Abstract Detail


Hiatt, Drew [1], Kendig, Amy [1], Flory, S. Luke [1].

Uncovering the hidden reaction norm: non-linearites in plastic responses to multiple stressors.

With rapid global change, there has been a renewed interest in modifying experimental approaches to more accurately evaluate plasticity across a wider range of environments. Recently, it has been recommended that more than two environmental treatments may better characterize the shape of the continuous reaction norm (i.e., variation in plasticity) of a species or population. However, our ability to accurately quantify phenotypic plasticity may not just depend on the number of environmental conditions tested, but also on the amount of variation among treatment levels. We evaluated phenotypic plasticity for an invasive shrub (Dichrostachys cinerea) in response to six levels of experimental shade, as well as two watering treatments (high and low water). Our goal was to answer three specific questions: 1) how common are non-linear reaction norms across a suite of functional traits; 2) how does phenotypic plasticity vary when comparing small to large differences in resource availability (light); and 3) how does an additional stressor (low water) affect phenotypic plasticity? Using the Environmentally Standardized Plasticity Index for individual distances (ESPIID), we demonstrate that phenotypic plasticity for traits associated with foraging for limited light resources exhibited non-linear relationships where small changes in resources often resulted in large differences in trait values. On average, plasticity was 100-300% greater under small changes in light availability (135 - 500 μmoles m2 s-1) compared to large changes (895 - 1580 μmoles m2 s-1) for traits such as plant height, leaf production, and specific leaf area (SLA). It is likely that individuals, and populations of a particular species, will interact more frequently with small, rather than large differences in resource availability. Thus, traditional experimental approaches that evaluate phenotypic plasticity using only two large differences in resource availability may not be examining the full range in resources experienced by a species and in turn severely underestimating plasticity. As a result, forecasting spread or performance of species based on such measures across landscapes with heterogeneous resource availability would likely be inaccurate.

1 - University of Florida, Gainesville, FL, 32601, USA

Phenotypic plasticity
Plant invasion
functional traits.

Presentation Type: Oral Paper
Number: EC08001
Abstract ID:610
Candidate for Awards:None

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