Consequences of diverse reproductive strategies in marine invertebrates

I utilized the diversity of life histories in marine invertebrates to examine ecological and evolutionary consequences of reproductive mode through three approaches. The first was an analysis of over 500 time series from the literature to test whether species with long planktonic periods had greater variation in recruitment and adult population size because of the hazards of planktonic life. My results run counter to the established concept and indicated that species with larval dispersal had less adult population variation than species without larval dispersal. None of the alternative hypotheses that I tested explained the pattern. Recruitment variation between species with long or short planktonic period was not significantly different. These results support a revised concept in marine ecology where larval dispersal confers an advantage in dampening population variation, and environmental variability causes population variation in both populations with and without larval dispersal.;The second approach was an experimental field study of Pachythyone rubra, a small sedentary sea cucumber that lacks dispersive larvae and has patchy and dense populations in the Channel Islands in Southern California. To identify the mechanisms which may explain this patchiness, I conducted transplant experiments in occupied and unoccupied habitat at two different locations at Santa Cruz Island in California. Predation and sedimentation were identified as potential mechanisms for decreased survival of transplanted P. rubra. Potential for population growth was very high in western sites in the absence of predation. Spatial differences in demographic rates and the lack of dispersal in the larval stage result in spatial differences in P. rubra population densities.;The third approach examined variation in egg size for over 600 species of marine invertebrates from 13 phyla to investigate relationships between egg size and developmental mode, egg size and planktonic period, and egg size and adult size. Egg size was largest for species with nonplanktonic development, next largest for species with planktonic, nonfeeding development, and smallest for species with planktonic, feeding development. When all development modes were considered at the class level, egg size was significantly negatively correlated with planktonic duration, but egg size was not correlated with adult size.