Bark and ambrosia beetles (Curculionidae: Scolytinae), their phoretic mites (Acari) and associated Geosmithia species (Ascomycota: Hypocreales) from Virgilia trees in South Africa

Abstract

Bark and ambrosia beetles are ecologically and economically important phloeophagous insects that often have complex symbiotic relationships with fungi and mites. These systems are greatly understudied in Africa. In the present study we identified bark and ambrosia beetles, their phoretic mites and their main fungal associates from native Virgilia trees in the Cape Floristic Region (CFR) of South Africa. In addition, we tested the ability of mites to feed on the associated fungi. Four species of scolytine beetles were collected from various Virgilia hosts and from across the CFR. All were consistently associated with various Geosmithia species, fungi known from phloeophagous beetles in many parts of the world, but not yet reported as Scolytinae associates in South Africa. Four beetle species, a single mite species and five Geosmithia species were recovered. The beetles, Hapalogenius fuscipennis, Cryphalini sp. 1 and Scolytoplatypus fasciatus were associated with a single species of Elattoma phoretic mite that commonly carried spores of Geosmithia species. Liparthrum sp. 1 did not carry phoretic mites. Similar to European studies, Geosmithia associates of beetles from Virgilia were constant over extended geographic ranges, and species that share the same host plant individual had similar Geosmithia communities. Phoretic mites were unable to feed on their Geosmithia associates, but were observed to feed on bark-beetle larvae within tunnels. This study forms the first African-centred base for ongoing global studies on the 1 associations between arthropods and Geosmithia species. It strengthens hypotheses that the association between Scolytinae beetles and dry-spored Geosmithia species may be more ubiquitous than commonly recognised.

Geosmithia species associated with fir-infesting beetles in Poland

“…where adults do not enter these tissues. Although, there are many studies confirming associations between ambrosia beetles and Geosmithia fungi [8,10,11,14,16], our study showed that T. lineatum does not transmit Geosmithia. There was also no evidence that this ambrosia beetle can transmit Geosmithia fungi in pine habitats [9].…”

“…There was also no evidence that this ambrosia beetle can transmit Geosmithia fungi in pine habitats [9]. The genus Geosmithia currently includes 44 recognized taxa with only 16 described to date, most of which are associated with phloem-breeding bark beetles [4,5,[7][8][9][10][11][12][13][14][15][16]. In the present study, we identified two distinct Geosmithia operational taxonomic units (OTUs) based on morphological and molecular characterizations.…”

“…Bark-and wood-boring beetles (Coleoptera) are commonly associated with various species of ascomycetes in three orders: Ophiostomatales, Microascales, and Hypocreales [1,2]. Members of the Hypocreales are common in all types of moist forests [3], however, only Geosmithia fungi that produce Penicillium-like conidiophores are associates of bark beetles on hardwood and conifer trees worldwide [4][5][6][7][8][9][10][11][12][13][14][15][16]. The bark beetle-Geosmithia relationships vary, ranging from specialists with a limited range of vectors to generalists recorded with numerous vectors [4,6,9,11].…”

Geosmithiaassociated with bark beetles and woodborers in the western USA: taxonomic diversity and vector specificity

“…Geosmithia (Ascomycota: Hypocreales) is a genus of mitosporic fungi associated with phloeoand mycophagous bark beetles worldwide . Geosmithia species appear to occur at least as frequently as ophiostomatoid fungal associates of many bark beetles that colonize hardwoods and conifers in the Cupressaceae (Kirschner 2001, Machingambi et al 2014. On other conifers (Pinaceae), the typical vectors of Geosmithia are bark beetles infesting small diameter branches and twigs of Pinus, Picea, and Abies (Jankowiak and Rossa 2008, Jankowiak and Kolařík 2010, Jankowiak et al 2014.…”

“…Bark beetle-vectored G. pallida has been reported as a causal agent of foamy bark canker in oak in California (Lynch et al 2014) (but see Discussion). Geosmithia species produce numerous biologically active compounds (Stodůlková et al 2009, Malak et al 2013a) and several species can inhibit populations of phoretic mites, including parasites of beetle vectors (Machingambi et al 2014). Some Geosmithia species engage in horizontal gene transfer with the pathogenic fungus Ophiostoma novo-ulmi (Bettini et al 2014), but the potential for horizontal acquisition of pathogenicity has not been investigated.…”