Genetic differentiation of seamount and basin populations of the deep-sea amphipod Eurythenes gryllus
Abstract
The nearly ubiquitous deep-sea amphipod, Eurythenes gryllus (Lichtenstein), occurs throughout the central North Pacific basin, and has recently been collected from the crests of three bathyal seamounts. Questions of the dispersal capabilities of the species are interesting in the light of this broad geographic and ecological distribution. We use population genetic techniques to describe the genetic structure and estimate migration rates of E. gryllus from allozymic frequencies in basin and seamount samples. Four basin samples were collected along a 4000 km transect from off the coast of California into the central North Pacific basin; two additional samples were collected at the base and on the crest of Horizon Guyot, a bathyal seamount 1300 km west of Hawaii. Allozymic variability at 15 enzyme loci was assayed by starchgel electrophoresis, and allozymic frequency differences were evaluated statistically. Except for two comparisons (both involving the station with smallest sample size), the basin transect samples were not significantly genetically heterogeneous (mean FST = 0.052 ± 0.18 and mean Nm = 5.0 ± 1.6), suggesting that individuals have excellent dispersal capabilities and/or that selection pressures do not differ over these large distances in the deep sea. In contrast, the sample from the crest of Horizon Guyot was genetically distinct from all basin transect samples (mean FST = 0.120 ± 0.03, P < 0.001 for all, and mean Nm = 2.0 ± 0.6), and from the sample at the base of the seamount ( FST = 0.162, P < 0.001, and Nm = 1.3). The genetic differentiation of the crest populations of E. gryllus may be explained by either of two hypotheses: (1) strong differential selection acting on the crest population, causing it to diverge in genetic character from basin populations, and (2) rarity of dispersal and interbreeding between the crest and basin populations. If the latter is true (as seems more probable based on biological information and genetic evidence), dispersal of E. gryllus is predominantly horizontal, and there may be a seamount form of the species that is genetically, and perhaps taxonomically, distinct from the basin form.
- Publication:
-
Deep Sea Research A
- Pub Date:
- November 1987
- DOI:
- 10.1016/0198-0149(87)90054-9
- Bibcode:
- 1987DSRA...34.1795B