THE MOST HIGHLY RESOLVED FOOD WEB EVER: THE EARLY EOCENE FOOD WEB OF MESSEL, GERMANY

Continental ecosystems were dramatically affected by the K-Pg crisis, with effects lasting from Paleocene to early Eocene. An extensively documented, highly resolved dataset of feeding interactions was constructed from the 48-million-year-old Messel Formation in central Germany. Messel is a small, fossil maar lake 0.7 km² in area and representing 0.6 myr of time. The spatiotemporally confined unit was deposited under considerable environmental stability, judged from pollen and sediment records. The oil-shale sediments preserve delicate biological structures such as color patterns, gut contents, and body outlines of feathering in pelage.

Data was compiled from 700 taxa representing lacustrine and surrounding paratropical forest environments. Taxonomic resolution included 54 % of taxa resolved to genus or species and 82 % to family. The dataset for the terrestrial Messel web was highly representative, consisting of 44 microorganisms, 187 plants, 326 invertebrates and 143 vertebrates. Trophic llinks were assigned from 10 sources of observations: 1) taxonomic uniformitarianism, 2) functional morphology, 3) gut contents, 4) plant damage patterns, 5) stratigraphic co-occurrences, 6) body size, 7) coprolites, 8) host relationships, 9) chemical and isotopic signatures, and 10) ichnological evidence. These lines of evidence were used to establish three certainty levels to provide degrees of confidence to the data.

The foodweb network structure of the Messel lake and forest foodwebs was compared to relevant extant webs using analyses that account for scale dependence of web structure with diversity and complexity. The much smaller lake web, with 94 taxa, 517 links and a connectance of 0.059 showed similar trophic structure to extant webs. By contrast, the Messel forest web, with 630 taxa, 5534 links and a connectance of 0.014 exhibited differences with modern webs. This discordance is attributable to the elevated diversity of the forest web and detailed resolution of plant-insect interactiions, explained by an effect of web scale dependence rather than fundamental difference in trophic structure. The Messel biota exhibited modern trophic structure, following an 18 million-year interval of post-extinction change, and provides a critical assessment of how modern webs are assembled, constructed and modeled.