No biogeographical pattern for a root‐associated fungal species complex

Abstract

AimThe biogeography of microbes is poorly understood and there is an open debate regarding if and how microbial biodiversity is structured. At the beginning of the 20th century, Baas Becking laid the foundations for the biogeography of microbes by stating that 'Everything is everywhere, but the environment selects' (the EisE hypothesis). This hypothesis remained dogma for almost a century. However, the recognition that microbial 'species' are often assemblages of reproductively isolated lineages challenged the EisE hypothesis, leading to the now common assumption that microbial communities possess cryptic biogeographic structures. We tested the presence of a cryptic biogeographical structure for a well-characterized fungal species complex (the Phialocephala fortinii s.l.-Acephala applanata species complex, PAC) using precise molecular species resolution. In addition, we analysed factors that could govern PAC community assembling.Locations Forty-four study sites in temperate and boreal forests across the Northern Hemisphere were included. Methods(1) The distance-decay relationship among PAC communities was calculated and a resampling procedure was applied to analyse the effect of sampling intensity and geographic distances among PAC communities. (2) Factors shaping PAC communities (e.g. climatic factors and tree species composition) were studied.(3) We tested PAC communities for random composition. ResultsWe found that the similarity of species assemblages did not decrease with increasing geographical distance. Moreover, species diversity did not increase by expanding the area sampled. Instead, species diversity increased by increasing the sampling effort. Community composition correlated neither with tree species composition nor climate, and no association among species was observed. Main conclusionsWe could not discover any cryptic biogeographic structure even after applying refined species assignment but we demonstrate the importance of sampling effort for understanding the biogeography of microorganisms. Moreover, we show that primarily stochastic effects are responsible for the species composition of PAC communities.

Strong effect of climate on ectomycorrhizal fungal composition: evidence from range overlap between two mountains

“…However, these correlations do not necessarily represent the direct links between plants and microorganisms, and the empirical evidence of direct links appears to be inconclusive (Waldrop et al, 2006;Bryant et al, 2008;Queloz et al, 2011;van der Putten et al, 2013). In fact, hosts per se had little predictive power with regard to the EM fungal composition in our analysis.…”

Unraveling the Dark Septate Endophyte Functions: Insights from the Arabidopsis Model

“…As a result, these are assigned to Phialocephala fortinii s.l. -Acephala applanata species complex (PAC) that constitute the bulk of DSE communities colonizing conifers and Ericaceae in the Northern Hemisphere including Europe, North America, and Asia (Jumpponen and Trappe 1998a ;Grünig et al 2008b ;Queloz et al 2011 ;Walker et al 2011 ). Second , thus far no evidence has been presented for an interface that would facilitate nutrient exchange between the host and its DSE symbionts (Petersen et al 2008 ).…”

Strong coupling of plant and fungal community structure across western Amazonian rainforests

“…For example, negative feedbacks are generally thought to depend on high levels of variability in the strength of plant-fungal interactions and on strong spatial heterogeneity in fungal community composition (Gilbert, 2002). However, theoretical (May, 1991) and empirical Smith et al, 2011Smith et al, , 2013) studies have suggested low levels of fungal host specificity in tropical forests, and many studies have questioned the importance of dispersal limitation in microbes (Finlay, 2002;Queloz et al, 2011). Detailed knowledge on the structure of fungal communities is thus necessary to guide research to answer these critical ecological questions.…”