Characterisation of fungal symbionts and microbial communities of Austroplatypus incompertus (Platypodinae) and other Australian ambrosia beetle species

Abstract

Insects are the most diverse taxonomic class and live often in a tight symbiotic associations with a microbial cosmos that is expected to be even more diverse. One of these symbioses is fungal farming, the ability to propagate, cultivate and harvest fungi as a primary food source. This ability evolved independently in three major insect orders, attine ants, macrotermitine termites and ambrosia beetles. While many studies have been conducted on the former two orders, the diversity and mechanisms of fungal farming in ambrosia beetles are less understood. Ambrosia beetles include two subfamilies, Scolytinae (bark beetles) and Platypodinae (pinhole borers). Platypodinae species are almost all fungal famers evolved roughly 90 million years ago, and fungal farming is likely to have evolved once in this lineage. Therefore, they possibly constitute the oldest lineage of fungal farming insects, while fungal farming in Scolytinae evolved multiple times and is much younger (~ 50 million years). There are 1,400 species of described Platypodinae species, however less than 1% of their fungal associates have been described. The diversity lurking in tropical biogeographic regions of South America, Asia and Australia is expected to be large, and this, therefore, creates a great opportunity to discover and describe new species in these regions. The aim of this thesis was to contribute to a better understanding of the fungal farming in Platypodinae by investigating the microbial community of four Australian platypodine species. So far 46 Platypodinae species have been recorded for this continent, however none of their fungal or bacterial partners have been formally described. This thesis is the first systematic analysis and characterisation of the fungal symbionts and the microbiome of Australian Platypodinae species. It provides a first insight in the microbial community diversity and mechanisms shaping these communities in two ancient and two more derived ambrosia beetle species, and therefore constitutes an important contribution to the study of the ecology and evolution of ambrosia beetles.

Date of Award	2019
Original language	English