Biology subjects

Phillips, B. L.

Publications and source records attributed to Phillips, B. L..

3 recordsLinked to original sources

bioRxiv2018

Estimating the value of quarantine: eradicating invasive cane toads from tropical islands

O_LIIslands are increasingly used to protect endangered populations from the negative impacts of invasive species. Quarantine efforts are particularly likely to be undervalued in circumstances where a failure incurs non-economic costs. One approach to ascribe value to such efforts is by modeling the expense of restoring a system to its former state.\nC_LIO_LIUsing field-based removal experiments on two very different islands off northern Australia separated by > 400 km, we estimate cane toad densities, detection probabilities, and the resulting effort needed to eradicate toads from an island, and use these estimates to examine the financial benefit of cane toad quarantine across offshore islands prioritized for conversation management by the Australian federal government.\nC_LIO_LIWe calculate density as animals per km of freshwater shoreline, and find striking concordance of density across our two island study sites: a mean density of 353 [286, 446] individual toads per kilometer on one island, and a density of 366 [319, 343] on the second. Detection probability differed between the two islands.\nC_LIO_LIUsing a removal model and the financial costs incurred during toad removal, we estimate that eradicating cane toads would, on average, cost between $9444 (based on Horan Island; high detectability) and $18093 AUD (Indian Island; low detectability) per km of available freshwater shoreline.\nC_LIO_LIAcross islands that have been prioritized for conservation benefit within the toads predicted range, we provide an estimate of the value of toad quarantine on each island, and estimate the net value of quarantine efforts to be between $27.25 - $52.20 Million AUD. We explore a proposed mainland cane toad containment strategy - to prevent the spread of cane toads into the Pilbara Bioregion, and estimate its potential value to be between $33.79 - $64.74 M AUD.\nC_LIO_LISynthesis and applications. We present a modelling framework that can be used to estimate the value of preventative management, via estimating the length and cost of an eradication program. Our analyses suggest that there is substantial economic value in cane toad quarantine efforts across Australian offshore islands and a proposed mainland toad containment strategy.\nC_LI

ecology↗

bioRxiv2018

Resource-dependent dispersal and the irrelevance of extra-patch information for Daphnia carinata

Dispersal is fundamental to population dynamics and it is increasingly apparent that, despite most models treating dispersal as a constant, many organisms make dispersal decisions based upon information gathered from the environment. Ideally, organisms would make fully informed decisions, with knowledge of both intra-patch conditions (conditions in their current location) and extra-patch conditions (conditions in alternative locations). Acquiring information is energetically costly however, and extra-patch information will typically be costlier to obtain than intra-patch information. As a consequence, theory suggests that organisms will often make partially informed dispersal decisions, utilising intra-patch information only. We test this proposition in an experimental two-patch system using populations of the aquatic crustacean, Daphnia carinata. We manipulated conditions (food availability) in the populations home patch, and in its alternative patch. We found that D. carinata made use of intra-patch information (resource limitation in the home patch induced a ten-fold increase in dispersal probability) but made no use of extra-patch information (resource limitation in the alternative patch did not affect dispersal probability). Our work highlights the very large influence that information can have on dispersal probability, but also that dispersal decisions will often be made in only a partially informed manner. The magnitude of the response we observed also adds to the growing chorus that condition-dependence may be a significant driver of variation in dispersal.

ecology↗

bioRxiv2018

Evolution transforms pushed waves into pulled waves

Understanding the dynamics of biological invasions is crucial for managing numerous phenomena, from invasive species to tumours. Despite the breadth of application, and substantial theoretical development, invasions have proven difficult to predict. This may partly be due to an underappreciation of the interaction between the Allee effect (where individuals in low-density populations suffer lowered fitness) and evolution during invasions. Since invasion fronts are regions of perpetually low population density, selection should favour vanguard invaders that are resistant to Allee effects. Evolution in response to this pressure could cause invasions to transition from pushed waves, propelled by dispersal from behind the invasion front, to pulled waves, driven by the invasion vanguard. To examine this possibility, we construct an individual-based model in which a trait that governs resistance to the Allee effect evolves during an invasion. We find that vanguard invaders rapidly evolve resistance to the Allee effect, causing invasions to accelerate. This also results in invasions transforming from pushed waves into pulled waves; an outcome with important consequences for the predictability of invasion speed. These findings underscore the importance of accounting for evolution in invasion forecasts, and suggest that it has the capacity to fundamentally alter broader invasion dynamics.

ecology↗