Characterisation of the dimorphic Deladenus beddingi n. sp. and its associated woodwasp and fungus

A new dimorphic species of Deladenus isolated from Sirex californicus from Washington, USA, is described as D. beddingi n. sp. Evolutionary relationships of the new species with other Deladenus species were assessed using multilocus sequencing. Phylogenetic relationships derived from analyses of mtCO1 and ITS showed D. beddingi n. sp. to be genetically distinct from other North American Deladenus parasitising Sirex. Molecular analyses indicated that D. beddingi n. sp. is a member of the D. siricidicola species complex, which also includes undescribed native Deladenus from Sirex cyaneus and S. nitidus, and D. siricidicola from S. noctilio. Mycophagous adults were characterised by the position of the excretory pore, which was located 32 (22-52) and 48 (38-69) μm anterior to the hemizonid in mycophagous females and males, respectively. Typologically, the new species is most similar to D. siricidicola, D. proximus and D. nitobei, but can be distinguished from these species by several morphometric traits, including the value of ratios a, b, c of the mycophagous females and males, ratio b of the infective females, and the morphology of the tail of the mycophagous females, which is narrow and gradually tapering. This novel nematode species feeds on the fungus Amylostereum chailletii during its mycophagous phase. Experimental results showed very little reproduction by D. beddingi n. sp. when feeding on A. areolatum compared to robust reproduction when feeding on A. chailletii.