Physiological variation in clonal anemones: Energy balance and quantitative genetics

Abstract

SYNOPSIS. Our understanding of evolutionary mechanisms leading to population differences in mean performance values relies on understanding performance variation within single populations. Unfortunately, relatively little information about physiological variability within natural populations of organisms is available. In particular, to begin to understand how physiological traits evolve we need information on the extent of physiological variability related to the extent of genetic variability over a range of environmental conditions experienced by individual populations. Clonal organisms may be particularly well-suited to such studies because they provide an opportunity to use replicated genotypes (i.e., clonemates) in controlled experiments. We are using the cosmopolitan sea anemone Haliplanella lineata to explore physiological variance in natural populations. Growth, absorption and routine rates of oxygen uptake do not vary among three clones from a single population when measured at 15°C, the approximate midpoint in the seasonal range of water temperatures experienced by this population. Broad-sense heritabilitics for routine rates of oxygen consumption and ammonia excretion (0.14 and 0.09, respectively), indicate a relatively low fraction of variance in these physiological rates is attributable to genetic variation among five clones in this population. Although some literature indicates that such low heritabilities may be expected when physiological traits are measured at environmental mid-range as opposed to extremes, other evidence indicates that it will be difficult to predict the trend between environmental stress and genetic variance in physiological performance.