Lignocellulose and lignin in the salt marsh grass Spartina alterniflora: initial concentrations and short-term,post-depositional changes in detrital matter

Individuals of Mytilus edulis of the same age (ca 2 months) were collected as spat from natural populations. Relative growth rates were determined among individuals differing in heterozygosity at five enzyme loci. Growth rate was positively correlated with individual heterozygosity and each of the five loci contributed about equally to the relatinship. More heterozygous individuals also achieved more uniform average growth rates. Although there was a deficiency of heterozygotes at each locus, relative to Hardy-Weinberg expectations, the magnitude of the deficiency, measured as F_IS, was less among faster growing mussels. Our results conform closely with those of Zouros et al. (1980) on the American oyster. We conclude that the relationship between multiple locus heterozygosity and growth rate is one that is general to a diversity of outbreeding plant and animal populations. Other studies indicate that this relationship is due to a greater average metabolic efficiency of more heterozygous individuals. This relationship does not emerge from experimental designs in which there has been limited genetic sampling of the natural genetic variation.