174 
Mitochondrial DMA diversity in 
and population structure of 
red grouper, Epinephelus morio, 
from the Gulf of Mexico* 
Linda R. Richardson 
John R. GoJd 
Department of Wildlife and Fisheries Sciences 
Texas A&M University 
College Station, Texas 77843-2258 
E-mail address: lindafish@tamu.edu 
Red grouper, Epinephelus morio, is 
a protogynous hermaphrodite found 
exclusively in the Atlantic Ocean 
from the coast of Massachusetts 
southward to Brazil (Smith, 1961). 
It is most abundant along the west- 
ern Florida shelf and off the north 
coast of the Yucatan Peninsula, 
Mexico (Brule and Canche, 1993). 
Studies on the biology of red grou- 
per are few. Adults are known to be 
associated with rocky reef bottoms 
and caverns, ledges, and crevices 
formed by limestone outcroppings 
(Moe, 1969). Other available data 
include food habits and some as- 
pects of early life history and pat- 
terns of migration (Moe, 1969; 
Brule and Canche, 1993). 
Red grouper are important to 
both commercial and recreational 
fisheries in the United States (U.S.) 
and Mexico (Moe, 1969). In recent 
years, declines in recreational and 
commercial landings have led to 
regulation of both fisheries in U.S. 
waters. The Mexican red grouper 
fishery, reportedly working above 
maximum sustainable yield (Solis 
Ramirez, 1970; Arreguin-Sanchez, 
1987), however, remains essentially 
unregulated. Important in formu- 
lating management plans for ma- 
rine fish species such as red grou- 
per is information on population 
structure or stocks and on levels of 
genetic variation. This information 
is critical for both stock assessment 
and adjustment of fishery regula- 
tions within regions. 
In a previous study (Richardson 
and Gold, 1993), we examined mi- 
tochondrial (mt)DNA variation 
among a sample of red grouper 
from the west coast of Florida. Es- 
timated within-population mtDNA 
diversity in this sample was among 
the lowest reported for a marine 
fish species. In this note, we report 
mtDNA variation within a sample 
of red grouper from the Campeche 
Banks, Mexico (Fig. 1). The main 
objectives were 1) to determine 
whether red grouper from Florida 
and Mexico represent different ge- 
netic stocks and 2) to compare lev- 
els of mtDNA diversity in red grou- 
per from Campeche Banks, Mexico, 
with those from west Florida. 
Materials and methods 
Specimens were obtained from 
commercial fishermen in Celestun 
and San Felipe, Mexico, during 
November, 1991 (Fig. 1). Heart and 
muscle tissue were removed from 
each individual, stored at -20°C in 
a fish house in Merida, Mexico, and 
transported on wet ice to Houston, 
Texas, where they were frozen in liq- 
uid nitrogen. Upon arrival at Texas 
A&M, tissues were stored at — 80°C. 
Details of DNA isolation, storage, 
restriction enzyme digestion, aga- 
rose electrophoresis of DNA frag- 
ments, and Southern blot hybrid- 
ization with a mtDNA probe may 
be found in Gold and Richardson 
(1991). The mtDNA probe used 
(MCm-mt2) was an entire red grou- 
per mtDNA genome cloned into 
lambda bacteriophage (Richardson 
and Gold, 1993). The ten restriction 
endonucleases used in this study 
were those previously identified to 
be polymorphic in red grouper 
(Richardson and Gold, 1993) and 
included Apa I, Kpnl, Ncol, Nde I, 
Nhe I, Nsil, Pvull, Sspl, Xbal, and 
Xmnl. 
Within-sample mtDNA diversity 
was assessed by nucleon diversity 
(probability that any two individu- 
als drawn at random will differ in 
mtDNA haplotype) and by intra- 
populational nucleotide sequence 
diversity (average nucleotide differ- 
ence between any two individuals 
drawn at random). Both estimates 
of mtDNA diversity were generated 
by using equations in Nei and 
Tajima (1981). 
Geographic partitioning of mtDNA 
variation was assessed by homoge- 
neity testing of mtDNA haplotype 
frequencies and by searching for 
phylogeographic cohesion or struc- 
ture of mtDNA haplotypes with a 
parsimony approach. Homogeneity 
tests included 1) a log-likelihood (G) 
test and 2) a Monte Carlo random- 
ization procedure developed by Roff 
and Bentzen ( 1989). Analyses were 
carried out with the BIOM-PC (a 
package of statistical programs, 
Applied Biostatistics Inc.; Rohlf, 
1987) and REAP (restriction en- 
* This paper represents number XV in the 
series “Genetic studies in marine fishes” 
and contribution number 48 of the Cen- 
ter for Biosystematics and Biodiversity at 
Texas A&M University, College Station, 
Texas 77843-2258. 
Manuscript accepted 25 July 1996. 
Fishery Bulletin 95:174—179 (1997). 
