and spring migration. We revealed that the Common Sandpipers tagged in England spent the winter in West Africa, and that at least some birds wintering in Senegal bred in Scandinavia; this provides insights into the links between European breeding populations and their wintering grounds. Furthermore, birds tagged in England, Scotland and Senegal overlapped considerably in their migration routes and wintering locations, meaning that local breeding populations could be buffered against habitat change, but susceptible to large-scale environmental changes. These findings also suggest that contrasting population trends in England and Scotland are unlikely to be the result of population-specific migration routes and wintering regions. Finally, we found that birds used wind to facilitate their migration in autumn, but less so in spring, when the wind costs associated with their migrations were higher than expected at random. This was despite the wind costs of simulated migrations being significantly lower in spring than in autumn. Indeed, theory suggests that individuals are under greater time pressures in spring than in autumn because of the time constraints associated with reproduction.     

Genetic differentiation among common and selected hatchery populations of flounder: Evidence from RAPD markers

Randomly amplified polymorphism DNA (RAPD) analysis was performed in order to evaluate one common population and two selected hatchery populations of flounder Paralichthys olivaceus. A total of 90 individuals belonging to three populations were screened using 12 different RAPD primers. A total of 71 loci were produced in the three studied populations, and 43.5%, 42.4% and 42.2% of these loci were polymorphic over all the genotypes tested in common, susceptible and resistant populations, respectively. The number of loci detected by single primers ranged from four to eight. The average heterozygosites of common, susceptible and resistant populations were 0.112, 0.103 and 0.111, respectively. Compared with the common population, the two selected hatchery populations, susceptible and resistant, showed some genetic differences including a smaller number of loci, a smaller number of polymorphic loci, a smaller number of genotypes and a smaller Shannon index. The present study confirmed that it is important to detect the genetic variability of the selected hatchery population for the conservation of natural flounder resources.     

First genetic evidence that invasive bullhead (Cottus L. 1758) in Scotland is of English origin and the difficulty of resolving the European Cottus species taxonomy

The European bullhead (Cottus gobio) is widely distributed across Europe, and within the UK is native to England and Wales, where it is protected under the Habitats Directive. In Scotland, however, the species is considered invasive and thriving populations are recorded in the Forth and Clyde river catchments, and the Ale Water in the Scottish Borders. The genetic identity of the Scottish populations has not been established. There is also debate about the status of the European bullhead and its validity as single species, a species complex with several unresolved species, or distinct different species in its European distribution range. There is therefore a need to determine the taxonomy and likely source of the novel Scottish populations. Genetic analyses using cytochrome oxidase 1 (COI) mitochondrial DNA sequences were undertaken on specimens from the Forth and Clyde catchments, and combined with the results of morphological characteristics to provide a comprehensive assessment of the taxonomic classification for Scottish bullheads. There was considerable variation in morphological characteristics between populations within Scotland and a wider range of variability than previously recorded for English populations. Genetically the Scottish populations were very closely related to English specimens, supporting the hypothesis of introduction directly from England to Scotland. In terms of broader relationships, Scottish specimens are genetically more closely related to the ostensible species Chabot fluviatile Cottus perifretum, which has been suggested as one of a complex of species across Europe. Morphologically they exhibit characteristics on the spectrum between C. perifretum and C. gobio. There is an urgent need for the clarification of the taxonomy of Cottus sp(p). to avoid confusion in future publications, legislation and management practices relating to bullheads throughout the UK and Europe.     

Toxicity of Bacillus sphaericus LP1-G against susceptible and resistant Culex quinquefasciatus and the cloning of the mosquitocidal toxin gene

Bacillus sphaericus LP1-G, belonging to flagellar serotype H3, has been found to have moderate toxicity against two resistant Culex quinquefasciatus colonies (RLCq1 and RLCq2) and the susceptible contrast (SLCq). With an aim of screening mosquitocidal acting factor, a partial genome library was prepared from a partial HindIII digest of the total DNA from Bacillus sphaericus LP1-G. Two thousand twenty Escherichia coli clones were screened for toxicity against susceptible SLCq, and a toxic clone, designated E-UL68, was chosen for further study. The recombinant E-UL68 performed toxicity against both susceptible and two resistant colonies, having the same level of toxicity as that of wide-type strain LP1-G. Sequence analysis revealed that the inserted fragment was composed of 3876 nucleotides and contained a complete gene, whose sequence was identical to that of the mtx gene from B. sphaericus SSII-1. Because the binary toxin produced during sporulation of strain LP1-G has no activity against the target mosquitoes, this indicates that the Mtx toxin or other active factors might perhaps be responsible for the toxicity of LP1-G against different colonies of mosquito larvae.     

ESTERASE PHENOTYPES IN NATURAL POPULATIONS OF CULEX PIPIENS PALLENS (DIPTERA: CULICIDAE) AND THEIR VARIATIONS UNDER INSECTICIDE SELECTION*

Abstract Three populations of Culex pipiens pallens Coquillett, from Hangzhou, Linhai and Jinhua, were determined for their probability of resistant esterase phenotypes. Further, each population was selected with dipterex, chlorpyrifos, temephos and malathion at a given dose of 60%‐70% mortality and was determined for the variation of resistant esterase phenotypes in its offspring. The results indicated that esterase B₁ phenotype was dominant in three populations although different natural populations have a different probability distribution of esterase B phenotypes. Insecticide selection showed that various esterase loci seemed to have different selective advantages under different insecticide pressures. The esterase B₁ phenotype was selected under temephos, and the esterase B₂ phenotype was selected under dipterex and chlorpyrifos. Except for the esterase B₁ phenotype, the heterozygote of B₁/B₂ phenotypes was detected under malathion pressure. These results are discussed in relation to the selective advantages of esterase genes to OP pressure and mosquito control strategies.