Trade-offs between reproduction and disease resistance have recently been explored in social insects. We exposed primary reproductives of the dampwood termite Zootermopsis angusticollis to spores of the entomopathogenic fungus Metarhizium anisopliae and recorded survivorship and reproductive output. Three treatment groups were created: naïve (unexposed), acute (a single exposure to 105 spores/ml) and serial (104 spores/ml followed by 105 spores/ml). Comparison of initial clutch sizes showed that serially exposed pairs produced significantly smaller clutches than naïve pairs but the acute treatment showed no significant reduction in clutch size compared with the naïve group. Therefore, reproduction during the incipient stages of colony formation appears resilient to a one-time acute pathogen exposure, but is negatively impacted by serial exposure. Long-term censuses were conducted at 300 and 560 days post-pairing to examine the influence of pathogen exposure on colony growth. Measures of colony composition, mass of reproductives and larvae, and survival of the primary reproductives were recorded. At 300 and 560 days post-pairing, there were no significant differences in total larvae number or total egg number between the three treatment groups. Overall, there appears to be no long-term reproductive cost to immune challenge in colony founding. This indicates that an investment in immunocompetence during colony foundation allows primary males and females to cope with infection while producing only a short-term trade-off in reproductive output.
Species 1: Isoptera Termopsidae Zootermopsis angusticollis (dampwood termite)
Species 2: Deuteromycotina Hyphomycetes Metarhizium anisopliae (green muscardine fungus)
Keywords: immunocompetence, reproductive trade-off
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