2017 Presidential Award

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Two immature Homo mathematicus individuals competing for a territory. (Credit: Peter Adler)

The recipient of the 2017 Presidential Award for the best paper published in The American Naturalist during the preceding calendar year is Robin E. Snyder and Stephen P. Ellner, 2016. “We happy few: Using structured population models to identity the decisive events in the lives of exceptional individuals.” American Naturalist 188:E28-E45. --  (lay summary here)

What lucky events make individuals truly exceptional?  That is the question posed by this engaging paper by Snyder and Ellner.  They develop and apply novel demographic methods to identify the events and the moments in life during which luck produces exceptional individuals.  They then apply those models to three contrasting plant systems. 

Using remarkably compelling and accessible language, the paper engages the phenomenon of chance and its contribution to individual differences.  Extending existing analyses of which events in a life cycle, on average, contribute most to demographic output, the authors ask, for which of those events does its variance produce individuals that acquire exceptional fitness.  They provide methods (and code) to identify “lucky” versus “unlucky” individuals, compare individual demographic parameters between those classes, and calculate the sensitivity and elasticity of the probability of becoming lucky with respect to individual demographic parameters across the life cycle.  Their application of these methods to empirical data shows how these methods can provide specific information on how taxa differ in the stages at which luck matters. 

The authors also look forward and outline how their general approach can be developed to apply to evolutionary theory.  First, the influence of stochastic variation creates reproductive skew among individuals, which influences effective populations size and genetic diversity. By identifying critical stages whose variance contributes most to such reproductive skew, moreover, the methods contribute to identifying potential targets of natural selection.  Finally, the methods can be adapted to evaluate not only stochastic variance in demographic parameters, but also fixed differences between individuals, as caused by, for example, genetic differences.  Future development of these methods has great potential to integrate demography and evolutionary theory to more fully understand what controls rates of adaptation and demographic performance.  In uncertain environments, understanding the contribution of chance is critical.

I thank all the authors who contributed to The American Naturalist in 2016, as reading their work was truly enjoyable.  I congratulate all of you for your excellent contributions. 

Kathleen Donohue
President, American Society of Naturalists