Biology subjects

McGeoch, M. A.

Publications and source records attributed to McGeoch, M. A..

15 recordsLinked to original sources

bioRxiv2026

Moisture structures litter faunal communities through productivity and trait filtering effects

Litter invertebrates mediate a substantial proportion of decomposition and nutrient cycling in terrestrial ecosystems, yet how moisture availability structures their communities remains poorly understood. We propose that moisture availability could shape litter faunal communities through two alternate pathways: (1) a productivity effect: greater productivity and detrital inputs in wetter forests should increase litter-faunal abundance, (2) a trait effect: phylogenetic differences in water balance should filter communities according to taxon-specific moisture tolerances. We tested these expectations across 100 forest sites spanning a moisture gradient in south-eastern Australia, from dry sclerophyll forest to cool temperate rainforest. Measuring 11 focal invertebrate taxa, total litter-faunal abundance increased threefold across the moisture gradient, from 400,000 individuals per hectare of dry forest to 1.2 million individuals per hectare of rainforest - consistent with greater resource availability in wetter and more productive habitats. However, this overall abundance trend masked pronounced variation in community composition across habitat types. While moisture-sensitive crustaceans and myriapods (particularly Isopoda and Chilopoda) were concentrated in rainforest litter, two groups of hexapods (Blattodea and Embioptera) were most abundant in dry forest litter and declined sharply toward rainforest habitat. These contrasting responses indicate that dry forests do not simply represent depauperate versions of wet-forest communities but harbour their own distinct and abundant litter invertebrate assemblages. Thus, moisture structures litter faunal communities via both proposed mechanisms: (1) a productivity effect and (2) a trait filtering effect. Given that moisture fundamentally structures litter faunal communities, shifts in forest moisture regimes under climate change may substantially alter detritivore communities, with consequences for decomposition processes and nutrient cycling globally.

ecology↗

bioRxiv2026

Revealing the Widespread Bias of Extinction Risk in the Antarctic and the Southern Ocean

Accelerating environmental change in the Antarctic and Southern Ocean (ASO) necessitates robust extinction risk assessments to inform conservation priorities and track progress towards global biodiversity targets. Nevertheless, no systematic, region-wide baseline of extinction risk currently exists for tracking ASO biodiversity responses to ongoing change, a significant barrier to global biodiversity monitoring. Here, we present the first comprehensive synthesis of extinction risk knowledge spanning plants, animals, and fungi across the ASO, examining biases in current assessments, the distribution of Threatened species and their associated threats. In the absence of a complete regional species checklist, species were compiled from >6,800,000 occurrences and existing checklists, yielding 5,403 assessments representing 2,806 species using a data-inclusive workflow that increased available assessments by over three-fold. Assessments are heavily biased towards vertebrates (56% assessed), while invertebrates, despite their ecological prevalence, are markedly underrepresented (4% assessed). Among vertebrates, mammals have the highest proportion of Threatened species (35%), while ASO birds are disproportionately Threatened (27%) compared to the global average (12%) with the greatest threat for ASO species being Biological Resource Use. Despite more Threatened species in the sub-Antarctic islands and the Antarctic Peninsula, relative to assessment effort, these regions had fewer Threatened species than expected, indicating these areas may function as refugia. These pronounced assessment biases highlight the need for more balanced, representative, and data-inclusive extinction risk assessments to be able to effectively detect conservation status change. This work represents an important step in ensuring ASO representation in global biodiversity monitoring frameworks strengthening the capacity of these frameworks to detect, attribute, and respond to future biodiversity changes.

ecology↗

bioRxiv2025

Resilient Antarctic soil bacteria consume trace gases across wide temperature ranges

Polar desert soils host diverse microbial communities despite limited nutrients and frequent temperature and light fluctuations. Adapting to these extremes, most bacteria possess high-affinity hydrogenases and carbon monoxide dehydrogenases, enabling them to use atmospheric trace gases such as hydrogen (H2) and carbon monoxide (CO) to generate energy and fix carbon. Despite the foundational importance of this process in polar desert ecosystems, little is known about the thermal sensitivity of trace gas oxidation or how this process will respond to climate warming. Here, we show through in situ and ex situ incubations that H2 consumption is an exceptionally thermally resilient process that can occur from -20 to +75{degrees}C, at rates comparable to temperate ecosystems (peaking at 8.56 nmol H2 h-1 g dry soil-1 at 25{degrees}C). Temperature ranges of CO (-20 to 42{degrees}C) and CH4 (-20 to 30{degrees}C) oxidation are also wider than expected, though the pattern of thermal sensitivity conforms with general theory. Metagenomic analyses support these data, revealing that atmospheric H2 and CO oxidisers are widespread, diverse, and abundant, and suggesting most Antarctic bacteria function below their temperature optima for these processes. Modelling of seasonal temperatures across ice-free Antarctica under current and future emissions scenarios indicates that H2 and CO oxidation can occur year-round, increasing by up to 35% or 44%, respectively, by 2100. Our results indicate constitutive aerotrophic activity contributing to Antarctic ecosystem functioning and biodiversity across spatial and temporal scales, with further studies required to understand how it interacts with photosynthesis in a changing climate.

microbiology↗

bioRxiv2024

Antarctic biosecurity policy effectively manages the rates of alien introductions

Reducing the rates and impacts of biological invasions is a major policy goal of international biodiversity agreements. Yet the extent to which this goal is being achieved and the agreements hence successful in this respect remains unclear. Here we use a comprehensive record of alien species introduction in the terrestrial Antarctic, including its surrounding Southern Ocean Islands, spanning 115 years (1900-2015), to quantify the impact of biosecurity policy on alien species introduction rates in the region, where invasive alien species are a primary environmental conservation threat and management priority. We show that although many parts of the Antarctic have been colonised by non-indigenous taxa, recent rates of introduction appear to be slowing or static in most parts, compared with increases in the past. Our results vindicate the regional Antarctic focus on biosecurity measures, but also demonstrate the need for stricter enforcement due to rapid socio-environmental changes. Three key pointsO_LIBiological invasions present a large and growing threat to Antarctic ecosystems under climate change and expanding human activity C_LIO_LIOver the 20th century, there was no trend in alien species introduction rate in five Antarctic regions and a significantly increasing trend in the remaining five regions C_LIO_LIDespite this variation, in most regions, the number of introductions remains low, indicating that Antarctic biosecurity has been effective at slowing the rate of introduction C_LI

ecology↗

bioRxiv2024

Microbial aerotrophy enables continuous primary production in diverse cave ecosystems

Most aerated cave ecosystems are assumed to be oligotrophic given they receive minimal inputs of light energy. Diverse microorganisms have nevertheless been detected within caves, though it remains unclear what strategies enable them to meet their energy and carbon needs. Here we determined the processes and mediators of primary production in aerated limestone and basalt caves through paired metagenomic and biogeochemical profiling. Based on 1458 metagenome-assembled genomes, over half of microbial cells in caves encode enzymes to use atmospheric trace gases as energy and carbon sources. The most abundant microbes in these systems are chemosynthetic primary producers, notably the novel gammaproteobacterial methanotrophic order Ca. Methylocavales and two uncultivated actinobacterial genera predicted to grow on atmospheric hydrogen, carbon dioxide, and carbon monoxide. In situ and ex situ biogeochemical and isotopic measurements consistently confirmed that these gases are rapidly consumed at rates sufficient to meet community-wide energy needs and drive continual primary production. Conventional chemolithoautotrophs, which use trace lithic compounds such as ammonium and sulfide, are also enriched and active alongside these trace gas scavengers. These results indicate that caves are unique in both their microbial composition and the biogeochemical processes that sustain them. Based on these findings, we propose caves are the first known ecosystems where atmospheric trace gases primarily sustain growth rather than survival and define this process as aerotrophy. Cave aerotrophy may be a hidden process supporting global biogeochemistry.

microbiology↗

bioRxiv2023

A kernel integral method to remove biases in estimating trait turnover

O_LITrait diversity, including trait turnover, that differentiates the roles of species and communities according to their functions, is a fundamental component of biodiversity. Accurately capturing trait diversity is crucial to better understand and predict community assembly, as well as the consequences of global change on community resilience. Existing methods to compute trait turnover have limitations. Trait space approaches based on minimum convex polygons only consider species with extreme trait values. Tree-based approaches using dendrograms consider all species but distort trait distance between species. More recent trait space methods using complex polytopes try to harmonise the advantages of both methods, but their current implementation have mathematical flaws. C_LIO_LIWe propose a new kernel integral method (KIM) to compute trait turnover, based on the integration of kernel density estimators (KDEs) rather than using polytopes. We explore how this difference and the computational aspects of the KDE computation can influence the estimates of trait turnover. We compare our novel method to existing ones using justified theoretical expectations for a large number of simulations in which we control the number of species and the distribution of their traits. We illustrate the practical application of KIM using plant species introduced to the Pacific Islands of French Polynesia. C_LIO_LIAnalyses on simulated data show that KIM generates results better aligned with theoretical expectations than other methods and is less sensitive to the total number of species. Analyses for French Polynesia data also show that different methods can lead to different conclusions about trait turnover, and that the choice of method should be carefully considered based on the research question. C_LIO_LIMathematical aspects for computing trait turnover are crucial as they can have important effects on the results and therefore lead to different conclusions. Our novel kernel integral method generates values that better reflect the distribution of species in the trait space than other existing methods. We therefore recommend using KIM in future studies on trait turnover. In contrast, tree-based approaches should be kept for phylogenetic diversity, as phylogenetic trees will then reflect the constrained speciation process. C_LI

ecology↗

bioRxiv2022

Invasive alien insects represent a clear but variable threat to biodiversity

Invasive alien insects as a driver of biodiversity change are an important yet understudied component of the general threat of biological invasions. The environmental impacts of invasive alien insects are varied and widespread, with evidence to suggest that an insect species global maximum impact is likely to increase in severity as it increases its non-native distribution. Two potential explanations are that large geographic distributions include environmental heterogeneity and increase resource availability, or that there are intrinsic factors of widely-spread species that also facilitate greater impacts. Determining which explanation is more likely, and developing a more comprehensive and general understanding of the environmental impacts of invasive alien species, can be assisted by addressing the information shortfalls highlighted in this research.

ecology↗

bioRxiv2022

The Global Register of Introduced and Invasive Species: Country Compendium

The Country Compendium of the Global Register of Introduced and Invasive Species (GRIIS) is a collation of data across 196 individual country checklists of alienspecies, along with a designation of those species with evidence of impact at a country level. The Compendium provides a baseline for monitoring the distribution and invasion status of all major taxonomic groups, and can be used for the purpose of global analyses of Introduced (alien, non-native, exotic) and Invasive species (invasive alien species), including regional, single and multi-species taxon assessments and comparisons. It enables exploration of gaps and inferred absences of species for countries, and provides a means for short to medium term refinement of GRIIS Checklists. The Country Compendium is, for example, instrumental, along with data on first records of introduction, for assessing and reporting on invasive alien species targets, including for the Convention on Biological Diversity and Sustainable Development Goals. The GRIIS Country Compendium provides a baseline and mechanism for tracking the spread of introduced and invasive alien species across countries globally. O_TBL View this table: org.highwire.dtl.DTLVardef@eb30fdorg.highwire.dtl.DTLVardef@dd338aorg.highwire.dtl.DTLVardef@62b8daorg.highwire.dtl.DTLVardef@1561763org.highwire.dtl.DTLVardef@119988e_HPS_FORMAT_FIGEXP M_TBL C_TBL

ecology↗

bioRxiv2021

G-IRAE: a Generalised approach for linking the total Impact of invasion to species' Range, Abundance and per-unit Effects

The total impact of an alien species was conceptualised as the product of its range size, local abundance and per-unit effect in a seminal paper by Parker and colleagues in 1999, but a practical approach for estimating the three components has been lacking. Here, we generalise the impact formula and, through use of regression models, estimate the relationship between the three components of impact, an approach we term G-IRAE (Generalised Impact - Range size - Abundance - per-unit Effect). Moreover, we show that G-IRAE can also be applied to damage and management costs. We propose two methods for applying G-IRAE. The species-specific method computes the relationship for a given species across multiple invaded sites or regions, assuming a constant per-unit effect across the invaded area. The multi-species method combines data from multiple species across multiple sites or regions to calculate a per-unit effect for each species. While the species-specific method is more accurate, it requires a large amount of data for each species. The multi-species method is more easily applicable and data-parsimonious. We illustrate the multi-species method using data about money spent managing plant invasions in different biomes of South Africa. We found clear differences between species in terms of money spent per unit area invaded, with per-unit expenditures varying substantially between biomes for some species. G-IRAE offers a versatile and practical method which can be applied to many different types of data, to better understand and manage invasions.

ecology↗

bioRxiv2021

Policy-relevant indicators for invasive alien species assessment and reporting

Invasive alien species are repeatedly shown to be amongst the top threats to biodiversity globally. Robust indicators for measuring the status and trends of biological invasions are lacking, but essential for monitoring biological invasions and the effectiveness of interventions. Here, we formulate and demonstrate three such indicators that capture the key dimensions of species invasions, each a significant and necessary advance to inform invasive alien species policy targets: 1) Rate of Invasive Alien Species Spread, which provides modelled rates of ongoing introductions of species based on invasion discovery and reporting. 2) Impact Risk, that estimates invasive alien species impacts on the environment in space and time and provides a basis for nationally targeted prioritization of where best to invest in management efforts. 3) Status Information on invasive alien species, that tracks improvement in the essential dimensions of information needed to guide relevant policy and data collection and in support of assessing invasive alien species spread and impact. We show how proximal, model-informed status and trend indicators on invasive alien species can provide more effective global (and national) reporting on biological invasions, and how countries can contribute to supporting these indicators.

ecology↗

bioRxiv2021

Alternative futures for global biological invasions

Scenario analysis has emerged as a key tool to analyze complex and uncertain future socio-ecological developments. However, current global scenarios (narratives of how the world may develop) have neglected biological invasions, a major threat to biodiversity and the economy. We used a novel participatory process to develop a diverse set of global biological invasion scenarios spanning a wide breadth of plausible global futures through 2050. We adapted the widely used "two axes" scenario analysis approach to develop four families of four scenarios each, resulting in 16 scenarios that were later clustered into four contrasting sets of futures. Our analysis highlighted that socio-economic developments and changes in sustainability policies and lifestyle have the potential to shape biological invasions, in addition to well-known ecological drivers, such as climate and human land use change. Our scenarios align fairly well with the recently developed shared socio-economic pathways, but the factors that drive differences in biological invasions are underrepresented there. Including these factors in global scenarios and models is essential to adequately consider biological invasions in global environmental assessments, and obtain a more integrative picture of future socio-ecological developments.

ecology↗

bioRxiv2021

Microclimates can be accurately predicted across ecologically important remote ecosystems

Microclimate information is often crucial for understanding ecological patterns and processes, including under climate change, but is typically absent from ecological and biogeographic studies owing to difficulties in obtaining microclimate data. Recent advances in microclimate modelling, however, suggest that microclimate conditions can now be predicted anywhere at any time using hybrid physically- and empirically-based models. Here, for the first time, we test the utility of this approach across a remote, inaccessible, and climate change threatened polar island ecosystem at ecologically relevant scales. Microclimate predictions were generated at a 100 x 100 m grain (at a height of 4 cm) across the island, with models parameterised using either meteorological observations from the islands weather station (AWS) or climate reanalysis data (CRA). AWS models had low error rates and were highly correlated with observed seasonal and daily temperatures (root mean squared error of predicted seasonal average Tmean [≤] 0.6 {degrees}C; Pearsons correlation coefficient (r) for the daily Tmean [≥] 0.86). By comparison, CRA models had a slight warm bias in all seasons and a smaller diurnal range in the late summer period than in situ observations. Despite these differences, the modelled relationship between the percentage cover of the threatened endemic cushion plant Azorella macquariensis and microclimate varied little with the source of microclimate data (r = 0.97), suggesting that both model parameterisations capture similar patterns of spatial variation in microclimate conditions across the island ecosystem. Here, we have shown that the accurate prediction of microclimate conditions at ecologically relevant spatial and temporal scales is now possible using hybrid physically- and empirically-based models across even the most remote and climatically extreme environments. These advances will help add the microclimate dimension to ecological and biogeographic studies, which could be critical for delivering climate change-resilient conservation planning in climate-change exposed ecosystems.

ecology↗

bioRxiv2020

A multiregional assessment of transnational pathways of introduction

Information on the pathways by which alien taxa are introduced to new regions is vital for prioritising policy and management responses to invasions. However, available datasets are often compiled using disparate methods, making comparison and collation of pathway data difficult. Using a standardised framework for recording and categorising pathway data can help to rectify this problem and provide the information necessary to develop indicators for reporting on alien introductions. We combine the Convention on Biological Diversitys Pathways Categorisation Scheme (CPC) with data compiled by the Invasive Species Specialist Group (ISSG) to report on multiregional trends on alien introduction pathways over the past 200+ years. We found a significant increase in the documented number of multiregional alien introduction events across all pathways of the CPCs three hierarchical levels. The escape pathway is the most common documented pathway used by alien taxa. Transport stowaways via shipping-related vectors are a rapidly increasing contribution to alien introductions. Most alien introduction events were of unknown pathway origin, highlighting the challenge of information gaps in pathway data and reiterating the need for standardised information-gathering practices. Combining the CPC framework with alien introduction pathways data will standardise pathway information and facilitate the development of global indicators of trends in alien introductions and the pathways they use. These indicators have the potential to inform policy and management strategies for preventing future biological invasions and can be downscaled to national and regional levels that are applicable across taxa and ecosystems.

ecology↗

bioRxiv2018

zetadiv: an R package for computing compositional change across multiple sites, assemblages or cases

Spatial variation in compositional diversity, or species turnover, is necessary for capturing the components of heterogeneity that constitute biodiversity. However, no incidence-based metric of pairwise species turnover can calculate all components of diversity partitioning. Zeta ({zeta}) diversity, the mean number of species shared by any given number of sites or assemblages, captures all diversity components produced by assemblage partitioning. zetadiv is an R package for analysing and measuring compositional change for occurrence data using zeta diversity. Four types of analyses are performed on bird composition data in Australia: (i) decline in zeta diversity; (ii) distance decay; (iii) multi-site generalised dissimilarity modelling; and (iv) hierarchical scaling. Some analyses, such as the zeta decline, are specific to zeta diversity, whereas others, such as distance decay, are commonly applied to beta diversity, and have been adapted using zeta diversity to differentiate the contribution of common and rare species to compositional change.\n\nHighlightsO_LIAn R package to analyse compositional change using zeta diversity is presented.\nC_LIO_LIZeta diversity is the mean number of species shared by any number of assemblages\nC_LIO_LIZeta diversity captures all diversity components produced by assemblage partitioning\nC_LIO_LIAnalyses relate zeta diversity to space, environment and spatial scale\nC_LIO_LIAnalyses differentiate the contribution of rare and common species to biodiversity\nC_LI

ecology↗

bioRxiv2017

The application of zeta diversity as a continuous measure of compositional change in ecology

Zeta diversity provides the average number of shared species across n sites (or shared operational taxonomic units (OTUs) across n cases). It quantifies the variation in species composition of multiple assemblages in space and time to capture the contribution of the full suite of narrow, intermediate and wide-ranging species to biotic heterogeneity. Zeta diversity was proposed for measuring compositional turnover in plant and animal assemblages, but is equally relevant for application to any biological system that can be characterised by a row by column incidence matrix. Here we illustrate the application of zeta diversity to explore compositional change in empirical data, and how observed patterns may be interpreted. We use 10 datasets from a broad range of scales and levels of biological organisation - from DNA molecules to microbes, plants and birds - including one of the original data sets used by R.H. Whittaker in the 1960s to express compositional change and distance decay using beta diversity. The applications show (i) how different sampling schemes used during the calculation of zeta diversity may be appropriate for different data types and ecological questions, (ii) how higher orders of zeta may in some cases better detect shifts, transitions or periodicity, and importantly (iii) the relative roles of rare versus common species in driving patterns of compositional change. By exploring the application of zeta diversity across this broad range of contexts, our goal is to demonstrate its value as a tool for understanding continuous biodiversity turnover and as a metric for filling the empirical gap that exists on spatial or temporal change in compositional diversity.

ecology↗