The influence of epistasis on the evolution of reproductive isolation by peak shifts is studied in a two-locus two-allele model of a quantitative genetic character under stabilizing selection. Epistasis is introduced by a simple multiplicative term in the function that maps gene effects onto genotypic values. In the model with only additive effects on the trait, the probability of a peak shift and the amount of reproductive isolation are always inversely related, i.e., the higher the peak shift rate, the lower the amount of reproductive isolation caused by the peak shift. With epistatic characters there is no consistent relationship between these two values. Interestingly, there are cases where both transition rates as well as the amount of reproductive isolation are increased relative to the additive model. This effect has two main causes: a shift in the location of the transition point, and the hybrids between the two alternative optimal genotypes have lower average fitness in the epistatic case. A review of the empirical literature shows that the fitness relations resulting in higher peak shift rates and more reproductive isolation are qualitatively the same as those observed for genes causing hybrid inferiority.
1. The studies included cultural landscapes of simple (agricultural land) and complex (forest) structure in Wielkopolska.
2. The goal of the studies was to define biocoenotic function of marginal habitats such as – shrubs, field border, road borders, and forest edges – structural elements of agricultural landscape making suitable habitats for parasitoid hymenoptera of subfamily Pimplinae (Hymenoptera, Ichneumonidae)
3. The authors wanted to establish:
i. which of marginal habitats are most attractive for Pimplinae;
ii. which of these habitats are similar to forest habitats, due to the qualitative and quantitative structure of parasitoid hymenoptera communities living there; and
iii. whether linear marginal habitats (like road sides) can fulfil the function of ecological corridors for parasitoid hymenoptera, between agricultural and forest habitats.
4. The species diversity of Pimplinae in all the habitats of agricultural landscape and forest environment (national park) was similar.
5. On the forest edges (high heterogeneity landscape), the communities of Pimplinae were most numerous. In the low heterogeneity landscape, the greatest species diversity occurred in shrubs. The majority of Pimplinae populations living in agricultural landscape and forest showed great similarity in their qualitative structure and less similarity in their quantitative structure.
6. The conclusion can be made that marginal habitats of agricultural landscape make attractive environment for parasitoids of Pimplinae and that vegetation alongside roads can make function as ecological corridors.
The cocoons of the great pond snail, Lymnaea stagnalis (L.), and the great ramshorn, Planorbarius corneus (L.) were exposed to mechanically and biologically treated sewage from different water treatment plants in the region of Cracow (southern Poland). The control group consisted of snails from the same cocoon as the experimental snails. Mineral water and pond water from Zabierzów Bochenski (near Cracow) were used for the control groups. We found that mechanically treated sewage from the Plaszów sewage treatment plant was highly toxic (100% embryo lethality). The toxicity was reduced after mixing sewage with the control water (25% solution). However, in this group, the development of embryos was slower than in the control. No toxicity was observed in the biologically treated sewage from the same plant. The sewage from the Myslenice plant (mechanical treatment) was also very toxic (100% lethality), but this toxicity disappeared after keeping the sample at room temperature for 1 year. Water from the Vistula River was not toxic.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.