A high-resolution pollen record from western Greece shows that the amplitude of millennial-scale oscillations in tree abundance during the last glacial period was subdued, with temperate tree populations surviving throughout the interval. This provides evidence for the existence of an area of relative ecological stability, reflecting the influence of continued moisture availability and varied topography. Long-term buffering of populations from climatic extremes, together with genetic isolation at such refugial sites, may have allowed lineage divergence to proceed through the Quaternary. Such ecologically stable areas may be critical not only for the long-term survival of species, but also for the emergence of new ones.

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The authors investigated perceived exercise and physical activity barriers of active youth with physical disabilities. Research Method/Design: A 46-item exercise barrier instrument was administered to 145 youth (117 boys and 28 girls, 12 to 19 years of age). Using the Rasch model, the authors estimated barrier severity and youths' exercise perseverance. Model-data fit was determined by Infit and Outfit statistics (Ն 0.5 and Յ 1.5). Results: Except for 1 item, the model fit the data well. The most difficult barriers that youth with physical disabilities faced were lack of time and pain or discomfort. The older youth demonstrated higher exercise perseverance than the younger youth. There were no differences in youths' exercise perseverance scores by gender or National Wheelchair Basketball Association classification. Implications: Removing severe barriers should be a part of future exercise and physical activity interventions targeting this population.

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