Risk assessment by crow phenotypes in a hybrid zone |
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Authors: | Christoph Randler |
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Institution: | (1) Institute of Biology I, University of Leipzig, Johannisallee 21-23, 04103 Leipzig, Germany |
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Abstract: | Predation is one of the most selective forces in evolution and, thus, predation may select against hybrids in narrow hybrid
zones. It may be possible that parental phenotypes and hybrids differ in their responses towards predators or humans. As predation
is difficult to observe I used flight-initiation distance (FID) as a metric of risk assessment. FID is a measurable outcome
of the trade-off between fleeing and remaining. Here, I tested whether hybrid and parent crow phenotypes (Corvus corone, Corvus cornix) from the hybrid zone in Eastern Germany differ in their FID. Further, I measured many environmental and social variables
to control statistically for their influence on FID. I sampled 154 individuals (53 hooded crows, 54 carrion crows, and 48
hybrids) in the hybrid zone in eastern Germany. I calculated a general linear model using a stepwise backward procedure to
establish a minimum model containing only significant variables that explained FID in crows. The variable phenotype (hooded,
carrion, hybrid) was then added to the model. There were no differences in FID between hybrids and both parental phenotypes
types, suggesting similar risk assessment. This suggests that hybrids may behave similarly in their decision to flee as their
parent phenotypes, which, in turn, provides no evidence for a selective disadvantage. An additional analysis focusing on pure
phenotypic flocks showed that hybrids in pure hybrid flocks had a lower FID than both parental species in pure flocks. This
suggests that hybrids in pure hybrid flocks may be at a disadvantage. |
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Keywords: | Corvidae Escape theory Fearfulness Flight-initiation distance Hybridization Predation Risk assessment |
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