Environmental and biogeographical drivers of the Leptospermum scoparium (mānuka) phyllosphere microbiome

Abstract

A substantial body of research exists on the physiology and genetics of Leptospermum scoparium (mānuka); however, the mānuka phyllosphere has not yet been investigated. This research, therefore, provides the first exploration of the bacterial communities comprising the mānuka phyllosphere. In total, 89 samples were collected from five native mānuka forests during the November 2016 – January 2017 mānuka flowering season, and examined alongside spatial, environmental, and host-tree related metadata. Cultivation-independent methods, including DNA extraction and 16S rRNA gene PCR amplicon sequencing analysis, were used to characterise phyllosphere communities. Using a combination of statistical tests, the BLAST algorithm, and a PICRUSt analysis, a habitat-specific core microbiome comprising members of Acidobacteria, Alphaproteobacteria, Bacteroidetes, and Verrucomicrobia, was present in all samples. Distinct microbial biogeographical patterning was also identified in the mānuka phyllosphere whereby spatially structured gradients in environmental variables, such as temperature and precipitation, correlated with bacterial community structure. The results from this study provide new insight pertaining to the structure, composition, and driving factors of the bacterial communities of the mānuka phyllosphere and shed light on theories of microbial ecology, such as microbial biogeography and core microbiomes. This research has the potential to open new avenues in both mānuka and microbial ecology fields of investigation within New Zealand.