Biology subjects

Phillips, B. L.

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

6 recordsLinked to original sources

bioRxiv2025

A neuron type-specific microexon in Ank3/ankyrin-G modulates calcium activity and neuronal excitability

Recent studies have revealed many alternative exons differentially spliced across diverse neuron types in the mammalian brain, but their links to neuronal physiology remain unclear. Here we characterize a deeply conserved microexon E35a in Ank3 encoding ankyrin-G (AnkG), a multifaceted adaptor protein best known as a master organizer of the axon initial segment (AIS) and as a leading genetic risk factor for bipolar disorder. E35a is predominantly skipped in cortical glutamatergic neurons but included in cortical GABAergic neurons and cerebellar neurons, which is dictated by multiple neuronal splicing factors. In E35a-deletion mice we generated, interneurons show increased excitability and somatic Ca2+ activity, without disruption in AIS. Biochemical analyses suggest that E35a inclusion facilitates AnkG interaction with a protein complex involving inositol trisphosphate receptors (InsP3Rs) important for intracellular Ca2+ signaling. Alternative splicing therefore allows AnkG to modulate neuron type-specific excitability in addition to its ubiquitous pan-neuronal role in organizing the AIS.

neuroscience↗

bioRxiv2025

Boring beetles and super models: mapping the distribution of a new invader

The impact of an invasive species is strongly influenced by the extent of its invaded range. Predicting the potential distribution of an invader is thus critical for informing decisions around surveillance, containment, and eradication. Such predictions ideally would come from a mechanistic species distribution model. These models directly describe how aspects of the environment affect organismal fitness, and may also provide insight into population dynamics, such as rates of population growth and spread. Here, we develop a temperature-dependent stage-structured population dynamic model for a globally significant invader, the polyphagous shot-hole borer (PSHB, Euwallacea fornicatus). We use this model to predict the beetles potential growth rate across its invaded range. Invasive PSHB causes serious damage to urban and agricultural trees, and so the continued expansion of its global distribution is a major concern. We synthesise previous studies to parameterise the model, yielding estimates of population growth as a function of daily temperatures within a host tree. We ran the model over one year using daily climate data across regions with invasive PSHB populations: South Africa, California, Israel and Australia. Our potential distribution maps indicate that PSHB currently occupies the most climatically suitable parts of California and Israel, but is yet to invade the most suitable regions in Australia and South Africa. The model shows the species is capable of very high population growth: in already-invaded locations, the average daily growth rate had an upper bound of [~] 0.05 (equivalent to population doubling in 14 days). Growth predictions were sensitive to the parameter for adult female mortality during between-host dispersal. This is an uncertain parameter (there is very little data available), but we estimated that for current populations to persist, the loss through dispersal mortality needs to be < 40%. We use our model to predict the maximum spread rate of PSHB (discounting transport by humans) to be 3 km/year. Our model provides insights into the spatial and temporal heterogeneity of invasion risk, which will assist global efforts to manage the ongoing invasion of this species.

ecology↗

bioRxiv2019

Trophic cascade driven by behavioural fine-tuning as naive prey rapidly adjust to a novel predator

AO_SCPLOWBSTRACTC_SCPLOWThe arrival of novel predators can trigger trophic cascades driven by shifts in prey numbers. Predators also elicit behavioural change in prey populations, via phenotypic plasticity and/or rapid evolution, and such changes may also contribute to trophic cascades. Here we document rapid demographic and behavioural changes in populations of a prey species (grassland melomys Melomys burtoni, a granivorous rodent) following the introduction of a novel marsupial predator (northern quoll Dasyurus hallucatus). Within months of quolls appearing, populations of melomys exhibited reduced survival and population declines relative to control populations. Quoll-invaded populations (n = 4) were also significantly shyer than nearby, quoll-free populations (n = 3) of conspecifics. This rapid but generalised response to a novel threat was replaced over the following two years with more threat-specific antipredator behaviours (i.e. predator-scent aversion). Predator-exposed populations, however, remained more neophobic than predator-free populations throughout the study. These behavioural responses manifested rapidly in avoidance of seeds associated with quoll scent, with discrimination playing out over a spatial scale of tens of metres. Presumably the significant and novel predation pressure induced by quolls drove melomys populations to fine-tune behavioural responses to be more predator-specific through time. These behavioural shifts could reflect individual plasticity (phenotypic flexibility) in behaviour or may be adaptive shifts from natural selection imposed by quoll predation. Our study provides a rare insight into the rapid ecological and behavioural shifts enacted by prey to mitigate the impacts of a novel predator and shows that trophic cascades can be strongly influenced by behavioural changed rates of seed predation by melomys across treatments. Quoll-invaded melomys populations exhibited lower per-capita seed take rates, and rapidly developed an as well as numerical responses.

ecology↗

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↗