First record of Fergusonina (Diptera: Fergusoninidae) and associated Fergusobia (Tylenchida: Neotylenchidae) forming galls on Leptospermum (Myrtaceae) in Australia, with descriptions of new species

Abstract

A new species of fly, Fergusonina madidum Taylor sp.n. (Diptera: Fergusoninidae) from Leptospermum madidum A.R. Bean in far north Queensland and a new species of nematode, Fergusobia leptospermum Davies sp.n. (Tylenchida: Neotylenchidae) from L. laevigatum (Gaertn.) F. Muell. in southern Victoria, Australia are described. These represent the first species of the Fergusonina fly/Fergusobia nematode mutualism to be described from the genus Leptospermum (Myrtaceae). Fergusonina madidum sp.n. forms lateral and terminal multilocular shoot bud galls enclosed in subterminal leaflets. It can be distinguished from all other species of Fergusonina by the lack of dorsal setae on abdominal segment 7 of the female. Unlike most described species of Fergusonina it also lacks the posterior cross vein m-cu in the wing. It shares this character with F. giblindavisi Taylor and F. thomasi Taylor from flower bud galls on Corymbia, but both these species are large and abdominal segment 7 of females is densely setose. Its larva is unknown but from the morphology of puparia the dorsal shield comprises 3 broad transverse bands comprising lateral rows of raised ridge-like sclerotised spicules. Its associated species of nematode is not known. Fergusobia leptospermum sp.n. is associated with cryptic lateral and terminal usually unilocular shoot bud galls. It is characterised by the combination of an open to tight C-shaped parthenogenetic female having a small ‘a’ ratio, with a short but sturdy stylet, flat anterior end; huge dorsal pharyngeal gland, reproductive system with a relatively long uterus, and a sub-conoid tail with a broadly rounded tip; a C-shaped infective female with an almost hemispherical tail tip which may or may not be ventrally hooked; and an open C-shaped male with angular spicules and peloderan bursa arising near the anterior end, and a relatively long (c’ = 2.2–3.2) sub-conoid tail with a bluntly to broadly rounded tip. Its status as a distinct species is confirmed by molecular analyses. Its associated species of fly is known only from several larvae and a puparium, and remains undescribed. The dorsal shield of this Fergusonina species comprises 7 broad bands, the first six having heavily sclerotised raised ridges and the seventh with a medial field of weak spicules. The widely separated collection localities, together with the large number of species in Leptospermum suggest that the mutualism is likely to be speciose and occupy a broad geographic range on this host.