Allozymic variability of Riftia pachyptila populations from the Galapagos Rift and 21$deg;N hydrothermal vents
Abstract
Species endemic to hydrothermal vent environments face difficult ecological and evolutionary conditions, especially since vent sites are irregularly distributed in space and ephemeral. Theoretical predictions for an optimal life history for an endemic organism may not be matched by one of the vent community's prominent species, the vestimentiferan Riftia pachyptila. Population samples were collected by submersible from vent sites along the Galapagos Rift and at 21°N along the East Pacific Rise.
Allozymes were used to examine the population genetics of R. pachyptila, including the estimation of genetic variability of the species and differentiation of populations at different vent sites. For the 13 enzyme loci assayed by starch-gel electrophoresis, 31% were polymorphic. Heterozygosity was low: 1.5%. Genetic divergence between samples from the two regions was small but significant: genetic distance, Nei's D, was 0.008 and Wright's measure of variance partitioning, FST = 0.025 (p < 0.05) after correction for small sample sizes. Genotypic frequencies also provided evidence of the differentiation of populations: there was a deficiency of one class of heterozygotes (Pgm-1 98/100) in the pooled samples. The slight genetic differentiation may result from low genetic variability, which may prevent the use of allozymes as markers of gene flow. Endemic vent species may experience bottlenecks during colonization of new vent sites and extinction as vents become inactive. Low variability is a predictable outcome of repeated bouts of colonization and extinction, during which the effects of random genetic drift may rapidly decrease genetic variability.- Publication:
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Deep Sea Research A
- Pub Date:
- October 1988
- DOI:
- 10.1016/0198-0149(88)90048-9
- Bibcode:
- 1988DSRA...35.1759B