Larger testes are associated with a higher level of polyandry, but a smaller ejaculate volume, across bushcricket species (Tettigoniidae)

While early models of ejaculate allocation predicted that both relative testes and ejaculate size should increase with sperm competition intensity across species, recent models predict that ejaculate size may actually decrease as testes size and sperm competition intensity increase, owing to the confounding effect of potential male mating rate. A recent study demonstrated that ejaculate volume decreased in relation to increased polyandry across bushcricket species, but testes mass was not measured. Here, we recorded testis mass for 21 bushcricket species, while ejaculate ( ampulla) mass, nuptial gift mass, sperm number and polyandry data were largely obtained from the literature. Using phylogenetic-comparative analyses, we found that testis mass increased with the degree of polyandry, but decreased with increasing ejaculate mass. We found no significant relationship between testis mass and either sperm number or nuptial gift mass. While these results are consistent with recent models of ejaculate allocation, they could alternatively be driven by substances in the ejaculate that affect the degree of polyandry and/or by a trade-off between resources spent on testes mass versus non-sperm components of the ejaculate

Olfactory Proteins in Timema Stick Insects

Most animals use olfaction to obtain important information from the environment, including the presence of food or mates. Insects detect odorants through receptors that are expressed in the sensory neurons of the olfactory sensilla, which cover the surface of the antennae. The olfactory capacities of an insect thus depend largely on the repertoire of the odorant receptors. Here, we study the repertoire of olfactory proteins in the stick insect Timema cristinae. We first generate transcriptomes from the antennae of adult males and females and identify, via homology searches, putative olfactory proteins of three different families: odorant binding proteins, odorant receptors, and chemosensory proteins (CSPs). We then attempt to categorize olfactory proteins likely involved in sexual communication by comparing gene expression between adults and juveniles, as well as between males and females. Notably, the olfactory proteins involved in the perception of food or abiotic environmental components, should be expressed in both adults and juveniles. By contrast, the olfactory proteins involved in sexual communication, such as the detection of sex pheromones, should be expressed in adults and often comprise different repertoires in males and females. Finally, we also tested whether olfactory proteins in general and the subset, with putative roles in sexual communication in particular, are under relaxed selection in the asexual species T. monikensis, a close relative of T. cristinae. We found that olfactory proteins are typically differentially expressed between juveniles and adults, but there is little overlap of differential expression between developmental stages and the level of sex bias in adults. Furthermore, while we find evidence that olfactory proteins are indeed under relaxed selection in the asexual species, there is no evidence that this is necessarily the case for olfactory genes with a putative role in sexual communication. Nevertheless, the list of olfactory genes generated in our study provides a useful tool for future studies on olfaction in Timema and other stick insects

Preparing for winter : the transcriptomic response associated with different day lengths in Drosophila montana

The work has been supported by a Natural Environment Research Council studentship to D.J.P. and an Academy of Finland grant to M.K. (project 268214).At northern latitudes, the most robust cue for assessing the onset of winter is the shortening of day lengths. Many species use day length as a cue to increase their cold tolerance and/or enter into diapause, but little is known about changes in gene expression that occur under different day lengths. We investigate the gene expression changes associated with differences in light/dark cycles in Drosophila montana, a northerly distributed species with a strong adult photoperiodic reproductive diapause. To examine gene expression changes induced by light both prior to and during diapause, we used both nondiapausing and diapausing flies. We found that the majority of genes that are differentially expressed between different day lengths in nondiapausing and diapausing flies differ. However, the biological processes involved were broadly similar. These included neuron development and metabolism, which are largely consistent with an increase in cold tolerance previously observed to occur in these flies. We also found that many genes associated with reproduction change in expression level between different day lengths, suggesting that D. montana use changes in day length to cue changes in reproduction both before and after entering into diapause. Finally, we also identified several interesting candidate genes for light-induced changes including Lsp2, para, and Ih.Publisher PDFPeer reviewe

The evolution, diversity, and host associations of rhabdoviruses.

Metagenomic studies are leading to the discovery of a hidden diversity of RNA viruses. These new viruses are poorly characterized and new approaches are needed predict the host species these viruses pose a risk to. The rhabdoviruses are a diverse family of RNA viruses that includes important pathogens of humans, animals, and plants. We have discovered thirty-two new rhabdoviruses through a combination of our own RNA sequencing of insects and searching public sequence databases. Combining these with previously known sequences we reconstructed the phylogeny of 195 rhabdovirus sequences, and produced the most in depth analysis of the family to date. In most cases we know nothing about the biology of the viruses beyond the host they were identified from, but our dataset provides a powerful phylogenetic approach to predict which are vector-borne viruses and which are specific to vertebrates or arthropods. By reconstructing ancestral and present host states we found that switches between major groups of hosts have occurred rarely during rhabdovirus evolution. This allowed us to propose seventy-six new likely vector-borne vertebrate viruses among viruses identified from vertebrates or biting insects. Based on currently available data, our analysis suggests it is likely there was a single origin of the known plant viruses and arthropod-borne vertebrate viruses, while vertebrate- and arthropod-specific viruses arose at least twice. There are also few transitions between aquatic and terrestrial ecosystems. Viruses also cluster together at a finer scale, with closely related viruses tending to be found in closely related hosts. Our data therefore suggest that throughout their evolution, rhabdoviruses have occasionally jumped between distantly related host species before spreading through related hosts in the same environment. This approach offers a way to predict the most probable biology and key traits of newly discovered viruses.BL and FMJ are supported by a NERC grant (NE/L004232/1), a European Research Council grant (281668, DrosophilaInfection), a Junior Research Fellowship from Christ’s College, Cambridge (BL). GGRM is supported by an MRC studentship. The metagenomic sequencing of viruses from D. immigrans, D. tristis and S. deflexa was supported by a Wellcome Trust fellowship (WT085064) to DJO.This is the final version of the article. It first appeared from Oxford University Press via http://dx.doi.org/10.1093/ve/vev01

Evidence for cryptic sex in parthenogenetic stick insects of the genus Timema

Obligately parthenogenetic species are expected to be short lived since the lack of sex and recombination should translate into a slower adaptation rate and increased accumulation of deleterious alleles. Some, however, are thought to have been reproducing without males for millions of years. It is not clear how these old parthenogens can escape the predicted long-term costs of parthenogenesis, but an obvious explanation is cryptic sex. In this study, we screen for signatures of cryptic sex in eight populations of four parthenogenetic species of Timema stick insects, some estimated to be older than 1 Myr. Low genotype diversity, homozygosity of individuals and high linkage disequilibrium (LD) unaffected by marker distances support exclusively parthenogenetic reproduction in six populations. However, in two populations (namely, of the species Timema douglasi and T. monikensis) we find strong evidence for cryptic sex, most likely mediated by rare males. These populations had comparatively high genotype diversities, lower LD, and a clear LD decay with genetic distance. Rare sex in species that are otherwise largely parthenogenetic could help explain the unusual success of parthenogenesis in the Timema genus and raises the question whether episodes of rare sex are in fact the simplest explanation for the persistence of many old parthenogens in nature

Validating the demethylating effects of 5-aza-2'-deoxycytidine in insects requires a whole-genome approach (A reply to Ellers et al.)

This work was initiated as part of Natural Environment Research Council grant NE/J024481/1.We previously demonstrated that treatment with the demethylating agent 5-aza-2′-deoxycytidine (5-azadC) alters the offspring sex ratios produced by females of the parasitoid wasp Nasonia vitripennis (Cook et al. 2015). Females allocate offspring sex ratio in line with Local Mate Competition theory, producing more or less female-biased sex ratios as the number of other females laying eggs on a patch varies, thereby reducing competition amongst their sons for mates. Interestingly, treatment with 5-aza-dC did not ablate the facultative sex allocation response. Instead, sex ratios became less female-biased, a shift in the direction of the optimum sex ratio for paternally-inherited alleles according to genomic conflict theory. This was the first (albeit indirect) experimental evidence for genomic conflict over sex allocation. Ellers et al. (2019) have since assayed the effects of 5-aza-dC on DNA methylation in ten Nasonia genes, finding no evidence of demethylation in these 10 genes, from which they conclude that 5-aza-dC has no demethylating capability in Nasonia vitripennis. Quantifying the efficacy of 5-aza-dC in terms of demethylation is indeed crucial to in-depth interpretation of studies using 5-aza-dC to link phenotypes to epigenetic regulation. Here, we outline the mode of action of 5-aza-dC and demonstrate that determining the efficacy of 5-aza-dC in insect systems requires a whole-genome approach.PostprintPeer reviewe

Transcriptomes of parents identify parenting strategies and sexual conflict in a subsocial beetle

This work was funded by UK NERC grants to M.G.R. and A.J.M. an NERC studentship to D.J.P. the University of Georgia and a US NSF grant to A.J.M. and M.G.R.Parenting in the burying beetle Nicrophorus vespilloides is complex and, unusually, the sex and number of parents that can be present is flexible. Such flexibility is expected to involve specialized behaviour by the two sexes under biparental conditions. Here, we show that offspring fare equally well regardless of the sex or number of parents present. Comparing transcriptomes, we find a largely overlapping set of differentially expressed genes in both uniparental and biparental females and in uniparental males including vitellogenin, associated with reproduction, and takeout, influencing sex-specific mating and feeding behaviour. Gene expression in biparental males is similar to that in non-caring states. Thus, being ‘biparental’ in N. vespilloides describes the family social organization rather than the number of directly parenting individuals. There was no specialization; instead, in biparental families, direct male parental care appears to be limited with female behaviour unchanged. This should lead to strong sexual conflict.Publisher PDFPeer reviewe

Telling partners about chlamydia: how acceptable are the new technologies?

BACKGROUND Partner notification is accepted as a vital component in the control of chlamydia. However, in reality, many sexual partners of individuals diagnosed with chlamydia are never informed of their risk. The newer technologies of email and SMS have been used as a means of improving partner notification rates. This study explored the use and acceptability of different partner notification methods to help inform the development of strategies and resources to increase the number of partners notified. METHODS Semi-structured telephone interviews were conducted with 40 people who were recently diagnosed with chlamydia from three sexual health centres and two general practices across three Australian jurisdictions. RESULTS Most participants chose to contact their partners either in person (56%) or by phone (44%). Only 17% chose email or SMS. Participants viewed face-to-face as the "gold standard" in partner notification because it demonstrated caring, respect and courage. Telephone contact, while considered insensitive by some, was often valued because it was quick, convenient and less confronting. Email was often seen as less personal while SMS was generally considered the least acceptable method for telling partners. There was also concern that emails and SMS could be misunderstood, not taken seriously or shown to others. Despite these, email and SMS were seen to be appropriate and useful in some circumstances. Letters, both from the patients or from their doctor, were viewed more favourably but were seldom used. CONCLUSION These findings suggest that many people diagnosed with chlamydia are reluctant to use the new technologies for partner notification, except in specific circumstances, and our efforts in developing partner notification resources may best be focused on giving patients the skills and confidence for personal interaction.The study was funded by the Australian Federal Government Department of Health and Ageing Chlamydia Pilot Program of Targeted Grants

On Two-Path Convexity in Multipartite Tournaments

Abstract In the context of two-path convexity, we study the rank, Helly number, Radon number, Caratheodory number, and hull number for multipartite tournaments. We show the maximum Caratheodory number of a multipartite tournament is 3. We then derive tight upper bounds for rank in both general multipartite tournaments and clone-free multipartite tournaments. We show that these same tight upper bounds hold for the Helly number, Radon number, and hull number. We classify all clone-free multipartite tournaments of maximum Helly number, Radon number, hull number, and rank. Finally we determine all convexly independent sets of clone-free multipartite tournaments of maximum rank