NEO: non equilibrium sampling on the orbits of a deterministic transform

Sampling from a complex distribution π and approximating its intractable normalizing constant Z are challenging problems. In this paper, a novel family of importance samplers (IS) and Markov chain Monte Carlo (MCMC) samplers is derived. Given an invertible map T, these schemes combine (with weights) elements from the forward and backward Orbits through points sampled from a proposal distribution ρ. The map T does not leave the target π invariant, hence the name NEO, standing for Non-Equilibrium Orbits. NEO-IS provides unbiased estimators of the normalizing constant and self-normalized IS estimators of expectations under π while NEO-MCMC combines multiple NEO-IS estimates of the normalizing constant and an iterated sampling-importance resampling mechanism to sample from π. For T chosen as a discrete-time integrator of a conformal Hamiltonian system, NEO-IS achieves state-of-the art performance on difficult benchmarks and NEO-MCMC is able to explore highly multimodal targets. Additionally, we provide detailed theoretical results for both methods. In particular, we show that NEO-MCMC is uniformly geometrically ergodic and establish explicit mixing time estimates under mild conditions

How to combine N supply and biological control in low input systems

How to combine N supply and biological control in low input systemsHow to combine N supply and biological control in low input system

Host Niches and Defensive Extended Phenotypes Structure Parasitoid Wasp Communities

Oak galls are spectacular extended phenotypes of gallwasp genes in host oak tissues and have evolved complex morphologies that serve, in part, to exclude parasitoid natural enemies. Parasitoids and their insect herbivore hosts have coevolved to produce diverse communities comprising about a third of all animal species. The factors structuring these communities, however, remain poorly understood. An emerging theme in community ecology is the need to consider the effects of host traits, shaped by both natural selection and phylogenetic history, on associated communities of natural enemies. Here we examine the impact of host traits and phylogenetic relatedness on 48 ecologically closed and species-rich communities of parasitoids attacking gall-inducing wasps on oaks. Gallwasps induce the development of spectacular and structurally complex galls whose species- and generation-specific morphologies are the extended phenotypes of gallwasp genes. All the associated natural enemies attack their concealed hosts through gall tissues, and several structural gall traits have been shown to enhance defence against parasitoid attack. Here we explore the significance of these and other host traits in predicting variation in parasitoid community structure across gallwasp species. In particular, we test the ‘‘Enemy Hypothesis,’’ which predicts that galls with similar morphology will exclude similar sets of parasitoids and therefore have similar parasitoid communities. Having controlled for phylogenetic patterning in host traits and communities, we found significant correlations between parasitoid community structure and several gall structural traits (toughness, hairiness, stickiness), supporting the Enemy Hypothesis. Parasitoid community structure was also consistently predicted by components of the hosts’ spatiotemporal niche, particularly host oak taxonomy and gall location (e.g., leaf versus bud versus seed). The combined explanatory power of structural and spatiotemporal traits on community structure can be high, reaching 62% in one analysis. The observed patterns derive mainly from partial niche specialisation of highly generalist parasitoids with broad host ranges (.20 hosts), rather than strict separation of enemies with narrower host ranges, and so may contribute to maintenance of the richness of generalist parasitoids in gallwasp communities. Though evolutionary escape from parasitoids might most effectively be achieved via changes in host oak taxon, extreme conservatism in this trait for gallwasps suggests that selection is more likely to have acted on gall morphology and location. Any escape from parasitoids associated with evolutionary shifts in these traits has probably only been transient, however, due to subsequent recruitment of parasitoid species already attacking other host galls with similar trait combinations

Adolescent psychopathy and the five factor model: domain and facet analysis

Given the consideration of callousness as a specifier for Conduct Disorder in the DSM-V, it seems imperative that researchers continue to investigate this personality style in adolescents to determine both its applicability and utility. The present study examined the Youth Psychopathic traits Inventory (YPI; Andershed et al. 2002) and the Interpersonal Adjective Scale Revised-Big 5 (IASR-B5; Trapnell and Wiggins 1990a, b) psychopathy scales in relation to the Five Factor Model (FFM) of personality. Using a sample of adolescent offenders (N  = 145), the YPI and IASR-B5 psychopathy scales showed adequate reliability and strong inverse bivariate relations with the FFM domains of Agreeableness (−A) and Conscientiousness (−C). Multivariate analyses, at the facet level, revealed that Tendermindedness (−A) and Assertiveness (+E) explained the association between FFM facets and the YPI, whereas Altruism (−A), Modesty (−A), Straightforwardness (−A), Assertiveness (+E), Warmth (−E), and Deliberation (+C) all uniquely contributed to the IASR-B5 psychopathy scale. Both measures were linked with general and violent recidivism. The authors discuss the implications of these findings in terms of the use of personality to help describe conduct problem youth and the need for future research in this important area