Yearly variation in polygyny in the termite Macrotermes michaelseni (Sjostedt)

摘要

Macrotermes michaelseni, an abundant termite species in semi-arid ecosystems of eastern Africa, exhibits considerable fluctuations in the proportion of polygynous colonies across years (between 5 and 50%). We found a negative correlation between rainfall and the proportion of polygynous colonies with a time lag of two years. A decrease in the percentage of polygynous colonies was particularly obvious in 1999 and 2000, two years after an El Nino-event. Rainfall and subsequent primary production seem to influence the degree of polygyny. Variation in the proportion of polygynous colonies could be due to several mutually non-exclusive factors, including better survival of polygynous colonies during years with low resource availability and increased aggression between nestmate queens with decreasing resource availability. Evaluating several lines of circumstantial evidence we suggest that the degree of polygyny depends on ecological factors.