Microbial dispersal limitation to isolated soil habitats in the McMurdo Dry Valleys of Antarctica

Abstract

1Dispersal is a critical yet poorly understood factor underlying macroecological 2 patterns in microbial communities. Airborne microbial transport is assumed to occupy a 3 central role in determining dispersal outcomes and extra-range dispersal has important 4 implications for predicting ecosystem resilience and response to environmental change. 5

Air mass source determines airborne microbial diversity at the ocean-atmosphere interface of the Great Barrier Reef marine ecosystem

“…The fungi from continental sources displayed a similar though more variable trend of phylogenetic structuring although in ocean-derived samples this clustering was relatively weak indicating they were more randomly assembled. Overall our analyses support the hypothesis that long-range transport of microbial taxa in air results in differential recruitment and selection during transit over oceanic or continental surfaces [12, 16, 17].…”

“…This minimised interference from microorganisms that are aerosolised by marine spray in heavier sea states at the Great Barrier Reef [11]. We recovered massive bulk-phase air samples at 25m above sea level using a high-volume liquid impinger apparatus (Coriolis μ, Bertin Technologies, France) [12] during a voyage of the RV Investigator to circumnavigate the reef (Supplementary Information, Supplementary Methods). We used the National Oceanic and Atmospheric Administration (NOAA) HYSPLIT-WEB model (https://ready.arl.noaa.gov/HYSPLIT.php) to identify back trajectories of air mass during the average residence time for microbial cells in air [10].…”

“…(a) HYSPLIT back trajectory analysis for modelled transit routes (3 d residence time [12]) with colours representing air mass origin over continent (green) or ocean (red) surface, scale bar = 500km; Rarefaction curves for samples by origin for (b) bacteria (Continent n = 8, Ocean n = 19) and (c) fungi (Continent n = 8, Ocean n = 17). Chao1 diversity index by origin for (d) bacteria and (e) fungi.…”

“…Consistent with predictions that microbial biomass is extremely low and unpredictable over the oceans, we achieved recoverable DNA from 27 of 53 bulk-phase air samples (mean recovery 0.23 ng/m 3 , STDEV 0.21 ng/m 3 ; Supplementary Information, Table S1) with no significant difference in DNA yield between sample groups (Mann-Whitney U Test, P = 0.37). High-throughput sequencing of the bacterial 16S rRNA gene and fungal Internal Transcribed Spacer (ITS) region were performed as previously described [12] and phylogenetic analysis of amplicon sequence variants (ASVs) were used to estimate diversity [13] (Supplementary Information, Supplementary Methods). Sequencing of control samples revealed very low recovery of putative contaminant microbial signatures.…”

“…We further interrogated the phylogenetic diversity of continental and oceanic air masses using Net Relatedness Index (NRI) analysis to estimate the level of phylogenetic structuring and putative recruitment from local (i.e. ocean or continental source only) and regional (all sources) pools [12]. The NRI analysis revealed that bacterial assemblages from both oceanic and continental origin displayed positive NRI values with effect sizes indicative of non-random assembly (Fig.…”