Maternal effects on phenotypic plasticity in larvae of the salamander <Emphasis Type="Italic">Hynobius retardatus</Emphasis> |
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Authors: | Hirofumi Michimae Kinya Nishimura Yoichiro Tamori Masami Wakahara |
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Institution: | (1) Division of Life System Sciences, Faculty of Advanced Life Science, Hokkaido University, Sapporo 060-0810, Japan;(2) Graduate School of Fishery Sciences, Hokkaido University, Hakodate 041-8611, Japan;(3) Department of Biological Science, Florida State University, Tallahassee, FL 32306-4370, USA;(4) Division of Biostatistics, School of Pharmaceutical Sciences, Kitasato University, Tokyo 108-8641, Japan |
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Abstract: | Maternal effects are widespread and influence a variety of traits, for example, life history strategies, mate choice, and
capacity to avoid predation. Therefore, maternal effects may also influence phenotypic plasticity of offspring, but few studies
have addressed the relationship between maternal effects and phenotypic plasticity of offspring. We examined the relationship
between a maternally influenced trait (egg size) and the phenotypic plasticity of the induction rate of the broad-headed morph
in the salamander Hynobius retardatus. The relationship between egg size and the induction of the broad-headed morph was tested across experimental crowding conditions
(densities of low conspecifics, high conspecifics, and high heterospecific anuran), using eggs and larvae from eight natural
populations with different larval densities of conspecifics and heterospecifics. The broad-headed morph has a large mouth
that enables it to consume either conspecifics or heterospecifics, and this ability gives survival advantages over the normal
morph. We have determined that there is phenotypic plasticity in development, as shown by an increase in the frequency of
broad-headed morph in response to an increase in the density of conspecifics and heterospecifics. This reaction norm differed
between populations. We also determined that the frequency of the broad-headed morph is affected by egg size in which larger
egg size resulted in expression of the broad-headed morph. Furthermore, we determined that selection acting on the propensity
to develop the broad-headed morph has produced a change in egg size. Lastly, we found that an increase in egg size alters
the reaction norm to favor development of the broad-headed morph. For example, an equal change in experimental density produces
a greater change in the frequency of the broad-headed morph in larvae developing from large eggs than it does in larvae developing
from small eggs. Population differences in plasticity might be the results of differences in egg size between populations,
which is caused by the adaptive integration of the plasticity and egg size. Phenotypic plasticity can not evolve independently
of maternal effects. |
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Keywords: | Character correlation Egg size Maternal effects Phenotypic plasticity Salamander |
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