Adaptive responses to cool climate promotes persistence of a non-native lizard

Successful establishment and range expansion of non-native species often require rapid accommodation of novel environments. Here, we use common-garden experiments to demonstrate parallel adaptive evolutionary response to a cool climate in populations of wall lizards (Podarcis muralis) introduced from southern Europe into England. Low soil temperatures in the introduced range delay hatching, which generates directional selection for a shorter incubation period. Non-native lizards from two separate lineages have responded to this selection by retaining their embryos for longer before oviposition-hence reducing the time needed to complete embryogenesis in the nest-and by an increased developmental rate at low temperatures. This divergence mirrors local adaptation across latitudes and altitudes within widely distributed species and suggests that evolutionary responses to climate can be very rapid. When extrapolated to soil temperatures encountered in nests within the introduced range, embryo retention and faster developmental rate result in one to several weeks earlier emergence compared with the ancestral state. We show that this difference translates into substantial survival benefits for offspring. This should promote short- and long-term persistence of non-native populations, and ultimately enable expansion into areas that would be unattainable with incubation duration representative of the native range

Using the spatial population abundance dynamics engine for conservation management

1. An explicit spatial understanding of population dynamics is often critical for effective management of wild populations. Sophisticated approaches are available to simulate these dynamics, but are largely either spatially homogeneous or agentbased, and thus best suited to small spatial or temporal scales. These approaches also often ignore financial decisions crucial to choosing management approaches on the basis of cost-effectiveness. 2. We created a user-friendly and flexible modelling framework for simulating these population issues at large spatial scales – the Spatial Population Abundance Dynamics Engine (SPADE). SPADE is based on the STAR model (McMahon et al. 2010) and uses a reaction-diffusion approach to model population trajectories and a cost-benefit analysis technique to calculate optimal management strategies over long periods and across broad spatial scales. It expands on STAR by incorporating species interactions and multiple concurrent management strategies, and by allowing full user control of functional forms and parameters. 3. We used SPADE to simulate the eradication of feral domestic cats Felis catus on sub-Antarctic Marion Island (Bester et al. 2002) and compared modelled outputs to observed data. The parameters of the best-fitting model reflected the conditions of the management programme, and the model successfully simulated the observed movement of the cat population to the southern and eastern portion of the island under hunting pressure. We further demonstrated that none of the management strategies would likely have been successful within a reasonable timeframe if performed in isolation. 4. SPADE is applicable to a wide range of population management problems, and allows easy generation, modification and analysis of management scenarios. It is a useful tool for the planning, evaluation and optimisation of the management of wild populations, and can be used without specialised training.Appendix S1. SPADE manual.Appendix S2. Details of algorithms used in SPADE.Appendix S3. Details of statistical models.Appendix S4. Source code for SPADE package.Appendix S5. Description of potential issues in using STAR.The development of SPADE was aided extensively by input from the Australian Alps National Parks Cooperative Management Programme’s Feral Horse Working Group, including participants from Parks Victoria, the NSW National Parks and Wildlife Service, the ACT Parks and Conservation Service and Forestry Corporation NSW.http://onlinelibrary.wiley.com/journal/10.1111/(ISSN)2041-210Xhb2017Mammal Research Institut

A comprehensive database of quality-rated fossil ages for Sahul\u27s Quaternary vertebrates

The study of palaeo-chronologies using fossil data provides evidence for past ecological and evolutionary processes, and is therefore useful for predicting patterns and impacts of future environmental change. However, the robustness of inferences made from fossil ages relies heavily on both the quantity and quality of available data. We compiled Quaternary non-human vertebrate fossil ages from Sahul published up to 2013. This, the FosSahul database, includes 9,302 fossil records from 363 deposits, for a total of 478 species within 215 genera, of which 27 are from extinct and extant megafaunal species (2,559 records). We also provide a rating of reliability of individual absolute age based on the dating protocols and association between the dated materials and the fossil remains. Our proposed rating system identified 2,422 records with high-quality ages (i.e., a reduction of 74%). There are many applications of the database, including disentangling the confounding influences of hypothetical extinction drivers, better spatial distribution estimates of species relative to palaeo-climates, and potentially identifying new areas for fossil discovery

Pdl1 Is a Putative Lipase that Enhances Photorhabdus Toxin Complex Secretion

The Toxin Complex (TC) is a large multi-subunit toxin first characterized in the insect pathogens Photorhabdus and Xenorhabdus, but now seen in a range of pathogens, including those of humans. These complexes comprise three protein subunits, A, B and C which in the Xenorhabdus toxin are found in a 4∶1∶1 stoichiometry. Some TCs have been demonstrated to exhibit oral toxicity to insects and have the potential to be developed as a pest control technology. The lack of recognisable signal sequences in the three large component proteins hinders an understanding of their mode of secretion. Nevertheless, we have shown the Photorhabdus luminescens (Pl) Tcd complex has been shown to associate with the bacteria's surface, although some strains can also release it into the surrounding milieu. The large number of tc gene homologues in Pl make study of the export process difficult and as such we have developed and validated a heterologous Escherichia coli expression model to study the release of these important toxins. In addition to this model, we have used comparative genomics between a strain that releases high levels of Tcd into the supernatant and one that retains the toxin on its surface, to identify a protein responsible for enhancing secretion and release of these toxins. This protein is a putative lipase (Pdl1) which is regulated by a small tightly linked antagonist protein (Orf53). The identification of homologues of these in other bacteria, linked to other virulence factor operons, such as type VI secretion systems, suggests that these genes represent a general and widespread mechanism for enhancing toxin release in Gram negative pathogens

From insect to man: Photorhabdus sheds light on the emergence of human pathogenicity

Photorhabdus are highly effective insect pathogenic bacteria that exist in a mutualistic relationship with Heterorhabditid nematodes. Unlike other members of the genus, Photorhabdus asymbiotica can also infect humans. Most Photorhabdus cannot replicate above 34°C, limiting their host-range to poikilothermic invertebrates. In contrast, P. asymbiotica must necessarily be able to replicate at 37°C or above. Many well-studied mammalian pathogens use the elevated temperature of their host as a signal to regulate the necessary changes in gene expression required for infection. Here we use RNA-seq, proteomics and phenotype microarrays to examine temperature dependent differences in transcription, translation and phenotype of P. asymbiotica at 28°C versus 37°C, relevant to the insect or human hosts respectively. Our findings reveal relatively few temperature dependant differences in gene expression. There is however a striking difference in metabolism at 37°C, with a significant reduction in the range of carbon and nitrogen sources that otherwise support respiration at 28°C. We propose that the key adaptation that enables P. asymbiotica to infect humans is to aggressively acquire amino acids, peptides and other nutrients from the human host, employing a so called “nutritional virulence” strategy. This would simultaneously cripple the host immune response while providing nutrients sufficient for reproduction. This might explain the severity of ulcerated lesions observed in clinical cases of Photorhabdosis. Furthermore, while P. asymbiotica can invade mammalian cells they must also resist immediate killing by humoral immunity components in serum. We observed an increase in the production of the insect Phenol-oxidase inhibitor Rhabduscin normally deployed to inhibit the melanisation immune cascade. Crucially we demonstrated this molecule also facilitates protection against killing by the alternative human complement pathway

Dynamical systems analysis of a model describing Tasmanian Devil Facial Tumour Disease

A susceptible–exposed–infectious theoretical model describing Tasmanian devil population and disease dynamics is presented and mathematically analysed using a dynamical systems approach to determine its behaviour under a range of scenarios. The steady states of the system are calculated and their stability analysed. Closed forms for the bifurcation points between these steady states are found using the rate of removal of infected individuals as a bifurcation parameter. A small-amplitude Hopf region, in which the populations oscillate in time, is shown to be present and subjected to numerical analysis. The model is then studied in detail in relation to an unfolding parameter which describes the disease latent period. The model’s behaviour is found to be biologically reasonable for Tasmanian devils and potentially applicable to other species. doi:10.1017/S144618111300001

An amoeba phagocytosis model reveals a novel developmental switch in the insect pathogen Bacillus thuringiensis

The Bacillus cereus group bacteria contain pathogens of economic and medical importance. From security and health perspectives, the lethal mammalian pathogen Bacillus anthracis remains a serious threat. In addition the potent insect pathogen Bacillus thuringiensis is extensively used as a biological control agent for insect pests. This relies upon the industrial scale induction of bacterial spore formation with the associated production of orally toxic Cry-toxins. Understanding the ecology and potential alternative developmental fates of these bacteria is therefore important. Here we describe the use of an amoeba host model to investigate the influence of environmental bactivorous protists on both spores and vegetative cells of these pathogens. We demonstrate that the bacteria can respond to different densities of amoeba by adopting different behaviours and developmental fates. We show that spores will germinate in response to factors excreted by the amoeba, and that the bacteria can grow and reproduce on these factors. We show that in low densities of amoeba, that the bacteria will seek to colonise the surface of the amoeba as micro-colonies, resisting phagocytosis. At high amoeba densities, the bacteria change morphology into long filaments and macroscopic rope-like structures which cannot be ingested due to size exclusion. We suggest these developmental fates are likely to be important both in the ecology of these bacteria and also during animal host colonisation and immune evasion

A model for the dynamics of Ross River Virus in the Australian environment

Ross River Disease is a mosquito-borne viral condition that affects pockets of the Australian human population, and can be debilitating in some instances. The evidence is that the virus reservoirs in marsupials, such as kangaroos, and this may account for the unpredictable outbreaks of the disease in humans. Accordingly, we present here a new model for the dynamics of Ross River Virus (RRV) in populations of mosquitoes and kangaroos. We calculate steady-state populations for the sub-groups in each species and demonstrate that naturally-occurring oscillations in the populations (limit cycles) do not occur. When seasonal forcing of vector populations and kangaroo birth rates is taken into account, however, the model may predict multi-annual outbreaks and chaos, perhaps explaining the unpredictability of some RRV disease epidemics, particularly across southern Australia. Detailed results in this case are presented