Data from: Endemism in Wyoming plant and insect herbivore communities during the early Eocene hothouse

The warm, equable, and ice-free early Eocene Epoch permits investigation
of ecosystem function and macro-ecological patterns during a very
different climate regime than exists today. It also provides insight into
what the future may entail, as anthropogenic CO2 release drives Earth
towards a comparable hothouse condition. Studying plant-insect herbivore
food webs during hothouse intervals is warranted because these account for
the majority of non-microbial terrestrial biodiversity. Here, we report
new plant and insect herbivore damage census data from two floodplain
sites in the Wind River Basin of central Wyoming, one in the Aycross
Formation (50-48.25 Ma) at the basin edge (WRE) and the second in the Wind
River Formation in the interior of the basin (WRI). The WRI site is in
stratigraphic proximity to a volcanic ash that is newly dated to 52.416 ±
0.016/0.028/0.063 (2σ). We compare the Wind River Basin assemblages to
published data from a 52.65 Ma floodplain flora in the neighboring Bighorn
Basin (BH) and find that only 5.6% of plant taxa occur at all three sites
and approximately 10% occur in both basins. The dissimilar floras support
distinct suites of insect herbivores, as recorded by leaf damage. The
relatively low diversity BH flora has the highest diversity of insect
damage, contrary to hypotheses that insect herbivore diversity tracks
floral diversity. The distinctiveness of the WRE flora is likely due to
its younger age and cooler reconstructed paleotemperature, but these
factors are nearly identical for the WRI and BH floras. Site-specific
microenvironmental factors that cannot be measured easily in deep time may
account for these differences. Alternatively, the Owl Creek Mountains
between the two basins may have provided a formidable barrier to the
thermophilic organisms that inhabited the basin interiors, supporting
Janzen’s hypothesis that mountain passes appear higher in tropical
environments.