Egg predation and cannibalism are believed to be common phenomena among many species of aphidophagous predatory ladybird beetles despite the presence of alkaloid based defensive chemicals in all life stages. We identified defensive chemicals from eggs of three congeneric species, one introduced into North America (Coccinella septempunctata L.), and two native (C. transversoguttata richardsoni Brown, and C. novemnotata Herbst), and examined the effects of ingested defensive chemicals on first instars. Ingested congeneric alkaloids were not toxic to first instars, likely because the three congeners produce the same principal alkaloids, precoccinelline and coccinelline, in similar amounts. First instars of the three congeners accumulated alkaloids ingested through egg cannibalism and congeneric predation. Egg consumption doubled the amount of alkaloids in first instars when they fed on conspecific or congeneric eggs, in comparison to a pea aphid diet. No detrimental effects of ingested congeneric alkaloids on development or survival of first instars were observed among these congeners. Chemical defenses of eggs are therefore not likely to be important in favoring the invasive species, C. septempunctata, in interactions with these native congeneric species. Because the invasive species is the most aggressive predator, having the same types of alkaloids may facilitate disproportionate intraguild predation on native congeners by C. septempunctata thereby potentially enhancing the invasion success of this introduced species.
|Number of pages||8|
|Journal||Journal of Chemical Ecology|
|State||Published - Dec 19 2014|
Bibliographical noteFunding Information:
Acknowledgments We thank S. Stamper, S. Bessin, S. Thompson, A. Taman, C. Fox, and B. Wallin, for insect collections, providing facilities and experimental help. We also thank L. Hesler, USDA-ARS, Brookings, SD, for providing us adults of Coccinella novemnotata for this study. This experiment was supported by USDA-NRI (2007–02286) and NSF award (DEB-1429163). We also thank two anonymous reviewers and the editor for their very helpful comments on the manuscript. The information reported in this paper (NO.14-08-031) is part of a project of the Kentucky Agricultural Experiment Station and is published with the approval of the Director.
© 2014, Springer Science+Business Media New York.
- Coccinella septempunctata
- Defensive alkaloids
- Intraguild predation
- Predatory ladybird beetles
ASJC Scopus subject areas
- Ecology, Evolution, Behavior and Systematics