Differences in structure of northern Australian hypolithic communities according to location, rock type, and gross morphology.

Susannah P Guenther,Keith A Christian,Karen S Gibb,Alea M Rose,Mirjam Kaestli

doi:10.3934/microbiol.2018.3.469

Abstract

Hypolithic communities (under translucent rocks) were compared between a semi-arid site (Wave Hill) and a site with considerably higher rainfall (Lake Bennett) to test the hypothesis that the communities at the higher rainfall site would be more diverse. A total of 153 cyanobacteria operational taxonomic units (OTUs) were identified, and only 50 of those were found at both sites. Of these, only two were core OTUs, as defined as being present in ≥90% of samples, highlighting the extreme differences in the cyanobacterial communities at the two sites. At Wave Hill, we compared the composition of the cyanobacterial components under two different rock types (quartz and prehnite) to determine if the different minerals would result in different hypolithic communities, but no differences were found. Of the 42 core OTUs found at Wave Hill, 22 (52%) were shared between the two rock types. As hypothesised, the diversity of both cyanobacteria and eukaryotes in the hypolithic communities was significantly higher at Lake Bennett. Some hypolithic communities were thin and tightly adhered to the rock surface, but others were thicker and could be peeled off the rock in sheets. However, the two types were not significantly different in OTU composition. Metazoans, primarily nematodes, were ubiquitous, raising the possibility that nematodes may act as vectors to transport the components of hypolithic communities from rock to rock as a mechanism of colonization.

Highlights

Extreme environments, such as hyper-arid deserts, can present challenges for survival of most species [1]
With respect to the objectives of this study, we found that: (1) Site had a significant effect on community composition and diversity with respect to both cyanobacteria and eukaryotes, with the higher rainfall site near Lake Bennett being more diverse
(2) There was no difference between the two rock types with respect to the community composition of cyanobacteria at

Summary

Introduction

Extreme environments, such as hyper-arid deserts, can present challenges for survival of most species [1] These environments often include biological soil crusts and hypolithic organisms, dominated by cyanobacteria, that are increasingly recognized as performing important ecosystem functions [2]. The composition of these communities is affected by the quality and quantity of radiation passing through the rock [10], the sodium content in the soil, and stochastic processes [11] Translucent rocks such as quartz are common in many arid zones, and they provide physical stability, UV protection, photosynthetically active radiation, and increased availability of moisture that allows these communities to develop [1,12,13]

Results

Discussion

Conclusion