PARENT SESSION
Friday, August 11, 8:00-11:30 am
COS 110 - Tropical ecology
Sultana, Mezzanine Level, Cook Convention Center
Presiders: G Selaya

Ecological rates of change in a biodiversity hotspot during the Late Quaternary.

Urrego, Dunia^*,1, Bush, Mark¹, Silman, Miles², ¹ Department of Biological Sciences, Melbourne, FL, USA² Department of Biology, Winston-Salem, NC, USA

ABSTRACT- Paleoecological records from high-biodiversity ecosystems provide an opportunity to study ecological processes across long temporal scales. Particularly in Amazonia, these reconstructions have attempted to elucidate patterns of speciation, endemism and diversity. Major events of speciation in the region have typically been linked to fragmentation and cooling during the last ice age. Glacial climate change is believed to have produced the greatest Late-Quaternary rates of ecological change. However, recent work has suggested that Holocene climatic fluctuations may have caused larger ecological change than glacial cooling. A sediment record from Lake Consuelo offers an opportunity to test hypotheses concerning Late-Quaternary rates of community change in Amazonia. The Lake sits on the eastern slope of the Andes and is surrounded by cloud forest. The past history of this highly-diverse ecosystem has been reconstructed through fossil-pollen analysis. This reconstruction has yielded a 43,500-year paleoecological record that includes the peak of the last ice age and the Holocene. The vegetation-history record was used to estimate rates of community change in the forest of Lake Consuelo over the Late Quaternary. These estimations are based on a robust chronological model and multidimensional distance measures among ca. 400-year time slices. Community rates of change over time showed significant differences between the Pleistocene and Holocene periods. Community changes associated with a regionally widespread mid-Holocene dry phase appear to be greater in magnitude than those caused by 5°C cooling during the peak of the last ice age. These results suggest the long-term sensitivity of cloud forest ecosystems to moisture changes and their relative resilience to temperature fluctuations.

Key words: Amazonia, Last Ice Age, Holocene