DNA-based techniques are providing valuable new approaches to tracking predator-prey interactions. The gut contents of invertebrate predators can be analysed using species-specific primers to amplify prey DNA to confirm trophic links. The problem is that each predator needs to be analysed with primers for the tens of potential prey available at a field site, even though the mean number of species detected in each gut may be as few as one or two. Conducting all these PCRs (polymerase chain reactions) is a lengthy process, and effectively precludes the analysis of the hundreds of predators that might be required for a meaningful ecological study. We report a rapid, more sensitive and practical approach. Multiplex PCRs, incorporating fluorescent markers, were found to be effective at amplifying degraded DNA from predators' guts and could amplify mitochondrial DNA fragments from 10+ species simultaneously without 'drop outs'. The combined PCR products were then separated by size on polyacrylamide gels on an ABI377 sequencer. New primers to detect the remains of aphids, earthworms, weevils and molluscs in the guts of carabid predators were developed and characterized. The multiplex-sequencer approach was then applied to field-caught beetles, some of which contained DNA from as many as four different prey at once. The main prey detected in the beetles proved to be earthworms and molluscs, although aphids and weevils were also consumed. The potential of this system for use in food-web research is discussed.

Ten polymorphic microsatellites for alpacas and llamas were used to evaluate paternity in 47 alpacas (18 crias, 18 mothers and 11 fathers) registered at IVITA-Maranganí Research Station, Canchis Province (Cusco-Peru). Analysis was carried out using two methodologies: Automatic Sequencer (ABI 377 DNA sequencers®) and silver staining techniques. Microsatellites were amplified in three multiple and ten single PCR reactions. The number of alleles varied between 4 and 20. The allelic frequencies and the exclusion probability were calculated using Cervus 2.0. All loci, except for two, were within the range published elsewhere. The accumulated exclusion probability for the ten loci was 0.9999. For each multiplex reaction the accumulated exclusion probability was more than 0.90. Both methodologies yielded the same results. The results confirmed paternity in 18 cases of parent-cria pairs, however in 22% of cases (n=4) were identified alternative parents than those indicated in farm records.

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