Presentation Detail

Phenotypic Plasticity

Sikkink, Kristin [1], Reynolds, Rose [2], Ituarte, Catherine [1], Cresko, William [1], Phillips, Patrick [1].

Assimilate this! Experimental evolution of phenotypic plasticity under heat stress in the nematode Caenorhabditis remanei.

How does adaptation to novel conditions occur? Many organisms can acclimate to new environments through phenotypic plasticity, the ability of a genotype to consistently produce an alternate phenotype in response to environmental variation. However, phenotypic plasticity itself is a complex trait that can be heritable, subject to selection, and can evolve. Just how important the evolution of plasticity is generally for adaptation in changing environments remains an open question in evolutionary biology. To address this question, we experimentally evolved outbred populations of the nematode Caenorhabditis remanei. Replicate populations were raised in a common lab environment, and were periodically subjected to an acute heat shock -- an ecologically relevant environment -- during early larval development. To characterize the response to selection, we measured an important fitness component, survivorship. In the native, selective environment, both the ancestor and control populations were highly sensitive to a 37°C heat shock,exhibiting high mortality following heat shock. In contrast, when raised in an alternative, high temperature environment,the ancestor and control lines induce a physiological response that substantially increases their resistance to heat shock. In lines selected for heat shock resistance in the native, non-stressful environment, we observed almost complete resistance to the 37°C heat shock in both environments. This apparent loss of plasticity across environments reflects an adaptive shift in the threshold for heat tolerance in the native environment, but not complete loss of plasticity for the physiological response across both environments. To better understand the molecular basis of this adaptation to heat stress, we used RNA-sequencing to identify changes in gene expression and to identify correlations with the observed changes in heat stress resistance across populations. In contrast to previous studies of phenotypic plasticity, we used a powerful experimental evolution framework to identify a very rapid evolutionary response to an ecologically relevant environment by an important fitness component. More importantly, we find that correlated changes in phenotypic plasticity across environments can also result.Our findings highlight the complexity of the interaction between genotype and environment that influences the ability of organisms to acclimate to novel environments, and the importance of studying phenotypic plasticity within a broader environmental context.

1 - University of Oregon, Institute of Ecology and Evolution, 335 Pacific Hall, 5289 University of Oregon, Eugene, OR, 97403, USA
2 - William Jewell College, Department of Biology, 500 College Hill, Liberty, MO, 64068, USA

Keywords:
genetic assimilation
phenotypic plasticity
Experimental Evolution
heat stress.

Presentation Type: Regular Oral Presentation
Session: 112
Location: Cotton A/Snowbird Center
Date: Monday, June 24th, 2013
Time: 10:45 AM
Number: 112002
Abstract ID:925
Candidate for Awards:W.D. Hamilton Award for Outstanding Student Presentation