Bursaphelenchus penai n. sp (Tylenchomorpha: Aphelenchoididae), a phoretic associate of ambrosia beetles (Coleoptera: Scolytinae) from avocado in Florida

During an experimental host-plant survey for the invasive redbay ambrosia beetle, Xyleborus glabratus, in Homestead, Florida, it and three native species of ambrosia beetle, Xyleborus affinis, X. volvulus and Xyleborinus gracilis were found to be associated with a Bursaphelenchus species. This nematode species, isolated from ambrosia beetles from the tribe Xyleborini, was cultured on Monilinia fructicola or Botryotinia fuckeliana for further study and was determined to be new to science and a putative sister species to B. kiyoharai because of two apomorphic characters in males, viz., possession of a tail spike vs the typical bursal flap, and the apparent absence of the P1 ventral single papilla, both typically plesiomorphic characters for the genus. Additionally, B. kiyoharai is associated with X. serriatus suggesting that the host and microbiome associations that are shared between these two species, both of which are carried by ambrosia beetles, may have ecological and biological significance in their evolution and lineage radiation. Molecular phylogenetic analyses of the near-full-length small subunit (SSU: 18S) and the D2/D3 expansion segments of the large subunit (LSU: 28S) confirmed that B. penal n. sp. is very closely related to B. kiyoharai which is a member of the B. fungivorus clade that includes B. thailandae and B. willibaldi. Bursaphelenchus penal n. sp. and B. kiyoharai both share very similar overall spicule morphology with the B. fungivorus clade. The new species is described and can be typologically differentiated from B. kiyoharai by the position of the hemizonid and excretory pore and its different geographical and host associations.