Chemical ecology of cryptic species of Eccritotarsus catarinensis (Carvalho) (Hemiptera: Miridae), biological control agents of water hyacinth (Eichhornia crassipes)

Chemical ecology of cryptic species of Eccritotarsus catarinensis (Carvalho) (Hemiptera: Miridae), biological control agents of water hyacinth (Eichhornia crassipes)
Sandiso MNGUNI, Unathi L.P. Heshula, Iain D. Paterson, Julie A. Coetzee
Biological Control Research Group, Department of Zoology & Entomology, Rhodes University, Grahamstown

Water hyacinth, Eichhornia crassipes (Martius) Solms-Laubach (Pontederiaceae), is a floating aquatic macrophyte and is one of the world’s worst weeds. Its distribution extends in tropical, subtropical and warm temperate regions and it was first seen in South Africa around the 1900s, where it is currently most prominent in the coastal regions of KwaZulu Natal, and in the Vaal and Crocodile rivers of the North-West Province. The mirid, Eccritotarsus catarinensis (Carvalho) (Hemiptera: Miridae), one of several biological control agents used against the weed, has two highly differentiated and distinct populations, one from Brazil and the other from Peru, that have recently been confirmed as reproductively isolated cryptic species. The aim of the project is to determine the pheromone production in these two reproductively-isolated cryptic species, and to determine whether pheromones have played a role in speciation. Odour-source experiments using Y-tubes and aeration chambers, as well as behavioural-observation experiments are in progress in the Chemical Ecology Laboratory, in the Department of Zoology and Entomology at Rhodes University (Grahamstown), to investigate the attraction of males towards females in both populations. Later, antennal preparations (antenna + ground electrode) will be connected to an Electroantennogram (EAG) to detect whether chemical compounds/olfactory stimuli have elicited an electrical response in the antenna of the mirids or not. Thereafter, chemical compounds will be analysed by Gas-Chromatography Mass-Spectometry (GC-MS) to identify specific compound(s) that stimulate the observed response. We predict that the quantity and quality of pheromones produced by these two reproductively isolated cryptic species will differ significantly.