Meeting Abstract

P2.7  Wednesday, Jan. 5  Induced host shift effects on morphology in the bean beetle, Callosobruchus maculatus SALOMON, Rocio*; MUSOLF, Barbara; Clayton State University; Clayton State University BarbaraMusolf@clayton.edu

Host effects on organisms that utilize them for food, shelter, and/or reproduction can be used to study the adaptive and evolutionary consequences of host choice. The bean beetle, Callosobruchus maculatus, is an ideal organism for host shift experiments because of its fast generation time, survival on a variety of bean hosts, and measurable changes in morphology. We investigated changes in egg load per bean, generation time, percent of adult emergence, and adult weight of both sexes at emergence between mung bean, Phaseolus aureus, and cowpea, Vigna unguiculata, raised beetles. We measured host shift effects on bean beetles raised on mung beans for twenty generations and nine generations on cowpeas. Virgin beetles were placed on petri dishes containing either mung beans or cowpeas and allowed to deposit eggs for forty-eight hours. Beetles laid more eggs on cowpeas with many single beans incurring multiple eggs. More cowpea-reared beetles emerged from eggs laid on cowpeas. No significant difference occurred in weight at emergence between males or females raised on either bean, however, we did see a trend that showed a greater increase in the weight of cowpea females from that of mung bean females. The average generation times for beetles were 29 days on mung beans and 27 days on cowpeas, a student’s t-test indicated no significant difference exists between the two. Coloration changes also became apparent in the elytra and abdomen of beetles raised on different legume hosts. A small sample size and the lack of replicates did not allow for a thorough analysis of the other traits, however, preliminary results suggest that bean beetle morphology is altered when a host shift occurs.