Environmental and genetic influences on mating strategies along a replicated food availability gradient in guppies (Poecilia reticulata) |
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Authors: | Gita R Kolluru Gregory F Grether Heidy Contreras |
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Institution: | (1) Department of Ecology and Evolutionary Biology, University of California, Los Angeles, 621 Charles E. Young Drive South, Los Angeles, CA 90095-1606, USA;(2) Present address: Department of Ecology and Evolutionary Biology, University of California, Irvine, Irvine, CA 92697-2525, USA |
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Abstract: | Food availability is expected to influence the relative cost of different mating tactics, but little attention has been paid
to this potential source of adaptive geographic variation in behavior. Associations between the frequency of different mating
tactics and resource availability could arise because tactic use responds directly to food intake (phenotypic plasticity),
because populations exposed to different average levels of food availability have diverged genetically in tactic use, or both.
Different populations of guppies (Poecilia reticulata) in Trinidad experience different average levels of food availability. We combined field observations with laboratory “common
garden” and diet experiments to examine how this environmental gradient has influenced the evolution of male mating tactics.
Three independent components of variation in male behavior were found in the field: courtship versus foraging, dominance interactions,
and interference competition versus searching for mates. Compared with low-food-availability sites, males at high-food-availability
sites devoted more effort to interference competition. This difference disappeared in the common garden experiment, which
suggests that it was caused by phenotypic plasticity and not genetic divergence. In the diet experiment, interference competition
was more frequent and intense among males raised on the greater of two food levels, but this was only true for fish descended
from sites with low food availability. Thus, the association between interference competition and food availability in the
field can be attributed to a genetically variable norm of reaction. Genetically variable norms of reaction with respect to
food intake were found for the other two behavioral components as well and are discussed in relation to the patterns observed
in the field. Our results indicate that food availability gradients are an important, albeit complex, source of geographic
variation in male mating strategies. |
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Keywords: | Mating tactic Resource availability Geographic variation Intrasexual competition Dominance Phenotypic plasticity Genotype by environment interaction |
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