Dataset Information

Spatial and temporal changes of parasitic chytrids of cyanobacteria.

ABSTRACT: Parasitism is certainly one of the most important driving biotic factors of cyanobacterial blooms which remains largely understudied. Among these parasites, fungi from the phylum Chytridiomycota (i.e. chytrids) are the only eukaryotic microorganisms infecting cyanobacteria. Here, we address spatiotemporal dynamics of the cyanobacterial host Dolichospermum macrosporum (syn. Anabaena macrospora) and its associated chytrid parasites, Rhizosiphon spp., in an eutrophic lake by studying spatial (vertical, horizontal) and temporal (annual and inter-annual) variations. Our results show homogenous chytrid infection patterns along the water column and across sampling stations. However, the prevalence of infection presented drastic changes with time, at both intra- and inter-annual scales. In 2007, a maximum of 98% of vegetative cells were infected by R. crassum whereas this fungal species was not reported seven years later. In opposite, R. akinetum, a chytrid infecting only akinetes, increased its prevalence by 42% during the same period. High chytrid infection rate on the akinetes might have sizeable consequences on host recruitment (and proliferation) success from year to year, as supported by the recorded inter-annual host dynamics (affecting also the success of other chytrid parasites). The spatial homogenous chytrid infection on this cyanobacterium, coupled to both seasonal and inter-annual changes indicates that time, rather than space, controls such highly dynamic host-parasite relationships.

SUBMITTER: Gerphagnon M

PROVIDER: S-EPMC5519717 | biostudies-literature | 2017 Jul

REPOSITORIES: biostudies-literature

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Spatial and temporal changes of parasitic chytrids of cyanobacteria.

Gerphagnon Mélanie M Colombet Jonathan J Latour Delphine D Sime-Ngando Télesphore T

Scientific reports 20170720 1

Parasitism is certainly one of the most important driving biotic factors of cyanobacterial blooms which remains largely understudied. Among these parasites, fungi from the phylum Chytridiomycota (i.e. chytrids) are the only eukaryotic microorganisms infecting cyanobacteria. Here, we address spatiotemporal dynamics of the cyanobacterial host Dolichospermum macrosporum (syn. Anabaena macrospora) and its associated chytrid parasites, Rhizosiphon spp., in an eutrophic lake by studying spatial (verti ...[more]

PMID: 28729657

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Project description:BackgroundExtinction and re-colonisation of local populations is common in ephemeral habitats such as temporary streams. In most cases, such population turnover leads to reduced genetic diversity within populations and increased genetic differentiation among populations due to stochastic founder events, genetic drift, and bottlenecks associated with re-colonisation. Here, we examined the spatio-temporal genetic structure of 8 alpine caddisfly populations inhabiting permanent and temporary streams from four valleys in two regions of the Swiss Alps in years before and after a major stream drying event, the European heat wave in summer 2003.ResultsWe found that population turnover after 2003 led to a loss of allelic richness and gene diversity but not to significant changes in observed heterozygosity. Within all valleys, permanent and temporary streams in any given year were not differentiated, suggesting considerable gene flow and admixture between streams with differing hydroperiods. Large changes in allele frequencies after 2003 resulted in a substantial increase in genetic differentiation among valleys within one to two years (1-2 generations) driven primarily by drift and immigration. Signatures of genetic bottlenecks were detected in all 8 populations after 2003 using the M-ratio method, but in no populations when using a heterozygosity excess method, indicating differential sensitivity of bottleneck detection methods.ConclusionsWe conclude that genetic differentiation among A. uncatus populations changed markedly both temporally and spatially in response to the extreme climate event in 2003. Our results highlight the magnitude of temporal population genetic changes in response to extreme events. More specifically, our results show that extreme events can cause rapid genetic divergence in metapopulations. Further studies are needed to determine if recovery from this perturbation through gradual mixing of diverged populations by migration and gene flow leads to the pre-climate event state, or whether the observed changes represent a new genetic equilibrium.

Project description:Parasitic chytrid fungi (phylum Chytridiomycota) are known to infect specific phytoplankton, including the filamentous cyanobacterium Planktothrix. Subspecies, or chemotypes of Planktothrix can be identified by the presence of characteristic oligopeptides. Some of these oligopeptides can be associated with important health concerns due to their potential for toxin production. However, the relationship between chytrid parasite and Planktothrix host is not clearly understood and more research is needed. To test the parasite-host relationship over time, we used a sediment core extracted from a Norwegian lake known to contain both multiple Planktothrix chemotype hosts and their parasitic chytrid. Sediment DNA of chytrids and Planktothrix was amplified and a 35-year coexistence was found. It is important to understand how these two antagonistic species can coexistence in a lake. Reconstruction of the time series showed that between 1979-1990 at least 2 strains of Planktothrix were present and parasitic pressure exerted by chytrids was low. After this period one chemotype became dominant and yet showed continued low susceptibility to chytrid parasitism. Either environmental conditions or intrinsic characteristics of Planktothrix could have been responsible for this continued dominance. One possible explanation could be found in the shift of Planktothrix to the metalimnion, an environment that typically consists of low light and decreased temperatures. Planktothrix are capable of growth under these conditions while the chytrid parasites are constrained. Another potential explanation could be due to the differences between cellular oligopeptide variations found between Planktothrix chemotypes. These oligopeptides can function as defense systems against chytrids. Our findings suggest that chytrid driven diversity was not maintained over time, but that the combination of environmental constraints and multiple oligopeptide production to combat chytrids could have allowed one Planktothrix chemotype to have dominance despite chytrid presence.

Dataset Information

Spatial and temporal changes of parasitic chytrids of cyanobacteria.

Publications

Spatial and temporal changes of parasitic chytrids of cyanobacteria.

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