Scalability of genetic biocontrols for eradicating invasive alien mammals

CRISPR-based gene drives offer novel solutions for controlling invasive alien species, which could ultimately extend eradication efforts to continental scales. Gene drives for suppressing invasive alien vertebrates are now under development. Using a landscape-scale individual-based model, we present the first estimates of times to eradication for long-lived alien mammals. We show that demography and life-history traits interact to determine the scalability of gene drives for vertebrate pest eradication. Notably, optimism around eradicating smaller-bodied pests (rodents and rabbits) with gene-drive technologies does not easily translate into eradication of larger-bodied alien species (cats and foxes).Aysegul Birand, Phillip Cassey, Joshua V. Ross, Paul Q. Thomas, Thomas A. A. Prows

Leveraging a natural murine meiotic drive to suppress invasive populations

Invasive rodents are a major cause of environmental damage and biodiversity loss, particularly on islands. Unlike insects, genetic biocontrol strategies including populationsuppressing gene drives with biased inheritance have not been developed in mice. Here, we demonstrate a gene drive strategy (tCRISPR) that leverages super-Mendelian transmission of the t haplotype to spread inactivating mutations in a haplosufficient female fertility gene (Prl). Using spatially explicit individual-based in silico modeling, we show that tCRISPR can eradicate island populations under a range of realistic field-based parameter values. We also engineer transgenic tCRISPR mice that, crucially, exhibit biased transmission of the modified t haplotype and Prl mutations at levels our modeling predicts would be sufficient for eradication. This is an example of a feasible gene drive system for invasive alien rodent population control.Luke Gierusa, Aysegul Birandc, Mark D. Buntinga, Gelshan I. Godahewa, Sandra G. Piltz Kevin P. Oh, Antoinette J. Piaggio, David W. Threadgill, John Godwin, Owain Edwards, Phillip Cassey, Joshua V. Ross, Thomas A. A. Prowse and Paul Q. Thoma

Three-stage lipid dynamics during development of planktotrophic echinoderm larvae

Published November 16The eggs of marine species with planktotrophic development must contain, at a minimum, sufficient material for production of a larva that can then sequester additional materials to grow and metamorphose successfully. In echinoderms, lipids perform crucial energy storage and structural functions during larval construction, but their roles during later development and metamorphosis are poorly understood. We investigated lipid-class depletion in early development and accumulation in late development and a lipid nutritional condition index (energetic lipid:sterol ratio) from the egg to the juvenile in the sea star Patiriella regularis and the sea urchin Heliocidaris tuberculata. Three phases were identified: (1) rapid depletion of energetic lipids during embryogenesis and the facultative feeding period (between feeding competence and exhaustion of energetic lipid reserves), (2) larval growth with no improvement in lipid nutritional condition, and (3) rapid lipid accumulation in advanced larvae prior to metamorphosis. Maternally derived energetic lipids were depleted more slowly in fed than unfed larvae but were still exhausted quickly. Patiriella regularis improved their lipid condition index during Phase 3 by accumulating energetic lipid (triacylglycerol [TAG], diacylglycerol ether [DAGE]) reserves that were then partially used to fuel settlement and metamorphosis. In contrast, Heliocidaris tuberculata did not accumulate TAG or DAGE during this phase, suggesting that metamorphosis is fuelled by other reserves, which we hypothesize may be phospholipids.Thomas A. A. Prowse, Mary A. Sewell, Maria Byrn

Gene drives for vertebrate pest control: realistic spatial modelling of eradication probabilities and times for island mouse populations

Invasive alien species continue to threaten global biodiversity. CRISPR-based gene drives, which can theoretically spread through populations despite imparting a fitness cost, could be used to suppress or eradicate pest populations. We develop an individual-based, spatially explicit, stochastic model to simulate the ability of CRISPR-based homing and X-chromosome shredding drives to eradicate populations of invasive house mice (Mus muculus) from islands. Using the model, we explore the interactive effect of the efficiency of the drive constructs and the spatial ecology of the target population on the outcome of a gene-drive release. We also consider the impact of polyandrous mating and sperm competition, which could compromise the efficacy of some gene-drive strategies. Our results show that both drive strategies could be used to eradicate large populations of mice. Whereas parameters related to drive efficiency and demography strongly influence drive performance, we find that sperm competition following polyandrous mating is unlikely to impact the outcome of an eradication effort substantially. Assumptions regarding the spatial ecology of mice influenced the probability of and time required for eradication, with short-range dispersal capacities and limited mate-search areas producing `chase' dynamics across the island characterised by cycles of local extinction and recolonization by mice. We also show that highly efficient drives are not always optimal, when dispersal and mate-search capabilities are low. Rapid local population suppression around the introduction sites can cause loss of the gene drive before it can spread to the entire island. We conclude that, although the design of efficient gene drives is undoubtedly critical, accurate data on the spatial ecology of target species is critical for predicting the result of a gene-drive release.Aysegul Birand, Phillip Cassey, Joshua V. Ross, James C. Russell, Paul Thomas, Thomas A. A. Prows

Author Correction: Effects of sampling effort on biodiversity patterns estimated from environmental DNA metabarcoding surveys (Scientific Reports, (2018), 8, 1, (8843), 10.1038/s41598-018-27048-2)

10.1038/s41598-019-43804-4Scientific Reports911589