PARENT SESSION
Symposium 17: Species range dynamics: Past, present, and future
Organized by: JS McLachlan and JW Williams
Thursday, August 11, 8:00 AM - 11:30 AM, Meeting Room 517 B, Level 5, Palais des congrès de Montréal

Climate variability, landscape texture, and the episodic dynamics of species ranges.

Jackson, Stephen^*,1, ¹ University of Wyoming, Laramie, WY, 82071

ABSTRACT- Paleoecological studies indicate that late Holocene range expansion of several woody plant species has been episodic, with periods of quiescence or slow expansion alternating with episodes of rapid areal expansion and population growth. Dendroecological studies of woody plant populations established within the past few centuries near advancing range margins similarly indicate episodic patterns, with quiescence alternating with rapid population expansion. Development and application of tools for independent inference of climate variability and change provides a means for determining whether these episodic patterns at different scales represent population responses to climate variability or to other factors (e.g., dispersal, population processes, geographic barriers). Comparisons of paleoecological and demographic records of range dynamics with independent paleoclimate records show that recent range dynamics of woody species in the central Rocky Mountains and western Great Lakes regions have been paced by climate variability at decadal, centennial, and millennial timescales. Climate variability alters the spatial mosaic of potentially suitable sites for establishment, with higher density of suitable sites during favorable climate episodes increasing the likelihood of successful establishment and population growth. Sites capable of sustaining adult populations at any time may alternate between being suitable and unsuitable for seedling establishment and juvenile survival. In some cases expansion of species into new territory appears to have been facilitated by mortality of incumbent populations related to climate extremes (e.g., severe drought) immediately preceding the period of favorable climate. Accurate forecasting of species range responses to ongoing and future climate change will require understanding of the environmental controls on recruitment/establishment and the influence of global change on climate variability regimes.

Key words: climate variability, species range, paleoecology, biogeography