Maternal investment in amphibian offspring varies a great deal among species, individuals and environments. However, larger egg size comes at the cost of producing fewer offspring. Furthermore, egg size variation in nature is often accompanied by differences in larval morphology and behavior (phenotype). The mechanistic relationship between egg size and larval phenotype remains controversial because species also differ in genetic and environmentally-induced traits. This project will examine experimentally the effects of egg size on larval phenotype in salamanders in which egg size evolutionarily doubled after a pond breeding species invaded streams. By surgically removing yolk from embryos, the effect of maternal investment on the phenotype will be assessed in light of stream adaptations. Specifically, we will examine egg size effects on hatching time and stage, body size and shape, escape performance and survival rates, and time to metamorphosis.
The intellectual merit of this research includes developing a powerful experimental research technique for studying a major component of amphibian life history evolution that can help identify correlated traits that respond to egg size. Broader impacts include training of a graduate student, six undergraduates with diverse backgrounds, and broad dissemination of the results - from YouTube to local, national and international meetings, and publication in peer-reviewed journals.
