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Multiple paternity is widespread across animal and plant taxa and can increase genetic diversity and enhance fitness, especially in unpredictable environments. A prior study of the intertidal zone porcelain crab, Petrolisthes cinctipes (Randall, 1840), found that most females carried polyandrous broods. We tested the hypothesis that multiple paternity in P. cinctipes enhances fitness through increased average brood tolerance to temperature stress. Embryonic survival of split broods (N = 27) was measured under ambient conditions and following a single one-hour heat shock at 30 °C. Two microsatellite loci were used to genotype embryos and mothers in order to distinguish multiple from single paternity in each brood. Mean overall hatching percentage did not differ between singly and multiply sired broods; however, when exposed to a heat-shock, single-sired broods experienced 11% lower hatching success. Though relative fitness was higher in single-sired broods under non-stressful conditions, extrapolation of our results to conditions where temperatures are at least 30 °C (present-day extremes for the California coast) for > 2 days of the embryonic brood period, multiply sired broods have a relative fitness that is approximately 24 times higher after 15 generations. Maternal quality (size) and the timing of the heat shock relative to developmental timing also influence the brood response to heat shock. Our results suggest that multiple paternity reduces embryo survival variance between ambient and heat-shock conditions and that polyandrous behavior could be an advantage for P. cinctipes in the thermally variable high-intertidal zone. We conclude that multiple paternity is an important strategy for increasing fitness by genetic diversification in organisms that experience severe and unpredictable levels of environmental stress. [ABSTRACT FROM AUTHOR]

Accelerated loss of sea ice in the Arctic is opening routes connecting the Atlantic and Pacific Oceans for longer periods each year. These changes may increase the ease and frequency with which marine birds and mammals move between the Pacific and Atlantic Ocean basins. Indeed, recent observations of birds and mammals suggest these movements have intensified in recent decades. Reconnection of the Pacific and Atlantic Ocean basins will present both challenges to marine ecosystem conservation and an unprecedented opportunity to examine the ecological and evolutionary consequences of interoceanic faunal exchange in real time. To understand these changes and implement effective conservation of marine ecosystems, we need to further develop modeling efforts to predict the rate of dispersal and consequences of faunal exchange. These predictions can be tested by closely monitoring wildlife dispersal through the Arctic Ocean and using modern methods to explore the ecological and evolutionary consequences of these movements. [ABSTRACT FROM AUTHOR]