NON-ANALOG ECOLOGICAL STRUCTURE OF MESOZOIC MAMMAL COMMUNITIES

Most mammalian taxa in the Mesozoic terrestrial Lagerstätten from the northeastern China are preserved as nearly complete fossil skeletons. This fossil record currently represents our best opportunity to move beyond the study of the autecology of individual species to analysis of Mesozoic mammal communities. Contextual information, such as abiotic and biotic factors, is well constrained for these Lagerstätten, enabling analysis of linkages between intrinsic and extrinsic factors that might have shaped the ecological structure of these ancient mammal communities. We quantified the ecological structure of four Mesozoic mammal communities from the northeastern China and 84 extant small-bodied mammal communities from tropical, arid, temperate, and cold environments across the globe using diet, body size, and locomotor mode. We used the resulting dataset to categorize habitat and vegetation structure differences among extant small-bodied mammal communities and compare their ecological structure with those Mesozoic mammal communities. We used ecological and ecological diversity as ecological parameters to characterize ecospace occupations for each mammal community. Results indicate that environmental factors play essential roles in shaping ecological structure of extant small-bodied mammal communities. In tropical regions small-bodied mammal communities have more clustered ecospace occupations, reflected by low ecological disparity and high ecological diversity, in contrast with mammal communities from arid and cold environments, which have more scattered ecospace occupations as reflected by high ecological disparity and low ecological diversity. Results also indicate the habitat preference of extant small-bodied mammal communities is well reflected by the ecological structure and the ecological diversity and disparity of the Mesozoic mammal communities are most comparable to extant small-bodied mammal communities either from tropical or arid environments. The significantly different ecological structure of the extant small-bodied and Mesozoic mammal communities might be primarily due to sampling biases of the fossil record, non-analog Mesozoic environments, and/or evolutionary ecology differences of species compositions among extinct and extant mammal communities.