HOW DO PROCESSES RESPONSIBLE FOR PATTERNS OF EXTINCTION AFFECT GEOGRAPHY AND COMMUNITY COMPOSITION? A CASE STUDY IN MIO-PLIOCENE PLANTS OF THE SOUTHEAST

Multiple studies now link ecological traits, such as seed dispersal, to macroevolutionary trends in diversification and extinction, in turn influencing geographic range size and related factors. While much research has focused upon the influence of these factors on community composition, relatively little work has been done documenting the pattern and tempo of these ecological changes.

We here compare the patterns of range collapse and extinction in four Miocene through Pliocene floras in the eastern United States. These floras are noteworthy in having experienced less climate change than most other North American fossil floras of comparable or earlier age. As a result, comparison of changes in the composition of these floras relative to their modern analogs is less likely to be influenced by differences in major habitat transitions (e.g. forest to desert), unlike most western interior North American fossil floras.

Preliminary results suggest that genera possessing biotic dispersal are less likely to undergo geographic range collapse or become extinct than genera that are abiotically dispersed; however, these results are not statistically significant with our current sample size. Additional fossil floras from the Oligocene and Miocene have yet to be analyzed. Further data may be available from late Miocene analogs to the California coastal mountain forests from Nevada, which can then be compared to patterns in the east. Updated data and results will be presented at the meeting.