Interactions between plants, gall midges, microfungi and parasitoid wasps
Gall-inducing midges may negatively impact flowering and seed production of taxonomically difficult species of saltbushes, bluebushes and beaded glassworts. However, little is known about the distribution, identity and specificity of these midges, the wasps parasitising them, or the microfungi lining the larval chambers.
Typically, different species of gall-inducing midge (eg. Asphondylia, Dacytlasioptera) form a unique gall morphology on their plant hosts, which may be found in floral or stem tissue. For example, Asphondylia sarcocorniae induces swellings in articles, and A. floriformis induces a complex flower-like structure of articles on Sarcocornia quinqeflora (Beaded Glasswort). On Tecticornia arbuscula, two species induce spherical galls, but differ in the number of larvae or larvae chambers present – A. peelei with multiple larvae and A. tecticorniae with a single larva. In Maireana species thus far most galls have the appearance of ‘florets’ or ‘pom-poms of leaves’; all are multi-chambered, and one new species has as many as 39 chambers in a single gall!
Herbarium specimens of Sarcocornia, Tecticornia and Maireana from the 1870s to 1890s have galls, so the gall midge–host plant interaction is not a recent phenomenon. However, botanists tend not to collect plant material for specimens if they are ‘parasitised’, so more recent material has few galls.
When fresh galls are sectioned and stained, a fungal layer (of varying thickness) lining the larval chamber is observed. The fungal layer appears the same morphologically in different galls. However, it is unclear if there is more than one species of fungus within a gall or if a given fungus occurs in more than one gall type. Preliminary DNA analysis of fungi lining the larval chamber of galls on Sarcocornia and Tecticornia showed that the same fungus was present: Botryosphaeria dothidea. This fungus is considered to be the causal agent of rot in various fruit and also cankers in woody plants, but is also shown to be endophytic and nonpathogenic in many hosts.
We plan to examine material from a broad geographic range to:
- determine the diversity of gall-inducing midges, parasitoid wasps and microfungi present in galls on different species of glassworts, saltbush and bluebush
- examine biogeographic and co-evolutionary patterns of gall-inducing midges, parasitoid wasps and microfungi
- determine whether or not the gall midge larvae are truly mycophagous
- determine the source of microfungal inoculum.
- Teresa Lebel (Royal Botanic Gardens Melbourne)
- Anneke Veenstra (Deakin University)
- Kelly Shepherd (Western Australian Herbarium)
- Mike Baily (University of Melbourne)
- Peter Kolesik (Bionomics, SA)
- Megan Erm (University of Melbourne, MSc)
Veenstra, A.A., West, J.M. and Milne, J. (2014). Infestation levels of the gall midge Asphondylia floriformis (Diptera: Cecidomyiidae) on its host plant Sarcocornia quinqueflora (Chenopodiaceae). Plant Protection Quarterly 29, 37–44.
Lebel, T., Peele, C. and Veenstra, A. (2012). Fungi associated with Asphondylia (Diptera: Cecidomyiidae) galls on Sarcocornia quinqueflora and Tecticornia arbuscula (Chenopodiaceae). Fungal Diversity 55, 143–154.
Veenstra, A.A., Michalczyk, A. and Kolesik, P. (2011) .Taxonomy of two new species of gall midge (Diptera: Cecidomyiidae) infesting Tecticornia arbuscula (Salicornioideae: Chenopodiaceae) in Australian saltmarshes. Australian Journal of Entomology 50, 393–404.
Veenstra-Quah, A.A., Milne, J. and Kolesik, P. (2007). Taxonomy and biology of two new species of gall midge (Diptera: Cecidomyiidae) infesting Sarcocornia quinqueflora (Chenopodiaceae) in Australian salt marshes. Australian Journal of Entomology 46, 198–206.