Multiple mating, fecundity and longevity in female Northern Corn Rootworm (Coleoptera: Chrysomelidae) in relation to body size

Authors: French, Bryan; HAMMACK, LESLIE - Retired ARS Employee

Submitted to: Annals of the Entomological Society of America
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/1/2011
Publication Date: 7/1/2011
Citation: French, B.W., Hammack, L. 2011. Multiple mating, fecundity and longevity in female Northern Corn Rootworm (Coleoptera: Chrysomelidae) in relation to body size. Annals of the Entomological Society of America. 104(4):834-840. DOI: 10.1603/AN11003.

Interpretive Summary: Despite a long history of cultural and chemical control strategies, corn rootworms still can inflict serious damage to corn. Currently, genetically modified corn produce a rootworm-toxic protein derived from a soil bacterium, Bacillus thuringiensis. To slow the progression of resistance to the toxin, producers are required to plant a refuge of non-transgenic corn intended to promote matings among susceptible and resistant beetles, which should kill subsequent offspring when feeding on toxic corn plants. However, the cost of resistance could affect fitness related traits such as longevity, fecundity, and body size. Also, resistant females could mate more than once and potentially with resistant males, which could allow their offspring to survive on toxic corn plants. We examined the frequency of female copulations in northern corn rootworm in relation to male and female body size. Large and small females and males were reciprocally mated and compared with average sized beetles. After the initial mating, each week of their life females were given the opportunity to mate with an average sized male. Of 201 females, 31% mated twice and 3% mated 3 times. There were no differences among pair types and frequency of copulations, however, the 2nd copulation from multiply mated females occurred at an earlier age when mated to small males. Multiply mated females lived significantly longer and produced more total eggs and potentially viable eggs than singly mated females. Egg production and potential egg viability were also significantly greater for multiply mated females over 12 weeks, a time period when most eggs are laid. These results suggest that a third of the resistant females could potentially mate a second time with resistant males and enhance survivability of her offspring that feed on transgenic corn.

Technical Abstract: Despite a long history of cultural and chemical control strategies, Diabrotica spp. still can inflict serious damage to maize (Zea mays L.). Currently, genetically modified maize produce a rootworm-toxic protein derived from the soil bacterium, Bacillus thuringiensis Berliner. To slow the progression of resistance to the toxin, producers are required to plant a refuge of non-transgenic maize intended to promote matings among susceptible and resistant beetles, which should kill subsequent offspring when feeding on toxic maize plants. However, the cost of resistance could affect fitness related traits such as longevity, fecundity, and body size. Also, resistant females could mate more than once and potentially with resistant males, which could allow their offspring to survive on toxic maize plants. We examined the frequency of female copulations in Diabrotica barberi Smith & Lawrence in relation to male and female body size. Large and small females and males were reciprocally mated and compared with average sized beetles. After the initial mating, each week of their life females were given the opportunity to mate with an average sized male. Of 201 females, 31% mated twice and 3% mated 3 times. There were no differences among pair types and frequency of copulations, however, the 2nd copulation from multiply mated females occurred at an earlier age when mated to small males. Multiply mated females lived significantly longer and produced more total eggs and potentially viable eggs than singly mated females. Egg production and potential egg viability were also significantly greater for multiply mated females over 12 weeks, a time period when most eggs are laid. These results suggest that a third of the resistant females could potentially mate a second time with resistant males and enhance survivability of her offspring that feed on transgenic maize.