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Life-history Consequences of Artificial Selection for Increased Egg Size in Hydroides Elegans (Polychaeta: Serpulidae)

出版	University of Florida, 2006
URL	http://books.google.com.hk/books?id=8q12AQAACAAJ&hl=&source=gbs_api

註釋ABSTRACT: Goals of this study were to estimate narrow sense heritability (h2) for egg size in the polychaete worm Hydroides elegans, to examine direct and correlated responses to selection on increased egg size in a suite of life history characters, and to explore how these correlations changed as egg size was increased by artificial selection. Narrow-sense heritability is a predictor of short-term response to selection. Many quantitative models have invoked selective response in egg size as a key transitional element in the evolution of life histories in marine invertebrates, assuming that egg size can and does respond to selection. I tested this assumption using a half-sib breeding design and obtained an estimate for h2 of 0.45 for egg size in a Pearl Harbor, HI population. I performed four generations of artificial selection for increased egg size that allowed me to estimate cumulative realized heritability in the same population as 0.58. Artificial selection resulted in a direct response of 2.5 [sigma sub p] in egg size relative to the common base population. Though I predicted negative correlated responses in some traits under selection, none was measured. A positive correlated response to selection was observed in fecundity, total egg energy, and larval size at competence, relative to control lines. No significant correlated response was observed in early larval size, juvenile tube length, or adult dry weight. H. elegans is a protandrous hermaphrodite, and sex ratio data across generations indicated that large egg selected lines were changing sex earlier than control lines. I propose that this earlier sex change resulted in selected individuals spending less time as males relative to controls, consequently decreasing their overall fitness.