Measurement of predatory behaviour in cow dung-colonising insect larvae, using compound-specific 13 C-tracing of dietary
- PDF / 268,691 Bytes
- 7 Pages / 595.276 x 790.866 pts Page_size
- 52 Downloads / 181 Views
ORIGINAL ARTICLE
Measurement of predatory behaviour in cow dung-colonising insect larvae, using compound-specific 13C-tracing of dietary fatty acids Luke Dickson & Richard P. Evershed & Richard Wall
Received: 25 May 2011 / Accepted: 17 July 2011 / Published online: 30 July 2011 # Springer-Verlag 2011
Abstract Studies of the trophic interactions between organisms in opaque environments where direct observation can be difficult, such as soil or leaf litter, often require the use of indirect inferential approaches. Here, the use of compound-specific 13C-tracing of dietary biomarker fatty acids is evaluated as a method for studying predation by larvae of the dung-breeding fly, Mesembrina meridiana (Diptera: Muscidae); the technique was used to differentiate dung from high-enrichment 13C-labelled prey in their gut contents. Potential prey, 13C-labelled larvae of the dungbreeding fly, Neomyia cornicina (Diptera: Muscidae), were placed into unlabelled dung microcosms in the laboratory. A single 7-day-old M. meridiana larva was allowed to feed in each microcosm for 8 h. The magnitude of increases in the δ13C values of fatty acids (i14:0, 14:0, i15:0, a15:0, 15:0, 16:0 and 18:0) in the gut contents, relative to those of M. meridiana deprived of prey, demonstrated the predation of N. cornicina larvae which were estimated to have constituted at least 35% of the average dietary wet mass of these M. meridiana larvae. The tracing of specific labelled compounds increased confidence in dietary assessment and helped to avoid systematic errors associated with compound-dependent efficiency of assimilation in the gut. The results demonstrate the potential value of this method in helping to elucidate trophic interactions in predator–prey L. Dickson : R. Wall (*) School of Biological Sciences, University of Bristol, Bristol, UK e-mail: [email protected] L. Dickson : R. P. Evershed Organic Geochemistry Unit, School of Chemistry, University of Bristol, Bristol, UK
systems within opaque environments. The precision of the quantitative dietary estimation that arose from these isotopic data was superior to that generated using fatty acid distributional data, a widely used and evidentially independent line of evidence. Keywords Cattle dung . Diptera . Gas chromatography– combustion–isotope ratio mass spectrometry . δ13C . Fatty acids . Mesembrina meridiana . Neomyia cornicina
Introduction The dung of large herbivores is often an abundant and nutritionally valuable resource in grazed ecosystems, which forms an ecologically distinct environment for a complex successional insect community, composed largely of Coleoptera and Diptera [12]. The presence of this diverse insect community within dung is of ecological and economic importance, since it promotes rapid dung decomposition, which helps to return nutrients to the soil, particularly nitrogen, a large proportion of which would otherwise be lost as ammonia [14, 23, 24]. Timely decomposition also may help to reduce dung-breeding pest-fly populations [16, 22, 25] and reduce the potenti
Data Loading...
