Availability of orchid mycorrhizal fungi on roadside trees in a tropical urban landscape

Muhammad Izuddin,Edward L Webb,Amrita Srivathsan,Tim Wing Yam,Ai Lan Lee

doi:10.1038/s41598-019-56049-y

Muhammad Izuddin, Edward L Webb + Show 3 more

Open Access

https://doi.org/10.1038/s41598-019-56049-y

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Abstract

Urban expansion threatens biodiversity worldwide, therefore urban spaces need to be amenable to biodiversity conservation. On trees in urban environments, natural colonisation and successful translocation of epiphytic orchids are necessary to enhance urban biodiversity, and depend on the availability of compatible orchid mycorrhizal fungi (OMF). However, the extent of OMF presence and distribution, as well as niche requirements for the OMF, remain poorly studied. To identify and quantify OMF on urban trees as well as assess their suitability for native epiphytic orchids, we conducted high-throughput sequencing on tree bark and orchid root samples. OMF were detected at 60% of the study sites on 16% of 270 bark samples (from stem, fork, and branch microsites within each tree). OMF presence and richness on bark samples were related to multiple biophysical factors; in general, humus presence and precipitation levels were positively predictive of OMF presence and richness. We found Ceratobasidiaceae- and Serendipitaceae-associated OMF both on bark and within roots. Orchid species also showed differing mycorrhizal specificity. Sites associated with fungal genera Ceratobasidium, Rhizoctonia, and Serendipita were considered suitable habitats for seven orchid species. The results suggest that urban trees support OMF and are therefore suitable for native orchid species; however, OMF availability are largely constrained by biophysical factors. To maximise the likelihood of translocation success and consequent natural establishment, we propose that (micro)sites are screened for compatible OMF prior to any intervention.

Highlights

Urban expansion threatens biodiversity worldwide, urban spaces need to be amenable to biodiversity conservation
We successfully retrieved orchid mycorrhizal fungi (OMF)-operational taxonomic units (OTUs) from roots of 8 of the 11 orchid species sampled
Non-rhizoctonia OTUs encountered on bark samples and in orchid roots were largely Ascomycetes, e.g., genera Fusarium (Hypocreales), Lachnum (Helotiales), and Curvularia (Pleosporales); basidiomycete representatives such as genera Mycena (Agaricales) and Marasmius (Agaricales) were detected

Summary

Introduction

Urban expansion threatens biodiversity worldwide, urban spaces need to be amenable to biodiversity conservation. On trees in urban environments, natural colonisation and successful translocation of epiphytic orchids are necessary to enhance urban biodiversity, and depend on the availability of compatible orchid mycorrhizal fungi (OMF). With urban areas becoming increasingly widespread, the need to assess the capacity of these spaces for biodiversity conservation becomes more urgent, necessitating knowledge of taxa and sites that are amenable to conservation in non-forest habitats. While root-based inferences can help determine species-specific mycorrhizal associations, they do not directly inform the extent of OMF presence and distribution[13]. High-throughput sequencing allows recovery of microbial amplicons, including unculturable microorganisms, from environmental samples such as soil and tree bark[41] In this context, high-throughput sequencing can facilitate large-scale screening for known OMF on potential (micro)sites. The availability of suitable OMF and niche conditions are imperative for both in situ as well as ex situ conservation to succeed[24,45,46,47,48]

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