Dynamics of a host–parasitoid interaction clarified by modelling and DNA sequencing

Abstract It has been hypothesised that the 2-year oscillations in abundance of Xestia moths are mediated by interactions with 1-year Ophion parasitoid wasps. We tested this hypothesis by modelling a 35-year time series of Xestia and Ophion from Northern Finland. Additionally, we used DNA barcoding to ascertain the species diversity of Ophion and targeted amplicon sequencing of their gut contents to confirm their larval hosts. Modelling of the time-series data strongly supported the hypothesised host?parasitoid dynamics and that periodic occurrence of Xestia moths is mediated by Ophion. DNA barcodes revealed that Ophion included five species rather than just one while targeted amplicon sequencing verified that Ophion does parasitise Xestia. At least one Ophion species employs 1-year Syngrapha interrogationis as an alternate host, but it did not detectably affect Xestia?Ophion dynamics. We also demonstrate the previously unrecognised complexity of this system due to cryptic parasitoid diversity.peerReviewe

Evolution of Massive Black Hole Binaries

We present the result of large-scale N-body simulations of the stellar-dynamical evolution of a massive black-hole binary at the center of a spherical galaxy. We focus on the dependence of the hardening rate on the relaxation timescale of the parent galaxy. A simple theoretical argument predicts that a binary black hole creates the ``loss cone'' around it. Once the loss cone is formed, the hardening rate is determined by the rate at which field stars diffuse into the loss cone. Therefore the hardening timescale becomes proportional to the relaxation timescale. Recent N-body simulations, however, have failed to confirm this theory and various explanations have been proposed. By performing simulations with sufficiently large N (up to $10^6$) for sufficiently long time, we found that the hardening rate does depend on N. Our result is consistent with the simple theoretical prediction that the hardening timescale is proportional to the relaxation timescale. This dependence implies that most massive black hole binaries are unlikely to merge within the Hubble time through interaction with field stars and gravitational wave radiation alone.Comment: Reviced version accepted for publication in ApJ. Scheduled to appear in the February 10, 2004 issu

Stellar Dynamics of Extreme-Mass-Ratio Inspirals

Inspiral of compact stellar remnants into massive black holes (MBHs) is accompanied by the emission of gravitational waves at frequencies that are potentially detectable by space-based interferometers. Event rates computed from statistical (Fokker-Planck, Monte-Carlo) approaches span a wide range due to uncertaintities about the rate coefficients. Here we present results from direct integration of the post-Newtonian N-body equations of motion descrbing dense clusters of compact stars around Schwarzschild MBHs. These simulations embody an essentially exact (at the post-Newtonian level) treatment of the interplay between stellar dynamical relaxation, relativistic precession, and gravitational-wave energy loss. The rate of capture of stars by the MBH is found to be greatly reduced by relativistic precession, which limits the ability of torques from the stellar potential to change orbital angular momenta. Penetration of this "Schwarzschild barrier" does occasionally occur, resulting in capture of stars onto orbits that gradually inspiral due to gravitational wave emission; we discuss two mechanisms for barrier penetration and find evidence for both in the simulations. We derive an approximate formula for the capture rate, which predicts that captures would be strongly disfavored from orbits with semi-major axes below a certain value; this prediction, as well as the predicted rate, are verified in the N-body integrations. We discuss the implications of our results for the detection of extreme-mass-ratio inspirals from galactic nuclei with a range of physical properties.Comment: 28 pages, 16 figures. Version 2 is significantly revised to reflect new insights into J and Q effects, to be published late

LYVE1 Marks the Divergence of Yolk Sac Definitive Hemogenic Endothelium from the Primitive Erythroid Lineage.

The contribution of the different waves and sites of developmental hematopoiesis to fetal and adult blood production remains unclear. Here, we identify lymphatic vessel endothelial hyaluronan receptor-1 (LYVE1) as a marker of yolk sac (YS) endothelium and definitive hematopoietic stem and progenitor cells (HSPCs). Endothelium in mid-gestation YS and vitelline vessels, but not the dorsal aorta and placenta, were labeled by Lyve1-Cre. Most YS HSPCs and erythro-myeloid progenitors were Lyve1-Cre lineage traced, but primitive erythroid cells were not, suggesting that they represent distinct lineages. Fetal liver (FL) and adult HSPCs showed 35%-40% Lyve1-Cre marking. Analysis of circulation-deficient Ncx1-/- concepti identified the YS as a major source of Lyve1-Cre labeled HSPCs. FL proerythroblast marking was extensive at embryonic day (E) 11.5-13.5, but decreased to hematopoietic stem cell (HSC) levels by E16.5, suggesting that HSCs from multiple sources became responsible for erythropoiesis. Lyve1-Cre thus marks the divergence between YS primitive and definitive hematopoiesis and provides a tool for targeting YS definitive hematopoiesis and FL colonization

Monte Carlo Simulations of Globular Cluster Evolution. III. Primordial Binary Interactions

We study the dynamical evolution of globular clusters using our 2D Monte Carlo code with the inclusion of primordial binary interactions for equal-mass stars. We use approximate analytical cross sections for energy generation from binary-binary and binary-single interactions. After a brief period of slight contraction or expansion of the core over the first few relaxation times, all clusters enter a much longer phase of stable "binary burning" lasting many tens of relaxation times. The structural parameters of our models during this phase match well those of most observed globular clusters. At the end of this phase, clusters that have survived tidal disruption undergo deep core collapse, followed by gravothermal oscillations. Our results clearly show that the presence of even a small fraction of binaries in a cluster is sufficient to support the core against collapse significantly beyond the normal core collapse time predicted without the presence of binaries. For tidally truncated systems, collapse is easily delayed sufficiently that the cluster will undergo complete tidal disruption before core collapse. As a first step toward the eventual goal of computing all interactions exactly using dynamical three- and four-body integration, we have incorporated an exact treatment of binary-single interactions in our code. We show that results using analytical cross sections are in good agreement with those using exact three-body integration, even for small binary fractions where binary-single interactions are energetically most important.Comment: Accepted for publication in ApJ. Minor changes to reflect accepted version. 28 pages, 17 figures; some figures low resolution. Full resolution paper available at http://www.mit.edu/~fregeau/paper3.pd

Effect of slow-release FSH on embryo recovery in dairy cows

AETE, Bath, UK, 8-9 September, 2017201

An across-breed validation study of 46 genetic markers in canine hip dysplasia

BackgroundCanine hip dysplasia (CHD) is a common disease, with a complex genetic background. Dogs with severe CHD sometimes also suffer from osteoarthritis (OA), an inflammatory, often painful and incurable condition. Previous studies have reported breed-specific genetic loci associated with different hip dysplasia and OA phenotypes. However, the independent replication of the known associations within or across breeds has been difficult due to variable phenotype measures, inadequate sample sizes and the existence of population specific variants.ResultsWe execute a validation study of 46 genetic markers in a cohort of nearly 1600 dogs from ten different breeds. We categorize the dogs into cases and controls according to the hip scoring system defined by the Federation Cynologique Internationale (FCI). We validate 21 different loci associated on fourteen chromosomes. Twenty of these associated with CHD in specific breeds, whereas one locus is unique to the across-breed study. We show that genes involved in the neddylation pathway are enriched among the genes in the validated loci. Neddylation contributes to many cellular functions including inflammation.ConclusionsOur study successfully replicates many loci and highlights the complex genetic architecture of CHD. Further characterisation of the associated loci could reveal CHD-relevant genes and pathways for improved understanding of the disease pathogenesis.Peer reviewe