Multiple mating mediates how ecological and evolutionary forces affect populations and there are many explanations for why it is so common. Despite this, taxonomic biases and observational approaches have limited a full understanding of when certain causes and consequences should manifest in certain taxa and ecosystems. Therefore, in this dissertation I used the marine gastropod, the Florida crown conch (Melongena corona) to 1) quantify natural levels of polyandry (i.e., number of sires) across a reproductive season, 2) experimentally manipulated the number of males that mate with females to test the hypothesis that polyandry produces more offspring that are larger and more variable in size at hatching. I also used genetic markers to quantify paternity share after development at hatching. I found that females mated with more males did not produce more offspring at the embryo or hatching stage. Multiple mating also did not affect mean offspring size at hatching. However, multiple mating increased within-brood variation in offspring size at hatching, suggesting differences in intracapsular competition in mixed broods. Paternity share within broods at hatching was skewed, rather than evenly distributed, resulting in a lower effective number of sires relative to the number of mates. Overall, commonly hypothesized benefits of polyandry were not detected in our experiments. Instead, multiple mating is likely controlled by males in this system where mate order, male size, or male copulation all contributed to sire success. The diversity and consequences of developmental mode in marine invertebrates has, for a long time, provided the opportunity to understand different evolutionary solutions to living in variable environments. In this dissertation, I report here novel behavioral variability in hatchlings of the marine gastropod Melongena corona, that has broad significance for understanding the correlated evolution of development, dispersal, and reproductive strategies in a variable environment. All hatchlings crawl-away from egg capsules after emergence as larval pediveligers. Many subsequently swim for a brief period (second to minutes) before crawling again. From detailed observations of 120 individuals over 30 days, I observed 28 (23.3%) hatchlings swimming at least once (8 – 50% per maternal brood). I manipulated hypothesized environmental cues and found that the proportion of hatchlings that swam was highest in the absence of cues related to habitat or food, and lowest when only habitat cues were present. The relative growth rate of hatchlings was highest when habitats contained a putative juvenile food source. About 44% of hatchlings were competent to metamorphose at emergence, but do not metamorphose. The rate of metamorphosis increased with age but depended on the presence of cues. Hatching from benthic egg capsules as crawl-away larvae, while also having the capacity to swim, may have evolved to maintain flexibility in balancing the benefits and risks of benthic versus pelagic mortality, and to maximize survival between reproductive locations and nursery habitat.
