Abundance and dynamics of filamentous fungi in the complex ambrosia gardens of the primitively eusocial beetleXyleborinus saxeseniiRatzeburg (Coleoptera: Curculionidae, Scolytinae)

Abstract

Insect fungus gardens consist of a community of interacting microorganisms that can have either beneficial or detrimental effects to the farmers. In contrast to fungus-farming ants and termites, the fungal communities of ambrosia beetles and the effects of particular fungal species on the farmers are largely unknown. Here, we used a laboratory rearing technique for studying the filamentous fungal garden community of the ambrosia beetle, Xyleborinus saxesenii, which cultivates fungi in tunnels excavated within dead trees. Raffaelea sulfurea and Fusicolla acetilerea were transmitted in spore-carrying organs by gallery founding females and established first in new gardens. Raffaelea sulfurea had positive effects on egg-laying and larval numbers. Over time, four other fungal species emerged in the gardens. Prevalence of one of them, Paecilomyces variotii, correlated negatively with larval numbers and can be harmful to adults by forming biofilms on their bodies. It also comprised the main portion of garden material removed from galleries by adults. Our data suggest that two mutualistic, several commensalistic and one to two pathogenic filamentous fungi are associated with X. saxesenii. Fungal diversity in gardens of ambrosia beetles appears to be much lower than that in gardens of fungus-culturing ants, which seems to result from essential differences in substrates and behaviours.

Wood resource and not fungi attract early‐successional saproxylic species of Heteroptera – an experimental approach

“…Mycetophagous saproxylic beetles inoculate dead wood with mycelia or spores of their host fungi, as has been demonstrated in particular for ambrosia beetles and other bark beetles (e.g. Kirisits, ; Biedermann et al ., ). Saproxylic heteropterans might do the same, which would allow them to colonise wood that is not yet occupied by suitable host fungi.…”

Know your farmer: Ancient origins and multiple independent domestications of ambrosia beetle fungal cultivars

“…A similar situation appears to have occurred in the Microascales cultivars where existing farming lineages appear to have independently domesticated at least three new fungal lineages (Mayers et al., ). Studies to confirm the exact nature of beetle‐fungi domestications are confounded by the fact that beetle‐fungi fidelity is (usually) limited, and beetles of the same species can carry multiple or different symbionts (Batra, ; Biedermann, Klepzig, Taborsky, & Six, ; Harrington et al., ; Kostovcik et al., ). It is possible there were two domesticated fungal lineages when the Platypodinae radiated.…”

A major symbiont shift supports a major niche shift in a clade of tree‐killing bark beetles

“…Instead, they must partner with microbes, often fungi, to help them meet their needs. Examples include wood-boring beetles that capitalise on the ability of wood-rotting fungi to move nutrients from soil into rotting stumps (Filipiak and Weiner, 2014, 2017, Filipiak et al, 2016 and ambrosia beetles that rely on fungal 'crops' they grow in tunnels constructed in sapwood (Biedermann et al, 2013;Hulcr and Stelinski, 2017).…”