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German wasp | Vespula germanica

German wasp

Vespula germanica

Coral bush | Ardisia crenata

Coral bush

Ardisia crenata

Purple loosestrife | Lythrum salicaria

Purple loosestrife

Lythrum salicaria

Pom pom weed | Campuloclinium macrocephalum

Pom pom weed

Campuloclinium macrocephalum

Canarybird bush | Crotalaria agatiflora

Canarybird bush

Crotalaria agatiflora

Peanut butter cassia | Senna didymobotrya

Peanut butter cassia

Senna didymobotrya

Rubber vine | Cryptostegia grandiflora

Rubber vine

Cryptostegia grandiflora

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Environmental Programmes

In order to tackle our country’s socio-economic challenges, the government adopted the Outcomes based approach to improve government performance and providing focus on service delivery. find out more

Does phenotypic plasticity influence the thermal physiology of Eccritotarsus catarinensis?

Does phenotypic plasticity influence the thermal physiology of Eccritotarsus catarinensis?
Tamzin GRIFFITH1, Iain D. Paterson1, Julie A. Coetzee2
1Biological Control Research Group, Department of Zoology & Entomology, Rhodes University, Grahamstown, 6140 South Africa
2Department of Botany, Rhodes University, Grahamstown, 6140 South Africa 

Eccritotarsus catarinensis (Carvalho) (Miridae), a biological control agent for water hyacinth, Eichhornia crassipes (Mart.) Solms (Pontederiaceae) has failed to establish in some parts of South Africa due to climatic incompatibility. Some insects have the ability to change their thermal tolerance according to the temperatures they are exposed to, without a change in their genotype. This is known as phenotypic plasticity. Thermal tolerance of two populations of E. catarinensis from different climatic regions of the native range were tested using degree day models. This showed that each population’s thermal physiology matched their particular climate. However, after years of being reared under the same conditions in quarantine, experiments showed that their thermal physiologies have converged, which may be the result of adaptation or thermal plasticity. Samples of E. catarinensis have been collected from the hottest and coldest establishment sites in South Africa. Thermal plasticity will be investigated by determining their critical and lethal thermal limits. This will be done in summer and winter for comparison. Thermal limits will be tested before and after cold hardening using E. catarinensis from the BCRG mass rearing facility. Preliminary results have shown that insects from the colder site have lower thermal tolerances compared to those of the warmer site. If the thermal physiology of E. catarinensis has the ability to change due to phenotypic plasticity then it would be beneficial to exploit that characteristic, thus increasing their chances of establishment in colder regions. This will be done through cold hardening during mass rearing. 

Read 2955 times Last modified on Tuesday, 03 May 2016 12:12

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