Cryptic Species in a Food Web Figure 1. Proportions of cryptic diversity revealed through barcoding the SBW quantified food web. A) Proportion of barcoding MOTU (provisional species) uncovered within each morphologically described species. B) Proportional representation of the identification of cryptic diversity within each level of the SBW food web. The number above each bar represents the absolute number of cases of cryptic diversity within each category. doi:10.1371/journal.pone.0014424.g001 inducing Hymenoptera occurring in the Quercus robor food web changed following barcoding [28].The discovery of cryptic diversity, particularly in parasitoid insects, is not singularly a story from the diverse tropics. It is a real, if unappreciated phenomena, in temperate [43], and even northern [29], systems as well. Consider one example where a parasitoid was previously considered a species and trophic generalist (Scambus hispae (Ichneumonidae; Pimplinae) – but often only identified as Scambus sp.): a facultative secondary parasitoid (Figure 5). Upon barcoding, the species split into 6 provisional species. Of these, 5 are trophic specialists, one appears to be a trophic generalist, while 4 are species specialists and two are species generalists. One of the provisional species remained both a trophic and species generalist. Our analysis permitted us to re-test a specific quantitative aspect that recent theory suggested was of critical importance to food web structure – the ‘‘bird-feeder effect’’. In our estimation, one of the most intriguing results presented here is that this measure of ecosystem function was not significantly affected by the increased nodal resolution offered by molecular ecology. When all three sites are pooled, the relationship between barcode-estimated diversity and SBW density is noisy and appears neither significant nor apparent. However, when sites are plotted separately, the barcode-estimated diversity was lowest in the homogeneous plot and higher in the more heterogeneous plot (Figure 4) and furthermore there is a positive relationship between SBW abundance and parasitoid diversity – just as predicted by the ‘‘bird-feeder effect’’. Does environmental heterogeneity apparently muddy the relationship between abundance and diversity, or is this an effect of measuring diversity via the barcode? The noise in the relationship may be due to barcode estimates of diversity resulting in a more fine grained estimation of biodiversity (See accumulation curves in Figure 2). In turn, this accentuated the differences between the three collection localities that differed in heterogene- ity. For instance, in demonstrating the ‘‘bird feeder effect’’ [as in Figure 2 from reference 9], our analysis of diversity calculated using barcodes (either in MOTU or PD) was not significant (Figure 4 A&C). However, when each locality was analyzed separately, a strong relationship was evident using both MOTU PLoS ONE | www.plosone.org 4 July 2011 | Volume 6 | Issue 7 | e14424