Circadian phase effects on reproductive success and population growth of two sibling species of cockroach, Blattella germanica and Blattella bisignata
Date Issued
2008
Date
2008
Author(s)
Wu, Hsin-Hue
Abstract
The goal of this study was to unveil the ecological significance of biological clock in cockroach. In particular, study demonstrated the differences of reproductive success in cockroach, Blattella germanica and B. bisignata, when the mate-finding locomotion was off-phased between sexes. In each step leading to a successful mating was investigated the significant effect by the locomotor circadian phase. The mate-finding rate, copulation rate and number of offspring in each major step were calculated when the pairs were grouped into four scenarios, of which 10L♀-10L♂ and 10L♀-10L♂ as on-phased scenarios and 22L♀-10L♂and 10L♀-22L♂ as the off-phased ones. The results indicated circadian phase significantly affected the success of mate-finding, timing of copulation, and number of offspring. In particular, the female’s circadian phase was the crucial factor to determine the success of reproduction. Since B. germanica is a domicile cockroach and B. bisignata is a feral species, the effect of circadian phase contributes significantly on reproductive success more in the former than the latter. Imagine the B. bisignata was able to establish in cockroach-free households, too. May the B. bisignata can win the competition with B. germanica? In this article, I develop a stage-structured population model of these two species and use two kinds of calculate methods (such as in time continuous and time discrete) to explore (i) whether their circadian clock impact their long-term population dynamics, (ii) which of these species is a superior competitor, and (iii) how stringent potential pest control strategies have to be to significantly impact established populations of the German cockroach. The results of the model are as follows. Firstly, variation in the circadian clock did not affect cockroach population dynamics unless males and females were out of phase and their mate finding abilities rather limited. Secondly, the German cockroach was the superior competitor: it was able to invade and drive out established populations of the double-striped cockroach and prevent any invasion of the latter. Finally, only a significant and simultaneous reduction in a number of most sensitive German cockroach parameters gave us a chance of species extirpation. Only careful and data-based models of German (and double-striped) cockroach population dynamics can become helpful tools in our quest to win the fight over this awkward yet very sturdy species.
Subjects
Mate-finding rate
masking effect
locomotion
circadian clock
German cockroach
double-striped cockroach
sensitivity and elasticity analysis
Type
thesis
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