POPULATION CHARACTERISTICS AND REPRODUCTIVE TRENDS OF THE GREEN PORCELAIN CRAB, <i>Petrolisthes armatus</i>, IN ITS INTRODUCED RANGE
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Popp, Teresa Elizabeth
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Abstract
The green porcelain crab, <i>Petrolisthes armatus</i>, is a highly abundant invader on intertidal oyster reefs along the southeastern coast of the US. Its poleward range expansion is thought to be thermally limited, and predicted to shift as water temperatures rise. Along with its thermal tolerance in the invasive range, several of its reproductive characteristics favor expansion. What remains unclear is whether this thermal intolerance for cold temperatures affects the reproductive potential of invasive populations. I conducted a field study monitoring the invasive population in Charleston, SC, a laboratory experiment determining the time between broods, and examined specimens from a long-term collection to determine if timing of larval recruitment to an area is related to the severity of the previous winter. <i>Petrolisthes armatus</i> abundances varied seasonally, with highest abundances during summer months and lowest during winter months. After a mild winter, adult-sized overwintering crabs began the reproductive season in spring as water temperatures increased. After recruits were first observed, they became part of the reproductive population 6-8 weeks later. Conversely, after a harsh winter, crabs were not present on the oyster reef and abundances were low throughout spring and early summer. However, 5-7 weeks after recruits were observed in June, adult abundances recovered to similarly high-densities observed the prior year. Both the field and laboratory data indicate that females are able to turn over broods within 4-6 days after releasing eggs. By examining <i>P. armatus</i> larvae in samples collected over a 24-year period in an estuary near the species’ range limit, I determined that larval recruitment started later in years after winters with several consecutive cold days where water temperatures declined to 5-6ºC In addition, earlier starts to recruitment were positively correlated with the duration or recruitment. It appears that if the frequency of harsh winters decreases, the thermal barrier inhibiting further range expansion for <i>P. armatus</i> will become less effective.