Advantages of biparental care in the wood-dwelling termite, Zootermopsis nevadensis
A field experiment conducted on 49 young termite colonies lends support to the hypothesis that ecological constraints on successful offspring production favour two-parent care. Colonies cared for by two parents were twice as likely to survive the six-month experiment as were colonies headed by single parents. Among surviving colonies, the percentage change in the number of offspring did not differ between colonies headed by two parents versus single parents. Workers (third instar juveniles and older), but not non-workers (first and second instar juveniles), were found in all surviving colonies, indicating that offspring survivorship, not new offspring production, accounts for difference in success of two parents and single parents. Three of the four surviving single-parent colonies became two-parent colonies by the end of the experimental period: in two colonies, offspring became replacement reproductives; in the third colony, an adult male re-paired with a nest-founding female. Conspecific pressures from new nest-founding adults that flew onto logs containing the experimental colonies may account for high mortality in all colony types. New nest-founding pairs settled near experimental colonies. The mean numbers of new nest-founding pairs per experimental-colony area were significantly positively correlated with the proportion of single-parent colony failures in that area.
Shellman-reeve
JS
Section of Neurobiology and Behavior, Cornell University