natebetweenS. albusandS. platorynchuswith the ferencesexistamong two ormorespawning pop-
expectationthathigherlevels of diversity would be ulations, they may be consideredseparatestocks
detectedwiththesemoresensitiveapproaches. Nu- and managed asdistinctunits (Waldman &Wirgin
clear DNAsequences were PCRamplified with 1994).Acipenseriforms investigated forstock dif-
conservedprimers and these PCR productswere ferencesinclude two freshwater species,Polyodon
thendigestedwith abattery ofdifferent restriction spathula(Americanpaddlefish) andA. fulvescens;
enzymes and DNAbandsharing wascompared be- and threeanadromoussturgeons.S. stellatus(stel-
tween the two putativetaxa.Variabilityamongindi- late sturgeon),A. transmontanus,andA. oxyrin-
viduals in the digestionpatterns ofamplicons was chus.
seenonly at aprealbumin-relatedlocus(Genetic Geneticstudies on populations ofP. spathula
Analyses,Inc.^1 ). A comparison ofallelicfrequen- havebeenconducted onboth theprotein and DNA
cies between S. albus andS. platorynchus at the levels.Carlson et al.(1982)observed extremely low
prealbumin-relatedlocusshowed nosignificant dif- levels ofproteinvariation inP. spathulaand did not
ferences. detectevidence of differentiationamong popula-
Campton et al.2sequencedmore than 400 bp of tions. In contrast,usingboth proteinanalysis and
mtDNAfrom the controlregions ofS. albus(N = restrictionfragmentlength polymorphism(RFLP)
18) andS. platorynchus(N = 20) and found 8haplo- analysis ofmtDNA,Epifanio et al.^4 found greater
typesfrom anarea ofsympatry in theupper Mis- levels ofgenetic polymorphismsamong P.spathula
souri River. However, thesehaplotypesoverlapped collectedfrom 21populations,including theMissis-
between the twospecies to theextentthatmaxi- sippi,Pearl,Alabama, andNeches drainages. How-
mum parsimonyanalysis did notreveal twodistinct ever, themajority ofproteinvariation was observed
species-congruentbranches, but χ^2 analysis did withinpopulations and was oflittle use inelucidat-
showsignificanthaplotypicfrequencydifferences ingpopulation structure.Mitochondrial DNA ge-
(p < 0.001)between thespecies.Controlregion of notypesshowed greatergeographic partitioning
otheracipenserids were similarly sequenced to with both northern (mid-Missouri River) and
serve as references: mean nucleotide diversity southernhaplotypes evident,suggesting the exist-
amongspecimens of thethreescaphirhynchids was ence of some population structurewithintheir
0.58%, compared to1.20% forA. transmontanus. overall distribution.
Also, themeannucleotidediversity was 0.62% be- Acipenserfulvescensalso iswidelydistributed in
tweenS. albusandS. platorynchus,comparedwith NorthAmerica. Porter et al.^5 usedproteinelectro-
14.1%between A .transmontanus andA. mediros- phoresis tocompare thegeneticstatus ofA. fulves-
tris(green sturgeon). Campton et al.^2 were unable censfromLake Eriewithotherpopulationsfrom
to dismisshybridization as afactor in thedifferen- the LaurentianGreatLakes.Only the lactate de-
tiation ofS. albusandS. platorynchus,but they fa- hydrogenase enzymesystem(LDH)revealed use-
vored thehypothesisthat the twospeciesmaintain fulpopulation-level variation.Although theLake
some degree ofreproductive isolation. Eriepopulation was theleast variable ofthose sur-
veyed, one of itsthree LDHphenotypes was not
foundamongotherpopulations.Guenette &Fortin
(1993)found lowlevels ofmtDNAvariation in A.
fulvescensfrom the St. Lawrence River andJames
(^4) Epifanio, J., M.Nedbal&D.P.Phillipp.1989. Apopulation ge-
neticanalysis of paddlefish (Polyodonspathula). Report to Mis-
souriDepartment ofConservation. 63 pp.
o^5 Porter, B., T. Cavender, P. Fuerst & T.Nickell. 1995 The genetic P The
status of lake sturgeon in LakeErie and otherpopulations from
the Laurentian Great Lakes. Report to Ohio Department of Na-
tural Resources. 47 pp.
Identification ofstocks andassessment of
genetic variability
Severalstudieshaveassessedgenetic differentia-
tionamonghypothesized stocks ofsturgeonsand
paddlefishes. Identification of genetic stocks re-
quiresthatindividualsfromhypothesized stocks be
surveyed forgeneticvariability,usually at rapidly
evolvingsites. Ifstatistically significantgeneticdif-