PERMANENT GENETIC RESOURCES: Isolation and characterization of polymorphic microsatellite loci in common evening primrose (Oenothera biennis)

We developed nine polymorphic microsatellite loci for evening primrose (Oenothera biennis). These loci have two to 18 alleles per locus and observed heterozygosities ranging from 0 to 0.879 in a sample of 34 individuals. In a pattern consistent with the functionally asexual reproductive system of this species, 17/36 pairs of loci revealed significant linkage disequilibrium and three loci showed significant deviations from Hardy-Weinberg equilibrium. The loci will be informative in identifying genotypes in multigenerational field studies to assess changes in genotype frequencies.     

The constancy of the G matrix through species divergence and the effects of quantitative genetic constraints on phenotypic evolution: a case study in crickets

Long-term phenotypic evolution can be modeled using the response-to-selection equation of quantitative genetics, which incorporates information about genetic constraints (the G matrix). However, little is known about the evolution of G and about its long-term importance in constraining phenotypic evolution. We first investigated the degree of conservation of the G matrix across three species of crickets and qualitatively compared the pattern of variation of G to the phylogeny of the group. Second, we investigated the effect of G on phenotypic evolution by comparing the direction of greatest quantitative genetic variation within species (g(max)) to the direction of phenotypic divergence between species (Delta(z)). Each species, Gryllus veletis, G. firmus, and G. pennsylvanicus, was reared in the laboratory using a full-sib breeding design to extract quantitative genetic information. Five morphological traits related to size were measured. G matrices were compared using three statistical approaches: the T method, the Flury hierarchy, and the MANOVA method. Results revealed that the differences between matrices were small and mostly caused by differences in the magnitude of the genetic variation, not by differences in principal component structure. This suggested that the G matrix structure of this group of species was preserved, despite significant phenotypic divergence across species. The small observed differences in G matrices across species were qualitatively consistent with genetic distances, whereas ecological information did not provide a good prediction of G matrix variation. The comparison of g(max) and Delta(z) revealed that the angle between these two vectors was small in two of three species comparisons, whereas the larger angle corresponding to the third species comparison was caused in large part by one of the five traits. This suggests that multivariate phenotypic divergence occurred mostly in a direction predicted by the direction of greatest genetic variation, although it was not possible to demonstrate the causal relationship from G to Delta(z). Overall, this study provided some support for the validity of the predictive power of quantitative genetics over evolutionary time scales.     

Estimation of heritability, evolvability and genetic correlations of two pollen and pistil traits involved in a sexual conflict over timing of stigma receptivity in Collinsia heterophylla (Plantaginaceae)

Background and Aims

Heritable genetic variation is crucial for selection to operate, yet there is a paucity of studies quantifying such variation in interactive male/female sexual traits, especially those of plants. Previous work on the annual plant Collinsia heterophylla, a mixed-mating species, suggests that delayed stigma receptivity is involved in a sexual conflict: pollen from certain donors fertilize ovules earlier than others at the expense of reduced maternal seed set and lower levels of pollen competition.

Methods

Parent–offspring regressions and sib analyses were performed to test for heritable genetic variation and co-variation in male and female interactive traits related to the sexual conflict.

Key Results

Some heritable variation and evolvability were found for the female trait (delayed stigma receptivity in presence of pollen), but no evidence was found for genetic variation in the male trait (ability to fertilize ovules early). The results further indicated a marginally significant correlation between a male''s ability to fertilize early and early stigma receptivity in offspring. However, despite potential indirect selection of these traits, antagonistic co-evolution may not occur given the lack of heritability of the male trait.

Conclusions

To our knowledge, this is the first study of a plant or any hermaphrodite that examines patterns of genetic correlation between two interactive sexual traits, and also the first to assess heritabilities of plant traits putatively involved in a sexual conflict. It is concluded that the ability to delay fertilization in presence of pollen can respond to selection, while the pollen trait has lower evolutionary potential.     

Mitochondrial DNA polymorphism and feminizing sex factors dynamics in a natural population of Armadillidium vulgare (Crustacea,Isopoda)

Sex determination in Armadillidium vulgare may be under the control of two parasitic sex factors that reverse genetic males into functional neo-females. The first feminizing factor (F) is a Wolbachia and the other (f) is probably a sequence of the F bacterial DNA unstably integrated into the host genome. Both of these feminizing factors are mainly maternally transmitted. Here we investigate the mitochondrial DNA polymorphism of wild iso-female lineages harbouring either F or f. Among the four haplotypes present in the population, two were the f-harbouring lineages, while two were common to the F- and f-harbouring lineages. This result suggests that there has been an introgression of the f factor into lineages infected by F Wolbachia. Based on previous data, we propose two different ways to account for such introgression. Given the particular dynamics of feminizing factors (f-harbouring lineages increase in populations at the expense of F-harbouring lineages), such an introgression should prevent the replacement of F-linked mitochondrial types by f-linked mitochondrial types in wild populations.     

Variability of Wing Size and Shape in Three Populations of a Recent Brazilian Invader, Zaprionus indianus (Diptera: Drosophilidae), from Different Habitats

Zaprionus indianus (Diptera: Drosophilidae) is an African species that was introduced in Brazil near the end of the 1990’s decade. To evaluate the adaptive potential of morphological traits in natural populations of this recently introduced species, we have investigated wing size and shape variation at Rio de Janeiro populations only two years after the first record of Z. indianus in Brazil. Significant genetic differences among populations from three distinct ecological habitats were detected. The heritability and evolvability estimates show that, even with the population bottleneck that should have occurred during the invasion event, an appreciable amount of additive genetic variation for wing size and shape was retained. Our results also indicated a greater influence of environmental variation on wing size than on wing shape. The importance of quantitative genetic variability and plasticity in the successful establishment and dispersal of Z. indianus in the Brazilian territory is then discussed.     

The genetic bases of high-level resistance to diflubenzuron and low-level resistance to cyromazine in a field strain of the Australian sheep blowfly, Lucilia cuprina (Wiedemann) (Diptera: Calliphoridae)

Abstract  Several genes on chromosomes IV and VI have a significant influence on high-level resistance to diflubenzuron in a strain of the Australian sheep blowfly from Tara, Queensland. Low-level resistance to cyromazine in the same strain is due to genes on these chromosomes with a gene (gene complex) in the sv marker region of chromosome IV being particularly important. For both insecticides, genetic background influences resistance status. If the results of the Tara strain prove typical for those of other populations, resistance to diflubenzuron in the Australian sheep blowfly has potentially significant consequences for woolgrowers.     

Determining effects of suspended sediment on condition of a suspension feeding bivalve (Atrina zelandica): results of a survey, a laboratory experiment and a field transplant experiment

The horse mussel Atrina zelandica (Gray) is a large, suspension feeding pinnid bivalve, common in coastal and estuarine areas of northern New Zealand. As a suspension feeder, Atrina is likely to be influenced by suspended sediment loads. We conducted a laboratory experiment to determine the effect of short-term elevations in turbidity levels, such as those commonly recorded during storms, on the physiological condition and clearance rates of Atrina. We also conducted a field survey and a 3-month transplant experiment at multiple sites along a gradient of increasing suspended sediment load in a New Zealand estuary. Laboratory clearance rates of Atrina declined above a threshold suspended sediment concentration, and Atrina physiological condition at the end of this experiment was lower in high cf. low turbidity treatments. Decreases in Atrina condition were detected after exposure to elevated levels for only 3 days. The field survey and transplant experiment provided empirical evidence of a strong, negative effect of increasing suspended sediment flux on the physiological condition of Atrina. We suggest that relationships between the physiological condition of suspension feeders and sediment settling flux could provide a link between sediment inputs, which commonly occur as a result of catchment runoff during rainfall events, and the ecological health of estuarine and shallow coastal areas. Our study also demonstrated that Atrina have a natural distribution limit controlled by suspended sediment load. Thus, there is potential for larger-scale functional and structural effects on benthic communities in estuarine and coastal areas with high rates of sedimentation.