Comparative spatial paleoecology: assessing niche competition between Eocene North American multituberculates and rodents regarding forest resources to elucidate the cause of multituberculate extinction

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Abstract 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.

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