Communicated by J. Grassle, New Brunswick. Abstract. Species endemic ... five sites along the East Pacific Rise (EPR) and two along the Galapagos Rift were ...
Marine Biology 114, 551-559 (1992)
Marine
,===BiOlOgy 9 Springer-Verlag 1992
Genetic differentiation between spatially-disjunct populations of the deep-sea, hydrothermal vent-endemic amphipod Ventiella sulfuris S. C. France t, R. R. Hessler 1 and R. C. Vrijenhoek 2
1 Scripps Institution of Oceanography 0202, University of California, San Diego, La Jolla, California 92093-0202, USA 2 Center for Theoretical and Applied Genetics, P.O. Box 231, Rutgers University, New Brunswick, New Jersey 08903-0231, USA Date of final manuscript acceptance: August 12, 1992. Communicated by J. Grassle, New Brunswick
Abstract. Species endemic to deep-sea hydrothermal vent ecosystems have disjunct distributions imposed by the island-like arrangement of their specialized habitats. Using allozyme electrophoresis, we examined genetic population structure of the hydrothermal vent amphipod Ventiella sulfuris Barnard and Ingram, 1990. Samples from five sites along the East Pacific Rise (EPR) and two along the Galapagos Rift were collected in 1990 and 1988, respectively. Variability, based on 12 enzyme loci, was relatively high [/595 (proportion of polymorphic loci whose most common allele not greater than 0.95 in frequency) = 41.6 % ; /7 (mean heterozygosity) = 0.158] compared with shallow-water marine and freshwater amphipods, and similar to the deep-sea lysianassid Eurythenes gryllus. Genetic divergence among populations spread along a contiguous rift axis (i.e., EPR) was low [Nei's genetic distance (D) ranged from 1 800 kin; however, it is likely that other undiscovered vent sites lie along the intervening ridge axes. Potentially significant topographic features which may further impede step-wise dispersers are fracture zones, such as the Rivera Fracture Zone (18 ~ to 19~ which offsets the ridge axis by approximately 240 kin, and the Hess Deep, a 50 km wide, 5 000 m deep depression at the western tip of the Galapagos Rift axis which separates the latter from the EPR (Lonsdale 1988). We examined Ventiella sulfuris collected from two sites on the Galapagos Rift and five sites along the East Pacific Rise from l l ~ to 21~ (Fig. 1). The Galapagos Rift sites, Rose Garden and New Vent, are only about 1 km apart; Genesis and Parigo, at 13~ are < 2 km apart; and Clam Acres and Hanging Gardens, at 21~ are 8 km apart. We used hierarchical F statistics (Wright 1951, 1965) to partition the total genetic diversity of V. sulfuris into several components: (a) diversity within
S.C. France et al.: Hydrothermal vent amphipod population genetics N
20 ~
13~
~ari~ ~. llON --
10 o
Rose Garden New Vent
o
~o
Galapagos Islands
120 ~
110 ~
100 ~
90 ~ W
1. Ventiellasulfuris. Location map showing hydrothermal vent collection sites. Continuous lines represent axes of East Pacific Rise (north-south) and Galapagos Rift (east-west).The two sites at 21~ separated by ~8 kin; the two 13~ sites separated by
