98th ESA Annual Meeting (August 4 -- 9, 2013)

August 03 - 09, 2013

OOS 15

Evaluating The Dynamics Of Tree Species Range Limits Under Climate Change For Sustaining Biodiversity

Species range limits are dynamic and subject to local, regional and global processes that encompass ecological and evolutionary phenomena. Genetic constraints on adaptation and biogeographic constraints on colonization of suitable habitats are the main drivers of species range limits. Understanding how these processes will play out at the range limits is critical to addressing the question whether species can adapt, migrate or go extinct under rapid climate change. Given the interplay of evolutionary and ecological factors, sustaining biodiversity in an era impacted by rapid climate change will require a merging of disciplines to study the various processes involved. The purpose of this organized session is to assess how these processes will affect the distribution of tree species at the range margins and to show how recent improvements in data and models can help manage for biodiversity and ecosystem functionality. There are three main factors that influence species range boundaries. A) Historical & evolutionary mechanisms: Species niches historically have remained relatively constant in the face of historical climatic change (niche conservatism) causing them to migrate in line with their native climatic-niches. Nevertheless many species migration involved some degree of adaptive evolutionary change during the Holocene. For example, gene-flow from pre-adapted range-centers can aid tree species adaptation; low levels of genetic variation in ecologically important traits due to genetic drift and low mutational input can hamper it. In contrast, the trailing edge does not receive pre-adapted genes – therefore adaptation is dependent on local variation and the populations are subjected to more intense competition and demographic effects that could result in range contraction. B) Source-sink dynamics: Spatial heterogeneity in the distribution of tree species due to geographic-environmental-stochastic processes has led to spatial variation in sources and sinks that could enable or impede range expansion in the temporal dimension. These processes are better evaluated at macro-ecological scales. C) Ecological processes: There is a host of ecological factors that influence tree species abundance like density dependent demography, Allee effects, smaller-scale metapopulation dynamics, intraspecific/interspecific competition/mutualism, parasitism and herbivory. These processes impact species abundance at more local scales and could be important in maintaining or expanding range margins.