Biotic interactions and range limits

What limits species’ distributions? Historically, we’ve largely thought about this question in terms of climate. However, most species are likely to be distributed over complex environmental gradients comprising changes in multiple abiotic and biotic variables. Transplant experiments, ideally combined with manipulations of putatively important environmental variables, are the most powerful method to test the relative influence of these variables on the location of the species’ range limit. In my dissertation, I used a variety of greenhouse and field experiments with the California native plant Clarkia xantiana ssp. xantiana (Onagraceae) to untangle complex environmental gradients and quantify the relative influence of both biotic and abiotic factors on plant lifetime fitness inside and outside the subspecies’ geographic range limit.

Relevant papers:

  • Benning, JW, Eckhart VM, Geber MA, and Moeller DA. 2019. Biotic interactions contribute to the geographic range of an annual plant: herbivory and phenology mediate fitness beyond a range margin. American Naturalist, 193:786-797. pdf
  • Benning, JW and Moeller DA. 2019. Maladaptation beyond a geographic range limit driven by antagonistic and mutualistic biotic interactions across an abiotic gradient. Evolution, 73:2044-2059. pdf
  • Benning, JW and Moeller DA. 2021. Microbes, mutualism, and range margins: testing the fitness consequences of soil microbial communities across and beyond a native plant’s range. New Phytologist, 229:2886-2900. pdf
  • Benning, JW and Moeller DA. 2020. Plant-soil interactions limit lifetime fitness outside a native plant’s geographic range margin. Ecology, in press. pdf

Testing and developing range limit theory

Range limits theory has highlighted that the shape of environmental gradients and the magnitude of dispersal play key roles in the probability of range expansion and the formation of stable range limits. However, we lack empirical tests of recent, and even foundational range limit theory. Furthermore, existing models do not account for temporal environmental variation, a ubiquitous feature of natural environments. Under the mentorship of Dr. Christopher Weiss-Lehman (Univ. of Wyoming) and Dr. Ruth Hufbauer (Colorado State Univ.), I’m using experimental evolution, genomic analyses, and novel models to test key predictions of range limit theory, further our understanding of the genetic basis of range dynamics, and build a comprehensive conceptual model of how spatio-temporal environmental variation interacts with dispersal to influence species range boundaries. This work is supported by an NSF Postdoctoral Fellowship.

Rapid adaptation

How quickly can plant populations adapt to environmental change? Along with a stellar Moeller Lab undergraduate, Lex Faulkner, we’ve been exploring the potential for rapid evolution of Clarkia xantiana populations in response to the recent California “megadrought.” We’re just analyzing the data from the full experiment now, but see Lex’s awesome poster with results from the first round of the experiment.

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