Macquarie University

About: Macquarie University is a education organization based out in Sydney, New South Wales, Australia. It is known for research contribution in the topics: Population & Laser. The organization has 14075 authors who have published 47673 publications receiving 1416184 citations. The organization is also known as: Macquarie uni.

Abundance of macrofauna in dense seagrass is due to habitat preference, not predation.

Abstract: Two main hypotheses compete to explain why prey abundance decreases when seagrass density is reduced. One proposes that predators are more successful amongst seagrass of lower density; the other invokes habitat choice by prey. We reduced the density of seagrass in the presence, and in the absence, of predators in a field experiment to discriminate between these hypotheses. When seagrass was manipulated abundances of all six prey species decreased simultaneously both in the presence and in the absence of predators. We conclude that correlations of prey abundance and shoot density within a seagrass bed are proximately due to habitat preference of dense seagrass by prey. We report another experiment which supports this conclusion and shows that habitat preference is exercised at the earliest opportunity. However, the habitat preferences may have been selected by predation pressure.

The timing of autumn senescence is affected by the timing of spring phenology: implications for predictive models

Abstract: Autumn senescence regulates multiple aspects of ecosystem function, along with associated feedbacks to the climate system. Despite its importance, current understanding of the drivers of senescence is limited, leading to a large spread in predictions of how the timing of senescence, and thus the length of the growing season, will change under future climate conditions. The most commonly held paradigm is that temperature and photoperiod are the primary controls, which suggests a future extension of the autumnal growing season as global temperatures rise. Here, using two decades of ground- and satellite-based observations of temperate deciduous forest phenology, we show that the timing of autumn senescence is correlated with the timing of spring budburst across the entire eastern United States. On a year-to-year basis, an earlier/later spring was associated with an earlier/later autumn senescence, both for individual species and at a regional scale. We use the observed relationship to develop a novel model of autumn phenology. In contrast to current phenology models, this model predicts that the potential response of autumn phenology to future climate change is strongly limited by the impact of climate change on spring phenology. Current models of autumn phenology therefore may overpredict future increases in the length of the growing season, with subsequent impacts for modeling future CO2 uptake and evapotranspiration.

Genetic structure of an aphid studied using microsatellites: cyclic parthenogenesis, differentiated lineages and host specialization

Abstract: In a previous study, samples of the grain aphid Sitobion avenae (F.) were collected from wheat and adjacent cocksfoot hosts in a population thought to be primarily parthenogenetic, and DNA from individual aphids was analysed with a multilocus technique. Here we have applied single-locus microsatellites and a mitochondrial DNA marker to a subset of the same DNA extracts, and have made several additional inferences about important genetic and population processes in S. avenae. Microsatellite analysis indicated very high levels of genic and genotypic variation. S. avenae fell into three genotypic groups inferred to be almost noninterbreeding, while analysis of linkage and Hardy-Weinberg equilibria suggested high levels of sexual recombination within each genotypic group. Host specialization was evident: one lineage was found only on wheat, and one (bearing many alleles inferred to be introgressed from the blackberry-grass aphid S. fragariae (Walker)) was found only on cocksfoot. The third group of interrelated genotypes was found commonly on both hosts. Although most genotypes were found only once, some were much more numerous in the sample than expected from the frequency of the alleles they contained. This, and rapid temporal changes in genotypic composition of samples, indicates strong selective differences between genotypes and lineages. In the major genotypic group, the commonest genotypes were significantly more homozygous than were rare ones: thus these data may help to explain the frequent observation of homozygous excess in aphid allozymes. The genotype group showing S. avenae-like as well as S. fragariae-like alleles also carried S. fragariae-like mitochondrial DNA in at least 25/31 cases, indicating gender-asymmetrical hybridization.

Genetic Management of Fragmented Animal and Plant Populations

Abstract: This is the concise version of the authoritative text book on the same subject (Frankham et al. 2017). To call it ‘The Big Dummy’s Guide’ to this discipline would diminish the significance, relevance and importance of this work. It has beenwritten for, but not limited to, students and practitioners (including administrators) of wildlife management. It has comprehensively condensed the most up to date studies in conservation genetics and presents them with actual examples in elegantly digestible clarity for those who may not have the time to pursue this complex discipline to a professional level. In the Preface, and at the back cover of the book, the authors have laid out and elaborated on the reasons for addressing this long overdue topic. They identified the need for a paradigm shift among inand ex-situ wildlife managers and breeders, from their ill-informed and unwarranted avoidance of encouraging and maintaining gene flows for fear of outbreeding depression. They emphasise the urgent need to embrace a more enlightened and holistic approach to encourage heterosis – to increase and enhance reproductive vigour and heterogeneity. It’s all in the definition of biological species. If you have this Guide, and by now some of the uniquely genetic terminologies, such as ‘effective population size’, are starting to bother you; there is a comprehensive glossary provided for your convenience. This book contains nine chapters and a list of take-home messages emphasising the need for re-establishing or establishing gene flow in fragmented populations and that inaction is usually more harmful to small populations than any attempt at genetic rescue. The Introduction goes through the FAQs on the subject from a list of mathematical symbols with cross references and the IUCN definitions of endangeredness to the genetic consequences for small fragmented populations from global climate change. I also found the Appendix that is available on-line useful and informative. Chapters provide figures and boxes with exquisite graphics for your enjoyment as you plough through and digest the various complex genetics concepts and principles in thoughtfully well laid out chapters. The publication of this Guide is particularly timely. With the recent extensive natural disasters occurring globally, I can only hope that returning to ‘business as usual’ is no longer an acceptable option. Chapter 9 goes into the effects of climate change and emphasises the imperatives for genetic management for increasingly fragmented and isolated populations. Since this book was launched, this urgency has been elevated to a critical level on the Australian continent as over 18 million hectares of land, representing some of the most iconic terrestrial ecosystems, has been lost to bush fires – and with diminished surviving wild plant and animal populations now even more fragmented and isolated. I recommend this Guide to anyone who has any interest in breeding or managing wildlife in this challenging time. The message: you need to, and have to, also consider the genetics.