Limited genetic diversity and high differentiation among the remnant adder (Vipera berus) populations in the Swiss and French Jura Mountains

Although the adder (Vipera berus) has a large distribution area, this species is particularly threatened in Western Europe due to high habitat fragmentation and human persecution. We developed 13 new microsatellite markers in order to evaluate population structure and genetic diversity in the Swiss and French Jura Mountains, where the species is limited to only a few scattered populations. We found that V. berus exhibits a considerable genetic differentiation among populations (global F_ST = 0.269), even if these are not geographically isolated. Moreover, the genetic diversity within populations in the Jura Mountains and in the less perturbed Swiss Alps is significantly lower than in other French populations, possibly due to post-glacial recolonisation processes. Finally, in order to minimize losses of genetic diversities within isolated populations, suggestions for the conservation of this species in fragmented habitats are proposed.     

Determinants of reproductive success in female adders,Vipera berus

Summary Female lifetime reproductive success in a small population of individually-marked adders in southern Sweden was studied over a period of seven years. Reproductive characteristics varied little from year to year and were consistent through time in individual females. Most females mature at four years of age and reproduce every two years. The total number of offspring produced by a female depends on her adult body size (and thus, litter size) and longevity (and thus, number of litters per lifetime). Adult body size in females is influenced mainly by subadult growth rates. Offspring size depends on maternal body size and a tradeoff between offspring size and offspring number. Maternal age does not affect litter sizes and offspring sizes except through ontogenetic changes in maternal body size.Survival of females after parturition is low because of the high energy costs of reproduction, compounded by low feeding rates of gravid females because of their sedentary behaviour at this time. About one-half of females produce only a single litter during their lifetimes, although some females live to produce four or five litters. On a proximate basis, rates of energy accumulation for growth (in subadults) and reproduction (in adults) may be the most important determinants of fitness in female adders.     

Costs of reproduction in Nyssa sylvatica: sexual dimorphism in reproductive frequency and nutrient flux

Summary We examined the influence of differential reproductive frequency between the sexes on tertiary (phenotypic) sex ratios in the the dioecious tree Nyssa sylvatica (Nyssaceae). Reproduction was evaluated in relation to sex, size and canopy exposure using flowering data collected from 1229 marked trees over a four year period. For subsets of each population we used data on flower number, fruit crop size, fruit/flower ratios, and individual flower and fruit mass to compare biomass invested in reproductive structures of males and females. We also examined seasonal changes in stem nitrogen and soluble carbohydrate content in relation to flower and fruit production for trees of each sex. Our results indicate that: 1) Male-biased tertiary sex ratios could be explained by more frequent reproduction by male trees; 2) Estimated secondary sex ratios based on sums of all known males and females were not significantly different from 1:1; 3) Flowering frequency of males and females was significantly related to plant size (DBH) and exposure of the canopy to light; 4) Estimtes of reproductive biomass allocation ranged from 1.36 to 10.8 times greater for females relative to males; 5) Flower production was related to stem nutrient status for both sexes, but nutrient depletion and its effect on subsequent flowering was much more pronounced for female trees. We conclude that less frequent flowering by female trees may result from depletion of stored reserves, and that differential flowering frequency in N. sylvatica may ultimately reduce apparent sexual differences in the costs of reproduction.     

Resource dependent growth and body condition dynamics in juvenile snakes: an experiment

We examined the manner in which animals adjust the proportion of energy allocated to growth and storage in response to food availability. We compared univariate growth and length-mass relationships between juvenile adders (Vipera berus) reared under two different feeding regimes. Animals in the low- and high-food experimental groups were fed suckling mice once and twice weekly, respectively. Snout-vent length, body mass, and body condition (residual scores from log-log regression of body mass on snout-vent length) were measured shortly after birth, and at 4, 9, and 14 weeks. We found that growth in length and mass, as well as changes in length-mass relationships, differed between treatments; snakes with access to more food not only increased faster in length but were also heavier at the completion of the experiment than were similar sized less frequently fed snakes. There was no association between body condition of individuals measured at birth and at the end of the experiment, whereas size at birth was a good predictor of final size. Our results provide evidence for resource-dependent allocation strategies in V. berus, and suggest that somatic growth is less sensitive to environmental fluctuations than body condition, presumably because body size is of greater importance for fitness.     

Metalloproteinase with factor X activating and fibrinogenolytic activities from Vipera berus berus venom

We have previously shown that Vipera berus berus venom contains several factor X activating enzymes. In the present study we have investigated one of them. The enzyme was separated from venom by gel filtration on Sephadex G-100 superfine and chromatography on agarose HPS-7 and phenyl-agarose. The enzyme is a glycosylated metalloproteinase containing hexoses, hexosamines and neuraminic acid. The purified factor X activating enzyme consists of two equal chains (59 kDa). The specificity studies have shown that enzyme is nonspecific factor X activating proteinase hydrolysing also proteins such as azocasein, gelatin and fibrinogen. The enzyme hydrolyses oxidized insulin B-chain at the positions Ala¹⁴–Leu¹⁵ and Tyr¹⁶–Leu¹⁷ but it is inactive on fibrin, plasminogen and prothrombin. We used 8–10 amino acid residues containing peptides, which reproduce the sequence around the cleavage sites in factor X, factor IX and fibrinogen, as potential substrates for enzyme. Cleavage products of peptide hydrolysis were determined by MALDI-TOF MS. The peptide Asn–Asn–Leu–Thr–Arg–Ile–Val–Gly–Gly—factor X fragment was cleaved by enzyme at positions Leu³–Thr⁴ and Arg⁵–Ile⁶. The fibrinogen peptide fragment Glu–Tyr–His–Thr–Glu–Lys–Leu–Val–Thr–Ser was hydrolysed at position Lys⁶–Leu⁷.     

Paternity determination in the adder (Vipera berus)—DNA fingerprinting or random amplified polymorphic DNA?

We performed breeding experiments with adders (Vipera berus) to determine whether multiple matings may result in multiple paternity. DNA fingerprinting of mothers, their offspring, and possible fathers using a polydinucleotide probe [(TG) _n ] gave a low overall similarity between unrelated individuals (0.18±0.07; SD) and an average of 17 bands that were male-specific. In no cases were there fewer than seven paternal-specific bands present in the fingerprint of an offspring, enabling us unambiguously to identify the biological father among five males. Multiple paternity was detected in the investigated broods with offspring sired exclusively by the captive males. PCR amplification of random amplified polymorphic DNA (RAPD) using 16 decamer primers gave 76 bands and an average similarity of 0.95 (±0.01) between the males, which were collected at different, geographically well-separated localities. Although there were on average 8.3 (±1.9) bands that differ between males in pairwise comparisons, there were only 1.9 (±1.1) bands per male that are specific for a particular individual. Thus, RAPDs are adequate for paternity determination only in experiments with a low number of males, whereas DNA fingerprinting offers sufficient information to discriminate between large numbers of putative fathers.The Swedish Natural Science Research Council, the Nilsson-Ehle Foundation, and the Erik Philip-Sörensen Foundation supported our research.     

Reduction in locomotor ability as a cost of reproduction in gravid snakes

Summary Recent studies suggest that lower survival among gravid squamate reptiles may be partially the result of decreased locomotor ability during gestation. In this study, we compared the speed and endurance of female garter snakes (Thamnophis marcianus), before, during, and after pregnancy. Gravid snakes had significantly lower locomotor performance than did non-gravid females, and performance varied among stages of gestation, reaching a minimum 0–6 weeks prior to parturition. Both number of offspring and relative clutch mass were inversely correlated with locomotor performance; as females increased these traits, locomotor ability decreased. If reduced locomotor performance results in greater risk of predation and/or lowered foraging ability, then natural selection (operating via differential mortality or feeding rates of gravid females) may result in important constraints on both clutch size and relative clutch mass in squamates.     

Wolbachia: intracellular manipulators of mite reproduction

Cytoplasmically transmitted Wolbachia (alpha-Proteobacteria) are a group of closely related intracellular microorganisms that alter reproduction in arthropods. They are found in a few isopods and are widespread in insects. Wolbachia are implicated as the cause of parthenogenesis in parasitic wasps, feminization in isopods and reproductive (cytoplasmic) incompatibility in many insects. Here we report on the widespread occurrence of Wolbachia in spider mites and predatory mites based on a PCR assay for a 730 bp fragment of the ftsZ gene with primers that are specific for Wolbachia. An additional PCR, using two primer pairs that amplify a 259 bp region of the ftsZ gene that are diagnostic for the two Wolbachia subdivisions A and B, showed that infected mites only carried type B and not type A Wolbachia. The fact that some species tested negative for Wolbachia does not mean that the entire species is uninfected. We found that natural populations of Tetranychus urticae are polymorphic for the infection. The possible effects of Wolbachia on mite reproduction and post-zygotic reproductive isolation are discussed.To whom correspondence should be addressed at: Kruislaan 320, 1098 SM Amsterdam, The Netherlands     

Sexual reproduction in Daphnia: interspecific differences in a hybrid species complex

To investigate whether reproductive variation in the Daphnia galeata-cucullata-hyalina hybrid species complex can explain the occurrence of hybrids and backcrosses, a total of 43 clones from three north German lakes were tested for allocation to sexual reproduction under equal stress conditions. Six replicates per clone were followed until the seventh adult instar. I used the following cues to promote sexual reproduction: short photoperiod, water from a crowded Daphnia culture, fish-conditioned water and low food concentration. For each animal, clutch size and clutch sex were recorded. Ephippia, which were empty since the animals were cultured individually, were only produced by D. cucullata and D. cucullata x hyalina (26% and 6% of the broods, respectively), whereas almost all taxa produced males (the range was 2–15%). Intraspecific variation for male and ephippial production was also found. The fact that the taxa tested show different responses to the stimuli of-fered may indicate that there is reproductive isolation between them. This is supported by field data from the Tjeukemeer (The Netherlands) which shows that D. galeata mostly produces ephippia in spring and D. cucullata in autumn. The presence of hybrids with ephippia in both seasons, however, shows that backcrossing is also possible.     

Trade-offs between sexual and asexual reproduction in the genus Mimulus

Summary Six estimates of resource allocation to sexual reproduction (nectar concentration, nectar volume, sugar production, pollinator visitation rates, fruit-set, and seed production) and a single estimate of resource allocation to asexual reproduction (the rate of rooted-branch production) were examined for five species of Mimulus. There were significant interspecific differences for all paramaters. With the exception of nectar concentration, there was 1) a consistent positive correlation among the parameters measuring allocation to sexual reproduction, and 2) a significant negative correlation between parameters measuring allocation to sexual reproduction and the rate of rooted-branch production (asexual reproduction). The results indicate that Mimulus species which produce the highest volumes of nectar 1) receive the most pollinator visits, 2) have the highest fruit-set, 3) produce the most seeds, and 4) produce the fewest rooted branches.     

Sex allocation in a field population of an autoparasitoid

Autoparasitoid wasps lay fertilized eggs in homopteran nymphs, and these eggs develop into female primary parasitoids. Unfertilized, male-producing eggs are laid in immatures of the wasps' own or another primary parasitoid species; males then develop as secondary or hyperparasitoids. In the population of Encarsia pergandiella studied in Ithaca, NY, fertilized eggs were laid in the nymphs of the whitefly Trialeurodes packardi (primary hosts) and unfertilized eggs were laid almost exclusively in pupal females of their own species (secondary hosts). In the two years the population was studied, secondary hosts were always much less abundant than primary hosts at both sites. However, secondary hosts were parasitized at a significantly greater rate than primary hosts. In a laboratory experiment, the encounter rate of females with primary and secondary hosts was not significantly different. Moreover, there was no evidence from the field that wasps found leaves bearing secondary hosts more frequently than leaves without secondary hosts. Dissections of field-collected females showed them to be mated, and thus capable of laying both unfertilized and fertilized eggs. These results suggest that wasps did not encounter secondary hosts at a greater rate, nor were they constrained to lay unfertilized eggs, but rather secondary hosts were preferred. The oviposition sex ratios were influenced by the proportion of secondary hosts, but were less female-biased than would be predicted from the proportion of secondary hosts alone. The results do not support the predictions of Godray and Waage (1990) for either strictly host-limited autoparasitoids (sex ratio should reflect the proportion of secondary hosts) or for egg-limited autoparasitoids (sex ratio should be equal, and independent of the proportion of secondary hosts).     

Density-dependent sexual reproduction in natural populations of the rotifer asplanchna girodi

The monogonont rotifer Asplanchna girodi was continuously present in daily and bi-daily plankton samples of Golf Course Pond during the spring of 1977. Two cycles of sexual reproduction occurred during this period. By isolation and culture of females it was possible to determine the reproductive type of collected individuals. Data thus obtained suggest that environmental cues associated with population density are responsible for the production of sexual females.     

Differential host utilization by two parasites in a population of ponderosa pine

We compared phloem characteristics of individual Pinus ponderosa attacked by the dwarf-mistletoe Arceuthobium vaginatum (Viscaceae) or by the beetle Dendroctonus ponderosae (Scolytidae) or by neither species. We quantified total nonstructural carbohydrates and a broad range of chemical elements for these three categories of trees. There were significant differences between trees parasitized by Arceuthobium, trees parasitized by Dendroctonus, and non-infected trees. Discriminant function analysis of trees attacked by either Arceuthobium or Dendroctonus correctly predicted group membership for 59 of 60 trees tested. Some of the differences detected may be induced, but many probably are not. Given that the accumulation of certain elements and compounds is under genetic control, and that both parasites often cause severe reductions in fitness, including death of their host, our results suggest that the two parasites may generate diversifying selection in ponderosa pine populations.     

Genetic polymorphism of <Emphasis Type="Italic">GSTT1</Emphasis> may be under natural selection in a population chronically exposed to natural sour gas

Objective In order to examine whether chronic exposure to natural sour gas containing sulfur compounds act as natural selection force on genetic polymorphisms of glutathione S-transferase M1 (GSTM1) and T1 (GSTT1), the present study was done. Methods The study was performed on two groups of healthy individuals of Masjid-i-Sulaiman (Khozestan province, southwest of Iran) citizens with the mean ages of 47.5 ± 12.4 (36 male and 58 female) and 16.3 ± 2.4 (47 male and 140 female) that were considered as first and second generation, respectively. The GSTT1 and GSTM1 genotypes were determined using a PCR-based method. Results The genotypic frequencies of GSTM1 did not change significantly (χ² = 0.085, df = 1, P = 0.770). The frequency of the GSTT1 null genotype was 52.1% in the first generation and reached to 36.4% in the second generation. There was significant difference between two generations for the GSTT1 polymorphism (χ² = 6.397, df = 1, P = 0.011). Conclusion It was suggested that the GSTT1 polymorphism may be under natural selection because of probably favored ability of GSTT1-active genotype to survival and reproduction.     

Repeated matings offset costs of reproduction in female crickets

Summary Courtship food gifts can be a significant source of nutrition to females and costly for males to produce; hence, costs of reproduction should be reduced for multiple-mating females and increased for multiplemating males in a gift-giving species. We tested this hypothesis by experimentally manipulating mating opportunities of males and females of two cricket species,Gryllodes sigillatus, a gift-giving species andGryllus veletis, a non-gift-giving species. Females of both species consume the externally attached spermatophore after mating, but inG. sigillatus, the sperm-containing ampulla is accompanied by a large gelatinous spermatophylax. In both species, survival of mated females given limited access to males was reduced relative to virgin females, thus suggesting a cost of reproduction to females. However, females given unlimited mating opportunities lived as long as virgins and also produced significantly more offspring than limited-access females. These results suggest that benefits of repeated matings, particularly those arising through spermatophore consumption, offset costs of reproduction in females. Lack of a treatment by species interaction suggests that females of both species derive nutritional benefits through spermatophore consumption, and that any additional advantage to the consumption of the spermatophylax inG. sigillatus is offset by more frequent mating byG. veletis females. In contrast to females, varying mating opportunities had no effect on male survival, suggesting that mating effort is not very costly to males. Male survival increased linearly with body mass but only when males were food-deprived, suggesting that larger males possess greater initial energy reserves to sustain their longevity when food-stressed.     

Varroa destructor reproduction during the winter in Apis mellifera colonies in UK

The reproductive behaviour of female Varroa destructor mites invading worker brood cells during the winter months (January to mid-March) was investigated in four Apis mellifera colonies in UK. The number of viable offspring produced during a reproductive cycle, per mite, was only 0.5 during winter compared with 1.0 during the summer. This was mainly due to a large increase in the population of non-reproductive mites (winter 20%, summer 8%). This increase can be explained by the high level of male offspring mortality observed in winter (42% vs. 18% in summer), which results in nearly half of the newly reared female mites being unfertilised. Since mites that do reproduce lay a similar number of eggs in winter ( ) as in summer ( ), and the level of mortality suffered by the first female offspring is similar in winter (7%) as in summer (6%), it is probably not the internal physiological state of the host which causes the high level of winter non-reproduction, as has been previously suspected.     

Similar gender dimorphism in the costs of reproduction across the geographic range of Fraxinus ornus

BACKGROUND AND AIMS: The reproductive costs for individuals with the female function have been hypothesized to be greater than for those with the male function because the allocation unit per female flower is very high due to the necessity to nurture the embryos until seed dispersal occurs, while the male reproductive allocation per flower is lower because it finishes once pollen is shed. Consequently, males may invest more resources in growth than females. This prediction was tested across a wide geographical range in a tree with a dimorphic breeding system (Fraxinus ornus) consisting of males and hermaphrodites functioning as females. The contrasting ecological conditions found across the geographical range allowed the evaluation of the hypothesis that the reproductive costs of sexual dimorphism varies with environmental stressors. METHODS: By using random-effects meta-analysis, the differences in the reproductive and vegetative investment of male and hermaphrodite trees of F. ornus were analysed in 10 populations from the northern (Slovakia), south-eastern (Greece) and south-western (Spain) limits of its European distribution. The variation in gender-dimorphism with environmental stress was analysed by running a meta-regression between these effect sizes and the two environmental stress indicators: one related to temperature (the frost-free period) and another related to water availability (moisture deficit). KEY RESULTS: Most of the effect sizes showed that males produced more flowers and grew more quickly than hermaphrodites. Gender differences in reproduction and growth were not minimized or maximized under adverse climatic conditions such as short frost-free periods or severe aridity. CONCLUSIONS: The lower costs of reproduction for F. ornus males allow them to grow more quickly than hermaphrodites, although such differences in sex-specific reproductive costs are not magnified under stressful conditions.     

Inbreeding in a french peasant population

Genealogical pedigrees were collected from 976 farming couples who lived in a canton of central France in the XIXth and XXth century. Several methods (genealogical, isonymic and probability of origin of genes) were used to appraise the evolution of the biological structure of this population, which has gone through two phases. The first phase from 1800 to the World War I, shows gene flows between the farming population of the canton and those of neighbouring rural districts which are linked to an increase in consanguineous marriages. The second phase, from 1920 onwards, shows important gene flow from distant areas. This trend implies a decrease in consanguineous marriages.