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2008

Sexual Dimorphism and Female Reproduction in
Lacerta vivipara in Northeast China
PENG LIU, WEN GE ZHAO*, ZHI TAO LIU, BING JUN DONG AND HUI CHEN
Department of Biology, Institute of Life and Environment Sciences,
Harbin Normal University, Harbin, 150025, China.
*Corresponding author E-mail: zhaowenge311@126.com
Abstract.- Lacerta vivipara is a small lacertid lizard that inhabits much of Europe and northern Asia. From the endof May to the beginning of October in 2003, these common lizards were collected from a population in Heilongjiang
Province (northeast China) in order to study sexual dimorphism and female reproductive traits. Through the examination of external morphological traits, such as snout-vent length, head length, head width, head height, tail length,
body weight, rows of ventral and mid-dorsals scales, ventral color, tail base and femoral pores, analyses revealed thepresence of a distinct sexual dimorphism. Males possessed a bulging tail base, a salmon-pink venter and a thorn inthe femoral pore. Females had significantly more rows of ventral scales and fewer mid-dorsal scales than males. Adult
males were larger in head size and had a longer tail, whereas adult females were larger in body size and weight. Male
juveniles and neonates were larger in head size than females of the same age and female neonates were larger in bodysize than male neonates. The rates at which head length, head width and head height increased with increasing SVL(snout-vent length) was allometric in females.
Females produced a single clutch every breeding season, with 3–12 young per clutch. While clutch size andneonate mass were not positively correlated with maternal SVL, clutch mass was, suggesting that sexual dimorphismin this species is due (in part) to differences in reproductive investment between the sexes. The larger head of males
is likely an adaptation for male-male combat while the larger relative body length of females is a result of selection
for higher fecundity.
Keywords.- Sexual dimorphism, female reproductive adaptations, allometry, Lacertidae, Lacerta vivipara.

Introduction
Sexual dimorphism in body size, body shape, and coloration is widespread in many Chinese lizards, including Takydromus septentrionalis, Sphenomorphus indicus, Eremias argus, Gekko japonicus, Plestiodon elegans, Plestiodon chinensis, Erendas brenchleyi,
Phrynocephalus vlangalii and Eremias multiocellata(Du and Ji, 2001; Ji and Du, 2000; Lin and Ji, 2000; Liet al., 2006; Xu and Ji, 2003; Zhang et al., 2005).
Previous studies strongly suggest that sexual dimorphism results from a balance between numerous selective pressures differing in influence between the sexes(Shine, 1989; Schoener et al., 1982; Vitt and Cooper,
1985). Consequently, various hypotheses have been proposed to explain sexual dimorphism, including, female
choice in mate selection, male aggressive behavior(Andersson, 1994; Cooper and Vitt, 1993), fecundity
selection (a selection leading to larger body-cavity sizein females) (Griffith, 1990), differential mortality due todifferences in longevity (Shine et al., 2002), and foodniche divergence (Lin and Ji, 2000). Because reproductive output is associated with numerous morphologicaltraits in lizards, data on female physiology and repro-© 2008 by Asiatic Herpetological Researchduction are crucial to understanding the origin of sexual
dimorphism in the group (Du and Ji, 2001; Ji and Du,
2000; Lin and Ji, 2000; Li et al., 2006; Zhang et al.,2005).
The common lizard, Lacerta vivipara Jacquin,
1787, has the largest geographic range of any terrestrial
squamate reptile, extending across Eurasia from western
Europe to Japan. In China, it is found in Heilongjiang
Province, Xijiang Province and Inner Mongolia. It is asmall (approximately 4–5 g), diurnal, non-territorial
lizard typically found in open spaces surrounded bypine-broadleaf mixed forest (Zhao et al., 2006).
Due to both its abundance in nature and unique dual
oviparous and ovoviviparous reproductive modes,
Lacerta vivipara has been the focus of numerous morphological studies (Guillaume, 2006; Šmajda and
Majláth, 1999; Lecomte et al., 1992; Wermuth, 1955).
Despite this abundance of detailed quantitative examination (Dong, et al. 2004; Fang and Tang, 1983; Zhao etal., 2006), however, details on Chinese populations of
the species and the relationship between its reproductive
ecology and morphometry remains poorly understood .
To examine the relationships between sexually dimorphic, morphometric traits in males and females (fromadults to neonates), and their relationships to offspring

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Figure 1. The tail base and ventral color of a male (top)and female (bottom) Lacerta vivipara.

number and mass, we studied a population of L. vivipara
in Sunwu County, Heilongjiang Province, in northeast
China (49° 39′ 19.2′′ N, 127° 34′ 10.1′′ E; elevation 304m). Morphological measurements were taken fromlizards collected in the field. Females gave birth toyoung under simulated field conditions. Particular attention was paid to examining (1) sexual dimorphism inecologically important morphological traits and (2) the
relationship between female size and offspring size andnumber. The results demonstrate that increased malehead size is an adaptation for combat and increased
female body length is an adaptation for higher fecundity.

Materials and Methods
Specimen collection and housing.- From the end of
May to the beginning of October in 2003, 183 lizards(121 females, 62 males) were collected and analyzed. It
was assumed that the lizards were collected randomly,
thereby making the sample representative of the population as a whole. Most of the males sampled were used
only for the collection of morphological data and werereleased immediately following measurement; allfemales were retained for subsequent analysis. The
retained lizards were transported to a nearby field stationand housed in a 7.5 x 1.8 x 1.0 (length x width x height)
m3 enclosure on the ground. The bottom of the enclosure
was covered with grass, branches and stones to simulate
the lizards’ natural habitat. Food (insects and spiders)
and water in small dishes were provided ad libitum. A
humid environment was maintained by spraying the substrate with water daily. The lizards were marked by toe
clipping and back-painting.
Morphometry.- For each lizard collected, the following
five variables were measured with digital calipers to thenearest 0.01 mm: snout-vent length (SVL; from the tip

Figure 2. Frequency distribution of rows of ventral scales
in males and females.

of the snout to the anterior margin of the cloacal lips);
head length (HL; from the tip of the snout to the posterior margin of the skull); head width (HW; the largest
width of the head); head height (HH; the largest heightof the head); tail length (TL; from the anterior margin of
the cloacal lips to the tip of the tail; specimens withregenerated tails were excluded); body weight (BW),number of ventral and mid-dorsals scale rows. Femoral
pores, venter color and tail base width were used to sex
individuals. Specimens with a SVL of 47 mm or more
were considered to be sexually mature adults (139 specimens total); specimens with a SVL of 36-47 mm wereconsidered juveniles (30 specimens); specimens with a
SVL of less than 36 mm were considered neonates (14specimens). .
Female reproduction.- Gravid females were separated
from each other in 30 x 25 x 25 (length x width x depth)
cm3 cages in order to accurately associate newborns with
their mothers. Enclosures were checked at least once a
day for neonates, which were immediately measured
and weighed after birth. Postpartum females were individually weighed and measured for SVL. Clutches

HH

HW

HL

BW

TL

SVL

Trait
34.56±1.74

31.80±1.30t4.13–5.03

4.61±0.42

4.14–5.04

5.00–6.00

4.40±0.42

5.5±0.30

5.53–6.03

7.11–7.52

5.70±0.44

7.11±0.22

7.80±0.27

7.53–8.03

0.66–0.93

0.54–0.87

0.82±0.09

0.78±0.1447.5±2.21
44.0–51.03

43.00–52.19

47.0±3.74

F-0.907

0.727
0.13

0.357

5.155*** 18.515**-0.601-0.24431.00–34.12 31.06–36.00 -3.073**(n = 9)FemaleNeonates(n = 5)Male42.39±2.27

4.20–6.55

4.81±0.51

5.50–8.03

6.81±0.77

6.03–11.00

9.07±1.43

1.17–3.97

2.33±0.79

43.25–80.14

65.74±9.34

38.01–45.14

Femalet

4.12–5.22

4.52±0.39

5.03–7.02

6.07±0.64

6.03–9.50

7.90±1.10

1.00–2.52

1.87±0.43

41.84–66.25

56.77±8.09

F

1.756

2.932

2.831** 12.134**

2.490* 11.380**

1.954

1.59

38.21–46.08 -0.821

43.11±2.55(n = 15)Juveniles(n = 15)Male

5.50–7.50

5.90±0.64

7.50–9.50

8.02±0.41

10.10–11.69

10.94±0.65

2.65–5.00

3.79±0.57

57.07–96.21

84.71±1.71

47.05–59.07(n = 97)

Femalet

4.50–7.01

5.66±0.65

6.45–9.01

7.67±0.57

9.00–11.03

10.47±0.69

2.26–7.36

4.35±0.71

43.76–93.86

79.37±1.25

F

1.937

50.035***4.037*** 48.800***

3.791*** 140.145***-3.710***2.519**

50.03–71.40 -9.304***

58.69±5.44

Adults

51.86±3.13(n = 42)

Male

Table 1. Descriptive statistics of morphological traits of Lacerta vivipara in China. Data are expressed as mean±SE and range (minimum-maximum) and comparedusing t-test (t) and ANCOVA (F) with SVL as the covariate. Length units are in mm, and mass in grams.
*p < 0.05, **p < 0.01, ***p < 0.001

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2.5

13
12

Litter mass (g)He ad le ngt h (mm)

2.0
11
10
9
8

1.5
1.0
.5

7
ႼHL=1.963+0.173SVL r =0.729
2

6
5
30

2

35

40

45

50

55

60

65

70

ჀLM=0.069SVL-3.298 r =0.30
2

0.0
54

ჀHL=2.603+0.133SVL r =0.797

56

58

60

62

64

66

68

70

72

75

Snout-vent length (mm)Snout-vent length (mm)Figure 4. Linear regression of litter mass on female SVL
in Lacerta vivipara. The regression equation is indicatedin the figure. See text for statistical analyses.

10

Head width (mm)9including dead young, stillborns, or unfertilized eggs
were excluded from statistical analyses. Clutch mass
(RLM) was calculated by dividing litter mass by postpartum female mass (Shine, 1992). Relative fecundity
was calculated by using the residuals derived from theregression of litter size on maternal SVL (Olsson andShine, 1997).

876ႼHW=2.023+0.115SVL r =0.753
25ჀHW=2.814+0.082SVL r =0.675
2

4
30

35

40

45

50

55

60

65

70

75

Snout-vent length (mm)8Head height (mm)

7

6

5

4

ႼHH=0.940+0.095SVL r =0.6462

ჀHH=2.106+0.061SVL r =0.550
2

3
30

35

40

45

50

55

60

65

70

75

Snout-vent length (mm)Figure 3. Linear regressions of head length, head widthand head height with SVL in Lacerta vivipara. The
regression equation is indicated in the figure. See text for
statistical analyses. Solid dots and lines: females; open
dots and dashed lines: males.

Statistical analysis.- Whenever parametric statistics
were applied, a normal distribution was verified using
the Kolmogorov-Smirnov test. Homoscedasticity wasverified using Levene's Test for Equality of Variances.
For significant departures from normality or
homoscedasticity, data were loge-transformed before
analysis. To test for sexual dimorphism in the data,
absolute values of morphometric measurements werecompared between sexes using a linear regression analysis, one-way analysis of variance (ANOVA) and oneway analysis of covariance (ANCOVA) with SVL as thecovariate.
All statistical analyses were performed using SPSS
(Statistical Package for the Social Science) v11.5 forWindows. Homogeneity of slopes was checked prior to
testing for differences between adjusted means. Values
are presented as mean ± standard error and the significance level in set at p ≤ 0.05 for all statistical tests.

Table 2. Slope (b), intercept (a) and adjusted R square (r2) estimated from reduced major axis regressions for each
trait against SVL in female neonates, juveniles, and adults.

Y

Neonates

Juveniles

Adultsn=9n = 15n = 97

a

b

r2

a

b

r2

0.118

4.316

0.083

0.037

4.939

0.094

0.555

0.093

-0.968

0.163

0.42

4.653

0.051

0.241

3.939

0.014

0.008

1.117

0.077

0.407

r2

a

b

Head length

8.617-0.044

Head width

7.378-0.053

Head height

1.837

0.08

0.112

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Table 3. Descriptive statistics of female reproductive
traits and snout-vent length of Lacerta vivipara (n = 26).
Mean Standard
error

Range

Female snout-vent
length (mm)

64.52

3.52

55.85–71.04

Postpartum bodymass (g)

4.82

0.71

3.63–6.03

Litter size

7.11

2.47

3–12

Litter mass (g)

1.18

0.44

0.53–2.29

Neonate mass (g)

0.17

0.03

0.11–0.24

Relative litter mass

0.25

0.1

0.09–0.32

Results
Sexual dimorphism.- In males, the base of the tailbulged because of the presence of the hemipenes and theventer of the tail was salmon pink. In females, the baseof the tail was slender and the venter had a saffron-yellow to off-white tint (Fig. 1). Femoral pores (8–12) were
small and black in females and neonates while it was
accompanied by a thorn in adult male. There were morevertical scale rows in females (24–29) than in males(21–25) (Mann-Whitney Test, Z = -10.377, p < 0.01;
Fig. 2), and males had more mid-dorsal scales(31.63±1.46) than females (30.61±1.48) (MannWhitney Test, Z = -3.514, p < 0.01).
The largest male and female were 59.07 and 71.40
mm SVL, respectively. The mean SVL was larger in
adult females (58.69±5.44 mm) than in adult males(51.86±3.13 mm) (t = -9.304, p < 0.001). Body weight
was greater in adult females (t = -3.710, p < 0.001) andtail length was larger in adult males (t = 2.519, p < 0.01).
An ANCOVA test controlling for SVL found that adultmales had a larger head size (head length, head widthand head height) compared to adult females of the same
SVL (ANCOVA; HL, F = 140.145, p < 0.001; HW,
F = 48.800, p < 0.001; HH, F = 50.035, P < 0.001). Head
length and head width were larger in juvenile males thanin juvenile females (ANCOVA; HL, F = 11.380,
p < 0.01; HW, F = 12.134, p < 0.01) and head length waslarger in neonate males than in neonate females (ANCOVA; HL, F = 18.515, p < 0.01). Body length was larger
in neonate females than in neonate males (t = -3.073,
p < 0.01) (Table 1).
The rates at which head length, head width, andhead height increased with increasing SVL were all
greater in males than in females (Fig. 3). Although therates of increase were the same in adult males as they
were for juvenile and neonate males (ANCOVA; HL,
F = 2.972, p = 0.059 > 0.05; HW, F = 0.476,
p = 0.624 > 0.05; HH, F = 5.091, p = 0.09 > 0.05), this2008

was not the case for females (ANCOVA; HL, F = 8.175,
p < 0.001; HW, F = 5.586, p = 0.005 < 0.01; HH,
F = 6.143, p = 0.03 < 0.05). In female neonates, headlength and width did not increase proportionally to SVL(b < 0) and rate of head width was greater in female
juveniles than in female adults (b = 0.163 vs. b = 0.051)(Table 2).
Female reproductive traits.- Female Lacerta vivipara
produced a single clutch of 3–12 young every breeding
season (Table 3). Clutch mass was positively correlatedwith maternal SVL (r = 0.55, F = 5.43, p < 0.01; Fig. 4),
whereas clutch size (r = 0.38, F = 3.75, p = 0.06) andneonate mass (r = 0.37, F = 3.38, p = 0.06) were not.
Neonate mass was independent of relative fecundity(r = 0.15, F = 0.56, p = 0.46).

Discussion
Consistent with previous studies of European populations of Lacerta vivipara (Gvoždík and Damme, 2003;
Kratochvil et al., 2003; Šmajda and Majláth, 1999;
Wermuth, 1955), the present study found that sexual
dimorphism in head size, abdomen length, and taillength was widespread in Chinese populations, suggesting that these sexually dimorphic traits evolved a very
long time ago and has remained in the species as it dispersed across Asia. Lacerta vivipara is similar to otherlizards (e.g., Plestiodon laticeps, Plestiodon elegans,
Phrynocephalus vlangalii, Takydromus septentrionalis,
Tropidurus torquatus) (Du and Ji, 2001; Vitt andCooper, 1985; Zhang and Ji, 2000; Zhang et al., 2005) inthat the males have a larger head and longer tail whilefemales have a longer snout-vent length, increased bodyweight a longer abdomen, and more rows of ventral
scales.
Sexual differences in head size are common within
the Lacertidae (Huang, 1998; Molina-Borja et al., 1998).
Since long periods of evolutionary time are often
required to manifest these differences (Kratochvil et al.,2003), proximate environmental factors can be lessimportant determinants of sexual dimorphism in headsize than ultimate ones, such as phylogenetic history.
Sexual dimorphism may simply be the result of phylogenetic history and is maintained through competition
over mates (intra- and inter-sexual selection)(Kratochvil et al., 2003; Shine, 1989).
According to most speculation, variations in allometry in Lacerta vivipara are adaptive responses related todifferences in both the ecology and reproductive behavior of the two sexes (Kratochvil et al., 2003). Although
it has been reported that a larger head is a male adaptation to feeding on larger prey (Schoener et al., 1982),
there is little intersexual dietary divergence in L. vivipa-

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ra (Zhao et al., 2006). In contrast, the present study supports the conclusion that larger male heads are an adaptation for intersexual combat (Gvoždík and Damme,
2003). There is also evidence to support the possibility
that a longer male tail provides armament in combat andimproves the male’s ability to escape (Barbadilloo andBauwens, 1997; Barbadilloo et al., 1995; Braña, 1996;
Herrel et al., 2001). Color dimorphism is hormonal inorigin, becoming noticeable at the onset of sexual maturity; this dimorphism apparently aids in sexual identification and maintaining social hierarchy (Adriana, 2005).
Females have a considerably larger number oftransverse rows of scales covering the venter of theabdomen and have a relatively large abdomen comparedto males of the same size. The present data showed thatmaternal size is the main determinant of reproductive
output in Lacerta vivipara, with larger females producing heavier clutches. This offers strong evidence to support the hypothesis that selection for higher fecundity
results in the evolution of a longer trunk.
In other species of lizards such as Takydromus
septentrionalis, Podarcis muralis, Gekko japonicus,
Plestiodon chinensis and Sphenomorphus indicus, sexual dimorphism in head size occurs at earlier ontogenetic
stages (Zhang et al., 2005). Our results reveal a similar
pattern in Lacerta vivipara, in that changes in allometry
vary at different ontogenetic stages between the sexes,
resulting in a distinct dimorphism. The neonates havelarger heads to obtain more foods to increase the trunk,so that the sex individuals have no significant differencein the size. With the growth of the body, the rate growthof the head slows in female and head length and headwidth is decreased, and quickly increased in juveniles
till the adults. Adult females of L. vivipara sacrifice head
and tail growth for increased abdomen (and body cavity)
length in order to achieve a greater reproductive output.
In conclusion, Lacerta vivipara exhibits a sexual dimorphism in size, color, and shape that can be linked to sexual selection. In females, characteristics allowing forhigher reproductive output are selected for in females,
resulting in larger bodies and energy allocation directedto early reproduction instead of growth. In males, characteristics selecting for increased numbers of copulations are selected for.

Acknowledgments
We are deeply indebted to Yu-guo Xia, Feng Zhao andZhi-gang Xie for collecting, housing and measuring
specimens in the field. Thanks also are given to Chunzhu Xu, Lin-lin Liu, Dian-wei Li and Zhi-ying Zhang
for dealing with the data. The Heilongjiang Provincial
Bureau of Education for scientific research funded this
work.

103

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