Lack of phenotypic and evolutionary cross-resistance against parasitoids and pathogens in Drosophila melanogaster

BackgroundWhen organisms are attacked by multiple natural enemies, the evolution of a resistance mechanism to one natural enemy will be influenced by the degree of cross-resistance to another natural enemy. Cross-resistance can be positive, when a resistance mechanism against one natural enemy also offers resistance to another; or negative, in the form of a trade-off, when an increase in resistance against one natural enemy results in a decrease in resistance against another. Using Drosophila melanogaster, an important model system for the evolution of invertebrate immunity, we test for the existence of cross-resistance against parasites and pathogens, at both a phenotypic and evolutionary level.MethodsWe used a field strain of D. melanogaster to test whether surviving parasitism by the parasitoid Asobara tabida has an effect on the resistance against Beauveria bassiana, an entomopathogenic fungus; and whether infection with the microsporidian Tubulinosema kingi has an effect on the resistance against A. tabida. We used lines selected for increased resistance to A. tabida to test whether increased parasitoid resistance has an effect on resistance against B. bassiana and T. kingi. We used lines selected for increased tolerance against B. bassiana to test whether increased fungal resistance has an effect on resistance against A. tabida.Results/ConclusionsWe found no positive cross-resistance or trade-offs in the resistance to parasites and pathogens. This is an important finding, given the use of D. melanogaster as a model system for the evolution of invertebrate immunity. The lack of any cross-resistance to parasites and pathogens, at both the phenotypic and the evolutionary level, suggests that evolution of resistance against one class of natural enemies is largely independent of evolution of resistance against the other

Offspring sex ratios in relation to mutual ornamentation and extra-pair paternity in the Black Swan Cygnus atratus

In sexually dichromatic birds, females may adaptively adjust the sex ratio of their offspring prior to hatching in relation to male ornamentation, for example, by producing more sons when paired to a highly attractive partner. However, to our knowledge no studies have investigated offspring sex ratio modification in species in which both sexes are ornamented, and it is unknown whether such a process would be adaptive. Here we examine variation in offspring sex ratio in the mutually ornamented Black Swan Cygnus atratus. Brood sex ratio was not related to the degree of ornament elaboration in either parent, or to extra-pair paternity. We suggest that parental attractiveness may not be inherited in a sex-linked manner, or may be largely non-heritable. Thus, females may not benefit from biasing the sex ratio of their offspring in relation to parental attractiveness

Haemodynamic and functional consequences of the iatrogenic atrial septal defect following Mitraclip therapy

Percutaneous MitraClip placement for treatment of severe mitral regurgitation in high surgical risk patients is a commonly performed procedure and requires a transseptal puncture to reach the left atrium. The resulting iatrogenic atrial septal defect (iASD) is not routinely closed, yet the haemodynamic and functional consequences of a persisting defect are not fully understood. Despite positive effects such as acute left atrial pressure relief, persisting iASDs are associated with negative consequences, namely significant bidirectional shunting and subsequent worse clinical outcome. Percutaneous closure of the iASD may therefore be desirable in selected cases. In this review we discuss the available literature on this matter

Implementation of the participatory approach for supervisors to prevent sick leave: a process evaluation

To perform a process evaluation of a multifaceted strategy to implement the participatory approach for supervisors to prevent sick leave in three organisations. The implementation strategy incorporated a working group meeting with stakeholder representatives, supervisor training, and optional supervisor coaching. Context, recruitment, reach, dose delivered, dose received, fidelity, and satisfaction with the strategy were assessed at organisational and supervisor level using questionnaires and registration forms. At least 4 out of 6 stakeholders were represented in the working group meetings, and 11 % (n = 116) of supervisors could be reached. The working group meetings and supervisor training were delivered and received as planned and were well appreciated within all three organisations. Three supervisors made use of coaching. At 6-month follow-up, 11 out of 41 supervisors (27 %) indicated that they had applied the participatory approach at least one time. The implementation strategy was largely carried out as intended. However, reach of both supervisors and department managers should be improved. Future studies should consider targeting employees with the strategy

Decay of Sexual Trait Genes in an Asexual Parasitoid Wasp.

Trait loss is a widespread phenomenon with pervasive consequences for a species’ evolutionary potential. The genetic changes underlying trait loss have only been clarified in a small number of cases. None of these studies can identify whether the loss of the trait under study was a result of neutral mutation accumulation or negative selection. This distinction is relatively clear-cut in the loss of sexual traits in asexual organisms. Male-specific sexual traits are not expressed and can only decay through neutral mutations, whereas female-specific traits are expressed and subject to negative selection. We present the genome of an asexual parasitoid wasp and compare it to that of a sexual lineage of the same species. We identify a short-list of 16 genes for which the asexual lineage carries deleterious SNP or indel variants, whereas the sexual lineag e does not. Using tissue-specific expression data from other insects, we show that fifteen of these are expressed in male-specific reproductive tissues. Only one deleterious variant was found that is expressed in the female-specific spermathecae, a trait that is heavily degraded and thought to be under negative selection in L. clavipes . Although the phenotypic decay of male-specific sexual traits in asexuals is generally slow compared with the decay of female-specific sexual traits, we show that male-specific traits do indeed accumulate deleterious mutations as expected by theory. Our results provide an excellent starting point for detailed s tudy of the genomics of neutral and selected trait decay

Absence of single-locus complementary sex determination in the braconid wasps Asobara tabida and Alysia manducator

In species with single-locus complementary sex determination (sl-CSD), sex is determined by multiple alleles at a single locus. In the haplodiploid Hymenoptera, sl-CSD results in females, if individuals are heterozygous at the sex locus, and in males, if individuals are hemizygous (haploid males) or homozygous (diploid males). Several hymenopteran species have been shown to have sl-CSD, but in several others sl-CSD is absent and the phylogenetic distribution remains unclear. In the family Braconidae, all four species tested so far were shown to possess sl-CSD. In this study, inbreeding experiments were used to test for the presence of sl-CSD in two species belonging to a subfamily of the Braconidae, Asobara tabida and Alysia manducator (Alysiinae). In both species inbreeding experiments showed no difference in brood size or sex ratio compared to the (outbred) control group. Furthermore, the sex ratios found in the inbreeding treatment differed significantly from the sex ratios expected under sl-CSD. Therefore, we conclude that sl-CSD is absent in these species. This study is the first to show the lack of sl-CSD in species of the Braconidae family and that hymenopteran sex-determining mechanisms can vary, even within a family.

No signal of deleterious mutation accumulation in conserved gene sequences of extant asexual hexapods.

Loss of sex and recombination is generally assumed to impede the effectiveness of purifying selection and to result in the accumulation of slightly deleterious mutations. Empirical evidence for this has come from several studies investigating mutational load in a small number of individual genes. However, recent whole transcriptome based studies have yielded inconsistent results, hence questioning the validity of the assumption of mutational meltdown in asexual populations. Here, we study the effectiveness of purifying selection in eight asexual hexapod lineages and their sexual relatives, as present in the 1 K Insect Transcriptome Evolution (1KITE) project, covering eight hexapod groups. We analyse the accumulation of slightly deleterious nonsynonymous and synonymous point mutations in 99 single copy orthologue protein-coding loci shared among the investigated taxa. While accumulation rates of nonsynonymous mutations differed between genes and hexapod groups, we found no effect of reproductive mode on the effectiveness of purifying selection acting at nonsynonymous and synonymous sites. Although the setup of this study does not fully rule out nondetection of subtle effects, our data does not support the established consensus of asexual lineages undergoing 'mutational meltdown'

No signal of deleterious mutation accumulation in conserved gene sequences of extant asexual hexapods.

Loss of sex and recombination is generally assumed to impede the effectiveness of purifying selection and to result in the accumulation of slightly deleterious mutations. Empirical evidence for this has come from several studies investigating mutational load in a small number of individual genes. However, recent whole transcriptome based studies have yielded inconsistent results, hence questioning the validity of the assumption of mutational meltdown in asexual populations. Here, we study the effectiveness of purifying selection in eight asexual hexapod lineages and their sexual relatives, as present in the 1 K Insect Transcriptome Evolution (1KITE) project, covering eight hexapod groups. We analyse the accumulation of slightly deleterious nonsynonymous and synonymous point mutations in 99 single copy orthologue protein-coding loci shared among the investigated taxa. While accumulation rates of nonsynonymous mutations differed between genes and hexapod groups, we found no effect of reproductive mode on the effectiveness of purifying selection acting at nonsynonymous and synonymous sites. Although the setup of this study does not fully rule out nondetection of subtle effects, our data does not support the established consensus of asexual lineages undergoing 'mutational meltdown'