St. Williams et Jah. Benzie, INDO-WEST PACIFIC PATTERNS OF GENETIC DIFFERENTIATION IN THE HIGH-DISPERSAL STARFISH LINCKIA-LAEVIGATA, Molecular ecology, 6(6), 1997, pp. 559-573
Genetic variation in four natural populations of the starfish Linckia
laevigata from the Indo-West Pacific was examined using restriction fr
agment analysis of a portion of the mtDNA including the control region
. Digestion with seven restriction enzymes identified 47 haplotypes in
a sample of 326 individuals. Samples collected from reef sites within
each location were not significantly differentiated based on Phi(ST)
or spatial distribution of haplotypes, indicating that dispersal is hi
gh over short to moderate distances. Evidence of gene flow is further
supported by the low divergence among haplotypes and the lack of any c
lear geographical structuring among different haplotypes in the gene p
hylogeny. However, analysis of molecular variance (AMOVA), Phi(ST) and
contingency chi(2) analyses of the spatial distribution of haplotypes
demonstrate the presence of significant broad scale population geneti
c structure among the four widespread locations examined. RFLP data ar
e consistent with high gene flow between the Philippines and Western A
ustralia and moderate gene flow between the Great Barrier Reef (GBR) a
nd Fiji, but only limited gene flow between either the Philippines or
Western Australia and either the GBR or Fiji. The presence of mtDNA st
ructure contrasts with previous allozyme data which suggest that dispe
rsal among widely separated locations is equivalent to dispersal among
populations within the highly connected GBR studies. This discordance
between patterns of gene flow inferred from these two markers cannot
be fully accounted for by differences in effective population size for
mtDNA. This might suggest that while mtDNA variation may represent co
ntemporary patterns of gene flow, allozyme variation among populations
is yet to reach equilibrium between drift and migration over the rang
e surveyed.