Meeting Abstract

1.1  Saturday, Jan. 4 08:00  Thermal tolerance of larvae of an antitropically-distributed barnacle species WALTHER, K; CRICKENBERGER, S; MARCHANT, S; MARKO, P; MORAN, A*; Clemson Univ., South Carolina; Clemson Univ., South Carolina; Clemson Univ., South Carolina; Univ. of Hawaii, Manoa; Univ. of Hawaii, Manoa morana@hawaii.edu

Many benthic marine organisms disperse by means of a free-living larval stage whose physiological tolerances may be key to determining species’ range limits. We investigated whether thermal tolerances of larvae from three widely-separated populations of an “antitropical” barnacle, Pollicipes elegans, might play a role in limiting connectivity between populations separated by warm tropical waters. We measured three indicators of physiological performance—swimming activity, oxygen consumption, and LT₅₀—and found strong evidence for population-dependent physiological adaptations that may affect dispersal. Thermal tolerance profiles were consistent with populations’ characteristic environmental temperatures, although the width of their optimum, pejus, and pessimum ranges varied. All three populations live within their respective optimal ranges, but larvae from the northern population (Mexico) are close to the upper border of their optimum during warm months and thus have limited capacity to disperse through warmer waters. Larvae from the southern population (Peru) also would not be likely to tolerate tropical temperatures, so for the southern and northern P. elegans populations, high tropical temperatures are likely to be a direct physiological barrier to equatorward larval dispersal. The critical temperature of larvae from El Salvador, the population in the warmest region, was well above environmental temperatures that population would normally experience, suggesting factors other than larval thermal tolerance limit this population’s distribution.