Description ofEucalyptodiplosis chionochloaesp. nov., a cecidomyiid feeding on inflorescences ofChionochloa(Poaceae) in New Zealand

Abstract

A cecidomyiid that feeds on developing seeds in the inflorescences of the New Zealand tussock grasses Chionochloa australis, C. conspicua, C. crassiuscula, C.flavescens, C. macra, C. oreophila, C. pallens, C. rigida, C. rubra, C. spiralis and C. teretifolia is formally described from C. pallens. The new species, named Eucalyptodiplosis chionochloae Kolesik, is the most ubiquitous of flower feeders of Chionochloa. Its larvae do not form galls but feed on the developing seeds in autumn, overwinter as diapausing larvae inside the floret, and pupate then rapidly eclose in summer, sometimes after extended diapause. Methods for rearing adults are described. Based on its morphological characters this species is most closely related to two described congeners that form galls on buds of Eucalyptus trees in Australia. Seed predation by Eucalyptodiplosis chionochloae larvae appears to be the primary driver of the extreme mast seeding (variation among years in flower crops) seen in the host Chionochloa species.

Description, phenology and biology ofZelostemma chionochloaeBuhl sp. nov., a platygastrid parasitoid ofEucalyptodiplosis chionochloae(Diptera: Cecidomyiidae) in New Zealand

“…The 1070 m site is dominated by Chionochloa pallens Zotov, and is the same location used in previous studies (kelly et al 1992;Rees et al 2002;kolesik et al 2007). The 450 m site contains large C. rubra Zotov that grow on a southeast-facing slope amongst otherwise exotic grassland vegetation.…”

“…The geographical range of Z. chionochloae is unknown, but because it appears to be host specific to E. chionochloae, it probably has a similar geographic distribution as its host, which has been found from the central North island, including Mt Taranaki, to Stewart island (Mckone et al 2001;kolesik et al 2007). however, Z. chionochloae may prefer lower elevations because during our study much higher numbers emerged at 450 m altitude than at 1070 m altitude.…”

“…As a host-specific seed predator, local populations of E. chionochloae would not be able to survive zero-flowering years because of a lack of breeding sites for the larvae. However, our recent studies have shown that this cecidomyiid can enter prolonged diapause to escape non-flowering years (Kolesik et al 2007). Similarly, parasitic wasps are dependent on their hosts for the development of the wasp larvae.…”

“…The cecidomyiid midge Eucalyptodiplosis chionochloae Kolesik was known for over 40 years in its larval and egg stages, but it was only recently formally described (Kolesik et al 2007) following the first rearing of adult males and females. Eucalyptodiplosis chionochloae, the snow tussock flower midge, is a seed feeder on Chionochloa tussock grasses which exhibit mast seeding (extreme variation of flowering among years; ).…”

The parasitoids of seed predators attacking snow tussocks,Chionochloaspp. (Poaceae)

“…Chionochloa species suffer high levels of pre-dispersal seed and flower predation (hereafter 'seed predation') by three herbivorous insects (White 1975;Kelly & Sullivan 1997;Sullivan & Kelly 2000;McKone et al 2001;Kolesik et al 2007). These are a chloropid fly (Diplotoxa similis Spencer), a gelechiid moth (Megacraspedus calamogonus Meyrick) and the recently described cecidomyiid fly Eucalyptodiplosis chionochloae Kolesik (Kolesik et al 2007). The extreme mast seeding of Chionochloa is thought to be an adaptive response to heavy seed predation (Kelly & Sullivan 1997;Rees et al 2002).…”