MESOZOIC PALEOCOMMUNITY STRUCTURE AND DYNAMICS IN THE WESTERN TETHYS

Predators influence community structure and dynamics in many modern ecosystems, yet the importance of predation on macroevolutionary timescales remains controversial. Paleocommunity interactions such as increasing predation intensity, ecospace utilization, and disturbance may have led to the diversification and evolution of species. However, it is difficult to determine how changes in richness and ecospace utilization have altered community structure and functioning.

Here we compare the topology of food web models of western Tethys shallow marine paleocommunities from the Triassic (Anisian) and Jurassic (Bathonian) to identify differences in ecosystem structure and functioning associated with the Mesozoic Marine Revolution (MMR). Richness increased from the Anisian (1182 species) to Bathonian (1325 species) as did the number of guilds (from 105 to 110), suggesting the MMR led to an increase in functional richness. Although the Bathonian network is partitioned into fewer subcommunities, suspension feeders form the largest subcommunity. The increase in the prevalence of suspension feeders coincides with radiations of phytoplankton in the Jurassic. Furthermore, Bathonian guilds include larger size classes and longer trophic chains (average path length increases from 1.879 to 1.889), supporting the hypothesis that an increase in primary productivity led to increased energy transfer and higher trophic levels during the MMR.

These findings suggest that new evolutionary innovations and biotic expansions observed during the MMR may have triggered significant ecosystem restructuring and changes in energy transfer pathways, facilitated by the radiation of phytoplankton. Given the current biodiversity crisis, understanding how and why ecological changes occur is vital for effective resource management.