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Adaptation of Diapause Induction Cue Enables Range Expansion of the Tamarisk Leaf Beetle Across Latitude; Eliza Clark

Resource Category: 
Biocontrol
Document: 
 
 
 
Adaptation of Diapause Induction Cue Enables Range Expansion of the Tamarisk Leaf Beetle Across Latitude
 
Eliza Clark1*, Ellyn Bitume2, Dan Bean3, Amanda Stahlke4, Paul Hohenlohe5, Ruth Hufbauer6
 
1Graduate Degree Program in Ecology, Colorado State University, Fort Collins, CO, USA; eliza.clark@colostate.edu
2US Forest Service, Hilo, HI, USA; ebitume@gmail.com
3Colorado Department of Agriculture, Palisade, CO, USA; dan.bean@state.co.us
4University of Idaho, Moscow, ID, USA; astahlke@uidaho.edu
5University of Idaho, Moscow, ID, USA; hohenlohe@uidaho.edu
6Graduate Degree Program in Ecology, Colorado State University, Fort Collins, CO, USA; ruth.hufbauer@colostate.edu
 
 
Biological control agents encounter novel environments as they expand from initial release points.  For hibernating and diapausing species, adapting to environmental cues that indicate seasonal change is crucial.  The northern tamarisk leaf beetle (Diorhabda carinulata), biological control agent of the invasive plant tamarisk, has rapidly adapted to different daylengths across latitudes that signal to the beetle to prepare for winter.  Understanding evolution of these cues will help us study the impacts of local adaptation during range expansions across heterogeneous environments. 
 
We define a new trait, days until diapause at one day length, to study adaptation to daylength at an individual level. We measured the genetic variation in days until diapause in one northern population in both home and away environments and the responses of eight populations from varying latitudes to both northern and southern environments.
 
We found that days until diapause was highly variable for the population in its home environment and not significantly variable in a novel environment. When comparing populations across the range, we found significant differences in the diapause behaviors of northern core beetles and southern edge beetles in each environment.
 
The variation in the trait days until diapause indicates that adaptive evolution is possible, but only when populations are near their home environment.  Days until diapause across the range indicated that populations have become locally adapted.  These results can be used to predict the rate of range expansion and control of the target weed and inform research on ecological factors important to range expansions.
 
 
 

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