Maternal effects and maternal selection arising from variation in allocation of free amino acid to eggs

Maternal provisioning can have profound effects on offspring phenotypes, or maternal effects, especially early in life. One ubiquitous form of provisioning is in the makeup of egg. However, only a few studies examine the role of specific egg constituents in maternal effects, especially as they relate to maternal selection (a standardized selection gradient reflecting the covariance between maternal traits and offspring fitness). Here, we report on the evolutionary consequences of differences in maternal acquisition and allocation of amino acids to eggs. We manipulated acquisition by varying maternal diet (milkweed or sunflower) in the large milkweed bug, Oncopeltus fasciatus. Variation in allocation was detected by examining two source populations with different evolutionary histories and life‐history response to sunflower as food. We measured amino acids composition in eggs in this 2 × 2 design and found significant effects of source population and maternal diet on egg and nymph mass and of source population, maternal diet, and their interaction on amino acid composition of eggs. We measured significant linear and quadratic maternal selection on offspring mass associated with variation in amino acid allocation. Visualizing the performance surface along the major axes of nonlinear selection and plotting the mean amino acid profile of eggs from each treatment onto the surface revealed a saddle‐shaped fitness surface. While maternal selection appears to have influenced how females allocate amino acids, this maternal effect did not evolve equally in the two populations. Furthermore, none of the population means coincided with peak performance. Thus, we found that the composition of free amino acids in eggs was due to variation in both acquisition and allocation, which had significant fitness effects and created selection. However, although there can be an evolutionary response to novel food resources, females may be constrained from reaching phenotypic optima with regard to allocation of free amino acids.     

Genomic correlates of recombination rate and its variability across eight recombination maps in the western honey bee (Apis mellifera L.)

Background

Meiotic recombination has traditionally been explained based on the structural requirement to stabilize homologous chromosome pairs to ensure their proper meiotic segregation. Competing hypotheses seek to explain the emerging findings of significant heterogeneity in recombination rates within and between genomes, but intraspecific comparisons of genome-wide recombination patterns are rare. The honey bee (Apis mellifera) exhibits the highest rate of genomic recombination among multicellular animals with about five cross-over events per chromatid.

Results

Here, we present a comparative analysis of recombination rates across eight genetic linkage maps of the honey bee genome to investigate which genomic sequence features are correlated with recombination rate and with its variation across the eight data sets, ranging in average marker spacing ranging from 1 Mbp to 120 kbp. Overall, we found that GC content explained best the variation in local recombination rate along chromosomes at the analyzed 100 kbp scale. In contrast, variation among the different maps was correlated to the abundance of microsatellites and several specific tri- and tetra-nucleotides.

Conclusions

The combined evidence from eight medium-scale recombination maps of the honey bee genome suggests that recombination rate variation in this highly recombining genome might be due to the DNA configuration instead of distinct sequence motifs. However, more fine-scale analyses are needed. The empirical basis of eight differing genetic maps allowed for robust conclusions about the correlates of the local recombination rates and enabled the study of the relation between DNA features and variability in local recombination rates, which is particularly relevant in the honey bee genome with its exceptionally high recombination rate.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-015-1281-2) contains supplementary material, which is available to authorized users.     

Involvement of prostaglandins and histamine in radiation-induced temperature responses in rats

Exposure of rats to 1-15 Gy of gamma radiation induced hyperthermia, whereas exposure to 20-150 Gy produced hypothermia. Since radiation exposure induced the release of prostaglandins (PGs) and histamine, the role of PGs and histamine in radiation-induced temperature changes was examined. Radiation-induced hyper- and hypothermia were antagonized by pretreatment with indomethacin, a cyclooxygenase inhibitor. Intracerebroventricular administration of PGE2 and PGD2 induced hyper- and hypothermia, respectively. Administration of SC-19220, a specific PGE2 antagonist, attenuated PGE2- and radiation-induced hyperthermia, but it did not antagonize PGD2- or radiation-induced hypothermia. Consistent with an apparent role of histamine in hypothermia, administration of disodium cromoglycate (a mast cell stabilizer), mepyramine (H1-receptor antagonist), or cimetidine (H2-receptor antagonist) attenuated PGD2- and radiation-induced hypothermia. These results suggest that radiation-induced hyperthermia is mediated via PGE2 and that radiation-induced hypothermia is mediated by another PG, possibly PGD2, via histamine.     

Blue tits are ultraviolet tits

The blue tit (Parus caeruleus) has been classified as sexually monochromatic. This classification is based on human colour perception yet, unlike humans, most birds have four spectrally distinct classes of cone and are visually sensitive to wavelengths in the near-ultraviolet (300 to 400 nm). Reflectance spectrophotometry reveals that blue tit plumage shows considerable reflection of UV light. For example, the blue crest shows peak reflectance at wavelengths around 352 nm. Furthermore, the blue tit is sexually dichromatic for multiple regions of plumage, including the crest. Choice trials performed in the laboratory indicate that females prefer males with the brightest crests. This study has implications for both intra- and interspecific studies of sexual selection, as well as future classification of dichromatism, which should not ignore the possibility of variation in reflectance in the UV.     

Relative developmental and reproductive fitness associated with pyrethroid resistance in the major southern African malaria vector, Anopheles funestus

The effect of pyrethroid resistance on the fitness of a laboratory strain of Anopheles funestus originating from southern Mozambique was evaluated by comparing the developmental and reproductive characteristics of a pyrethroid resistant strain with an insecticide susceptible strain. Fitness was evaluated in terms of fecundity, fertility, egg production, developmental time and life stage progression and survival. Of the eggs laid by females of the resistant strain, 81.5% hatched while only 66.9% were recorded in the susceptible strain. The time from egg hatch to adult emergence was longer for the resistant strain (15.9 days) than the susceptible strain (15.2 days). A significantly higher proportion of eggs from the resistant strain (61.6%) survived to adulthood compared with those of the susceptible strain (49%). Fecundity and larval and pupal survival did not differ significantly between strains. Of spermathecae dissected from females of the resistant strain, 56.8% were fertilized compared to 52.6% from the susceptible strain. The proportion of females that successfully produced eggs was 43.3% and 23.3% for the resistant and susceptible strains respectively. Complete failure of larval hatch was recorded in 28.6% of susceptible strain families compared to 7.7% of resistant families. Our results show that pyrethroid resistance in southern African An. funestus does not incur any loss of fitness under laboratory conditions. These results suggest that the removal of pyrethroid insecticide selection pressure may not lead to a regression of resistance alleles in pyrethroid resistant An. funestus populations in southern Africa.     

Seroepidemiology of cholera in Gulf coastal Texas.

Single serum samples from 559 volunteers from a Texas Gulf Coast area were examined for vibriocidal antibody to Vibrio cholerae O1 (biotype El Tor, serotype Inaba) by a microtiter method. Elevated levels of vibriocidal antibody were present in 14% of the subjects. Also, 6.8% of the subjects had elevated levels of antibody to the enterotoxin of V. cholerae O1 by the immunoglobulin G enzyme-linked immunosorbent assay. Recent infection, defined on the basis of elevations in both vibriocidal and antitoxin antibodies, had occurred in 1.3% of the subjects. When subjects who reported Brucella infection, travel to a cholera-endemic area, and/or cholera vaccination within a year of the study were removed from the analysis, a prevalence of recent infection of 0.89% was obtained. Significantly higher titers of vibriocidal antibody were found in those with exposure to seawater (fishermen, shrimpers, merchant marines, and dock workers) than in those without such exposure (P less than 0.005). Furthermore, titers of antitoxin antibody were significantly higher in those who consumed shellfish than in nonconsumers. Finally, titers of vibriocidal antibody were significantly higher in Vietnamese subjects than in non-Vietnamese subjects. The results of this study indicate that an endemic focus of infection with V. cholerae occurs in this area.     

The rate of progression and stability of progressive nitrogen limitation at elevated atmospheric CO2 in a grazed grassland over 11 years of Free Air CO2 enrichment

A decline in the availability of nitrogen (N) for plant growth (progressive nitrogen limitation or PNL) is a feedback that could constrain terrestrial ecosystem responses to elevated atmospheric CO₂. Several long-term CO₂ enrichment experiments have measured changes in plant and soil pools and fluxes consistent with PNL but evidence for PNL in grasslands is limited. In an 11 year Free Air CO₂ Enrichment (FACE) experiment on grazed grassland we found the amount of N harvested in aboveground plant biomass was greater at elevated CO₂ but declined over time to be indistinguishable from ambient after 5 years. Re-wetting after a major drought resulted in a large input of N from mineralisation and a return to a higher N harvested under elevated CO₂ followed by a further decline. Over these two periods the amount of N in soil significantly increased at elevated CO₂. Data from mesocosms introduced into the rings at intervals, and therefore having different lengths of exposure to CO₂, showed plant N availability declined at elevated CO₂ reaching a new equilibrium after 6 years of exposure. We conclude that the availability of N for plants in this grassland is dynamic but the underlying trend at elevated CO₂ is for PNL.