QTL-mapping of individual resistance against American foulbrood in haploid honeybee drone larvae (Apis mellifera)

American foulbrood (AFB) is a severe brood disease in honeybees. Since sustainable treatment is not available, selection of genetically resistant honeybee stock is highly desirable. Using a set of 291 heterozygous microsatellite markers in a bulk segregant analysis with subsequent finemapping of haploid drone offspring from a single honeybee queen, we identified one significant and three suggestive quantitative trait loci as well as one significant epistatic interaction influencing prepupal survival after AFB infection. While we were not able to verify specific genes responsible for tolerance, we suggest that developmental genes may have played an important role. The identified markers can be used as regions of interest in future mapping or expression studies. In order to use them for markerassisted selection in breeding programmes for AFB-resistant honeybee stock, it will be required to evaluate these loci more extensively under variable experimental conditions.European Commission through the 6th framework collaborative Specific Targeted Research Project BEE SHOP (Bees in Europe and Sustainable Honey Production; EU contract number: FOOD-CT-2006-022568) and by the German Ministry for Education and Science (BMBF) through the FUGATO-plus project FUGAPIS (Functional genome analysis of disease resistance in honeybees, Apis mellifera; project number: 0315125A).http://link.springer.com/journal/135922015-07-31hb201

RNA interference in honeybees : off-target effects caused by dsRNA

RNA interference involves the targeted knockdown of mRNA triggered by complementary dsRNA molecules applied to an experimental organism. Although this technique has been successfully used in honeybees (Apis mellifera), it remains unclear whether the application of dsRNA leads to unintended expression knockdown in unspecific, non-targeted genes. Therefore, we studied the gene expression of four non-target genes coding for proteins that are involved in different physiological processes after treatment with three dsRNAs in two abdominal tissues. We found unspecific gene downregulation depending on both the dsRNA used and the different tissues. Hence, RNAi experiments in the honeybee require rigid controls and carefully selected dsRNA sequences to avoid misinterpretation of RNAi-derived phenotypes.This study was financially supported by the DFG (RFAM).http://link.springer.com/journal/13592hb2016Zoology and Entomolog

The Red Queen process does not select for high recombination rates in haplodiploid hosts

One of the main competing theories to describe the evolution of recombination is the Red Queen Hypothesis (RQH). Presently, many theoretical analyses of the RQH typically examine fitness interactions in host-parasite frameworks. Less emphasis has been placed on understanding the impact of host ploidy in these systems. In this study, we look to investigate the high observed rates of recombination observed in two common haplodiploid species (Apis mellifera and Bombus terrestris). We compared haplodiploid to diploid host populations under infection with haploid asexual parasites, using a Matching Allele (MAM) model. Results from a simulation analysis showed that the Red Queen does not run in haplodiploid hosts and is therefore, probably not responsible for the high recombination rates observed so far in haplodiploid hosts.Deutsche Forschungsgemeinschaft (DFG)as part of the SPP project number 1399.http://link.springer.com/journal/11692hb2013ab201

Host-parasite evolution in male-haploid hosts : an individual based network model

Host-parasite co-evolution is a key component of the Red Queen Hypothesis (RQH). The RQH currently being one of the main hypotheses describing the evolution of sex and recombination. However, most analyses in this area have either ignored parasite transmission or included it either with mean field or simple frequency based models. Moreover models have rarely addressed the issue of male haploid species. We here use agent based models to qualify the interactions between host- and parasite-based transmission parameters and virulence comparing diploid with male-haploid species. We found diploid hosts to have a higher fitness under the inverse matching allele mode compared to male haplodiploid hosts which in turn have a higher fitness under the matching allele model . Selection for recombination was rare but whenever selection for recombination was evident (\6.6 %), the resulting recombination rates were both consistently higher and more frequent in male haploids.Funding for the research was provided by the Deutsche Forschungsgemeinschaft within the priority program SPP 1399 and by yDiv, the Synthesis Centre for Biodiversity Sciences—a unit of the German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig, also funded by the Deutsche Forschunggemeinschaft (FZT 118).http://link.springer.com/journal/106822016-01-30hb201

The social parasite Phengaris (Maculinea) nausithous affects genetic diversity within Myrmica rubra host ant colonies

Evolutionary theory predicts that high genetic variation maintains plasticity in a species’ response to parasite pressure. However, higher genetic diversity might also cause easier infiltration by social parasites, because odour diversity is high and nest-mate recognition poor. Here we test if the obligate myrmecophile Lycaenid butterfly Phengaris nausithous, a parasite of colonies of the highly polygynous ant Myrmica rubra causes local adaptation by enhancing genetic variance in parasitized versus non parasitized ant populations M. rubra colonies from six infested and three uninfested sites were assayed at five microsatellite loci to quantify genetic variation. Our results reveal isolation by distance and a significantly enhanced intracolonial variance due to the parasite pressure.HIGRADE scholarship. CLIMIT project.http://link.springer.com/journal/10841hb201

Genetic underpinnings of division of labor in the honeybee (Apis mellifera)

Honeybees have been studied for centuries, starting with Aristotle, who wrote the first book about bee breeding. More than 2000 years later, the honeybee entered the genomic era as the first social insect whose genome was sequenced, leading to significant insight into the molecular mechanisms underlying social behavior. In addition, gene expression studies and knockdown using RNAi have extended the understanding of social interactions. Much of the work has focused on caste determination – the mechanism that results in reproductive division of labor, division of labor within the worker caste, and worker reproduction – an essential process underlying eusociality. Here we review the molecular factors involved in caste determination and the differential regulation of caste-specific genes. Recent findings suggest that division of labor is influenced by a small number of loci showing high levels of pleiotropy, suggesting that changes in a small number of genes lead to large changes in the phenotype.German Research Foundation DFG (grants Mo 373/26-2 and Mo 373/30-1) to R.F.A.M. and the Federal Ministry for Education and Research BMBF (FKZ: 0315126) to H.M.G.L.http://www.journals.elsevier.com/trends-in-geneticshb201

Genetic differentiation at species level in the Neotropical army ant Labidus praedator

The nomadic, swarm-raiding army ant Labidus praedator (Smith, 1858) is an important arthropod predator in the Neotropics with a strong ecological impact on invertebrate communities. However, despite its high abundance and ubiquity over a large distribution range, it received relatively little scientific attention. Moreover, the taxonomic status is confusing because some morphological descriptions point towards the co-occurrence of several distinct taxa which are lumped together as L. praedator in most classical keys. Yet, clarifying genetic studies are lacking. Here, we show strong genetic differentiation within an L. praedator population in Mexico. Both microsatellite genotype patterns and phylogenetic analyses (concatenated nuclear and mtDNA sequences, including the coxI genetic barcoding region), reveal the occurrence of two strongly isolated lineages. Colonies from the very same location, clearly identified as the same species (L. praedator) according to classical morphological keys, exhibit an extremely high average sequence divergence (9.7–12.8 %), which was well in the range of divergence among GenBank sequences from other Labidus species. Thus, our data very likely show genetic differentiation at species level or cryptic speciation within L. praedator, which should be recognized when investigating biodiversity and ecological importance of army ants (or other arthropods) in the Neotropics.Finances were granted by the Graduate Scholarship of Saxony Anhalt (MBB) and the Mexican-European FONCICYT 94293 Grant “MUTUAL” for travel expenses.http://link.springer.com/journal/40hb2016Zoology and Entomolog

Patterns of evolutionary conservation of microsatellites (SSRs) suggest a faster rate of genome evolution in hymenoptera than in Diptera

Microsatellites, or simple sequence repeats (SSRs), are common and widespread DNA elements in genomes of many organisms. However, their dynamics in genome evolution is unclear, whereby they are thought to evolve neutrally. More available genome sequences along with dated phylogenies allowed for studying the evolution of these repetitive DNA elements along evolutionary time scales. This could be used to compare rates of genome evolution. We show that SSRs in insects can be retained for several hundred million years. Different types of microsatellites seem to be retained longer than others. By comparing Dipteran with Hymenopteran species, we found very similar patterns of SSR loss during their evolution, but both taxa differ profoundly in the rate. Relative to divergence time,Diptera lost SSRs twice as fast as Hymenoptera.The loss of SSRs on the Drosophila melanogaster X-chromosome was higher than on the other chromosomes. However, accounting for generation time, the Diptera show an 8.5-fold slower rate of SSR loss than the Hymenoptera, which, in contrast to previous studies, suggests a faster genome evolution in the latter. This shows that generation time differences can have a profound effect. A faster genome evolution in these insects could be facilitated by several factors very different to Diptera, which is discussed in light of our results on the haplodiploid D. melanogaster X-chromosome. Furthermore, large numbers of SSRs can be found to be in synteny and thus could be exploited as a tool to investigate genome structure and evolution.German Science Foundation DFG.http://gbe.oxfordjournals.orgam201

Genetic structure of Balearic honeybee populations based on microsatellite polymorphism

The genetic variation of honeybee colonies collected in 22 localities on the Balearic Islands (Spain) was analysed using eight polymorphic microsatellite loci. Previous studies have demonstrated that these colonies belong either to the African or west European evolutionary lineages. These populations display low variability estimated from both the number of alleles and heterozygosity values, as expected for the honeybee island populations. Although genetic differentiation within the islands is low, significant heterozygote deficiency is present, indicating a subpopulation genetic structure. According to the genetic differentiation test, the honeybee populations of the Balearic Islands cluster into two groups: Gimnesias (Mallorca and Menorca) and Pitiusas (Ibiza and Formentera), which agrees with the biogeography postulated for this archipelago. The phylogenetic analysis suggests an Iberian origin of the Balearic honeybees, thus confirming the postulated evolutionary scenario for Apis mellifera in the Mediterranean basin. The microsatellite data from Formentera, Ibiza and Menorca show that ancestral populations are threatened by queen importations, indicating that adequate conservation measures should be developed for protecting Balearic bees