Bo Stille

Inbreeding depression in an isolated population of adders Vipera berus

Abstract Although inbreeding depression is well-studied in captive animals, its role in natural populations remains controversial. We provide information on an isolated population of snakes (adders Vipera berus) that has been separated from neighbouring populations by the expansion of agricultural activities in southern Sweden. Total adult population size is

Polygyny, relatedness and nest founding in the polygynous myrmicine ant Leptothorax acervorum (Hymenoptera; Formicidae)

SummaryThere is high within-nest relatedness for functional queens (with corpora lutea), nonfunctional queens (without corpora lutea), and workers in polygynous nests of Leptothorax acervorum. The high functional queen relatedness suggests that young mated queens are adopted back to their mother nest. Functional queen relatedness does not change with the number of queens present in the nest, suggesting that the number of generations of queens, on average two to three, is rather stable. Worker relatedness decreases with increasing number of functional queens per nest (Tables 5, 6). The number of queens contributing offspring to the nest (mothers), estimated from worker and functional queen relatedness, is lower than the number of functional queens, particularly in highly polygynous nests. Estimates of number of mothers in monogynous nests indicate that these nests previously were polygynous (Table 7). There is no correlation between nest relatedness and distance between nests, and budding-off, if present, thus appears to be a rare mode of nest founding (Table 8). There are no indications of inbreeding in the two populations studied since the frequency of heterozygotes is as high as expected from random mating (Table 4). Most likely, polygyny is the rule in L. acervorum and serves to secure the presence of queens in the nest.

Relatedness among queens in polygynous nests of the ant Leptothorax acervorum

One hundred and fifty one colonies of the ant L. acervorum comprising 815 queens were sampled in dry pine forest at nine sites in SE Sweden. 63% of the colonies contained more than one queen and of these 79% had more than one egg-laying (functional) queen, i.e. were polygynous. By using the electrophoretic variation at the PGI locus a high overall relatedness (0.4) among queens from the same colony was found indicating that young queens are adopted by their mother nest. No spatial microdifferentiation in allele frequencies could be detected and it thus seems that despite restricted movements of queens there is a free gene flow in the populations.

The effect of hosptlant and parasitoids on the reproductive success of the parthenogenetic gall wasp Diplolepis rosae (Hymenoptera, Cynipidae)

SummaryThe univoltine cynipid gall wasp Diplolepis rosae reproduces by an obligate homozygosity promoting system known as gamete duplication. The wasp is confined to roses (Rosa spp) on which it induces large, complex and multichambered galls. In southern Sweden, D. rosae was found to parasitize Rosa canina, R. dumalis, R. rubiginosa, R. villosa, R. sherardi and R. rubrifolia, but not R. majalis and R. rugosa. The distribution of galls shows that there are differences in the relation between wasp and hosplant with respect both to species and individual plants. There is a positive correlation between wasp size and gall (clutch) size. Parasitoid pressure was found to be high, causing D. rosae an estimated average larval loss of approximately 75%, mainly due to the attack of the ichneumonid wasp Orthopelma mediator. The very common cynipid inquiline Periclistus brandtii does not seem to have any negative effects. Overall parasitism and probability of no hatched offspring per gall decrease with increasing gall (clutch) size. The probability of loosing all of a given number of offspring decreases with the number of galls produced. It is suggested that D. rosae, in order to escape parasitoids, needs high ability to establish new colonies. Hence the production of many comparatively small galls, which increases the chance of leaving any offspring, rather than the production of few large galls, maximizing the number of offspring, should be favoured by selection.

EVOLUTION OF CLONAL DIVERSITY IN THE PARTHENOGENETIC FLY LONCHOPTERA DUBIA

In a cytogenetic study of the spearwinged fly Lonchoptera dubia, Stalker (1956) identified four clones on the basis of gene arrangements arising from inversions visible on the banded polytene chromosomes of ovarian nurse cells. Cytological observations have demonstrated that egg formation is automictic, and that diploidy is restored by the fusion of haploid nuclei formed in meiosis (Baud, 1973). To account for the permanent inversion heterozygosity on some or all chromosome arms in the clones, Stalker (1956) hypothesized that viable progeny normally arise from the fusion of haploid nuclei derived from different oocytes (central fusion), a process which forms a karyotype identical to that of the mother. The failure of 25% of eggs laid by flies in the laboratory to develop has been attributed to the production of lethal chromosome-arm combinations through fusion of sister nuclei (terminal fusion) or to the formation of chiasmata between the centromere and heterozygous gene arrangements (Stalker, 1956; Baud, 1973). Stalkers (1956) survey of North American populations of L. dubia showed that two or three clones commonly occur together in populations, but only at Rochester, New York, were all four clones found. In the present study, we have examined electrophoretically demonstrable allelic variation at enzyme loci in Roch-

Identification of thetrans-stilbene oxide-active glutathione transferase in human mononuclear leukocytes and in liver as GST1

A glutathione transferase from human mononuclear leukocytes with a high activity towardtrans-stilbene oxide (GT-tSBO) has been studied in liver and blood from fetus and adults and in blood from neonates. Using starch gel electrophoresis, different phenotypes of GST1 have been determined, GST1 0, GST1 1, and GST1 2. As judged from activity measurements and the fact that only those individuals who express the null allele of GST1, the GST1 0, which has a low activity towardtrans-stilbene oxide, it is concluded that the hepatic transferase GST1 is identical to GT-tSBO, as well as to hepatic transferase μ. In addition, it has been shown that the different genotypes of GST1 1 (GST1 1-1, GST1 1-0) and GST1 2 (GST1 2-2, GST1 2-0) can be separated by measuring the GT-tSBO activity in whole blood from the same individual. It is also demonstrated that GT-tSBO activity is much lower in fetal liver, approximately 10 times, compared with adult liver, while this activity seems to be unchanged in the blood from fetus and adults, as well as in neonates.

Allozyme variation supports the recognition of Agabus lapponicus (Thomson) (Coleoptera, Dytiscidae) as a distinct species

Allozyme electrophoresis of the diving beetles Agabus congener (Thunberg) and A. lappanicus (Thomson) yie)ds clear interspecific differences. Populations of A. congener from Sweden and Seotland are monomorphic at a phosphogtucomutase locus, whereas in populations of A. lapponicus from N Sweden two alleles appear at about equal frequencies. In samples from the area of sympatry in northern Sweden only mates could be identified and tested for allozyme variation. The results provide evidence in favour of the recognition of A. congener and A. lapponicus as separatc species.

Isozyme differences between the developmental stages of the parthenogenetic gall wasp Diplolepis rosae

Abstract The value of electrophoretic analysis of enzymes as an aid in connecting a morphologically deviating form to one of several possible species is dependent on the proportion of shared enzyme loci between the forms. In order to determine this proportion for the different instars of the parthenogenetic gall wasp Diplolepis rosae , 16 different enzyme systems were analysed. Out of the 37 loci detected, 25 (68%) were active in all instars. The larvae, pupae, and imagines had two, one and five unique loci, respectively. Larvae and pupae shared four loci not expressed in the imagines. In the ten enzymes analysed for comparison of males and females a total of 22 loci were detected, 21 found in both sexes and one unique to the females. The difference in isozyme pattern was found to be much more pronounced between pupa and imago than between larva and pupa. The chance to find a locus in an instar when already detected in another was calculated to 87%. If this estimate is valid for other forms within species, differential activity should not present a problem when electrophoretic analysis is used in order to connect such forms.