Comparison of colony foundation success between sexual pairs and female asexual units in the termite Reticulitermes speratus (Isoptera: Rhinotermitidae) |
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Authors: | Kenji Matsuura Takayoshi Nishida |
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Institution: | (1) Laboratory of Insect Ecology, Graduate School of Agriculture, Kyoto University, Kyoto 606-8502, Japan Tel. +81-75-753-6147; Fax +81-75-753-6474 e-mail: kenji1@kais.kyoto-u.ac.jp, JP |
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Abstract: | In termites, a male and a female usually found a colony cooperatively. However, pairing efficiency tends to be low in Reticulitermes speratus because of a limited mate-searching range, the female-biased sex ratio, and a relatively low calling ability. Females that
fail to pair with males found colonies either in female–female pairs or even alone. In the laboratory, we examined colony
foundation by single females (F), female–female pairs (FF), and normal male–female pairs (FM). The time until colony foundation
(when termites began excavating wood baits) differed significantly among the unit types. Time until excavation was much longer
for single females than for FF and FM units, which reflects the relative success of colony foundation. The survival rate of
single females was also significantly lower than that of FF- and FM-unit females, although there was no difference between
FF and FM units. This result demonstrates that cooperation, even female–female, promotes female survivorship. Nevertheless,
the number of progeny per female was significantly lower in FF units than in FM units, possibly because females of FF units
must share reproductive output. These results lead us to the conclusion that a normal monogamous pair is the best unit for
colony foundation. Nevertheless, females alone can establish colonies by parthenogenesis, and even female–female cooperation
promotes colony foundation success if pairing with males is not possible. Considering the functional decision for females
in F and FF units of how much time to spend searching for a male mate, we believe that these facultative pathways of colony
foundation by parthenogenesis have adaptive significance.
Received: November 30, 2000 / Accepted: March 6, 2001 |
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Keywords: | Facultative parthenogenesis Subterranean termite Mate searching Alate flight |
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