Renee Rosier


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PhD     2012    Penn State University

BS       2007    Lock Haven University


Research Interests


I am interested in sibling variation, with specific emphasis on growth rate and behavior variation.  Sibling differences in general have been an area of interest for decades across a range of disciplines that includes fields such as psychology, ethology, and ecology.  As a behavioral ecologist, my aim is to determine the relationship between behavior and growth rate variation, and ultimately how these behaviors may affect survival or reproductive success.  Differences in growth have been attributed to a suite of environmental factors, including feeding rates, stress hormones, local temperatures, and even latitudinal gradients.  


When animals are raised in the same environmental conditions, however, there is still evidence of growth rate variation, even among siblings (see right), which are assumed to be very similar in genetic makeup.  Behavior measures such as boldness, dominance, aggression, and higher activity rates have been associated with increased body size across species.  These behaviors could potentially be driving growth rate variation, or could be the result of growth rate variation.  In other words, is an animal big because it is bold, or is it bold because it is big?

Eastern fence lizards (Sceloporus undulatus) provide an

excellent study system for behavior and growth rate

questions, because they:


· Have large sibling groups


· Are independent after hatching


· Hatch at approximately the same size,

           but have growth rate variation


· Have measurable and variable behavior


· And their growth rates can be manipulated

          (for more on this, check out allometric

         engineering by Barry Sinervo)


Since these lizards hatch at the same size (see above, right) and are independent as soon as they hatch, I can test their behavior before they develop differences in body size.  Additionally, females in this species will lay anywhere from 6 to 16 eggs in a single clutch, providing for comparisons of behavior and growth rates among siblings.  My most recent projects have investigated whether early behavior can be used to predict body size later in life, and also whether these relationships are impacted by the presence of competitors.























Additional Research Interests


I am also interested in some of the physiological and genetic mechanisms that may be driving growth rates, including:


· yolk hormones - Differences in yolk hormone levels, such as testosterone, may affect development and growth rates of hatchlings


· digestive efficiency - Some animals are better at obtaining energy and nutrients from their food, and may grow more as a consequence


· multiple paternity - Female fence lizards mate multiple times in a season and can store sperm; therefore, it is possible that hatchlings from the same clutch may actually have different fathers









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