Allozyme Variation among Populations of Rana pirica (Amphibia: Anura)

Abstract GeneticvariationofRana pirica,aneastAsianbrownfrogoftheR. temporaria group,waselucidatedbyanalysing140specimensfrom11populationsfromHokkaidoandSakhalin,bothlocatingneartheeasterncoastsoftheAsiancontinent,and12specimensofR.ornativentrisfromHonshu,Japanmainland,asanoutgroup,throughhorizontalstarchgelelectrophoresis. Ranapiricashowsrelativelylowgeneticdiﬀerentiation,andhighgeneticaﬃnitiesarefoundbetweenHokkaidoandSakhalinpopulations. Populationsfromtheseislandsaremorphologicallysomewhatdiﬀerentiatedbutshouldberegardedasconspeciﬁc. DegreeofgeneticdivergenceamongpopulationsofamphibianspeciesfromHokkaido,includingR.pirica,isnotsoextensiveasthatreportedforspeciesfromJapanmainlandandrelativelyrecentformationofamphibianfaunainHokkaidoissuggested.Keywords: Biogeography–Hokkaido–geneticvariation–Ranapirica–Sakhalin–electrophoresis–allozyme Introduction The European common frog, Rana temporaria, is nowconsideredtohaveitsrangeinEuropeeasttotheUrals(Frost1985). However,untilsome40yearsago,somespeciesofbrownfrogsfromeastAsia(i.e.R.chensinensis,R.dybowskii,R.ornativentrisandR.pirica)havebeenidentiﬁedasR. temp-oraria(e.g.Boulenger1920;LiuandHu1961;NakamuraandUe´no1963). ThisisbecausetheseAsianbrownfrogsaresosimilarinappearancetoR. temporariathatidentiﬁcationbasedonlyonexternalmorphologyisverydiﬃcult. AmongthesearethepopulationsofbrownfrogsfromHokkaido(Boulenger1886)andSakhalin(Stejneger1907),bothneartheeasternperipheryoftheAsiancontinent.SincetheywererecordedasR. temporaria,theyhavebeenconsideredtobeconspeciﬁcwiththis European species without distinction of even at asubspecies level (Okada and Kawano 1923; Okada 1930,1931;NakamuraandUe´no1963). However,brownfrogsfromJapan,includingHokkaido,wereprovedtohave24chromosomesunlikeR. temporariawith26chromosomes,andtoproducesterilehybridsbetweenR. temporaria (Kawamura1962). Later,similarkaryologicalreportsweremadeonbrownfrogsfromRussia,KoreaandChina,andresultedinrejectionoftraditionaltaxonomyinwhichEuropeanandAsianspeciesweretreatedasconspeciﬁc(e.g.Kawamura1962;TianandJiang1986). Inthisway,thetaxonomicproblemsleftunresolvedweretherelationshipsofbrownfrogswithinAsia.Afterelucidationofitschromosomenumber(2n¼ 24),thebrownfrogfromHokkaidowasconsideredtobeconspeciﬁcwitheastAsianspecieswith24chromosomes(i.e.R.chensinensis:Kawamura1962;Frost1985;Kuzminetal.1988). Finally,fromanextensivestudyofmorphologicalandgeneticcharacteristics,thepopulationfromHokkaidowasrecognizedasadistinctspecies,R.pirica,endemictothatisland(Matsui1991). Morerecently,Tanaka-Uenoetal. (1998)performedmitochondrialDNA analysis and concluded that the brown frog fromSakhalinshouldalsobeidentiﬁedasR.pirica.AlthoughR.piricaisconsideredtobewidelydistributedinHokkaido(Matsui1991)andSakhalin(Tanaka-Uenoetal.1998;MaedaandMatsui1999),butnotinHonshu,afossilidentiﬁedasR.piricahasbeenfoundfromAomori,northern-mostHonshu(Hasegawaetal.1988)suggestingitswiderdistributioninthepast.PopulationsfromHokkaidoandSakhalin,however,werereportedtobedeﬁnitelydiﬀerentinmorphology(Matsuietal.1994),andfurtheranalyseshavebeenrequired. Wethusanalysed allozymic properties of the populations fromHokkaidoandSakhalinelectrophoretically.Electrophoretictechniquehasbeenusedasavaluabletoolforthesurveyofgeneticvariationsofbrownfrogs(GreenandBorkin1993;Nishiokaetal.1987a,1992a;SumidaandNishioka1994,1996)andforelucidatingtaxonomicproblemsofthistaxo-nomicallycomplicatefroggroup(Matsui1991). Inthisstudy,weprovidedataforallozymicvariationsamongR. piricapopulationsanddiscussrecentfaunalformationoftheregionincludingHokkaidoandSakhalin.