<i>Serratia</i> spp. bacteria evolved in Aotearoa-New Zealand for infection of endemic scarab beetles

<p dir="ltr">The Melolonthinae branch of the beetle family Scarabaeidae has evolved in isolation in Aotearoa, radiating into >100 endemic species, since Aotearoa separated from Gondwanaland 82 million years ago. The group includes important pasture pests, such as the New Zealand grass grub <i>Costelytra giveni</i> and the manuka beetle <i>Pyronota festiva</i>. These beetles, like other organisms, host their own distinctive microflora including beneficial microbial symbionts and pathogens. A wide range of microbial pathogens infect the Scarabaeidae, but in Aotearoa the bacteria <i>Serratia entomophila</i>, <i>S. proteamaculans</i> and <i>S. quinivorans</i> (Enterobacteriaceae) are frequently found causing natural disease epizootics in <i>C. giveni</i>. <i>S. entomophila</i> is widespread in Aotearoa pasture soils, with only rare isolations of <i>S. entomophila</i> documented in other countries. In contrast <i>S. proteamaculans</i> and <i>S. quinivorans</i> are globally ubiquitous, and are widely distributed within Aotearoa, with some isolates active against either <i>C. giveni</i> or <i>Pyronota</i> spp. larvae, or both. Virulence determinants that impart differential host specificity and potency are located on variants of the amber disease associated plasmid (pADAP). The host specificity of the <i>Serratia</i>-scarab system and the absence of similar systems in other geographies, suggests that the relationship between <i>Serratia</i> spp. and endemic scarabs has evolved in Aotearoa.</p>