MANGROVE GENETICS .2. OUTCROSSING AND LOWER SPONTANEOUS MUTATION-RATES IN PUERTO-RICAN RHIZOPHORA

The frequency of red mangrove trees, Rhizophora mangle L., that were monohybrid heterozygotes for chlorophyll-deficient alleles was determined for populations along the southwest coast of Puerto Rico. Segregation ratios for the offspring of these trees were also calculated. Although nuclear, the different mutant homozygous genotypes had profound effects on chloroplast ultrastructure. In comparison to Florida and San Salvador Island R. mangle populations, Puerto Rican mangroves were more outcrossed (28.8% vs. 4.8%) and had lower per generation per genome mutation rates for chlorophyll-deficient mutations (2.1 x 10(-3) vs. 5.8 x 10(-3)).