Contrasting distribution patterns between aquatic and terrestrial Phytophthora species along a climatic gradient are linked to functional traits

Miguel A Redondo,Johanna Boberg,Jan Stenlid,Jonàs Oliva

doi:10.1038/s41396-018-0229-3

Miguel A Redondo, Johanna Boberg + Show 2 more

Open Access

https://doi.org/10.1038/s41396-018-0229-3

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Abstract

Diversity of microbial organisms is linked to global climatic gradients. The genus Phytophthora includes both aquatic and terrestrial plant pathogenic species that display a large variation of functional traits. The extent to which the physical environment (water or soil) modulates the interaction of microorganisms with climate is unknown. Here, we explored the main environmental drivers of diversity and functional trait composition of Phytophthora communities. Communities were obtained by a novel metabarcoding setup based on PacBio sequencing of river filtrates in 96 river sites along a geographical gradient. Species were classified as terrestrial or aquatic based on their phylogenetic clade. Overall, terrestrial and aquatic species showed contrasting patterns of diversity. For terrestrial species, precipitation was a stronger driver than temperature, and diversity and functional diversity decreased with decreasing temperature and precipitation. In cold and dry areas, the dominant species formed resistant structures and had a low optimum temperature. By contrast, for aquatic species, temperature and water chemistry were the strongest drivers, and diversity increased with decreasing temperature and precipitation. Within the same area, environmental filtering affected terrestrial species more strongly than aquatic species (20% versus 3% of the studied communities, respectively). Our results highlight the importance of functional traits and the physical environment in which microorganisms develop their life cycle when predicting their distribution under changing climatic conditions. Temperature and rainfall may be buffered differently by water and soil, and thus pose contrasting constrains to microbial assemblies.

Highlights

Plant pathogenic microorganisms pose an increasing threat to natural ecosystems globally [1, 2]
We studied the association between four functional diversity parameters, namely functional richness (FRic), functional dispersion (FDis), functional evenness (FEve), and the community-level weighted mean (CWM) and five explanatory variables, namely climatic score, precipitation, temperature, the land use of the site, and water chemistry using generalized linear models
To address any inconsistencies in the literature regarding functional trait information, we followed the criteria for all species as explained in Supporting Information Methods S2. For both years, we studied the functional diversity of 56 terrestrial communities and 145 water communities, and the CWM of 164 terrestrial and 192 water communities

Summary

Introduction

Plant pathogenic microorganisms pose an increasing threat to natural ecosystems globally [1, 2]. Fungal-like species belonging to the genus Phytophthora are the causal agents of major disease outbreaks worldwide [3,4,5]. Phytophthora species are distributed with plant nursery stock [6, 7]. Once introduced into new ecosystems, not all species manage to establish and spread further. A better understanding of the mechanisms underlying the success or failure of the establishment of Phytophthora plant pathogens is needed in order to predict future outbreaks. Climatic factors have been shown to affect the establishment and distribution of some Phytophthora species [10], the extent to which climate is associated with the distribution of plant pathogenic Phytophthora species at the genus level is still unknown

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