Accelerated Evolution of Mitochondrial but Not Nuclear Genomes of Hymenoptera: New Evidence from Crabronid Wasps

Mitochondrial genes in animals are especially useful as molecular markers for the reconstruction of phylogenies among closely related taxa, due to the generally high substitution rates. Several insect orders, notably Hymenoptera and Phthiraptera, show exceptionally high rates of mitochondrial molecular evolution, which has been attributed to the parasitic lifestyle of current or ancestral members of these taxa. Parasitism has been hypothesized to entail frequent population bottlenecks that increase rates of molecular evolution by reducing the efficiency of purifying selection. This effect should result in elevated substitution rates of both nuclear and mitochondrial genes, but to date no extensive comparative study has tested this hypothesis in insects. Here we report the mitochondrial genome of a crabronid wasp, the European beewolf (Philanthus triangulum, Hymenoptera, Crabronidae), and we use it to compare evolutionary rates among the four largest holometabolous insect orders (Coleoptera, Diptera, Hymenoptera, Lepidoptera) based on phylogenies reconstructed with whole mitochondrial genomes as well as four single-copy nuclear genes (18S rRNA, arginine kinase, wingless, phosphoenolpyruvate carboxykinase). The mt-genome of P. triangulum is 16,029 bp in size with a mean A+T content of 83.6%, and it encodes the 37 genes typically found in arthropod mt genomes (13 protein-coding, 22 tRNA, and two rRNA genes). Five translocations of tRNA genes were discovered relative to the putative ancestral genome arrangement in insects, and the unusual start codon TTG was predicted for cox2. Phylogenetic analyses revealed significantly longer branches leading to the apocritan Hymenoptera as well as the Orussoidea, to a lesser extent the Cephoidea, and, possibly, the Tenthredinoidea than any of the other holometabolous insect orders for all mitochondrial but none of the four nuclear genes tested. Thus, our results suggest that the ancestral parasitic lifestyle of Apocrita is unlikely to be the major cause for the elevated substitution rates observed in hymenopteran mitochondrial genomes

Long telomeres are associated with clonality in wild populations of the fissiparous starfish Coscinasterias tenuispina

7 páginas, 4 figuras, 3 tablasTelomeres usually shorten during an organism’s lifespan and have thus been used as an aging and health marker. When telomeres become sufficiently short, senescence is induced. The most common method of restoring telomere length is via telomerase reverse transcriptase activity, highly expressed during embryogenesis. However, although asexual reproduction from adult tissues has an important role in the life cycles of certain species, its effect on the aging and fitness of wild populations, as well as its implications for the long-term survival of populations with limited genetic variation, is largely unknown. Here we compare relative telomere length of 58 individuals from four populations of the asexually reproducing starfish Coscinasterias tenuispina. Additionally, 12 individuals were used to compare telomere lengths in regenerating and non-regenerating arms, in two different tissues (tube feet and pyloric cecum). The level of clonality was assessed by genotyping the populations based on 12 specific microsatellite loci and relative telomere length was measured via quantitative PCR. The results revealed significantly longer telomeres in Mediterranean populations than Atlantic ones as demonstrated by the Kruskal–Wallis test (K=24.17, significant value: P-valueo0.001), with the former also characterized by higher levels of clonality derived from asexual reproduction. Telomeres were furthermore significantly longer in regenerating arms than in non-regenerating arms within individuals (pyloric cecum tissue: Mann–Whitney test, V=299, P-valueo10− 6; and tube feet tissue Student's t= 2.28, P-value =0.029). Our study suggests that one of the mechanisms responsible for the long-term somatic maintenance and persistence of clonal populations is telomere elongation.This research was financially supported by a PhD fellowship FPI-MICINN (BES-2011-044154) (ACG), the European ASSEMBLY project (227799), the Swedish Royal Academy of Sciences (ACG) and the Spanish Government project CTM2010-22218-C02. The research was also supported by a ‘Juan de la Cierva’ contract from the Spanish Government (RPP) and by the Adlerbertska Research Foundation (HNS).Peer reviewe

Increased Cardiovascular Reactivity to Acute Stress and Salt-Loading in Adult Male Offspring of Fat Fed Non-Obese Rats

Diet-induced obesity in rat pregnancy has been shown previously to be associated with consistently raised blood pressure in the offspring, attributed to sympathetic over-activation, but the relative contributions to this phenotype of maternal obesity versus raised dietary fat is unknown. Sprague-Dawley female rats were fed either a control (4.3% fat, n = 11) or lard-enriched (23.6% fat, n = 16) chow 10 days prior to mating, throughout pregnancy and lactation. In conscious adult (9-month-old) offspring cardiovascular parameters were measured (radiotelemetry). The short period of fat-feeding did not increase maternal weight versus controls and the baseline blood pressure was similar in offspring of fat fed dams (OF) and controls (OC). However, adult male OF showed heightened cardiovascular reactivity to acute restraint stress (p<0.01; Δ systolic blood pressure (SBP) and Δheart rate (HR)) with a prolonged recovery time compared to male OC. α1/β-adrenergic receptor blockade normalised the response. Also, after dietary salt-loading (8%-NaCl ad libitum for 1 week) male OF demonstrated higher SBP (p<0.05) in the awake phase (night-time) and increased low/high frequency ratio of power spectral density of HR variability versus OC. Baroreflex gain and basal power spectral density components of the heart rate or blood pressure were similar in male OF and OC. Minor abnormalities were evident in female OF. Fat feeding in the absence of maternal obesity in pregnant rats leads to altered sympathetic control of cardiovascular function in adult male offspring, and hypertension in response to stressor stimuli

Barcoding a Quantified Food Web: Crypsis, Concepts, Ecology and Hypotheses

The efficient and effective monitoring of individuals and populations is critically dependent on correct species identification. While this point may seem obvious, identifying the majority of the more than 100 natural enemies involved in the spruce budworm (Choristoneura fumiferana – SBW) food web remains a non-trivial endeavor. Insect parasitoids play a major role in the processes governing the population dynamics of SBW throughout eastern North America. However, these species are at the leading edge of the taxonomic impediment and integrating standardized identification capacity into existing field programs would provide clear benefits. We asked to what extent DNA barcoding the SBW food web would alter our understanding of the diversity and connectence of the food web and the frequency of generalists vs. specialists in different forest habitats. We DNA barcoded over 10% of the insects collected from the SBW food web in three New Brunswick forest plots from 1983 to 1993. For 30% of these specimens, we amplified at least one additional nuclear region. When the nodes of the food web were estimated based on barcode divergences (using molecular operational taxonomic units (MOTU) or phylogenetic diversity (PD) – the food web became much more diverse and connectence was reduced. We tested one measure of food web structure (the “bird feeder effect”) and found no difference compared to the morphologically based predictions. Many, but not all, of the presumably polyphagous parasitoids now appear to be morphologically-cryptic host-specialists. To our knowledge, this project is the first to barcode a food web in which interactions have already been well-documented and described in space, time and abundance. It is poised to be a system in which field-based methods permit the identification capacity required by forestry scientists. Food web barcoding provided an effective tool for the accurate identification of all species involved in the cascading effects of future budworm outbreaks. Integrating standardized barcodes within food webs may ultimately change the face of community ecology. This will be most poignantly felt in food webs that have not yet been quantified. Here, more accurate and precise connections will be within the grasp of any researcher for the first time

Evaluation of appendicitis risk prediction models in adults with suspected appendicitis

Background Appendicitis is the most common general surgical emergency worldwide, but its diagnosis remains challenging. The aim of this study was to determine whether existing risk prediction models can reliably identify patients presenting to hospital in the UK with acute right iliac fossa (RIF) pain who are at low risk of appendicitis. Methods A systematic search was completed to identify all existing appendicitis risk prediction models. Models were validated using UK data from an international prospective cohort study that captured consecutive patients aged 16–45 years presenting to hospital with acute RIF in March to June 2017. The main outcome was best achievable model specificity (proportion of patients who did not have appendicitis correctly classified as low risk) whilst maintaining a failure rate below 5 per cent (proportion of patients identified as low risk who actually had appendicitis). Results Some 5345 patients across 154 UK hospitals were identified, of which two‐thirds (3613 of 5345, 67·6 per cent) were women. Women were more than twice as likely to undergo surgery with removal of a histologically normal appendix (272 of 964, 28·2 per cent) than men (120 of 993, 12·1 per cent) (relative risk 2·33, 95 per cent c.i. 1·92 to 2·84; P < 0·001). Of 15 validated risk prediction models, the Adult Appendicitis Score performed best (cut‐off score 8 or less, specificity 63·1 per cent, failure rate 3·7 per cent). The Appendicitis Inflammatory Response Score performed best for men (cut‐off score 2 or less, specificity 24·7 per cent, failure rate 2·4 per cent). Conclusion Women in the UK had a disproportionate risk of admission without surgical intervention and had high rates of normal appendicectomy. Risk prediction models to support shared decision‐making by identifying adults in the UK at low risk of appendicitis were identified