Collaborative Research: LTREB Renewal: Evolutionary Demography - The Contribution of Adaptation and Environment to Population Dynamics, Range Size, and Niche Width

A fundamental objective of ecology and evolutionary biology is to explain the geographic distributions of species. But species are dynamic entities, and their geographic distributions respond to changing environments. If the environment of their suitable habitat changes, populations of a species can sustain themselves in their current habitat by adaption through natural selection, or they need to shift to new locations. Understanding the mechanisms that account for species distributions is especially timely because of the accelerating pace of environmental change. The contribution of adaptation to population dynamics, local persistence, and to the geographic range inhabited by a species, has rarely been quantified. Although comparative ecological studies and species distribution models typically assume genetic uniformity across a species geographic range, genetic studies have repeatedly demonstrated local adaptation. This project explicitly examines the contribution of adaptation to population growth and the extent of a species geographic range, through the continuation of a long-term field population demographic study and the use of a species distribution model. The project will also involve outreach to a rural middle school, engaging students in research activities, and it will connect citizens to research scientists through an innovative outreach program, Market Science, where researchers engage the public at farmer's markets.

The research team will focus on a well-studied California native plant species, Clarkia xantiana, which has been the focus of intensive field research for over 12 years. This research will provide new, exceptionally detailed information about how species' ranges evolve and the factors that are likely to influence species responses to climate variation. The specific objectives of this project are to examine: (1) whether population dynamics vary from the center to margins of the species' range and what environmental factors drive this variation; (2) the spatial scale of local adaptation and how it relates to demographic similarity among populations; and (3) the interplay of population dynamics and adaptation in shaping environmental tolerances (niche width) and geographic range size. Only long-term studies can provide robust predictions about what controls population persistence, evolutionary adaptation, and their consequences for species ranges. Long-term demographic datasets of vital rates (e.g. survival, reproduction), population growth, and abiotic and biotic (herbivory) factors, have been collected in 35 natural populations spanning the major portion of the species' range. All monitoring of field populations will be continued an additional ten years. Past work has examined local adaptation using a large reciprocal transplant experiment among demographically-divergent populations. This experiment will be repeated in the project's second five-year phase.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.