Abstract
Abstract The mycobiome (fungal microbiome) influences plants—from seed germination to full maturation. While many studies on fungal‐plant interaction studies have focused on known mutualistic and pathogenic fungi, the functional role of ubiquitous endophytic fungi remains little explored. We examined how root‐inhabiting fungi (endophytes) influence range‐expanding plant species. We isolated endophytes from three European intra‐continental range‐expanders and three congenerics that are native both in the range expander's original (southern Europe) and new (northern Europe) range. To standardize our collection, endophytes were obtained from all six plant species growing under controlled conditions in northern (new range of the range expander) and southern (native range of the range expander) soils. We cultivated, molecularly identified and tested the effects of all isolates on seed germination, and growth of seedlings and older plants. Most of the 34 isolates could not be functionally characterized based on their taxonomic identity and literature information on functions. Endophytes affected plant growth in a plant species–endophyte‐specific manner, but overall differed between range‐expanders and natives. While endophytes reduced germination and growth of range‐expanders compared to natives, they reduced seedling growth of natives more than of range‐expanders. Synthesis. We conclude that endophytic fungi have a direct effect on plant growth in a plant growth stage‐dependent manner. While these effects differed between range expanders and natives, the effect strength and significance varied among the plant genera included in the present study. Nevertheless, endophytes likely influence the establishment of newly arriving plants and influence vegetation dynamics.
Highlights
Many studies have examined the ecology of alien plant species that have been introduced from other continents, as a small proportion of them is highly invasive, changing local biodiversity and ecosystem functioning, and causing significant economic costs (Pimentel et al, 2001; Vilà et al, 2015; Vitousek et al, 1996)
We show that effects on plants of fungal and oomycete root endophytes isolated from range-expanding and congeneric native plant species are variable depending on plant life stage
This is partly due to the fact that there is a lack of functional knowledge of endophytes in non-crop plant species suggesting that a priori functional assignment in the little studied endophytes can be misleading especially in natural plant species (Lofgren et al, 2018; Malcolm et al, 2013)
Summary
Many studies have examined the ecology of alien plant species that have been introduced from other continents, as a small proportion of them is highly invasive, changing local biodiversity and ecosystem functioning, and causing significant economic costs (Pimentel et al, 2001; Vilà et al, 2015; Vitousek et al, 1996). Those micro-organisms that directly penetrate plant roots have well-acknowledged positive (e.g. mycorrhizal fungi, rhizobial bacteria) and negative (e.g. bacterial, fungal and fungal-like oomycete pathogens) effects on plant growth (Raaijmakers et al, 2009) Among those players, fungi and oomycetes hold key functional roles and include major mutualists (Richardson et al, 2000; van der Heijden et al, 2015) and pathogens (Coats & Rumpho, 2014; Gilbert, 2002; Klironomos, 2002; Mendes et al, 2013; Mills & Bever, 1998). We tested the following general hypotheses: (1) Range-expanders will have higher germination rates and produce more biomass when inoculated with endophytes isolated from the expanded northern range soil than from the native southern range soil; we did not expect differences for native plant species, as endophytes with negative effects might not have expanded together with the range-expanders but have developed with natives. (2) The effects of endophytes are irrespective of plant growth stages, because we expected a functional conservatism of endophytes
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