Biology subjects

Davis, K. J.

Publications and source records attributed to Davis, K. J..

18 recordsLinked to original sources

bioRxiv2026

From Recovery to Risk: Intensifying ENSO Events Drive Extirpation Risk in a Marine Predator

Climate change poses a major threat to marine mammal populations, many of which remain vulnerable after years of overexploitation during the 17th to 20th centuries. Extreme climate events have grown in both frequency and severity in recent decades, and this trend is projected to accelerate under continued greenhouse gas emissions. Here, we assess how this intensification affects a top marine predator at the epicentre of extreme El Nino events - the Peruvian population of Otaria byronia (South American sea lion). We first apply a Bayesian population model that best predicts observed population dynamics to reconstruct female O. byronia population trends, estimate vital rates, and evaluate the effects of environmental drivers on survival and reproduction. We then use the same model to project extirpation risk under multiple future climate scenarios reflecting anticipated increases in both the intensity and frequency of extreme El Nino events. Our reconstruction reveals that the Peruvian O. byronia population has shown considerable resilience to episodic El Nino events over the past quarter-century, likely sustained by high female survival during normal and favourable years. However, under a scenario of moderate increases in El Nino frequency and intensity, the probability of extirpation over the next 50 years is 83.4% higher than under current conditions. As disturbance regimes intensify globally, we suggest that resilience-oriented management frameworks, grounded in species-specific demographic data and environmental context, as demonstrated here, will be essential for safeguarding marine mammal populations against an increasingly volatile climate.

ecology↗

bioRxiv2026

Life-history traits explain variation in the larval dispersal potential of corals

1. Protecting and restoring corals is critical to conserve marine biodiversity and ecosystem services in the Anthropocene. Knowledge of coral larval dispersal dynamics can be used to identify important sites for coral metapopulation connectivity and to spatially optimise coral conservation efforts. However, we know little regarding the larval dispersal of many coral species and our understanding of the relationships between coral larval dispersal and life-history traits (e.g., reproductive mode, colony morphology), phylogenetic relationships, and biogeography is incomplete. These knowledge gaps impede coral conservation. 2. In this research, we systematically reviewed the species, regions, and methodologies of studies of coral larval dispersal. Additionally, we conducted a meta-analysis to quantify the heterogeneity in reported coral larval duration values and identified the roles of life-history traits in driving that heterogeneity. 3. We found that various methods (experimental, biophysical modelling, and population genetics) were used to study 221 coral species across many regions. Soft and temperate corals received comparatively lower research attention. Our meta-analysis reveals that reproductive mode and colony morphology explain significant heterogeneity in larval settlement times, and that closely-related species have more similar larval settlement times. 4. Our findings suggest that reproductive mode and colony morphology could be used to predict larval duration in under-studied coral species, and that larval duration could be approximated from closely-related corals when trait data is unavailable. Our results support strategies focused on modelling differing larval durations across corals with different life-history traits to predict realised dispersal in under-studied coral species and identify conservation priority sites.

ecology↗

bioRxiv2026

Wildlife depredation stabilizes ecological-economic systems and can lead to improved economic outcomes

Human-wildlife conflicts over shared resources are often interpreted as direct competition, whereby resources consumed by wildlife are unavailable to people. Yet, individuals of wild populations can differ in their propensity to exploit resources, and the demographic, ecological, and economic consequences of such behavioural heterogeneity remain poorly understood. We developed an integrated demographic-bioeconomic model of Atlantic cod (Gadus morhua), grey seals (Halichoerus grypus), and a coastal gillnet fishery. Stage-structured population models incorporated density dependence, predator-prey interactions, adaptive harvesting, and transitions of adult seals into a bold, depredating state. We compared four scenarios of increasing complexity over 50 years across 100 coupled demographic realisations and examined sensitivity to the energetic contribution of depredated catch, harvest levels, and social amplification of depredation behaviour. Cod and seals persisted in all demographic realisations, supporting our ecological-persistence hypothesis. Contrary to our predictions, however, adding bold seals neither reduced long-term fishery performance nor destabilised the system. Median net present value was approximately three-fold greater in the full system than without depredation, and was greater in 76% of paired realisations. The full system was also the most temporally stable: median cod variability declined by 74% relative to the otherwise equivalent fishery without depredation, while seal variability declined by 45%. Behavioural depredation therefore altered predator population structure and imposed direct catch losses, but these effects were counterbalanced by indirect demographic feedbacks. Synthesis and applications. Depredating predators should not necessarily be viewed simply as competitors that reduce contested resources. Behavioural heterogeneity can introduce compensatory pathways that alter population stability and long-term economic outcomes. Management should therefore consider not only predator abundance and immediate catch losses, but also how harvest creates opportunities for behavioural change and how those changes propagate through coupled ecological-economic systems.

ecology↗

bioRxiv2026

Why are fishers retaining manta and devil ray bycatch?

Increasing fishing pressure, including from small-scale fisheries, has caused declines in more than one-third of all elasmobranch species. Tackling conservation issues in small-scale fisheries requires interdisciplinary approaches due to the coastal community's interdependence on marine resources. To support inclusive policy change and fisher engagement, an understanding of the motivations driving fishers' operational choices (i.e., the retention of elasmobranch bycatch) is needed. We assess the motivational drivers behind bycatch retention of one of the slowest-growing and most vulnerable elasmobranch groups, manta and devil rays (collectively, mobulids), through a case study in India, their largest fishery in the world. We conducted a best-worst scaling survey in the fishery-intensive states of Tamil Nadu and Andhra Pradesh, which make significant contributions to mobulid landings on India's east coast. Our results suggest that fishers exhibit varied motivations for retaining mobulid bycatch across states. Financial motivation to sell mobulids for additional revenue was the most important motivator for bycatch retention in both states. In Tamil Nadu, the top three motivators were all financially driven, whereas in Andhra Pradesh, the top three motivators included both financial and non-financial attributes, such as nutritional importance and storage optimisation. As the first socio-economic study of mobulid fisheries in India, we show that motivations underlying bycatch retention decisions vary geographically and may be influenced by cultural differences between states and the socio-economic characteristics of decision makers. Based on identified fisher motivations, we provide context-specific recommendations to align conservation strategies with the values fishers derive from the mobulid fishery and encourage participation in conservation. These include subsidies for net repair to encourage mobulid release; promotion of a minimum price measure for sustainably sourced alternative species; quality improvement of target species; and increased awareness of national and international regulatory obligations (e.g., CITES, CMS, IOTC).

ecology↗

bioRxiv2026

The emerging medium-scale: Prioritising fisheries management for elasmobranch conservation.

Fishing pressure has substantially increased over time and elasmobranchs are among the most vulnerable marine taxa impacted. 'Small-scale' and 'large-scale' are terms frequently used to describe fisheries, yet definitions used across the globe are inconsistent. The global impact of small-scale fisheries on elasmobranch decline is increasingly evident. However, ambiguous vessel-capacity classifications undermine effective conservation management. Technological advancements have led to the emergence of medium-capacity vessels that sit between small and large-scale classifications, creating regulatory gaps that increase bycatch impacts on vulnerable elasmobranchs. Beyond vessel size, the gear specificities and practices also affect interaction with species caught incidentally, and can alter bycatch risk for vulnerable elasmobranchs. Manta and devil rays (collectively, mobulids) represent a pelagic ray group that includes species listed as Critically Endangered with high risk of extinction, largely due to bycatch threats. To prioritise fisheries management for conservation, we assess the contribution of fishing gear specifications and practices to mobulid bycatch as a case study in their largest fishery globally. We use a Huber-robust extension to a Hurdle negative binomial model to assess the impact of fishery characteristics and operational specificities on mobulid bycatch risk. We find that within the Food and Agriculture Organization (FAO) of the United Nations' broad international fleet classification of small-scale vessels based on overall length ([≤]24 m), the 'medium-capacity vessels' in India are twice as likely to catch mobulids than small-scale vessels. Further, increased fishing intensity, measured in five-day increments, doubles mobulid bycatch risk. Our results indicate the emergence of a distinct medium-capacity fishery class in rapidly developing blue-economy nations, shaped by rising technological capacity and exemptions from large-scale management measures. We propose a comprehensive re-conceptualisation of small-scale fisheries to ensure that advanced medium-capacity vessels are subject to management measures commensurate with their bycatch impact. Our recommended re-conceptualisation is complementary to FAO's SSF characterisation matrix and would promote fishery-level sustainability and enable bycatch risk mitigation for elasmobranchs, including manta and devil rays. Further, for congruence between elasmobranch demography and regulations, we recommend that fisheries management measures distinguish vessel capacities for elasmobranch bycatch risk and apply biologically relevant regulations to the associated fisheries scale.

ecology↗

bioRxiv2026

No single measure is enough: Recovery of the Critically Endangered Mobula mobular requires integrated maximum bycatch mitigation and nursery area protection.

As anthropogenic threats have intensified over the past 500 years, we find ourselves in the midst of a sixth mass extinction, with continued losses of biodiversity threatening ecosystem stability. This biodiversity loss has caused species extinctions across taxa, and placed several others at high risk of functional extinction. These disturbance-driven impacts represent one of the most acute biodiversity crises facing global marine systems. Species exhibiting slow life histories characteristically have low resilience to disturbance. Here, we assess the risk of functional extinction and identify policy pathways for population recovery of the slow-living, Critically Endangered elasmobranch, the spinetail devil ray (Mobula mobular). We develop a stochastic, state-structured Integral Projection Model (IPM) parameterised with demographic data collected from fishery landings data in India, the world's largest mobulid fishery, and supplemented with data on vital rates from published literature. Using the IPM, we estimate that the population is declining at approximately 12% annually, experiencing substantial limiting pressure from fisheries overexploitation and failing to approach its biological maximum growth potential. Our results indicate that populations of M. mobular will be at high risk of functional extinction if 'business as usual' harvest scenario persists for another decade. We further show that long-term population recovery is only possible if survival increases significantly across all size classes, especially among large reproductive females, alongside a concurrent increase in fecundity. We conclude that no single policy measure is sufficient to recover population of M. mobular along the southeastern coast of India. Instead, combined protection through maximum bycatch mitigation and protection of nursery areas in no-take zones will be required for population recovery. This research demonstrates that recovery of overexploited populations often requires integrated resource management across life stages, and that the Critically Endangered M. mobular warrants urgent conservation action to avoid functional extinction.

ecology↗

bioRxiv2026

Host CD59 Potentiates the Type III Secretion System in Yersinia pseudotuberculosis

Type III secretion systems (T3SS) play critical roles in disease for many Gram-negative pathogens. Although the structural details of T3SS assembly have been extensively studied, the intimate interactions between T3SS components and the target host plasma membrane are poorly characterized. A previous RNA interference (RNAi) study identified the GPI-linked surface protein CD59 as a critical host component that supports the movement of Yersinia pseudotuberculosis (Yptb) T3SS effectors into the host cytosol. We show here that both depletion and increased levels of CD59 reduced Yptb T3SS pore formation and Yop translocation into host target cells. CD59 is unlikely to act as a receptor for the T3SS translocon, as physical blockade of CD59 or enzymatic removal of all GPI-linked surface proteins had no effect on T3SS function. Consistent with its importance in supporting T3SS function, efficient bacterial effector-mediated focal adhesion disassembly was dependent on CD59. Surprisingly, depletion of CD59 interfered with the rearrangement of the lipid raft marker GM1 that occurs after Yptb adhesion to host cells, indicating that CD59 supports lipid microdomain dynamics. Consistent with a role in modulating lipid composition, the loss of CD59 led to the accumulation of phosphatidylcholine and alterations in both fatty acid chain lengths and saturation levels. This work points to a role for CD59 in maintaining plasma membrane dynamics necessary for efficient T3SS translocon function. In addition, a polarization index is described that quantifies the asymmetric association of membrane compartments with organelles.

microbiology↗

bioRxiv2025

Support for the social buffering hypothesis, especially under unpredictable precipitation regimes

Sociality is hypothesised to buffer populations against environmental stochasticity by stabilising key vital rates, yet this has rarely been tested across diverse taxa. We compiled demographic time series from 87 populations for 66 animal species spanning 12 taxonomic classes to test whether sociality promotes demographic buffering and whether this relationship depends on environmental context. Using stochastic elasticities and phylogenetically comparative analyses, we find broad support for the social buffering hypothesis: more social species exhibit lower sensitivity of population growth to vital rate variance (lower stochastic elasticity to vital rate variances, |T{sigma}|), particularly in juvenile survival and reproduction. Contrary to expectations, juvenile vital rates, but not adult survival, showed the strongest buffering patterns in social taxa, suggesting life-stage-specific social mechanisms. Furthermore, we show that social species invest more in maximising the average performance of adult survival and reproduction (higher stochastic elasticity to vital rate means, T), consistent with adaptive strategies favouring canalisation of fitness-related traits. This buffering benefit is especially relevant in highly unpredictable environments: in climates with erratic precipitation, social species have greater demographic advantages, exhibiting even lower T{sigma} values. Together, these findings provide support for the social buffering hypothesis, especially in highly stochastic environments. Social traits confer some demographic stability under moderate climatic conditions, but may become more relevant under extreme stochasticity--an insight particularly important for understanding population resilience in a rapidly changing world.

animal behavior and cognition↗

bioRxiv2025

Poaching exacerbates the effects of climate change on the long-term viability of an endemic South African succulent plant species

O_LINatural populations often face multiple threats that jeopardise their viability, yet most population forecasts consider only single threats, such as shifts in precipitation or temperature. To better understand ecological and conservation challenges, incorporating multiple threats is essential. South African endemic dwarf succulents, for example, are under dual threats from climate change and illegal harvesting for the ornamental plant trade. C_LIO_LIWe developed a stochastic integral projection model (IPM) using demographic data from 1999-2003, for 4776 individuals of the dwarf succulent, Argyroderma pearsonii, to evaluate the impacts of climate change and harvesting on its short-term (<40 years) extinction risk and long-term viability. We built simulations to explore 90 scenarios combining climate conditions (historical, mild climate change [SSP126], and moderate climate change [SSP245]), harvesting methods (fruit harvesting, non-selective plant harvesting, or size-selective plant harvesting), and harvest frequencies (annual to once every decade). We supplemented our approach with perturbation analyses to identify critical demographic components influencing population persistence. C_LIO_LIWe show that historically A. pearsonii populations have been stable or growing. Populations are predicted to remain viable under mild climate change, but moderate climate change results in declines in approximately 50% of simulated populations, though extinctions are not projected within 40 years without harvesting. In contrast, plant harvesting significantly increases extinction risk, especially size-selective harvesting of mature individuals, which disrupts demographic components critical to population growth. Even harvesting as infrequently as once per decade under historical climates leads to declines, with climate change exacerbating these effects. C_LIO_LISynthesis: Illegal harvesting poses a critical threat to biodiversity, as shown in this case study of a South African endemic succulent. Our findings indicate that plant harvesting is unsustainable under any scenario, particularly with projected climatic pressures. However, fruit collection emerges as a potentially sustainable alternative to meet the ornamental plant trades demands. Our study highlights the importance of incorporating multiple threats into population forecasts, providing valuable tools for ecologists and conservation managers. C_LI

ecology↗

bioRxiv2024

Diseases and invasive species have synergistic effects with other anthropogenic threats on the functional and phylogenetic diversity in Testudines and Crocodilia

Understanding how multiple threats interact is crucial for the prioritization of conservation measures. Here, we investigate how interactions between six common threats (climate change, habitat disturbance, global trade, overconsumption, pollution, and emerging diseases/invasive species) affect the functional and phylogenetic diversity of 230 species of Testudines and 21 of Crocodilia. We classify two-way threat interactions into additive, synergistic, and antagonistic according to their effects on functional and phylogenetic diversity. Most threat interactions are antagonistic, the effect of threats jointly is lower than the sum of the effects of threats separately. However, we find that the interaction between emerging diseases or invasive species with other threats has synergistic and additive effects, meaning that the combined effects are greater or equal to the effects of threats separately. Our work can help target conservation strategies and detect key places to address multiple threats when they appear together.

ecology↗

bioRxiv2023

An unmanned aerial vehicle pipeline to estimate body volume at scale for ecological monitoring

O_LIDemographic data are essential to construct mechanistic models to understand how populations change over time and in response to global threats like climate change. Existing demographic data are either lacking or insufficient for many species, particularly those that are challenging to study, such as marine mammals. A pipeline for collecting accurate demographic data to construct robust demographic models at scale would fill this knowledge gap for many species, including marine mammals like pinnipeds (seals, sea lions, and walruses). C_LIO_LIWe introduce a non-invasive pipeline to estimate the 3D body size (volume) of species that will allow monitoring at high spatial and temporal scales. Our pipeline integrates 3D structure-from-motion photogrammetry data collected via planned flight missions using off-the-shelf, multirotor unmanned aerial vehicles (UAVs). We apply and validate this pipeline on the grey seal Halichoerus grypus, a marine species that spends much of its time at sea but is predictably observable during its annual breeding season. We investigate the optimal ground sampling distance (GSD) for surveys by calculating the success rates and accuracy of volume estimates of individuals at different elevations. C_LIO_LIWe establish an optimal GSD of 0.8 cm px-1 for animals similar in size to UK grey seals ([~]1.4 - 2.5 m length), making our pipeline reproducible and applicable to a broad range of organisms. Volume estimates were accurate and could be made for up to 68% of hauled-out seals in the study areas. Finally, we highlight six key traits that make a species well-suited to estimating body volume following this pipeline. Good candidates include large reptiles like crocodiles, large mammals such as hippopotamus, and shrubs or bushes in deserts and Mediterranean habitats. C_LIO_LIOur pipeline accurately estimates individual body volume of marine macrovertebrates in a time-and cost-effective manner whilst minimising disturbance. Whilst the approach is applied to pinnipeds here, the pipeline is adaptable to many different taxa that are otherwise challenging to study. Our proposed approach therefore opens up previously inaccessible areas of the Tree of Life to demographic studies, which will improve our ability to protect and conserve these species into the future. C_LI

ecology↗

bioRxiv2022

A meta-analysis of operational interactions between pinnipeds and fisheries

The global recovery of pinniped populations is a conservation success. However, pinniped population recovery has increased human-wildlife conflict with fisheries, an issue often reported and requiring management, but one that lacks global synthesis. We conduct a meta-analysis to estimate the impacts of operational interactions (specifically, lost catch) between pinnipeds and fisheries. Where quantifiable interactions are reported (n = 36), on average fishers have a 33.7% chance of interacting with pinnipeds on any given fishing day, and 13.8% lost catch. We find a large degree of heterogeneity between studies, with some fisheries experiencing much more negative interactions than others. Specifically, smaller-scale fisheries using nets are up to twice as likely to have negative interactions and lose up to five times more catch compared to large-scale fisheries. We conclude that pinniped-fishery conflict is a substantial global issue, but its impacts are not uniform. To successfully manage long-term coexistence between pinnipeds and humans, explicit data quantifying operational interactions is required. Population recoveries can have unintended consequences for fisheries, and management of ecological, social and economic outcomes is needed for long-term coexistence. TeaserPinniped population recoveries have led to significant impacts on fisheries, but small-scale fisheries lose out most.

zoology↗

bioRxiv2021

Human pressures filter out the less resilient demographic strategies in natural populations of plants and animals worldwide

Human activities are drastically reshaping Earths ecosystems. Across the tree of life, species become threatened and ultimately go extinct when they are unable to cope with these changes. Hence, understanding the resilience of natural populations is necessary to understand and predict species capacity to cope with increasing human pressures. Here, we use high-resolution demographic information for 921 populations of wild plants and animals to assess how they respond to increasing levels of human pressure. We show that fewer successful resilience strategies, allowing population to persist in disturb environments, exist in human-influenced habitats compared to pristine habitats. In contrast, pristine habitats host species with higher resistance and faster recovery than more altered environments. Importantly, the examined macroecologial patterns of demographic resilience are kingdom- and mobility-specific: natural populations of plants recover faster and have a propensity to grow faster after a disturbance (i.e., compensation) in urban areas than in pristine habitats, while these tendencies do not appear in animals. Likewise, populations of animals with limited mobility are less able to resist or compensate for disturbances in human altered environments than highly mobile populations. Our results suggest that human activities have eroded the diversity of natural populations resilience strategies. This finding implies that species will be less tolerant to disturbance in the future, as continuing biodiversity loss and increasing human impacts will ultimately shrink the spectrum of resilience strategies of organisms.

ecology↗

bioRxiv2021

Managed culls mean extinction for a marine mammal population when combined with extreme climate impacts

Human actions led to the worldwide decline of marine mammal populations in the 18th-19th centuries. However, the global uptake in protective legislation during the 20th century has recently allowed many marine mammal populations to recover. This positive trend is particularly true of pinnipeds (e.g., seals and sea lions), whose recovering populations are increasingly in conflict with fisheries. Many fisheries organisations call for managed culls of sea lion populations to reduce competition for target fish species as well as damage to catch and fishing gear through operational interactions. However, despite widespread perceptions that sea lion populations are generally increasing, to-date culls have been considered or implemented without quantitative evidence of their impacts on seal lion population viability. This knowledge gap is particularly concerning given the expected increase in extreme climate conditions, such as extreme El Nino events, which together with culls could push sea lion populations in some parts of the world into the extinction vortex. In this analysis, I develop and parameterise stochastic matrix population models of the South American sea lion (Otaria flavescens) to project the impact of (1) three cull scenarios with different intensity and temporal frequency targeting adult females, (2) extreme El Nino events whose frequency is modelled using a Markovian transition matrix, (3) and the interaction of culls and extreme climate events on population dynamics. I focus on the Chilean population of O. flavescens, where recent increases in sea lion numbers have triggered widespread conflict with small-scale fisheries, and where sea lion populations will increasingly be affected by extreme El Nino conditions. I find that sea lion populations decline below minimum viable population sizes under all scenarios involving culls and extreme climate events. By explicitly considering parameter uncertainty, this approach is a call to action for future research to focus on collecting stage-specific, annual population data to reduce uncertainty regarding marine mammal vital rates.

ecology↗

bioRxiv2020

Disconnects in global discourses - the unintended consequences of marine mammal protection on small-scale fishers

Globally, the populations of many marine mammals remain of critical concern after centuries of exploitation and hunting. However, some marine mammal populations (e.g. pinnipeds) have largely recovered from exploitation, and interactions between these species and fisheries--particularly small-scale fisheries--is once again of concern globally. The large scope and widespread scale of interactions highlights the local disconnect between two global policies: marine mammal conservation and small-scale fisheries protection. In this research, we explore these conflicting global policies by assessing the perceptions of coastal small-scale fishers in Peru and Chile regarding their interactions with pinnipeds, including the South American sea lion (Otaria flavescens) and South American fur seal (Arctocephalus australis). We surveyed 301 gill net fishers and assess perceptions using a best-worst scaling methodology. We find that fishers are chiefly concerned with the increase in pinniped populations, perceive that their interactions with pinnipeds have significantly increased over the past 80 years, and report pinniped-driven catch and income losses [≥] 26 per cent. Surprisingly, fishers do not believe that compensation schemes will resolve this issue--instead they overwhelmingly call for pinniped population culls. The reported number of pinnipeds illegally killed by fishers suggests the potential for large negative impacts on these protected species, and a loss of legitimacy in marine regulation. Collectively, our results portray a sense of marginalisation from fishers--that global policy treats them as less "important" than marine mammals. Our results highlight the increasing disconnect in global policy, which on one hand seeks to protect threatened marine mammal populations, and on the other seeks to promote the welfare of small-scale fishers.

ecology↗

bioRxiv2019

Severe Hyposmia Distinguishes Neuropathologically Confirmed Dementia with Lewy Bodies from Alzheimer’s Disease Dementia

Due to the absence of core clinical features, many subjects with neuropathologically-confirmed dementia with Lewy bodies (DLB) are never diagnosed as such during life. Most of these are diagnosed with Alzheimers disease dementia (ADD) or unspecified dementia. Unrecognized DLB therefore is a critical impediment to clinical studies and treatment trials of both ADD and DLB. There are numerous published studies that suggest that olfactory function tests may be able to differentiate some neurodegenerative conditions from each other and from normal subjects, but there are very few studies with neuropathological confirmation of diagnosis. We compared University of Pennsylvania Smell Identification Test (UPSIT) results in 209 subjects: 1) 29 concurrently meeting intermediate or high consensus clinicopathological criteria for both DLB and ADD 2) 96 meeting criteria for ADD without DLB 3) 84 control subjects that were non-demented and without parkinsonism at death. The DLB subjects had significantly lower (one-way ANOVA p < 0.0001, pairwise Bonferroni p < 0.05) first and mean UPSIT scores (13.7 and 13.2) than ADD (23.3 and 22.2) or controls (29.6 and 28.9). For subjects with first and mean UPSIT scores less than 20 and 17, respectively, Firth logistic regression analysis, adjusted for age, gender and mean MMSE score, conferred statistically significant odds ratios of 17.5 and 18.0 for predicting a DLB vs ADD diagnosis, as compared to 3.3 for the presence or absence of visual hallucinations throughout the clinical observation period. To our knowledge, this is the largest study to date comparing olfactory function in subjects with neuropathologically confirmed DLB and ADD. Olfactory function testing may be a convenient and inexpensive strategy for enriching dementia studies or clinical trials with DLB subjects, or conversely, reducing the inclusion of DLB subjects in ADD studies or trials.

neuroscience↗

bioRxiv2019

Ethanolamine regulates CqsR quorum-sensing signaling in Vibrio cholerae

The pathogen that causes cholera, Vibrio cholerae, uses the cell-cell communication process known as quorum sensing (QS) to regulate virulence factor production and biofilm formation in response to changes in population density and complexity. QS is mediated through the detection of extracellular chemical signals called autoinducers. Four histidine kinases, LuxPQ, CqsS, CqsR and VpsS, have been identified as receptors to activate the key QS regulator LuxO at low cell density. At high cell density, detection of autoinducers by these receptors leads to deactivation of LuxO, resulting in population-wide gene expression changes. While the cognate autoinducers that regulate the activity of CqsS and LuxQ are known, the signals that regulate CqsR have not been determined. Here we show that the common metabolite ethanolamine specifically interacts with the ligand-binding CACHE domain of CqsR in vitro and induces the high cell-density QS response through CqsR kinase inhibition in V. cholerae cells. We also identified residues in the CqsR CACHE domain important for ethanolamine detection and signal transduction. Moreover, mutations disrupting endogenous ethanolamine production in V. cholerae delay the onset of, but do not abolish, the high cell-density QS gene expression. Finally, we demonstrate that modulation of CqsR QS response by ethanolamine occurs inside animal hosts. Our findings suggest that V. cholerae uses CqsR as a dual-function receptor to integrate information from the self-made signals as well as exogenous ethanolamine as an environmental cue to modulate QS response.\n\nIMPORTANCEMany bacteria use quorum sensing to regulate cellular processes that are important for their survival and adaptation to different environments. Quorum sensing usually depends on the detection on chemical signals called autoinducers made endogenously by the bacteria. We show here ethanolamine, a common metabolite made by various bacteria and eukaryotes, can modulate the activity of one of the quorum-sensing receptors in Vibrio cholerae, the etiological agent of the disease cholera. Our results raise the possibility that V. cholerae or other quorum-sensing bacteria can combine environmental sensing and quorum sensing to control group behaviors.

microbiology↗

bioRxiv2019

Faster Cognitive Decline in Dementia due to Alzheimer Disease with Clinically Undiagnosed Lewy Body Disease

Neuropathology has demonstrated a high rate of comorbid pathology in dementia due to Alzheimers disease (ADD). The most common major comorbidity is Lewy body disease (LBD), either as dementia with Lewy bodies (AD-DLB) or Alzheimers disease with Lewy bodies (AD-LB), the latter representing subjects with ADD and LBD not meeting neuropathological distribution and density thresholds for DLB. Although it has been established that ADD subjects with undifferentiated LBD have a more rapid cognitive decline than those with ADD alone, it is still unknown whether AD-LB subjects, who represent the majority of LBD and approximately one-third of all those with ADD, have a different clinical course. Subjects with dementia included those with \"pure\" ADD (n = 137), AD-DLB (n = 64) and AD-LB (n = 114), all with two or more complete Mini Mental State Examinations (MMSE) and a full neuropathological examination. Linear mixed models assessing MMSE change showed that the AD-LB group had significantly greater decline compared to the ADD group ({beta} = -0.69, 95% CI: -1.05, -0.33, p<0.001) while the AD-DLB group did not ({beta} = -0.30, 95% CI: -0.73, 0.14, p = 0.18). Of those with AD-DLB and AD-LB, only 66% and 2.1%, respectively, had been diagnosed with LBD at any point during their clinical course. The probable cause of LBD clinical detection failure is the lack of a sufficient set of characteristic core clinical features. Core DLB clinical features were not more common in AD-LB as compared to ADD. Compared with clinically-diagnosed AD-DLB subjects, those that were clinically undetected had significantly lower prevalences of parkinsonism (p = 0.046), visual hallucinations (p = 0.0008) and dream enactment behavior (0.013). Clinical identification of ADD with LBD would allow stratified analyses of ADD clinical trials, potentially improving the probability of trial success.

neuroscience↗