Date of Award

5-2009

Level of Access Assigned by Author

Open-Access Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Biological Sciences

Advisor

Andrei Alyokhin

Second Committee Member

Frank Drummond

Third Committee Member

Eleanor Groden

Abstract

Lady beetles (Coleoptera: Coccinellidae), as a group, are considered beneficial because they prey on plant pests. A number of studies suggest that non-native species introduced for biological control have replaced native species in agriculture. Agricultural and non-agricultural habitats were thus surveyed in Maine to determine if native species were still dominant in some areas. In 2004 and 2005, 3,487 and 2,903 beetles were collected, respectively, with non-native species dominant in all but one habitat (coniferous forest). Native species were found in very low numbers in all habitats surveyed. Comparisons between species were then conducted to determine if differences exist that might provide an advantage to some species over others. Consumption of four aphid species by one native (Coccinella trifasciata) and three non-native (Coccinella septempunctata, Harmonia axyridis, Propylea quatuordecimpunctata) species were compared. Harmonia axyridis generally consumed the most aphids; P. quatuordecimpunctata consumed the fewest. Coccinella trifasciata, however, consumed the most of one aphid species, Macrosiphum albifrons. Direct competition for prey was compared between native (C. trifasciata, Coleomegilla maculata, Hippodamia convergens) and non-native (C. septempunctata, H. axyridis, Hippodamia variegata, P. quatuordecimpunctata) species. Harmonia axyridis had the highest aphid consumption, shortest prey discovery time, and generally exhibited the most aggression towards other species. Consumption by C. trifasciata and C. maculata varied depending on with which species they were paired. Interactions between native and non-native species (same species as above) and the European fire ant (Myrmica rubra) tending aphid prey were compared. Harmonia axyridis consumed more aphids than all other species but C. septempunctata. Hippodamia variegata and C. septempunctata were effected the most by ant stings. These differences may explain, in part, the successful establishment of some non-native coccinellids in new habitats and suggest that asymmetric interactions between species may affect their ability to co-exist. Studies evaluating relationships between newly sympatric coccinellids, tending ants, and plant-feeding insects were summarized. Research has been driven by concerns about the effects of invasive ants (primarily Pheidole megacephala, Solenopsis invicta, and Linephithema humile) on the effectiveness of pest control by coccinellids (primarily Cryptolaemus montrouzieri and C. septempunctata). Ants interfered with coccinellid predation in 56 of 77 studies.

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