Steven L. Chown’s research while affiliated with Monash University (Australia) and other places

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Publications (174)


Repeat photography reveals long‐term climate change impacts on sub‐Antarctic tundra vegetation
  • Article

December 2024

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40 Reads

Journal of Vegetation Science

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Michael Timm Hoffman

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[...]

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Michael Denis Cramer

Questions At high latitudes, anthropogenic climate change and invasive species threaten biodiversity, often with interacting effects. Climate change not only impacts native plant species directly by driving distribution and abundance of species, but indirectly through the influence on community dynamics and habitat suitability to invasive species. A key obstacle to quantifying vegetation change in the sub‐Antarctic is the scarcity of cloud‐free satellite imagery in a region with near‐permanent cloud cover and lack of long‐term plot data. In this paper, we aim to address the following questions: how has vegetation in the sub‐Antarctic changed between 1965 and 2020? What are the roles of climate change and invasive species in driving these changes? Location The study was conducted on Marion Island in the sub‐Antarctica. Methods We quantified vegetation change by analysing repeat ground photography between 1965 and 2020, accompanied by an analysis of climate trends and invasive plant species’ cover changes over the same period. Results Total vegetation cover was significantly higher in 2020 than in 1965 in all habitats other than in the coastal saltspray habitat, indicating an increase in overall biomass on the island. The more responsive ‘generalist’ plant species have expanded across the island, whilst the more ‘specialised’ plant species have not significantly changed in cover, with the exception of the mire graminoids, which have declined. Marion Island has thus undergone significant vegetation change, showing a greening trend across most habitats in the last five decades. This has been accompanied by aridification, an increase in mean air temperature, changes in wind direction and wind speed, and an increase in invasive mouse populations. The three most widespread invasive plant species have also expanded their ranges, especially in areas influenced by animal disturbance and nutrient input. Conclusions In congruence with research from Northern‐hemisphere tundra and other islands in the sub‐Antarctic, these results provide substantive empirical evidence for the interacting effects of climate change and invasive species on sub‐Antarctic tundra vegetation, as has long been predicted.


Microbial aerotrophy enables continuous primary production in diverse cave ecosystems
  • Preprint
  • File available

June 2024

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119 Reads

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.

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Fig. 1. The sum of Working Papers and Information Papers submitted to the Antarctic Treaty Consultative Meetings either as primary author or as a collaborating author in the case of (a) SCAR (mcp analysis (see Supplementary Information) outcome: first break mean 1993 (lower estimate 1989, upper estimate 2005), second break 2016 (2013-2019)) and (b) country Parties (mcp analysis outcome: first break 1995 (1986-2005), second break 2016 (2006-2019)), over the period 1972-2023. Red line segments are means of numbers of papers for each of the periods. Note the difference in scale of the y-axis.
Fig. 2. (a) The summed number of Working Papers (WP) and Information Papers (IP) written in collaboration with SCAR either for Observers and Experts (blue), Treaty Parties excluding the seven claimant states plus Russia and the USA (black) or the seven claimant states plus Russia and the USA (orange) as a function of the total number of WPs and IPs submitted by each of those groups, with points representing years between 1972 and 2023. Differences among group intercepts and slopes are all significant or nearly so in a quasipoisson generalised linear model (see SI). (b) The proportion of all WPs and IPs submitted as collaboration with Parties by SCAR (orange) or as collaboration by Parties with other Parties (black) between 1972 and 2023. The differences in slopes and intercepts are significant at p < 0.01 in a quasibinomial generalised linear model (see Supplementary Information).
Fig. 3. Time line of Antarctic Treaty Consultative Meetings (ATCMs) indicating the discussion of or decisions about climate change by the Antarctic Treaty Consultative Parties (ATCPs) and the information submitted in response by SCAR, and in turn the decisions taken by the ATCPs from ATCM XV of 1989 to ATCM XLV of 2023. Note that Recommendation XV-14 (1989) recognises SCAR's contributions with appreciation and encourages further scientific research. Antarctic Treaty Recommendations, Decisions and Resolutions above the centre orange ATCM time line, SCAR submissions below.
Fig. 4. Log (base e) of the total number of (a) Working Papers (WPs) or (b) Information Papers (IPs) submitted by SCAR (orange) or country Parties (black) over time since 1972, irrespective of whether the author category is lead or collaborating author. For WPs, neither the submitter (SCAR vs. Country Parties) (t = 1.396, p = 0.167), nor the interaction term between year and submitter (t = 1.312, p = 0.194) are significant in the quasipoisson generalised linear model (see SI). For IPs, neither the submitter (SCAR vs. Country Parties) (t = 1.126, p = 0.264), nor the interaction term between year and submitter (t = 1.039, p = 0.302) are significant in the quasipoisson generalised linear model (see Supplementary Information).
Fig. 5. The proportion of (a) Working Papers (WPs) or (b) Information Papers (Ips) written as a collaboration with any other Party or Observer or Expert for SCAR (orange) or for country Parties (black) over time. For WPs, neither the submitter (SCAR vs. Country Parties) (z = 0.614, p = 0.539), nor the interaction term between year and submitter (z = 0.609, p = 0.542) are significant in the binomial generalised linear model. For IPs, neither the submitter (SCAR vs. Country Parties) (z = 0.325, p = 0746), nor the interaction term between year and submitter (z = 0.314, p = 0.753) are significant in the binomial generalised linear model (see Supplementary Information).
Science advice for international governance – An evidence-based perspective on the role of SCAR in the Antarctic Treaty System

May 2024

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98 Reads

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5 Citations

Marine Policy


Figure 2. Phylogeny containing the 163 honeyeater species for which we obtained song variables for and used in analysis. Branches are colored according to peak frequency. Size of bars at the tips of the phylogeny represent body size (mass in grams) and are colored according to open (white) and closed (black) habitat types. Four examples of honeyeater song spectrograms are included: blue-faced honeyeater (Entomyzon cyanotis; xeno-canto accession number = XC439288; body size = 105.26 g), singing honeyeater (Gavicalis virescens; xeno-canto accession number = XC334251; body size = 23.33 g), noisy friarbird (Philemon corniculatus; xeno-canto accession number = XC287056; body size = 100.71 g) and eastern spinebill (Acanthorhynchus tenuirostris; xeno-canto accession number = XC490800; body size = 10.44 g). Birds are illustrated by Eleanor Hay.
Body size shapes song in honeyeaters

April 2024

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254 Reads

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1 Citation

Birdsongs are among the most distinctive animal signals. Their evolution is thought to be shaped simultaneously by habitat structure and by the constraints of morphology. Habitat structure affects song transmission and detectability, thus influencing song (the acoustic adaptation hypothesis), while body size and beak size and shape necessarily constrain song characteristics (the morphological constraint hypothesis). Yet, support for the acoustic adaptation and morphological constraint hypotheses remains equivocal, and their simultaneous examination is infrequent. Using a phenotypically diverse Australasian bird clade, the honeyeaters (Aves: Meliphagidae), we compile a dataset consisting of song, environmental, and morphological variables for 163 species and jointly examine predictions of these two hypotheses. Overall, we find that body size constrains song frequency and pace in honeyeaters. Although habitat type and environmental temperature influence aspects of song, that influence is indirect, likely via effects of environmental variation on body size, with some evidence that elevation constrains the evolution of song peak frequency. Our results demonstrate that morphology has an overwhelming influence on birdsong, in support of the morphological constraint hypothesis, with the environment playing a secondary role generally via body size rather than habitat structure. These results suggest that changing body size (a consequence of both global effects such as climate change and local effects such as habitat transformation) will substantially influence the nature of birdsong.


Fig. 2 Terrestrial conservation features in the Antarctic Peninsula identified by stakeholders. a Number of features identified by each of three stakeholder groups, coloured by category. Some features were considered important by multiple stakeholders. b Number of features identified under 19 subcategories, that fall into seven broader categories (colours). Examples of features belonging to subcategories are identified in the pictures. c Number of features identified under each of the seven categories with colours indicating comprehensive data availability for those features. The numbers underlying this figure are found in Table S2.
Number of features in each category that were identified as important by one or more stakeholders. Table S1 lists each feature and the stakeholders that identified it as important
Conservation features of the terrestrial Antarctic Peninsula

April 2024

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233 Reads

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2 Citations

AMBIO A Journal of the Human Environment

Conserving landscapes used by multiple stakeholder groups requires understanding of what each stakeholder values. Here we employed a semi-structured, participatory approach to identify features of value in the terrestrial Antarctic Peninsula related to biodiversity, science and tourism. Stakeholders identified 115 features, ranging from Adélie penguin colonies to sites suitable for snowshoeing tourists. We split the features into seven broad categories: science, tourism, historic, biodiversity, geographic, habitat, and intrinsic features, finding that the biodiversity category contained the most features of any one category, while science stakeholders identified the most features of any stakeholder group. Stakeholders have overlapping interests in some features, particularly for seals and seabirds, indicating that thoughtful consideration of their inclusion in future management is required. Acknowledging the importance of tourism and other social features in Antarctica and ensuring their integration into conservation planning and assessment will increase the likelihood of implementing successful environmental management strategies into the future.



Biodiversity checklist compilation protocol.
Basic Antarctic Tree of Life. Some lesser animal phyla with less than five species total are not visually depicted (e.g. Annelida).
TerrANTALife 1.0 Biodiversity data checklist of known Antarctic terrestrial and freshwater life forms

February 2024

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573 Reads

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2 Citations

Background Incomplete species inventories for Antarctica represent a key challenge for comprehensive ecological research and conservation in the region. Additionally, data required to understand population dynamics, rates of evolution, spatial ranges, functional traits, physiological tolerances and species interactions, all of which are fundamental to disentangle the different functional elements of Antarctic biodiversity, are mostly missing. However, much of the fauna, flora and microbiota in the emerged ice-free land of the continent have an uncertain presence and/or unresolved status, with entire biodiversity compendia of prokaryotic groups (e.g. bacteria) being missing. All the available biodiversity information requires consolidation, cross-validation, re-assessment and steady systematic inclusion in order to create a robust catalogue of biodiversity for the continent. New information We compiled, completed and revised eukaryotic species inventories present in terrestrial and freshwater ecosystems in Antarctica in a new living database: terrANTALife (version 1.0). The database includes the first integration in a compendium for many groups of eukaryotic microorganisms. We also introduce a first catalogue of amplicon sequence variants (ASVs) of prokaryotic biodiversity. Available compendia and literature to date were searched for Antarctic terrestrial and freshwater species, integrated, taxonomically harmonised and curated by experts to create comprehensive checklists of Antarctic organisms. The final inventories comprises 470 animal species (including vertebrates, free-living invertebrates and parasites), 306 plants (including all Viridiplantae: embryophytes and green algae), 997 fungal species and 434 protists (sensu lato). We also provide a first account for many groups of microorganisms, including non-lichenised fungi and multiple groups of eukaryotic unicellular species (Stramenophila, Alveolata and Rhizaria (SAR), Chromists and Amoeba), jointly referred to as "protists". In addition, we identify 1753 bacterial (obtained from 348117 ASVs) and 34 archaeal genera (from 1848 ASVs), as well as, at least, 14 virus families. We formulate a basic tree of life in Antarctica with the main lineages listed in the region and their “known-accepted-species” numbers.


Biogeographic survey of soil bacterial communities across Antarctica

January 2024

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478 Reads

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14 Citations

Background Antarctica and its unique biodiversity are increasingly at risk from the effects of global climate change and other human influences. A significant recent element underpinning strategies for Antarctic conservation has been the development of a system of Antarctic Conservation Biogeographic Regions (ACBRs). The datasets supporting this classification are, however, dominated by eukaryotic taxa, with contributions from the bacterial domain restricted to Actinomycetota and Cyanobacteriota. Nevertheless, the ice-free areas of the Antarctic continent and the sub-Antarctic islands are dominated in terms of diversity by bacteria. Our study aims to generate a comprehensive phylogenetic dataset of Antarctic bacteria with wide geographical coverage on the continent and sub-Antarctic islands, to investigate whether bacterial diversity and distribution is reflected in the current ACBRs. Results Soil bacterial diversity and community composition did not fully conform with the ACBR classification. Although 19% of the variability was explained by this classification, the largest differences in bacterial community composition were between the broader continental and maritime Antarctic regions, where a degree of structural overlapping within continental and maritime bacterial communities was apparent, not fully reflecting the division into separate ACBRs. Strong divergence in soil bacterial community composition was also apparent between the Antarctic/sub-Antarctic islands and the Antarctic mainland. Bacterial communities were partially shaped by bioclimatic conditions, with 28% of dominant genera showing habitat preferences connected to at least one of the bioclimatic variables included in our analyses. These genera were also reported as indicator taxa for the ACBRs. Conclusions Overall, our data indicate that the current ACBR subdivision of the Antarctic continent does not fully reflect bacterial distribution and diversity in Antarctica. We observed considerable overlap in the structure of soil bacterial communities within the maritime Antarctic region and within the continental Antarctic region. Our results also suggest that bacterial communities might be impacted by regional climatic and other environmental changes. The dataset developed in this study provides a comprehensive baseline that will provide a valuable tool for biodiversity conservation efforts on the continent. Further studies are clearly required, and we emphasize the need for more extensive campaigns to systematically sample and characterize Antarctic and sub-Antarctic soil microbial communities. APsmQ8MphSAgg4BzZyqdNTVideo Abstract


Data collection and evaluation in #GlobalCollembola. Most of the data are raw data collected from archives of the contributing authors of the paper. The data were collected using an Excel template and included in the final database after technical and expert cleaning of each dataset. No data were excluded, instead, expert evaluation is provided for each dataset. Whenever possible, we recorded species occurrences in individual samples (soil cores).
Database structure of #GlobalCollembola. Database consists of three main spreadsheets: (1) Events, (2) Occurrences, and (3) Taxonomy. The spreadsheets can be linked, summarised, and filtered using the associated R script to produce site-level averages.
Global distribution of the sampling points and habitat types represented in the database. Density of samples per pixel in a global 100 × 100 coordinate grid are shown with grayscale (light – few samples, dark – many samples). Number of collected samples in each habitat type are shown with a doughnut chart; habitat classification follows the European Environmental Agency.
Temporal coverage of the database. Frequency histograms show the number of samples collected in different years (a) and months (b), and the number of sites where samples were collected in multiple years (c) in a certain time range (d).
Collection methods and identification precision represented in the database. Number of collected samples with different methods and the number of samples where springtails were identified to a certain taxonomic resolution level are shown with doughnut charts.
Global fine-resolution data on springtail abundance and community structure

January 2024

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1,218 Reads

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2 Citations

Scientific Data

Springtails (Collembola) inhabit soils from the Arctic to the Antarctic and comprise an estimated ~32% of all terrestrial arthropods on Earth. Here, we present a global, spatially-explicit database on springtail communities that includes 249,912 occurrences from 44,999 samples and 2,990 sites. These data are mainly raw sample-level records at the species level collected predominantly from private archives of the authors that were quality-controlled and taxonomically-standardised. Despite covering all continents, most of the sample-level data come from the European continent (82.5% of all samples) and represent four habitats: woodlands (57.4%), grasslands (14.0%), agrosystems (13.7%) and scrublands (9.0%). We included sampling by soil layers, and across seasons and years, representing temporal and spatial within-site variation in springtail communities. We also provided data use and sharing guidelines and R code to facilitate the use of the database by other researchers. This data paper describes a static version of the database at the publication date, but the database will be further expanded to include underrepresented regions and linked with trait data.



Citations (85)


... Under the Convention on the Conservation of Antarctic Marine Living Resources, the CAMLR Commission (CCAMLR) makes evidence-informed decisions on the basis of the best-available science advice provided by its Scientific Committee (Article IX(4), CAMLR Convention). The Scientific Committee on Antarctic Research (SCAR), a thematic organization of the International Science Council, provides an important knowledge brokering function by delivering high quality, policy-relevant (usually synthesized) scientific information to ATS policy bodies (among others) (Chown et al., 2024;Walton, 2011). which means that agreements are reached in the absence of objection, and there is no formal voting process . ...

Reference:

Practitioners' perspectives on the enablers and barriers to successful Antarctic science‐policy knowledge exchange
Science advice for international governance – An evidence-based perspective on the role of SCAR in the Antarctic Treaty System

Marine Policy

... The songs of the emerald-spotted and blue-spotted wood-doves share a similar structure (refer to Figure 1), yet their average values for several basic measurements differ significantly (see Table S2). In general, the blue-head wood-dove has lower frequency (including peak frequency) and shorter songs than its congener, which, in the case of frequency, is consistent with differences in body size (Hay et al., 2024). ...

Body size shapes song in honeyeaters

... Biodiversity also supports tourism by offering ecological experiences and educational opportunities, such as birdwatching and plant exploration, which attract visitors and encourage repeat tourism 105 . Preserving biodiversity facilitates the sustainable development of rural tourism by ensuring the availability of natural resources, promoting economic growth, and fostering environmental stewardship. ...

Conservation features of the terrestrial Antarctic Peninsula

AMBIO A Journal of the Human Environment

... The dataset is released under a Creative Commons Attribution 4.0 International (CC BY 4.0) license, granting users the Makarevicz et al. 163 , Poelt 164 , Wei and Chen 165 , Wei 166 , Obermayer 167 , Zhao et al. 168 , Baniya et al. 169 , Huang and Guo 170 , Timdal et al. 171 , Wei and Jiang 172 Nakanishi 173 , Kappen and Redon 174 , Li 175 , Sancho et al. 24 , Li et al. 176 , Yin et al. 177 , Kim et al. 178 , Seymour et al. 179 , Han and Wei 180 , Seppelt et al. 181 , Casanovas et al. 182 , Peat et al. 183 , Søchting et al. 25 , Øvstedal and Lewis-Smith 23 , Olech et al. 184 , Pertierra et al.185 Main literature sources for lichen species used in this study. ...

TerrANTALife 1.0 Biodiversity data checklist of known Antarctic terrestrial and freshwater life forms

... Moreover, access to cool (for example, air conditioned) refugia can cause individually experienced conditions to be compensable, even when the outdoor environment is not. However, for those without such access, the outlook is more concerning -not least because humid heat, both indoors and outside, is often more extreme in urban environments than is recorded at official weather stations 11 . ...

Humid heat stress overlooked for one billion people in urban informal settlements
  • Citing Article
  • January 2024

One Earth

... Given the low division rates, we believe that it becomes reasonable to predict that the slow evolutionary processes acting on microbial communities in this environment are likely to delay selection. There is some support for this assertion including the divergent ecological patterns of Antarctic soil microbiota 53,54 and the substantial differences in community composition compared with soils from outside the continent 45 . ...

Biogeographic survey of soil bacterial communities across Antarctica

... Many other OTUs cluster with species of bacteria which are typical of extreme environments, such as Truepera radiovictrix, an extremely ionizing radiation resistant strain [53], or with cryophilic species, including the following: Abditibacterium utsteinense, which was originally isolated from Antarctic oligotrophic soils and reported to be very resistant to toxins and antibiotics [54]; Spirosoma arcticum, collected from an arctic glacier [55]; Hymenobacter tibetensis, a high UV tolerant isolate from the Tibetan plateau [56]; Luteolibacter arcticus isolated from the Arctic tundra [57]; and Actimicrobium antarcticum, described in Antarctic coast waters [58]. The recent molecular detection of novel species in Arctic/Antarctic habitats has led to the hypothesis that an endemic polar microbiome exists [59]. Although this is very plausible, none of the aforementioned isolates can be described as endemic to the Polar Regions, as our study provides a new record for them in temperate zones. ...

Polar lake microbiomes have distinct evolutionary histories

Science Advances

... Thermal physiology varies with climate regimes. Organisms experiencing more seasonal and diurnal temperature variation have broader thermal tolerance and increased physiological plasticity (Janzen 1967;Chown et al. 2004;Sheldon et al. 2018;Chown and McGeoch 2023). Depending on environmental conditions, thermal tolerance and plasticity may vary among populations of the same species (Lenz et al. 2011;Narum and Campbell 2015;Cvetanovska et al. 2021). ...

Functional Trait Variation Along Animal Invasion Pathways
  • Citing Article
  • August 2023

Annual Review of Ecology Evolution and Systematics

... They can conserve energy and fix carbon by scavenging atmospheric trace gases such as H₂ and CO (Ji et al., 2017;Ray et al., 2022). They also contribute to nitrogen cycling, with the ability to perform the entire nitrification process (Han et al., 2024) and to oxidize methane (Lebre et al., 2023). Additionally, they retain protein complexes essential for oxidative phosphorylation (Lebre et al., 2023). ...

Expanding Antarctic biogeography: microbial ecology of Antarctic island soils

... As Figure 1 illustrates, males forage both north and south of the Antarctic Polar Front and so could experience improved or diminished foraging conditions depending on their chosen foraging location, potentially masking an overall relationship with foraging success. Alternatively, it is possible that this dichotomy emerges from between-sex differences in plasticity, a pattern that has been observed across a very small but a diverse, range of other species (Bonier et al. 2007;Meuthen et al. 2018;Brand et al. 2023). It is difficult, however, to disentangle this Note: Total path distance was fitted with a Gamma distribution (log link); ratio search: Travel with a beta distribution, and landings per day with a Poisson distribution (log link): Estimates are provided on the relevant link scale. ...

Temperature change exerts sex-specific effects on behavioural variation