Species have adapted to variation in time and space in a multitude of ways, and even similar species can use their life cycles in remarkably different manners to successfully carry on their lineages. Throughout my dissertation I examined how two similar species have adapted to use their life cycles differentially to cope with variability in both time and space in a rock pool metacommunity. These different life cycle strategies reflect the constraints that each organism faces within the context of extreme environmental variability. Here, I combine field and laboratory experiments to examine competition, environmental tolerance, and dispersal ability of the cladocerans Daphnia pulex × pulicaria and Moina macrocopa that live in the freshwater rock pools on Appledore Island, Maine, USA. In Chapter One, I show that these species do not compete in the freshwater rock pools on Appledore Island, but that they appear to be limited by different factors: Moina by a disease that causes temporal population crashes, and Daphnia by salinity of the rock pools, which can change abruptly and has no consistent temporal pattern. In Chapter Two, I show that even though Moina produce an order of magnitude more dormant propagules throughout the summer, Daphnia are better able spatially disperse by wind to move among pools. In Chapter Three, I examine the temporal pattern of dormant propagule emergence and hatching of both cladocerans, and relate this to their abiotic and biotic limitations. Ultimately, these species each appear to use spatial and temporal dispersal differently throughout their life cycles, but in ways that are consistent with their environmental limitations.