Comparison of Life History Traits between the Naled-resistant and -susceptible Lines of the Oriental Fruit Fly (Bactrocera dorsalis)
Date Issued
2009
Date
2009
Author(s)
Fang, Chi-Chun
Abstract
The oriental fruit fly (Bactrocera dorsalis (Hendel)) is an important economic pest for tropical fruits in the world. In recent years, fruit flies (Bactrocera spp.) resistances to organophosphate insecticides (OPs) in the field have been reported in Taiwan. Generally, the resistant populations are hypothesized to have fitness costs as compared to the normal group, because they have the ability to generate resistance. There are three parts in this research for finding the differences of the life history traits between the resistant line and susceptible line to make the pest controls more efficient. Firstly, we investigate the fitness performance by comparing life-history traits (life table) between the naled-resistant and -susceptible lines of oriental fruit flies. We mainly compare the hatchability, the duration of egg, larval, and pupal stages as well as adult longevity and fecundity of the two lines under three constant temperatures (20, 25, and 30°C). We also compared the relationship between the OPs resistant allele frequency and temperature conditions in the field for proving the situation of adult longevity between the two lines in the laboratory. As to the application of the life table results into pest management of the oriental fruit fly, the third part of this study is predicting the population parameters by the matrix model and estimating the influences of different controlling rates to the fruit fly populations. The first part of the results showed no significant differences of egg hatching rate between the two lines. However, the susceptible line significantly possesses shorter developmental time of egg, larval, and pupal stage at every temperature than those in the resistant line, except the egg stage at 30°C, where there was no significant difference. The adult longevity of the resistant line significantly outlives susceptible populations under 20°C, but is significantly shorter than the susceptible line at 30°C. The highest fecundity values occur at 25°C in both lines though there are no significant differences between the two lines at 20°C. However, the fecundity of the susceptible line at 25 and 30°C are significantly higher than the resistant line. The values of mean generation time (T), intrinsic rate (rm), finite rate of increase (λ), and the doubling time (DT) are increased from 20 to 30°C. The highest and lowest values of the net reproductive rate (R0) in the susceptible line are 362.97 and 229.86 at 25 and 20°C, respectively. However, the highest and lowest values of the net reproductive rate (R0) in the resistant line are 234.57 and 189.90 at 25 and 30°C, respectively. As to the mean generation time (T) in the susceptible line, the lowest and highest values are 46.55 d and 58.06 d at 30 and 20°C, respectively. In contrast, the resistant line also has the lowest and highest values at 30 and 20°C, which are 41.66 d and 62.01 d, respectively. On the aspect of the intrinsic rate (rm), the highest and lowest values are 0.123 and 0.093 in the susceptible line, respectively; the highest and lowest values of the intrinsic rate (rm) are 0.126 and 0.087 at 30 and 20°C, respectively. The highest and lowest values of the doubling time (DT) in the susceptible line are 7.40 d and 5.64 d at 20 and 30°C, respectively, and the highest and lowest values of the doubling time (DT) in the resistant line are 7.93 d and 5.50 d at 20 and 30°C, respectively. Results of the relative fitness costs from this study are generally consistent with the hypothesis of fitness cost on the resistant line at 25 and 30°C. On the concept of field investigation, the results of detecting the gene point mutation of acetylcholinesterase show that the resistant allele frequency at July, 2008 and March, 2009 are 69% and 43%, respectively, indicating that the amount of the resistant population was higher than the susceptible population when the temperature was lower. Hence, the differences of the adult longevity between both lines at 20 and 30°C can be explained. In the estimation by the matrix model, the life cycle of the oriental fruit fly was divided into 5 stages, including the egg, larval, pupal, sexually immature adult (SIA), and sexually mature adult (SMA) stage, for evaluating the eigenvector. The estimations of the λ change with daily survival probability which show that the eigenvector of the resistant line is 20°C at SIA and SMA stages and the eigenvector of the susceptible line are 25 and 30°C at the SIA stage. In contrast, the same estimations of the eigenvectors of the susceptible line at 20, 25, and 30°C are pupal stage, SIA, and SIA stages, respectively. Finally, the estimations of the λ by changing in stage duration show that if the egg duration is elongated, the λ will decrease sharply in both lines. However, elongating the SMA little influences the population growth of both lines. It suggests that we can do the pest control based on the resistant allele frequencies and the temperature conditions in certains area at the SIA stage.
Subjects
Bactrocera dorsalis
life table
naled
fitness cost
resistant allele frequency
matrix model
Type
thesis
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