Note added in proof: we note that Hautier et al. (2008: Chemoecology, 18, 191–196) have recently published a study where they used GC–MS of ladybird prey alkaloids to identify intraguild predation by Harmonia axyridis in the field.
Identification and quantification of predation: novel use of gas chromatography–mass spectrometric analysis of prey alkaloid markers
Article first published online: 13 OCT 2008
© 2008 The Authors. Journal compilation © 2008 British Ecological Society
Volume 23, Issue 2, pages 416–426, April 2009
How to Cite
Sloggett, J. J., Obrycki, J. J. and Haynes, K. F. (2009), Identification and quantification of predation: novel use of gas chromatography–mass spectrometric analysis of prey alkaloid markers. Functional Ecology, 23: 416–426. doi: 10.1111/j.1365-2435.2008.01492.x
- Issue published online: 13 MAR 2009
- Article first published online: 13 OCT 2008
- Received 22 March 2008; accepted 11 September 2008; Handling Editor: Hefin Jones
- chemical defence;
- chemical taxonomy;
- intraguild predation;
- Harmonia axyridis;
- trophic interactions
- 1Predation can be difficult to measure in the field and immunological and DNA-based gut analyses are now routinely used to identify and quantify prey items consumed by predators. Alternative methods have largely fallen into disuse.
- 2Chromatography has been largely ignored as a method of studying predation on the grounds of low specificity and an inability to provide quantitative results. We demonstrate here that this is not so, using gas chromatography–mass spectrometry of alkaloids of prey ladybird beetles.
- 3The alkaloid hippodamine from a single egg of the ladybird Hippodamia convergens was detected in all ten third instar larvae of another ladybird, Harmonia axyridis, for 12 h after they had consumed a H. convergens egg; in one case of ten, hippodamine was still detected 36 h after egg consumption. Hippodamine was detectable in all 10 second instar larvae of the lacewing Chrysoperla rufilabris sampled 12 h after consuming a H. convergens egg.
- 4The amount of hippodamine in H. axyridis larvae was quantifiable with an internal standard. Larvae that had consumed more eggs exhibited higher levels of hippodamine. The method therefore can be used to estimate the amount of prey biomass consumed.
- 5A comparison of the alkaloids of five ladybird species that co-occur in Kentucky field crops found that, in general, the alkaloids were sufficiently distinct to allow species identification of ladybirds that had been consumed by predators, although there was some overlap between species in alkaloid content.
- 6Especially when combined with mass spectrometry, chromatography is thus a method that potentially can be used to identify multiple prey simultaneously, while also obtaining quantitative information on the prey biomass consumed. This has not been achieved by the commonly-used molecular gut-analyses. We suggest the method is suitable for a wide diversity of prey types possessing endogenous taxon-specific chemicals such as defence compounds or pheromones.
- 7As a secondary consequence of this study, several alkaloids have been identified from new ladybird species. We also have shown that H. axyridis, an invasive intraguild predator of other ladybirds, does not sequester alkaloids from allospecific ladybird prey.