KELAKUAN DAN EKOLOGI PEMBIAKAN LALAT BUAH BACTROCERA CARAMBOLAE DAN B. PAPAYAE
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Date
2000-11
Authors
LING, WEESUK
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Abstract
Fruit flies, Bactrocera carambolae and B. papayae which are economically important species
in the B. dorsalis complex were investigated. B. papayae attained earlier sexual maturation,
higher mating propensity and intraspecific mating success compared with B. carambolae.
Remating was common in both sexes of B. papayae and B. carambolae males except B.
carambolae female. Both species exhibited similar courtship and sexual behavioural
sequences but B. papayae males exhibited earlier courtship and were more aggressive, besides
a longer courtship period and shorter time in copulation. Endogenous components present in
B. carambolae male rectal gland were shown to increase with age, which corresponded with
sexual maturity. These compounds were emitted by sexually mature B. carambolae males
during courtship period and were more attractive to conspecific females than males. The
synthetic components were able to elicit positive anemotactic response of B. carambolae
female in a decreasing order of: male emission,> 6-oxo-1-nonanol > N-3-methylbutyl
acetamide. A whole rectal gland extract stimulates female ovipositor extrusion, i.e. sexual
acceptance stance. The age-related anti-predation effect of B. carambolae male corresponded
with the changes of these endogenous components in the male rectal gland. Compound 6-oxo-
1-nonanol when topically applied onto female's thorax, was able to deter gecko predation.
Comparison of the anti-predation strategy of B. carambolae and B. papayae further revealed
that immature B. carambolae male < mature methyl eugenol-deprived B. carambolae male =
methyl eugenol-fed B. carambo!ae male< methyl eugenol-fed B. papayae male in deterring
gecko predation. The evolutionary aspects of the defensive repertoire exhibited by these fruit
flies are discussed. Using gas chromatographic analysis, the phenylpropanoids (methyl
eugenol metabolites) were detected in both males' rectal glands 15-min post-feeding on
methyl eugenol. The accumulation profile of these phenylpropanoids showed subsequent
increase with time. The phenylpropanoids were also detected in wild male rectal gland of
Bactrocera spp. These findings further ascertained the ecological importance of ME in the
fruit fly chemical ecology. B. papayae males exhibited a higher sensitivity, consumption and
better utilization of ME with a longer storage of the phenylpropanoids than B. carambolae
males. Volatile emission from B. papayae and B. carambolae males after methyl eugenol
consumption were shown to contain phenylpropanoids but an improved mating performance
was only observed for B. carambolae males 3 days post methyl eugenol feeding. Coniferyl
alcohol, a phenylpropanoid, was demonstrated to act as a sex and male aggregation
pheromones in B. carambolae. Females of both species responded to heterospecific male
pheromone in a wind tunnel assay. B. papayae females preferred to mate with conspecific
males while B. caranibolae female was less discriminative. In the absence of conspecific
males, females of both species are likely to mate with h~_terospecific males. Pre-mating
isolation, in terms of temporal, spatial and sexual factors, governs better than post-mating
isolation in sexual isolation between B. carambolae and B. papayae. Hybridization bet\veen
these sibling species produced hatchable eggs and viable offspring with an adult sex ratio of
1: 1 and a synchronized sexual maturity when compared with the parental species. Male
pheromone analysis is found to be more effective than scanning electron microscopy or
morphometric on the fruit fly genitalia in determining hybrids from the parental populations
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KELAKUAN DAN EKOLOGI PEMBIAKAN LALAT BUAH