The impact of temperature on several fitness traits of two populations of Eccritotarsus catarinensis, a biological control agent for water hyacinth in South Africa

The impact of temperature on several fitness traits of two populations of Eccritotarsus catarinensis, a biological control agent for water hyacinth in South Africa
Mohannad Ismail, Steve Compton, Martin P. Hill
Department of Zoology and Entomology, Rhodes University, Grahamstown

Water hyacinth (Eichhornia crassipes Mart), a native of South America, has been spread throughout the tropics and subtropics, and is the world’s most damaging aquatic weed. One of the biological control agents released against water hyacinth in South Africa is the sap-sucking bug Eccritotarsus catarinensis Carvalho (Hemiptera: Miridae). The effectiveness of weed control agents is often influenced by local temperatures, which can determine both their distribution and performance. We evaluated the responses of two populations of E. catarinensis to three constant temperatures (20°,

25° and 30°C) using laboratory cultures that originated from Peru and Brazil. The two populations are morphologically identical, but genetically distinct. The objective was to determine if the populations differ in their responses to temperature and consequently whether they may prefer different areas of the plant’s introduced range. Reproductive output, hatching rates and sex ratios were recorded at each temperature. Reproductive output of both populations was significantly reduced at 30°C compared with that at 25 and 20°C. Peruvian individuals, nonetheless, continued their development at

30ºC, whereas Brazilian individuals, that hatched successfully, did not continue their development. The two populations displayed the same adult sex ratio (55% female), which was unaffected by temperature. In conclusion, the Peruvian population of E. catarinensis performed differently according to the temperatures and was more resistant than the Brazilian population at the highest temperature and could be best suited to control water hyacinth in the field.