Plant species’ distributions are often thought to overwhelmingly reflect their climatic niches. However, climate represents only a fraction of the n-dimensional environment to which plant populations adapt, and studies are increasingly uncovering strong effects of nonclimatic factors on species’ distributions. We used a manipulative, factorial field experiment to quantify the effects of soil environment and precipitation (the putatively overriding climatic factor) on plant lifetime fitness outside the geographic range boundary of a native California annual plant. We grew plants outside the range edge in large mesocosms filled with soil from either within or outside the range, and plants were subjected to either a low (ambient) or high (supplemental) spring precipitation treatment. Soil environment had large effects on plant lifetime fitness that were similar in magnitude to the effects of precipitation. Moreover, mean fitness of plants grown with within-range soil in the low precipitation treatment approximated that of plants grown with beyond-range soil in the high precipitation treatment. The positive effects of within-range soil persisted in the second, wetter year of the experiment, though the magnitude of the soil effect was smaller than in the first, drier year. These results are the first we know of to quantify the effects of edaphic variation on plant lifetime fitness outside a geographic range limit and highlight the need to include factors other than climate in models of species’ distributions.
Bibliographical noteFunding Information:
The authors thank Anna Peschel, Alexai Faulkner, Monica Geber, Sarita Charap, Zachary Radford, Adam Kostanecki, and Eric Bakken for assistance with field and lab work. The authors appreciate insightful comments from Peter Kennedy, Ruth Shaw, and Peter Tiffin, as well as two anonymous reviewers, on experimental design, analyses, and interpretation of results. Our work was generously supported by grants from the National Science Foundation (DEB‐1701072 to JWB and DAM and DEB‐1255141 to DAM). Any opinions, findings, and conclusions expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation.
© 2020 by the Ecological Society of America
Copyright 2021 Elsevier B.V., All rights reserved.
- Clarkia xantiana ssp. xantiana
- geographic range limit
- local adaptation
- range expansion
- species distributions
PubMed: MeSH publication types
- Journal Article
- Research Support, U.S. Gov't, Non-P.H.S.