EVOLUTION OF

VARIATION

 
 
 
Megalagrion-calliphya-green-female.jpg

We are interested in the evolution and ecology of phenotypic variation. What selection pressures lead to variation between sexes and between species? To study this, we investigate color and behavior of species in two damselfly genera, Megalagrion (an endemic Hawaiian radiation) and Calopteryx (Jewelwings of the mainland US and Canada). See below for publications and images.

 
 
 
 
 
 
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ECOLOGICAL AND SEXUAL SELECTION

MEGALAGRION Fieldwork (HAWAII)

What determines color variation within damselflies species, including female-limited dimorphism and sexual dimorphism?

The answer, at least in Hawaiian damselflies, is found in the ecological setting. Species or sexes that share habitats with high solar radiation are typically red in color. The function of the red pigmentation, an ommochrome, appears to be as an antioxidant, which could provide protection from UV damage. We are investigating the antioxidant function further using UV exposure experiments in the field.

To our surprise, red females aren’t trying to look like males; they are just using the same mechanism to withstand high solar radiation with red pigmentation. Understanding selection on females will help clarify the evolution of sexual dimorphism and may support a more prominent role for viability selection.

 

SEXUAL SELECTION AND SPECIES RECOGNITION

JEWELWING FIELDWORK (ONTARIO & MAINLAND US)

We are investigating the effects of sexual selection and species recognition on wing traits and behavior of overlapping species pairs. The ranges of Calopteryx maculata and C. aequabilis overlap in the northern U.S. and show character displacement where they overlap (very cool research by J. K. Waage). C. aequabilis females have much lighter wings where they encounter C. maculata. We also study allopatric and sympatric populations of Hetaerina americana and H. titia in CA and TX. The questions that we are investigating: (1) How is wing color used in mate choice and species recognition? Does this explain character displacement? (2) To what extent and why are species ranges changing, and how does that affect species interactions?  

 

PUBLICATIONS 

Email cooperia@jmu.edu to request any of these papers

Cook P, Rasmussen R, Brown JM, and Cooper IA. 2018. Sexual conflict does not maintain female color polymorphism in a territorial damselfly. Animal Behaviour 140:171-176. pdf

Cooper IA, Brown JM, and Getty T. 2016. A role for ecology in the evolution of colour variation and sexual dimorphism in Hawaiian damselflies. Journal of Evolutionary Biology 29(2):418-27. pdf

terHorst CP, Lau JA, Cooper IA, Keller K, La Rosa RJ, Royer AM, Schultheis EH, Suwa T, and Conner JK. 2015. Quantifying Non-Additive Selection Caused by Indirect Ecological Effects. Ecology 96(9):2360-2369. pdf

Conner JK, Cooper IA, La Rosa R, Perez S, and Royer A. 2014. Patterns and causes of phenotypic correlations among morphological traits across plants and animals. Philosophical Transactions of the Royal Society B 369: 20130246. pdf

Cooper IA, Gilman RT, and Boughman JW. 2011. Sexual dimorphism and speciation on two ecological coins: patterns from nature and theoretical predictions. Evolution 65(9):2553-2571. pdf

Cooper IA. 2010. Ecology of sexual dimorphism and clinal variation of coloration in a damselfly. American Naturalist 176:566–572. pdf

Brown JM and Cooper I. 2006. Evolution of wing pigmentation patterns in a tephritid gallmaker: divergence and hybridization. Pp. 253-261 in Galling Arthropods and Their Associates – Ecology and Evolution, K. Ozaki, J. Yukawa, T. Ohgushi, and P.W. Price, eds. Springer-Verlag, Tokyo. link

Cooper IA, Roeder L, and Brown JM. 2003. Arthropod response to burning and mowing in a reconstructed prairie. Ecological Restoration 21(3):204-205. pdf