Sexual size dimorphism in steppe tortoises (Testudo horsfieldi): growth, maturity, and individual variation

Age and size at maturity are determined through complex interactions among size at birth, growth rate, maturation, and survival. We studied sexual size dimorphism and growth rate and maturation patterns in a long-lived organism, the steppe tortoise (Testudo horsfieldi), using the scute lamina number and width as age and growth measures. There was no sexual difference in the juvenile growth rate, but females matured later and hence were larger at maturity than males. We also observed considerable inter-individual variation in age and size at maturity. In both sexes, precocious animals grew faster during the juvenile phase but matured at a smaller body size than did tardy animals. Consequently, maturity did not seem size-dependent per se but rather was determined by growth rate. The strong variation between and within the sexes in age and size at maturity suggest that different growth trajectories and maturation schedules depend upon sex and individual responses to resource availability.

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Sexual size dimorphism in relation to age and growth based on skeletochronological analysis in a Tibetan frog

Amphibia-Reptilia ◽

10.1163/156853809788795155 ◽

2009 ◽

Vol 30 (3) ◽

pp. 351-359 ◽

Cited By ~ 14

Author(s):

Xin Lu ◽

Xiaoyan Ma

Keyword(s):

Growth Rate ◽

Cross Sections ◽

Sexual Difference ◽

Sexual Size Dimorphism ◽

Population Level ◽

Age And Growth ◽

Size Difference ◽

Size Dimorphism ◽

Asymptotic Size ◽

Central Tibet

AbstractThe number of lines of arrested growth (LAGs) in diaphyseal cross-sections of phalanges or femora was used to assess individual age and growth of 612 Nanorana parkeri, including 363 males, 143 females, 70 juveniles, and 36 tadpoles, in a population from central Tibet, China. The oldest immature frogs had an age of 6 years; both the youngest sexually mature males and females were 3 years old. However, the majority of individuals bred for the first time at 5 years in males and 6 years in females. Females had greater average age (6.27 years) and lifespan (11 years) than males (5.72 and 10 years). At the population level, females, on average, were significantly larger in body length (40.3 mm) than males (37.0 mm). However, the significant size difference only occurred when both sexes were over 6 years old, at which most frogs attained maturity. Growth curve and growth rate estimated for each sex based on a von Bertalanffy model showed that females had a larger asymptotic size (54.2 mm) but smaller growth coefficient k (0.16) than males (40.0 mm, 0.37), and that females had greater growth rate than males in all age classes, except at metamorphosis. According to these results, we concluded that the sexual difference of growth between pre- and post-maturation periods contributed to the age-specific sexual size dimorphism of N. parkeri.

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A skeletochronological estimate of age and growth in a large riparian frog from Madagascar (Anura, Mantellidae, Mantidactylus)

Herpetozoa ◽

10.3897/herpetozoa.32.e35576 ◽

2019 ◽

Vol 32 ◽

pp. 39-44 ◽

Cited By ~ 1

Author(s):

Fabio M. Guarino ◽

Angelica Crottini ◽

Marcello Mezzasalma ◽

Jasmin E. Randrianirina ◽

Franco Andreone

Keyword(s):

Growth Rate ◽

Body Size ◽

Sexual Size Dimorphism ◽

The Body ◽

Age And Growth ◽

Growth Trajectories ◽

Growth Coefficient ◽

Size Dimorphism ◽

Adult Females ◽

Similar Growth

We characterized the body size (as snout-vent length), age, sexual size dimorphism, and growth rate in a population of one of the larger riparian frog from Madagascar (Mantidactylusgrandidieri) from a rainforest patch close to Vevembe, SE Madagascar. We identified a significant female-biased sexual size dimorphism. Age was estimated using phalangeal skeletochronology and was significantly higher in females than in males. Modal age class turned out to be 4 years in both sexes but a large percentage of adult females (75%) fell in the 5–6 years-old classes, while no male exceeded 4 years. We here report M.grandidieri as a medium-long-lived anuran species. Von Bertalanffy’s model showed similar growth trajectories between the sexes although the growth coefficient in females (k = 0.335) was slightly but not significantly higher than in males (k = 0.329).

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Effects of food restriction on growth, energy allocation, and sexual size dimorphism in Yarrow’s Spiny Lizard, Sceloporus jarrovii

Canadian Journal of Zoology ◽

10.1139/z08-002 ◽

2008 ◽

Vol 86 (4) ◽

pp. 268-276 ◽

Cited By ~ 18

Author(s):

Robert M. Cox ◽

Michele M. Barrett ◽

Henry B. John-Alder

Keyword(s):

Growth Rate ◽

Food Restriction ◽

Sexual Difference ◽

Sexual Size Dimorphism ◽

Energy Allocation ◽

Size Dimorphism ◽

Available Energy ◽

Sexually Antagonistic Selection ◽

Fat Bodies ◽

Growth Energy

Evolutionary biologists often view sexual size dimorphism (SSD) as a fixed genetic consequence of sexually antagonistic selection, but the actual magnitude of SSD may often be strongly dependent upon proximate environmental factors. Sexual differences in growth rate lead to male-biased SSD in wild populations of Yarrow’s Spiny Lizard ( Sceloporus jarrovii Cope, 1875), yet both sexes grow at similar rates under controlled laboratory conditions. We hypothesized that male-biased SSD in S. jarrovii reflects an obligatory sexual difference in energy allocation to growth versus competing functions, but that an ad libitum diet provides an energy surplus which overwhelms this sex-specific energetic trade-off. To test this hypothesis, we reared juveniles under high (3 crickets/d) and low (1 cricket/d) food availabilities. Food restriction dramatically reduced growth in both sexes but did not differentially affect growth of females relative to males. Food consumption did not differ between sexes, but males grew slightly faster than females at both levels of food availability, indicating a greater fractional allocation of available energy to growth. By contrast, females had larger fat bodies than did males, particularly under food restriction. This sexual difference in energy allocation to storage could explain the slightly higher growth rate of males relative to females.

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Age and growth of the red-belied lizard, Darevskia parvula

Animal Biology ◽

10.1163/15707563-00002489 ◽

2016 ◽

Vol 66 (1) ◽

pp. 81-95 ◽

Cited By ~ 9

Author(s):

Ufuk Bülbül ◽

Muammer Kurnaz ◽

Ali İhsan Eroğlu ◽

Halime Koç ◽

Bilal Kutrup

Keyword(s):

Growth Rate ◽

Sexual Size Dimorphism ◽

Climatic Factors ◽

High Elevation ◽

Older Age ◽

Age And Growth ◽

Growth Coefficient ◽

Size Dimorphism ◽

Lower Elevation ◽

Two Populations

In the present study, we investigated potential effects of some environmental climatic factors on life-history traits of twoDarevskia parvulapopulations located at different elevation sites and evaluated age, body size, SSD and growth rate results in these lizards. The age at maturity and longevity were found to be similar in both populations. Males of the highland population had significantly larger snout-vent length and older age than those of the lowland population. Although the mean ages of females were not significantly different between the two populations, the highland population had significantly larger snout-vent length than the lowland population. Considering all individuals (both males and females), we found that specimens from the population in the higher-elevation site had significantly larger snout-vent length and older age than those of the lower-elevation site. A low level of male-biased sexual size dimorphism was observed in both populations. The growth coefficient was lower in the high-elevation site than the lower elevation site. Growth rates were not significantly different between the populations. Our preliminary results indicate that although our studied populations were located at different elevation sites and had distinct climate, longevity, age at sexual maturity and growth rate results were similar. This may be a reason of the lower male-biased sexual size dimorphism in both populations.

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Ontogenetic mechanisms underlying sexual size dimorphism in Urodele amphibians: An across-species approach

Current Zoology ◽

10.1093/czoolo/59.1.142 ◽

2013 ◽

Vol 59 (1) ◽

pp. 142-150 ◽

Cited By ~ 7

Author(s):

Lixia Zhang ◽

Xin Lu

Keyword(s):

Growth Rate ◽

Body Size ◽

Evolutionary Biology ◽

Sexual Size Dimorphism ◽

Demographic Data ◽

High Growth ◽

Annual Growth Rate ◽

Size Dimorphism ◽

Ontogenetic Trajectory ◽

Delayed Maturation

Abstract Why do two sexes of the same species differ in body size holds a long-standing question of evolutionary biology. While many across-species comparisons have focused on ultimate causes behind sexual size dimorphism (SSD), only have a few been directed toward elucidating its ontogenetic basis. Urodeles are an amphibian group in which the direction and degree of SSD vary greatly among species. Using demographic data yielded by skeletochronology for 33 urodele species, the current study reveals a positive across-species correlation between SSD and the sex difference in mean age of adult animals, and the latter increases with the corresponding difference in age at maturity; annual growth rate does not differ between the sexes. We conclude that extended longevities in one sex, which is mediated by delayed maturation, would allow it to grow for longer and get larger, with growth rate making a weak contribution to body size. The sex-specific divergence in ontogenetic trajectory might be explained by potentially high growth costs of reproduction to females in association with stronger fecundity selection, and to males that are expected to experience stronger sexual selection.

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Experimental and demographic analyses of growth rate and sexual size dimorphism in a lizard, Sceloporus undulatus

Oikos ◽

10.1034/j.1600-0706.2002.10915.x ◽

2002 ◽

Vol 96 (1) ◽

pp. 70-81 ◽

Cited By ~ 44

Author(s):

Gregory J. Haenel ◽

Henry B. John-Alder

Keyword(s):

Growth Rate ◽

Sexual Size Dimorphism ◽

Sceloporus Undulatus ◽

Size Dimorphism

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Size-Dependent Selective Mechanisms on Males and Females and the Evolution of Sexual Size Dimorphism in Frogs

The American Naturalist ◽

10.1086/678455 ◽

2014 ◽

Vol 184 (6) ◽

pp. 727-740 ◽

Cited By ~ 33

Author(s):

Renato C. Nali ◽

Kelly R. Zamudio ◽

Célio F. B. Haddad ◽

Cynthia P. A. Prado

Keyword(s):

Sexual Size Dimorphism ◽

Size Dimorphism ◽

Size Dependent ◽

Males And Females

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Male and female pups of the highly sexually dimorphic northern elephant seal (Mirounga angustirostris) differ slightly in body size

Canadian Journal of Zoology ◽

10.1139/cjz-2018-0220 ◽

2019 ◽

Vol 97 (3) ◽

pp. 241-250

Author(s):

E. Salogni ◽

F. Galimberti ◽

S. Sanvito ◽

E.H. Miller

Keyword(s):

Body Size ◽

Early Life ◽

Sexual Size Dimorphism ◽

Elephant Seal ◽

Sexually Dimorphic ◽

Mirounga Angustirostris ◽

Northern Elephant Seal ◽

Size Dimorphism ◽

Selective Forces ◽

Size At Birth

In mammals, males generally are larger than females, though such sexual-size differences have been documented primarily in adults and are relatively poorly known in early life. We studied sexual-size differences in pups of the northern elephant seal (Mirounga angustirostris (Gill, 1866)), which in adulthood is one of the most sexually dimorphic mammals. We studied body size at birth and weaning, at Islas San Benito, Mexico, at the southernmost limit of the species’ breeding range. Males were 10% heavier and 2% longer than females at birth. Sexes did not differ significantly in either measure of body size at weaning, although males were slightly heavier (4%) and longer (1%) than females. Neither growth rate nor suckling duration differed between the sexes. In previous studies in California, USA, pups at weaning were heavier than in our study, and males were heavier than females. These differences may reflect ecological, temporal, or life-history differences across populations. The modest difference in sexual-size dimorphism early in life in this species compared with the great difference in adulthood likely reflects multiple selective forces, including constraints on neonatal size set by body size of females, and the weakness of sexual selection at that stage of life.

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Growth and sexual size dimorphism in Alberta populations of the eastern short-horned lizard, Phrynosoma douglassi brevirostre

Canadian Journal of Zoology ◽

10.1139/z85-023 ◽

1985 ◽

Vol 63 (1) ◽

pp. 139-154 ◽

Cited By ~ 17

Author(s):

G. Lawrence Powell ◽

Anthony P. Russell

Keyword(s):

Growth Model ◽

Sexual Difference ◽

Sexual Size Dimorphism ◽

Growth Models ◽

Tail Length ◽

Growth Patterns ◽

Head Width ◽

Adult Size ◽

Adult Males ◽

Size Dimorphism

Alberta populations of Phrynosoma douglassi brevirostre display marked sexual size dimorphism, adult females being considerably larger than adult males. Discriminant analyses of whole mensural characters and of scaled mensural characters indicate that this dimorphism is present from birth, although it is more strongly expressed after sexual maturity. Recapture data were used to generate modified logistic by weight growth models for snout–vent length (SVL), and allometric models for each sex were generated for growth in tail length, head length, and head width. The SVL growth model for females indicates delayed maturity leading to greater adult size, an expected feature of a female viviparine. The SVL growth model for males indicates that growth ceases sooner than in females, resulting in a smaller adult size. This is possibly a result of male dispersal competition, an hypothesis further borne out by the results of a preliminary analysis of mobility in the two sexes, and may also be influenced by intersexual dietary competition. Differences in head dimensions between the sexes are a function of the differences in SVL at adulthood, but there is a significant sexual difference in the allometric relationship of tail length to SVL. No difference in the growth patterns and adult size of either sex was found to exist over the range in Alberta.

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