Physiological bases of genetic differences in cannibalism behavior of the confused flour beetle Tribolium confusum

Physiological causes of genetic differences in cannibalism were examined to gain a better understanding of constraints on behavior evolution. Cannibal ism has complex population level consequences in Tribolium confusum, includ ing dramatic effects on population size. Laboratory strains with low and hi gh cannibalism rates, obtained through inbreeding, have maintained distinct levels of cannibalism for over two decades even in the absence of artifici al selection to maintain the differences. Why strains differ in their canni balism. rates was examined by measuring: (1) the nutritional benefit from c annibalism in both nutritionally good and poor environments, and (2) the po ssibility that eggs are an important source of water. How strains achieve d ifferences in cannibalism was examined by testing for differences between s trains in their ability to find eggs and in their tendency to eat eggs. Beetles from both strains survive equally well in a nutritionally good envi ronment, but they accomplish this in different ways. The low cannibalism st rain has high survivorship with and without cannibalism. The high cannibali sm strain has low survivorship when not fed eggs and survivorship equivalen t to the low cannibalism strain when fed eggs, suggesting it compensates fo r poor nutritional adaptation by eating eggs. The strains also differ in fe eding behavior; beetles from the high cannibalism strain have a higher appe tite for eggs. Beetles from the two strains did not differ in locomotor act ivity, search efficiency, or need for water. The observed behavioral and nu tritional differences may contribute to the maintenance of different levels of cannibalism.