The genetic architecture of fitness in a seed beetle: assessing the potential for indirect genetic benefits of female choice

<p>Abstract</p> <p>Background</p> <p>Quantifying the amount of standing genetic variation in fitness represents an empirical challenge. Unfortunately, the shortage of detailed studies of the genetic architecture of fitness has hampered progress in several domains of evolutionary biology. One such area is the study of sexual selection. In particular, the evolution of adaptive female choice by indirect genetic benefits relies on the presence of genetic variation for fitness. Female choice by genetic benefits fall broadly into good genes (additive) models and compatibility (non-additive) models where the strength of selection is dictated by the genetic architecture of fitness. To characterize the genetic architecture of fitness, we employed a quantitative genetic design (the diallel cross) in a population of the seed beetle <it>Callosobruchus maculatus</it>, which is known to exhibit post-copulatory female choice. From reciprocal crosses of inbred lines, we assayed egg production, egg-to-adult survival, and lifetime offspring production of the outbred F1 daughters (F1 productivity).</p> <p>Results</p> <p>We used the bio model to estimate six components of genetic and environmental variance in fitness. We found sizeable additive and non-additive genetic variance in F₁productivity, but lower genetic variance in egg-to-adult survival, which was strongly influenced by maternal and paternal effects.</p> <p>Conclusion</p> <p>Our results show that, in order to gain a relevant understanding of the genetic architecture of fitness, measures of offspring fitness should be inclusive and should include quantifications of offspring reproductive success. We note that our estimate of additive genetic variance in F₁productivity (<it>CV</it>_{<it>A </it>}= 14%) is sufficient to generate indirect selection on female choice. However, our results also show that the major determinant of offspring fitness is the genetic interaction between parental genomes, as indicated by large amounts of non-additive genetic variance (dominance and/or epistasis) for F₁productivity. We discuss the processes that may maintain additive and non-additive genetic variance for fitness and how these relate to indirect selection for female choice.</p

Temperature dependence of secondary organic aerosol yield from the ozonolysis of ?-pinene

International audienceThe temperature dependence of secondary organic aerosol (SOA) formation from ozonolysis of ?-pinene was studied in a flow reactor at 263?303 K and 1007 hPa. The observed SOA yields were of similar magnitude as predicted by a two-product model based on detailed gas phase chemistry (Jenkin, 2004), reaching maximum values of 0.22?0.39 at high particle mass concentrations. However, the measurement data exhibited significant deviations (up to 50%) from the predicted linear dependence on inverse temperature. When fitting the measurement data with a two-product model, we found that both the partitioning coefficients (Kom,i) and the stoichiometric yields (?i) of the low-volatile and semi-volatile species vary with temperature. The results indicate that not only the reaction product vapour pressures but also the relative contributions of different gas-phase or multiphase reaction channels are dependent on temperature. We suggest that the modelling of secondary organic aerosol formation in the atmosphere needs to take into account the effects of temperature on the pathways and kinetics of the involved chemical reactions as well as on the gas-particle partitioning of the reaction products

Temperature and humidity dependence of secondary organic aerosol yield from the ozonolysis of ?-pinene

International audienceThe temperature dependence of secondary organic aerosol (SOA) formation from ozonolysis of ?-pinene was studied in a flow reactor at 263 K?303 K and 1007 hPa under dry and humid conditions (0% and 26%?68% relative humidity, respectively). The observed SOA yields were of similar magnitude as predicted by a two-product model based on detailed gas phase chemistry (Jenkin, 2004), reaching maximum values of 0.18?0.39 at high particle mass concentrations (Mo). Under dry conditions, however, the measurement data exhibited significant oscillatory deviations from the predicted linear increase with inverse temperature (up to 50% at high Mo). Under humid conditions the SOA yield exhibited a linear decrease with inverse temperature, which is opposite to modelled temperature dependence and implies that the model substantially overestimates the yield at low temperatures and underestimates it at high temperatures (deviations up to 80% at high Mo). For the atmospherically relevant concentration level of Mo=10 ?g m?3 and temperature range 263 K?293 K, the results from humid experiments in this study indicate that the SOA yield of ?-pinene ozonolysis may be well represented by an average value of 0.15 with an uncertainty estimate of ±0.05. When fitting the measurement data with a two-product model, both the partitioning coefficients (Kom,i) and the stoichiometric yields (?i) of the low-volatile and semi-volatile model species were found to vary with temperature. The results indicate that not only the reaction product vapour pressures but also the relative contributions of different gas-phase or multiphase reaction channels are strongly dependent on temperature and the presence of water vapour. In fact, the oscillatory positive temperature dependence observed under dry conditions and the negative temperature dependence observed under humid conditions indicate that the SOA yield is governed much more by the temperature and humidity dependence of the involved chemical reactions than by vapour pressure temperature dependencies. We suggest that the elucidation and modelling of SOA formation need to take into account the effects of temperature and humidity on the pathways and kinetics of the involved chemical reactions as well as on the gas-particle partitioning of the reaction products

Sperm competition intensity affects sperm precedence patterns in a polyandrous gift-giving spider

Abstract Sperm competition drives traits that enhance fertilization success. The amount of sperm transferred relative to competitors is key for attaining paternity. Female reproductive morphology and male mating order may also influence fertilization, however the outcome for sperm precedence under intense sperm competition remains poorly understood. In the polyandrous spider Pisaura mirabilis, males offer nuptial gifts which prolong copulation and increase sperm transfer, factors proposed to alter sperm precedence patterns under strong sperm competition. First, we assessed the degree of female polyandry by genotyping wild broods. A conservative analysis identified up to four sires, with a mean of two sires per brood, consistent with an optimal mating female rate. Then we asked whether intense sperm competition shifts sperm precedence patterns from first male priority, as expected from female morphology, to last male advantage. We varied sexual selection intensity experimentally and determined competitive fertilization outcome by genotyping broods. In double matings, one male monopolised paternity regardless of mating order. A mating order effect with first male priority was revealed when females were mated to four males, however this effect disappeared when females were mated to six males, probably due to increased sperm mixing. The proportion of males that successfully sired offspring drastically decreased with the number of competitors. Longer copulations translated into higher paternity shares independently of mating order, reinforcing the advantage of traits that prolong copulation duration under intense competition, such as the nuptial gift. Sperm competition intensity enhances the impact of competitive sexual traits and imposes multiple effects on paternity

Moderate Multiple Parentage and Low Genetic Variation Reduces the Potential for Genetic Incompatibility Avoidance Despite High Risk of Inbreeding

Background: Polyandry is widespread throughout the animal kingdom. In the absence of direct benefits of mating with different males, the underlying basis for polyandry is enigmatic because it can carry considerable costs such as elevated exposure to sexual diseases, physical injury or other direct fitness costs. Such costs may be balanced by indirect genetic benefits to the offspring of polyandrous females. We investigated polyandry and patterns of parentage in the spider Stegodyphus lineatus. This species experiences relatively high levels of inbreeding as a result of its spatial population structure, philopatry and limited male mating dispersal. Polyandry may provide an opportunity for post mating inbreeding avoidance that reduces the risk of genetic incompatibilities arising from incestuous matings. However, multiple mating carries direct fitness costs to females suggesting that genetic benefits must be substantial to counter direct costs. Methodology/Principal Findings: Genetic parentage analyses in two populations from Israel and a Greek island, showed mixed-brood parentage in approximately 50 % of the broods. The number of fathers ranged from 1–2 indicating low levels of multiple parentage and there was no evidence for paternity bias in mixed-broods from both populations. Microsatellite loci variation suggested limited genetic variation within populations, especially in the Greek island population. Relatedness estimates among females in the maternal generation and potentially interacting individuals were substantial indicating fullsib and half-sib relationships

Variable Incidence of Spiroplasma Infections in Natural Populations of Drosophila Species

Spiroplasma is widespread as a heritable bacterial symbiont in insects and some other invertebrates, in which it sometimes acts as a male-killer and causes female-biased sex ratios in hosts. Besides Wolbachia, it is the only heritable bacterium known from Drosophila, having been found in 16 of over 200 Drosophila species screened, based on samples of one or few individuals per species. To assess the extent to which Spiroplasma infection varies within and among species of Drosophila, intensive sampling consisting of 50–281 individuals per species was conducted for natural populations of 19 Drosophila species. Infection rates varied among species and among populations of the same species, and 12 of 19 species tested negative for all individuals. Spiroplasma infection never was fixed, and the highest infection rates were 60% in certain populations of D. hydei and 85% in certain populations of D. mojavensis. In infected species, infection rates were similar for males and females, indicating that these Spiroplasma infections do not confer a strong male-killing effect. These findings suggest that Spiroplasma has other effects on hosts that allow it to persist, and that environmental or host variation affects transmission or persistence leading to differences among populations in infection frequencies

Joint Practice Guidelines for Radionuclide Lymphoscintigraphy for Sentinel Node Localization in Oral/Oropharyngeal Squamous Cell Carcinoma

Involvement of the cervical lymph nodes is the most important prognostic factor for patients with oral/oropharyngeal squamous cell carcinoma (OSCC), and the decision of whether to electively treat patients with clinically negative necks remains a controversial topic. Sentinel node biopsy (SNB) provides a minimally invasive method for determining the disease status of the cervical node basin, without the need for a formal neck dissection. This technique potentially improves the accuracy of histologic nodal staging and avoids overtreating three-quarters of this patient population, minimizing associated morbidity. The technique has been validated for patients with OSCC, and larger-scale studies are in progress to determine its exact role in the management of this patient population. This document is designed to outline the current best practice guidelines for the provision of SNB in patients with early-stage OSCC, and to provide a framework for the currently evolving recommendations for its use. Preparation of this guideline was carried out by a multidisciplinary surgical/nuclear medicine/pathology expert panel under the joint auspices of the European Association of Nuclear Medicine (EANM) Oncology Committee and the Sentinel European Node Trial (SENT) Committee

Ki-67 expression predicts locoregional recurrence in stage I oral tongue carcinoma

Oral tongue squamous cell carcinoma (OTSCC) is an aggressive cancer associated with poor prognosis. Methods for determining the aggressiveness of OTSCC from analysis of the primary tumour specimen are thus highly desirable. We investigated whether genomic instability and proliferative activity (by means of Ki-67 activity) could be of clinical use for prediction of locoregional recurrence in 76 pretreatment OTSCC paraffin samples (stage I, n=22; stage II, n=33; stage III, n=8; stage IV, n=13). Eleven surgical tumour specimens were also analysed for remnants of proliferative activity after preoperative radiotherapy. Ninety-seven percent of cases (n=72) were characterised as being aneuploid as measured by means of image cytometry. Preoperative radiotherapy (50–68 Gy) resulted in significant reduction of proliferative activity in all patients for which post-treatment biopsies were available (P-value=0.001). Proliferative activity was not associated with response to radiation in stage II patients. However, we report a significant correlation between high proliferation rates and locoregional recurrences in stage I OTSCC patients (P-value=0.028). High-proliferative activity is thus related to an elevated risk of recurrence after surgery alone. We therefore conclude that Ki-67 expression level is a potentially useful clinical marker for predicting recurrence in surgically treated stage I OTSCC

Automated Discovery of Food Webs from Ecological Data Using Logic-Based Machine Learning

Networks of trophic links (food webs) are used to describe and understand mechanistic routes for translocation of energy (biomass) between species. However, a relatively low proportion of ecosystems have been studied using food web approaches due to difficulties in making observations on large numbers of species. In this paper we demonstrate that Machine Learning of food webs, using a logic-based approach called A/ILP, can generate plausible and testable food webs from field sample data. Our example data come from a national-scale Vortis suction sampling of invertebrates from arable fields in Great Britain. We found that 45 invertebrate species or taxa, representing approximately 25% of the sample and about 74% of the invertebrate individuals included in the learning, were hypothesized to be linked. As might be expected, detritivore Collembola were consistently the most important prey. Generalist and omnivorous carabid beetles were hypothesized to be the dominant predators of the system. We were, however, surprised by the importance of carabid larvae suggested by the machine learning as predators of a wide variety of prey. High probability links were hypothesized for widespread, potentially destabilizing, intra-guild predation; predictions that could be experimentally tested. Many of the high probability links in the model have already been observed or suggested for this system, supporting our contention that A/ILP learning can produce plausible food webs from sample data, independent of our preconceptions about “who eats whom.” Well-characterised links in the literature correspond with links ascribed with high probability through A/ILP. We believe that this very general Machine Learning approach has great power and could be used to extend and test our current theories of agricultural ecosystem dynamics and function. In particular, we believe it could be used to support the development of a wider theory of ecosystem responses to environmental change

No Evidence for Immune Priming in Ants Exposed to a Fungal Pathogen

There is accumulating evidence that invertebrates can acquire long-term protection against pathogens through immune priming. However, the range of pathogens eliciting immune priming and the specificity of the response remain unclear. Here, we tested if the exposure to a natural fungal pathogen elicited immune priming in ants. We found no evidence for immune priming in Formica selysi workers exposed to Beauveria bassiana. The initial exposure of ants to the fungus did not alter their resistance in a subsequent challenge with the same fungus. There was no sign of priming when using homologous and heterologous combinations of fungal strains for exposure and subsequent challenges at two time intervals. Hence, within the range of conditions tested, the immune response of this social insect to the fungal pathogen appears to lack memory and strain-specificity. These results show that immune priming is not ubiquitous across pathogens, hosts and conditions, possibly because of immune evasion by the pathogen or efficient social defences by the host