Population Genetics of Tigriopus californicus (Copepoda: Harpacticoida): I. Population Structure Along the Central California Coast

Abstract

Polyacrylam~de gel electrophoresis revealed three genetic polymorphisms among central California populations of the supralittoral copepod Tigriopus californicus. Laboratory analysis of mated pairs and their progeny confirmed the allelic nature of esterase (EST), phosphoglucose isomerase (PGI), and leucine aminopeptidase (LAP) electromorphs. Polymorphism within each enzyme system was localized such that only a few of the nine or more sites sampled were polymorphic while the others were fixed on the same allele. While the Pescadero site (located near the middle of the 250 km transect studied) was polymorphic for PG1 with two alleles at 0.5 frequency, one of these forms never reached a frequency of 0.04 or higher in any of the other populations sampled, including a population located only 1.5 km to the south. Similar population differentiation was observed with respect to the EST locus, and to a lesser extent, the LAP locus. EST phenotype frequencies at Moss Beach exhibited both microgeographic and temporal variation. No obvious patterns, however, were observed among the phenotype frequencies, and estimated allele frequencies indicate that remarkable consistency existed among all the 'Moss Beach population samples. These data indicate that T. californicuspopulations located within habitat patches are genetically relatively homogeneous, while populations occupying habitats isolated by stretches of sandy beach can show strong genetic differentiation over short geographic distances.

POPULATION GENETICS OFTIGRIOPUS CALIFORNICUS. II. DIFFERENTIATION AMONG NEIGHBORING POPULATIONS

“…allele changed from .04 to .50 between two populations located approximately 1.5 km apart. These data, representing one of the sharpest discontinuities in gene frequency yet observed in the marine environment, indicate that gene flow among T. californicus populations is highly restricted (Burton et al, 1979).…”

“…1); most of these sites have been under study since 1977 (Burton et al, 1979) and have been sampled several times each year since that time. With the exceptions of HMB and SCK, all of these sites have had numerous pools inhabited by T. californicus at every sampling.…”

“…Except when esterase (EST) allozymes were to be scored, gels were run for 4 h at 120 volts (constant). EST gels were run for 2.5 h at 120 V and stained as in Burton et al (1979).…”

“…Inter-population comparisons were obtained by running individuals from two or more populations on the same gel. Data establishing the mode of inheritance of the observed banding patterns have been obtained for all loci studied following the methods of Burton et al (1979). Progeny phenotype distributions never deviated significantly from expected Mendelian ratios.…”

“…Scheltema (1975) has pointed out that knowledge of the length of larval life is insufficient for understanding the dispersal capabilities of invertebrate species. He suggests that in order to estimate the ex- Burton et al, 1979), BH = Bean Hollow, SCK = Scott's Creek, SC = Santa Cruz, MY = Monterey, CL = Carmel.…”