Sexual size dimorphism in Rana (Pelophylax) ridibunda ridibunda Pallas, 1771 from a population in Darre-Shahr Township, Ilam Province, western Iran

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by  Behzad Fathinia

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Sexual size dimorphism in Rana {Pelophyla)^ ridibunda
ridibunda Paiias, 1771 from a popuiation in Darre-Shahr
Township, Ham Province, western Iran
'BEHZAD FATHINIA, ’‘NASRULLAH RASTEGAR-POUYANI, ^HAMID DARVISHNIA,
^HOSSEIN MOHAMADI, AND 'HIWA FAIZI
'^DepartmentofBiology,FacultyofScience,RaziUniversity, 6714967346Kermanshah,IRAN-DepartmentofBiology,Payam-e-NoorUniversity,
Talesh, Guilan,IRAN;^HeadofBiodiversityandWildlifeManagement,DepartmentoftheEnvironment, Tehran,IRAN
—
Abstract. In this surveywe investigated occurrence of sexuai size dimorphism (SSD), in a popuia-
tion of Rana {Pelophylax) ridibunda ridibunda Paiias, 1771 from Darre-Shahr Township, liam Prov-
ince, western Iran. Ninety-six specimens (52 femaies and 44 maies) were captured, measured and
reieased into their naturai habitat. Tweive metric characters were measured by digitai caiipers to
the nearest 0.01 mm. Statisticai anaiyses showed considerabie differences between sexes for mea-
mm
sured characters. The iargestfemaieand maiewere89.55 and 73.16 SVL, respectiveiy,whiiethe
smaiiestfemaieand maiewere68.52and 61.65 mm SVL, respectiveiy. SPSSversion 16was usedfor
running the anaiysis. The Independent-Sampie Mest (2-taiied) showed that each character has sig-
nificant differences between the sexes (p< 0.01), and for each variabie the femaie vaiue was iarger
than for maies on average.
Keywords. Sexual sizedimorphism(SSD),Rana (Pelophylax) ridibunda ridibunda.PrincipalComponentAnalysis
(PCA),HamProvince, westernIran
Citation;FathiniaB, Rastegar-PouyaniN,DarvishniaH,MohamadiH,FaiziH.2012.Sexualsizedimorphismin Rana(Pelophylax)ridibundaridibunda
Pallas, 1771 fromapopulationinDarr-ShahrTownship, HamProvince,westernIran.Amphibian&ReptileConservation5(1):92-97(e44).
Introduction
2004; Bruner et al. 2005; Kaliontzopoulou et al. 2007),
Sexual dimorphism refers to the existence ofphenotyp- andsnakes (Shine 1978, 1993, 1994;Fericheetal. 1993;
ic differences between males and females of a species, KminiakandKaluz 1983; Shineetal. 1999).
and is widespread in animals (Andersson 1994; Faizi et To our knowledge, such a survey has not yet been
al. 2010). Kuo et al. (2009) considers the presence of documentedfortheMarshfrog,Ranaridibundaridibun-
morphological differences between males and females dainIran.TheMarshfrog,Rana(Pelophylax)ridibunda
of species to have two aspects, size and shape, but Se- ridibundaPallas, 1771,has arelativelywidedistribution
lander (1972) credits behavioral aspects as well. Differ- throughoutIran,exceptforsoutheasternregions(i.e.,Sis-
ent factors can influence sexual dimorphism including tanandBaluchistanProvince;BaloutchandKami 1995).
female reproductive strategy (Tinkle et al. 1970; Ver- We analyzed sexual size dimorphism in this species to
rastro2004), sexual selection (Carothers 1984; Verrastro reveal sexually dimorphic traits that canbeimportantin
2004), and competition for food resources (Schoener systematic andevolutionaryresearch.
1967; VeiTastro 2004). Sexual size dimorphism (SSD)
is a common and widespread phenomenon in animal
taxa, but highly variable in magnitude and direction Materials and methods
(Andersson 1994; Fairbairn 1997; Brandt and Andrade
2007). Sexually dimorphic traits have been surveyed The current survey was carried out about flve km from
in different classes of vertebrates, including birds (Se- Darre-Shalir city. Ham province, western Iran (Fig. I),
lander 1966, 1972; Temeles 1985; Temeles et al. 2000), 33°ir N and47°22' E, 620 mabove sea level (asl) and
primates (Crook 1972), amphibians (Shine 1979; Wool- with 486 millimeter (nun) annual precipitation. All 96
bright 1983; Monnet and Cherry 2002; Schauble 2004; specimens (52 $ and44 S)wereeollectedusmgahand-
Vargas-Salinas 2006; McGarrity andJohnson2008), liz- made butterfly net in streams, brooks, and cultivation
ards(Stamps 1983;Rocha 1996;Carothers 1984;Trivers waterways. Twelve morphometric characters were cho-
1976; Molina-Borja 2003; Baird et al. 2003; Verrastro sen andmeasuredby adigitalcaliperto thenearest0.01
Correspondence.Email:^[email protected]
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Fathinia et al.
mm
and are presentedinTable 1. Morphometric varible
measurementswereobtainedfromasmanyspecimensas
possibleperlocality andreleasedunharmed atthe origi-
nalcapturelocation.Thesameprocedurewasrepeatedin
localities separatedasfaraspossibleto ensurethatnone
of the individuals were counted twice. Two distinctive
characters wereusedto distinguishmales fromfemales:
first, the vocal pouches at the ends ofbuccal slits, just
under the tympana at the sides ofhead and second, the
digital pads on thumbs (Fig. 2). To test significance of
sexually dimorphic characters. Independent Sample t-
test (2-tailed) as well as Principal ComponentAnalysis
(PCA: correlation matrix) at the significance level of
0.01 wereemployed. SPSS softwareversion 16wasused
forrunningthe statisticalanalyses.
Results
Independent-Samples f-test (2-tailed)
The results ofthe Independent-Samples Mest (2-tailed)
showallvariablesdifferedsignificantlybetweensexes(p
<0.01),witheachvariablebeinggreaterinfemalesthan
males (Table2).
Principal Component Analysis (PCA)
Figure 1.Map showingthe studyareain11amprovince, west-
The two axes of the PCA explain 82.08% of the total ernIran.
variation.ThePrincipalComponentOne(PCI) accounts not fully separated from each other. The first axis is a
for73.95% andthePrincipal ComponentTwo (PC2) for reflection ofsize with about 45% ofmales and 23% of
8.13% ofthetotalvariation(Table3). ForPCI, thevari- females inseparable in these characters. The PC2 on the
ables SVL, LHL, LFL, FHL, HL, HW, NNL, TL, and otherhand shows almost no discrimination between the
L4T (see Table 1 for the morphometric characters used sexes, explaining only 8.13% of the total variation in
inthe study) arethemost sexuallydimorphiccharacters. whichthe charactersEELandLEWhavingthemostim-
All these variables have the same direction (positive = portantrole(Fig. 3,Table3).
largerfemales)butnotthe samemagnitude (Fig. 3). The
values ofthefemales alongPCI dooverlap, to someex-
tent, with those for males, indicating that the sexes are Conclusion
Table1.Themorphometriccharactersusedinthisstudy. There is an accepted hypothesis that explains the sta-
tus and direction of sexual size dimorphism in anurans,
Characters Definition
wheremales areusually smallerthanfemales as aresult
SVL Snouttoventlength of sexual selection (Monnet and Cherry 2002). In 90%
LHL Lengthofhindlimb ofthe anuran species, the females are larger than males
LFL Lengthofforelimh (Shine 1979).AsisobviousfromTable2,eachcharacter
FHL Forelimhtohindlimblength tested forRana r. ridibunda was significantly (p < 0.01)
HL Headlength differentformales andfemales onaverage and 100% of
HW Headwidth themeasuredcharacters areindicativeofthepresenceof
sexualdimorphismin size.
EEL Eyelidtoeyelidlength Insomespeciesoffrogs,malesaremuchsmallerthan
SEL Snouttoeyelength females and it is not necessary to carry out statistical
ELW Eyelidwidth analyses(HayekandHeyer2005).ButforR. r ridibunda
NND Distancebetweennostrils it was not completely clear that males are smaller than
TL Tympanumlength females without the help of statistical analyses. Shine
(1979) showed that in species exhibiting male combat,
L4T Lengthofthe4*toe
males are often larger than females, but in our analyses
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Sexual size dimorphism in Rana {Pelophylax) ridibunda ridibunda
Table2.Comparisonofmorphometriccharacters(mm)inmalesandfemalesofRanaridibundaridibunda.n:number; SEM: stan-
darderrorofmean; *=significantatlevel0.01.Morphometricabbreviations: SVL(snout-ventlength),LHL(lengthofhindlimb),
LEE(lengthofforelimb),EHE(forelimbtohindlimb length),HE(headlength),HW(headwidth),EEL(eyelidto eyelidlength),
SEE(snouttoeyelength),LEW(eyelidwidth),NND(distancebetweennostrils),TL(tympanumlength),L4T(lengthofthe4'*’toe).
SEX SVL* LHL* LFL* FHL* HL* HW* EEL* SEL* ELW* NNL* TL* L4T*
6' mean 67.16 103.33 36.27 30.36 18.80 23.12 3.33 10.50 4.82 3.97 4.74 18.54
(n=44) SEM 0.48 0.70 0.25 0.32 0.16 0.18 0.05 0.09 0.09 0.04 0.05 0.14
? mean 78.36 120.14 41.12 36.04 21.71 26.52 3.94 12.29 5.19 4.47 5.45 21.13
(n=52) SEM 0.78 1.01 0.37 0.43 0.24 0.31 0.07 0.22 0.07 0.05 0.06 0.17
p-value(<0.001) 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.002 0.000 0.000 0.000
Differencebetween
means 11.2 16.81 4.85 5.68 2.91 3.4 0.61 1.79 0.37 0.5 0.71 2.59
here, all measured characters in Table 2, size offemale
characters are significantly larger than males. Accord-
ing to Shine (1979), in most cases the causes of sexual
dimorphism in frogs are not known and also inR. r. ri-
dibunda the actual causes ofthis high degree of sexual
dimorphism in our data are not fully understood. Given
this, it seems thatthereis anoutstandingproblemin sta-
tistical significance versus biological significance when
evaluating sexualdimorphisminmeasuredcharacters of
R. r. ridibunda. Regardless of any evolutionary or eco-
logical causes of observed sexual dimorphism in Rana
r. ridibunda, withrespecttothethreeusual andaccepted
hypotheses ofsexual sizedimorphisminall animals: (1)
fecundity selection on female body size (Wiklund and
Karlsson 1988; Fairbaim and Shine 1993), (2) sexual
selection on male body size (Cox et al 2003), and (3)
ecological divergence between sexes due to intraspe-
cific competition (Butler et al. 2000; Bolnick and Doe-
Figure 3. Ordination ofthe individual males and females of
beli 2003); there is anuncertainty in clarifying the main Rana(Pelophylax) ridibundaridibundaonthefirsttwoprinci-
force(s)causingahighdegreeofsexualsizedimorphism pal components. Notetherelative degree ofisolationbetween
inthis species.Moreprofoundsurveys areneededtoun- males and females, which is mainly attributed to SVL, LHL,
coverthemaincause(s)ofSSDinR. r. ridibunda. LEE,HE,andHWinthePCI andEELandLEWinthePC2.
Figure2.Thepresenceofvocalpouches(a)anddigitalpads(b)inmaleRana(Pelophylax)ridibundaridibundadistinguishesthem
fromfemales.
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Fathinia et al.
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LlFiEHmELb(t(eolyehenilgintddhltoiofmhebyielnledinhgdmtlbhe))n,,gtHLhF)F,L(Sh(EelaeEndg(ltsehnnooguftthf)ot,oreHelyiWmebl)(e,hneFgatHdh)Lw,i(EdftoEhr)eW,- CoxralRiMst,(SCkhieclalgyo)SL1,2J4o(2h)n:-2a4l4d-2e5r4H.B.2003.Acompara-
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Published: 07April2012
BEHZADFATHINIA earnedhisB.A. andM.S. fromIsfahanandLorestanuniversities,respeetively.
HisM.S. researchfocusedon“TheBiosystematic StudyofLizards of11amProvince.”Heis aPh.D.
student atRazi University, Kermanshah, western Iranunderthe supervision ofNasrullahRastegar-
Pouyani,MozafarSharifi,andEskandarRastegar-Pouyani.Hisdissertationreaserchinvolvesecology,
phylogeography, molecularsystematics, andpopulationgenetics oftheIranianviperPseudocerastes
urarachnoidesinwesternIran.Heisalsointerestedinotherreptiles,especiallysnakes.
NASRULLAH RASTEGAR-POUYANI earnedhis B.S. in zoology from Razi UniversityKerman-
shah, Iranin 1986 andhis M.S. inzoologyfromTehranUniversity, Tehran, Iranin 1991, wherehe
studiedherpetologywiththeagamidsasthecentralobject.HestartedhisPh.D.inGothenburgUniver-
sity,Swedenin 1994undertheadvisementofProfessorGoranNilsonandgraduatedin1999,working
ontaxonomy andbiogeographyofIranianPlateauagamidswith Trapelusas themainobjective. His
research interests include taxonomy andbiogeography ofthe Iranian Plateau, the Middle East and
centralAsianherpetofauna.
Amphib. ReptileConserv. | amphibian-reptile-conservation.org 096 April2012 | Volume5 | Number 1 | e44
Fathinia et al.
HAMIDDARVISHNIAearnedaB.A.fromBooaliUniversityofRamadanandhisM.S.fromShahid
Beheshti University ofTehran (his thesis was on developmentalbiology). He is currently afaculty
memberoftheDepartmentofBiology,Payam-e-NoorUniversity,Talesh,Guilan,northofIran. Dar-
vishniaisinterestedinsystematics,ecology,andethologyofamphibiansandreptiles.
HUSSEIN MOHAMADI is the Head ofNatural HistoryMuseums and genetic resources. Environ-
mentalProtectionOrganization,Tehran,Iran. HeearnedhisB.A. andM.S. degreesfromtheNatural
Resource College ofTehran University. His M.S. thesis was “The Ecological study ofthe Marsh
crocodile, Crocodyluspalustris, inBaluchistan.” He is now continuinghis study as aPh.D. student
inenvironmental science, branchofscience andresearchatIslamicAzadUniversity. The subjectof
hisPh.D. thesisis “Theassessmentofchangingtrends andmodelingofhabitatpreferenceinyellow
Persiandeer,Damadamamesopotamica.’’
HIVAPAIZIearnedhisB.Sc.inplantbiologyfromShahidBeheshtiUniversity(SBU)andhisM.Sc.
inAnimalBiosystematics fromRazi University. During his M.Sc. he studied the genus Trachylepis
in Iran from different perspectives, including morphology, osteology, parasitology, and systematics
ofTrachylepisaurata transcaucasica. He studiedtheNearEasternfire salamander, Salamandra in-
fraimmaculataseminovi,fromKurdistanprovince,westernIran. Currrently,heiscollectingdataand
samples ofNeurergusmicrospilotus andNeurerguskaiserito startaPh.D. projectonpopulationge-
neticandgeneticdiversityofthetwomentionedspecies.
Amphib. ReptileConserv. | amphibian-reptile-conservation.org 097 April2012 | Volume5 | Number 1 | e44