Comparative Spatial Paleoecology: Assessing Niche Competition between Eocene North American Multituberculates and Rodents Regarding Forest Resources to Elucidate the Cause of Multituberculate Extinction

Multituberculate extinction is often cited as a classic case of
competitive exclusion, coinciding with the first rodent arrivals in the
late Paleocene. Analyzing 124 North American multituberculate last
occurrence records during the Eocene from 56 to 34 million years ago, this
study aimed to differentiate Eocene multituberculate and coeval rodent
floral associations through geographic spatial analysis to understand
niche overlap between the two groups.  If competitive exclusion
with rodents was a factor in multituberculate extinction, both
multituberculates and rodents would be predicted to share similar forest
habitat preferences and have competed for similar ecological niches
regarding their forest associations. Using spatial analysis, this study
found that Eocene rodents and multituberculates did not overlap in their
forest associations. The findings indicate that multituberculates were
unique in inhabiting a specific type of ancient forest habitat, favoring
forests composed of Metasequoia, Glyptostrobus, and Alnus, and thus
thrived in wetter northern temperate forest communities during the Eocene.
Metasequoia and Glyptostrobus declined significantly in North America
during the later Cenozoic, coinciding with multituberculate decline and
extinction as the global climate shifted toward colder and drier climates
around the Eocene-Oligocene boundary. In contrast, the success of rodents
is attributed to their much broader forest affinity. These preferences
align with the widespread distribution of rodents today, contributing to
their modern success. The absence of any similar reconstructed forest
habitat preferences between rodents and multituberculates suggests that
changing forest structure, rather than competitive exclusion, drove
multituberculate extinction.